With a radius between 640 and 764 times that of the Sun,[14][11] if it were at the center of our Solar System, its surface would lie beyond the asteroid belt and it would engulf the orbits of Mercury, Venus, Earth, and Mars. Calculations of Betelgeuse's mass range from slightly under ten to a little over twenty times that of the Sun. For various reasons, its distance has been quite difficult to measure; current best estimates are of the order of 400–600light-years from the Sun–a comparatively wide uncertainty for a relatively nearby star. Its absolute magnitude is about −6. With an age of less than 10million years, Betelgeuse has evolved rapidly because of its large mass, and is expected to end its evolution with a supernova explosion, most likely within 100,000years. When Betelgeuse explodes, it will shine as bright as the half-Moon for more than three months; life on Earth will be unharmed. Having been ejected from its birthplace in the Orion OB1 association–which includes the stars in Orion's Belt–this runaway star has been observed to be moving through the interstellar medium at a speed of 30km/s, creating a bow shock over four light-years wide.
Betelgeuse became the first extrasolar star whose photosphere's angular size was measured in 1920, and subsequent studies have reported an angular diameter (i.e., apparent size) ranging from 0.042 to 0.056 arcseconds; that range of determinations is ascribed to non-sphericity, limb darkening, pulsations and varying appearance at different wavelengths. It is also surrounded by a complex, asymmetric envelope, roughly 250times the size of the star, caused by mass loss from the star itself. The Earth-observed angular diameter of Betelgeuse is exceeded only by those of R Doradus and the Sun.
Starting in October 2019, Betelgeuse began to dim noticeably, and by mid-February 2020 its brightness had dropped by a factor of approximately 3, from magnitude 0.5 to 1.7. It then returned to a more normal brightness range, reaching a peak of 0.0 visual and 0.1 V-band magnitude in April 2023. Infrared observations found no significant change in luminosity over the last 50 years, suggesting that the dimming was due to a change in extinction around the star rather than a more fundamental change. A study using the Hubble Space Telescope suggests that occluding dust was created by a surface mass ejection; this material was cast millions of miles from the star, and then cooled to form the dust that caused the dimming.
Nomenclature
The star's designation is αOrionis (Latinised to Alpha Orionis), given by Johann Bayer in 1603.
The traditional name Betelgeuse was derived from the Arabicيد الجوزاءYad al-Jawzā’ "the hand of al-Jawzā’ [i.e. Orion]".[20][21] An error in the 13th-century reading of the Arabic initial yā’ (يـ) as bā’ (بـ—a difference in i‘jām) led to the European name.[21][22] In English, there are four common pronunciations of this name, depending on whether the first e is pronounced short or long and whether the s is pronounced /s/ or /z/:[1][2]
Betelgeuse and its red coloration have been noted since antiquity; the classical astronomer Ptolemy described its color as ὑπόκιρρος (hypókirrhos = more or less orange-tawny), a term later described by a translator of Ulugh Beg's Zij-i Sultani as rubedo, Latin for "ruddiness".[26][lower-alpha 1] In the 19th century, before modern systems of stellar classification, Angelo Secchi included Betelgeuse as one of the prototypes for his ClassIII (orange to red) stars.[27] Three centuries before Ptolemy, in contrast, Chinese astronomers observed Betelgeuse as yellow; Such an observation, if accurate, could suggest the star was in a yellow supergiant phase around this time,[28][12] a credible possibility, given current research into these stars' complex circumstellar environment.[29]
Nascent discoveries
Aboriginal groups in South Australia have shared oral tales of the variable brightness of Betelgeuse for at least 1,000 years.[30][31]
The variation in Betelgeuse's brightness was described in 1836 by Sir John Herschel in Outlines of Astronomy. From 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone Rigel in October 1837 and again in November 1839.[32] A 10-year quiescent period followed; then in 1849, Herschel noted another short cycle of variability, which peaked in 1852. Later observers recorded unusually high maxima with an interval of years, but only small variations from 1957 to 1967. The records of the American Association of Variable Star Observers (AAVSO) show a maximum brightness of 0.2 in 1933 and 1942, and a minimum of 1.2, observed in 1927 and 1941.[33][34] This variability in brightness may explain why Johann Bayer, with the publication of his Uranometria in 1603, designated the star alpha, as it probably rivaled the usually brighter Rigel (beta).[35] From Arctic latitudes, Betelgeuse's red colour and higher location in the sky than Rigel meant the Inuit regarded it as brighter, and one local name was Ulluriajjuaq ("large star").[36]
In 1920, Albert A. Michelson and Francis G. Pease mounted a six-meter interferometer on the front of the 2.5-meter telescope at Mount Wilson Observatory, helped by John August Anderson. The trio measured the angular diameter of Betelgeuse at 0.047″, a figure that resulted in a diameter of 3.84×108km (2.58AU) based on the parallax value of 0.018″.[37] But limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements.
The 1950s and 1960s saw two developments that affected stellar convection theory in red supergiants: the Stratoscope projects and the 1958 publication of Structure and Evolution of the Stars, principally the work of Martin Schwarzschild and his colleague at Princeton University, Richard Härm.[38][39] This book disseminated ideas on how to apply computer technologies to create stellar models, while the Stratoscope projects, by taking balloon-borne telescopes above the Earth's turbulence, produced some of the finest images of solar granules and sunspots ever seen, thus confirming the existence of convection in the solar atmosphere.[38]
Imaging breakthroughs
1998/9 UVHST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles
Astronomers saw some major advances in astronomical imaging technology in the 1970s, beginning with Antoine Labeyrie's invention of speckle interferometry, a process that significantly reduced the blurring effect caused by astronomical seeing. It increased the optical resolution of ground-based telescopes, allowing for more precise measurements of Betelgeuse's photosphere.[40][41] With improvements in infrared telescopy atop Mount Wilson, Mount Locke, and Mauna Kea in Hawaii, astrophysicists began peering into the complex circumstellar shells surrounding the supergiant,[42][43][44] causing them to suspect the presence of huge gas bubbles resulting from convection.[45] However, it was not until the late 1980s and early 1990s, when Betelgeuse became a regular target for aperture masking interferometry, that breakthroughs occurred in visible-light and infrared imaging. Pioneered by J.E.Baldwin and colleagues of the Cavendish Astrophysics Group, the new technique employed a small mask with several holes in the telescope pupil plane, converting the aperture into an ad hoc interferometric array.[46] The technique contributed some of the most accurate measurements of Betelgeuse while revealing bright spots on the star's photosphere.[47][48][49] These were the first optical and infrared images of a stellar disk other than the Sun, taken first from ground-based interferometers and later from higher-resolution observations of the COAST telescope. The "bright patches" or "hotspots" observed with these instruments appeared to corroborate a theory put forth by Schwarzschild decades earlier of massive convection cells dominating the stellar surface.[50][51]
In 1995, the Hubble Space Telescope's Faint Object Camera captured an ultraviolet image with a resolution superior to that obtained by ground-based interferometers—the first conventional-telescope image (or "direct-image" in NASA terminology) of the disk of another star.[52] Because ultraviolet light is absorbed by the Earth's atmosphere, observations at these wavelengths are best performed by space telescopes.[53] This image, like earlier pictures, contained a bright patch indicating a region in the southwestern quadrant 2,000K hotter than the stellar surface.[54] Subsequent ultraviolet spectra taken with the Goddard High Resolution Spectrograph suggested that the hot spot was one of Betelgeuse's poles of rotation. This would give the rotational axis an inclination of about 20° to the direction of Earth, and a position angle from celestial North of about 55°.[55]
2000s studies
In a study published in December 2000, the star's diameter was measured with the Infrared Spatial Interferometer (ISI) at mid-infrared wavelengths producing a limb-darkened estimate of 55.2±0.5mas – a figure entirely consistent with Michelson's findings eighty years earlier.[37][56] At the time of its publication, the estimated parallax from the Hipparcos mission was 7.63±1.64mas, yielding an estimated radius for Betelgeuse of 3.6AU. However, an infrared interferometric study published in 2009 announced that the star had shrunk by 15% since 1993 at an increasing rate without a significant diminution in magnitude.[57][58] Subsequent observations suggest that the apparent contraction may be due to shell activity in the star's extended atmosphere.[59]
In addition to the star's diameter, questions have arisen about the complex dynamics of Betelgeuse's extended atmosphere. The mass that makes up galaxies is recycled as stars are formed and destroyed, and red supergiants are major contributors, yet the process by which mass is lost remains a mystery.[60] With advances in interferometric methodologies, astronomers may be close to resolving this conundrum. Images released by the European Southern Observatory in July 2009, taken by the ground-based Very Large Telescope Interferometer (VLTI), showed a vast plume of gas extending 30AU from the star into the surrounding atmosphere.[61] This mass ejection was equal to the distance between the Sun and Neptune and is one of multiple events occurring in Betelgeuse's surrounding atmosphere. Astronomers have identified at least six shells surrounding Betelgeuse. Solving the mystery of mass loss in the late stages of a star's evolution may reveal those factors that precipitate the explosive deaths of these stellar giants.[57]
2019–2020 fading
AAVSOV-band magnitude of Betelgeuse, between September2016 and August2023Comparison of SPHERE images of Betelgeuse taken in January2019 and December2019, showing the changes in brightness and shape
A pulsating semiregular variable star, Betelgeuse is subject to multiple cycles of increasing and decreasing brightness due to changes in its size and temperature.[18] The astronomers who first noted the dimming of Betelgeuse, Villanova University astronomers Richard Wasatonic and Edward Guinan, and amateur Thomas Calderwood, theorize that a coincidence of a normal 5.9year light-cycle minimum and a deeper-than-normal 425day period are the driving factors.[62] Other possible causes hypothesized by late 2019 were an eruption of gas or dust or fluctuations in the star's surface brightness.[63]
By August2020, long-term and extensive studies of Betelgeuse, primarily using ultraviolet observations by the Hubble Space Telescope, had suggested that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space. The material cooled and formed a dust cloud that blocked the starlight coming from about a quarter of Betelgeuse's surface. Hubble captured signs of dense, heated material moving through the star's atmosphere in September, October and November before several telescopes observed the more marked dimming in December and the first few months of 2020.[64][65][66]
By January2020, Betelgeuse had dimmed by a factor of approximately 2.5 from magnitude0.5 to 1.5 and was reported still fainter in February in The Astronomer's Telegram at a record minimum of +1.614, noting that the star is currently the "least luminous and coolest" in the 25years of their studies and also calculating a decrease in radius.[67]Astronomy magazine described it as a "bizarre dimming",[68] and popular speculation inferred that this might indicate an imminent supernova.[69][70] This dropped Betelgeuse from one of the top 10 brightest stars in the sky to outside the top20,[62] noticeably dimmer than its near neighbor Aldebaran.[63] Mainstream media reports discussed speculation that Betelgeuse might be about to explode as a supernova,[71][72][73][74] but astronomers note that the supernova is expected to occur within approximately the next 100,000years and is thus unlikely to be imminent.[71][73]
By 17February 2020, Betelgeuse's brightness had remained constant for about 10days, and the star showed signs of rebrightening.[75] On 22February 2020, Betelgeuse may have stopped dimming altogether, all but ending the dimming episode.[76] On 24February 2020, no significant change in the infrared over the last 50 years was detected; this seemed unrelated to the recent visual fading and suggested that an impending core collapse may be unlikely.[77] Also on 24February 2020, further studies suggested that occluding "large-grain circumstellar dust" may be the most likely explanation for the dimming of the star.[78][79] A study that uses observations at submillimetre wavelengths rules out significant contributions from dust absorption. Instead, large starspots appear to be the cause for the dimming.[80] Followup studies, reported on 31March 2020 in The Astronomer's Telegram, found a rapid rise in the brightness of Betelgeuse.[81]
Betelgeuse is almost unobservable from the ground between May and August because it is too close to the Sun. Before entering its 2020 conjunction with the Sun, Betelgeuse had reached a brightness of +0.4. Observations with the STEREO-A spacecraft made in June and July2020 showed that the star had dimmed by 0.5 since the last ground-based observation in April. This is surprising, because a maximum was expected for August/September2020, and the next minimum should occur around April2021. However Betelgeuse's brightness is known to vary irregularly, making predictions difficult. The fading could indicate that another dimming event might occur much earlier than expected.[82] On 30August 2020, astronomers reported the detection of a second dust cloud emitted from Betelgeuse, and associated with recent substantial dimming (a secondary minimum on 3August) in luminosity of the star.[83]
In June 2021, the dust was explained as possibly caused by a cool patch on its photosphere[84][85][86][87] and in August a second independent group confirmed these results.[88][89] The dust is thought to have resulted from the cooling of gas ejected from the star. An August 2022[90][91][92] study using the Hubble Space Telescope confirmed previous research and suggested the dust could have been created by a surface mass ejection. It conjectured as well that the dimming could have come from a short-term minimum coinciding with a long-term minimum producing a grand minimum, a 416-day cycle and 2010day cycle respectively, a mechanism first suggested by astronomer L.Goldberg.[93] In April2023, astronomers reported the star reached a peak of 0.0 visual and 0.1 V-band magnitude.[94]
As a result of its distinctive orange-red color and position within Orion, Betelgeuse is easy to find with the naked eye. It is one of three stars that make up the Winter Triangleasterism, and it marks the center of the Winter Hexagon. It can be seen rising in the east at the beginning of January of each year, just after sunset. Between mid-September and mid-March (best in mid-December), it is visible to virtually every inhabited region of the globe, except in Antarctica at latitudes south of 82°. In May (moderate northern latitudes) or June (southern latitudes), the red supergiant can be seen briefly on the western horizon after sunset, reappearing again a few months later on the eastern horizon before sunrise. In the intermediate period (June–July, centered around mid June), it is invisible to the naked eye (visible only with a telescope in daylight), except around midday low in the north in Antarctic regions between 70° and 80° south latitude (during midday twilight in polar night, when the Sun is below the horizon).
Betelgeuse is a variable star whose visual magnitude ranges between 0.0 and +1.6.[5] There are periods during which it surpasses Rigel to become the sixth brightest star, and occasionally it will become even brighter than Capella. At its faintest, Betelgeuse can fall behind Deneb and Beta Crucis, themselves both slightly variable, to be the twentieth-brightest star.[34]
Betelgeuse has a B–V color index of 1.85 – a figure which points to its pronounced "redness". The photosphere has an extended atmosphere, which displays strong lines of emission rather than absorption, a phenomenon that occurs when a star is surrounded by a thick gaseous envelope (rather than ionized). This extended gaseous atmosphere has been observed moving toward and away from Betelgeuse, depending on fluctuations in the photosphere. Betelgeuse is the brightest near-infrared source in the sky with a Jbandmagnitude of −2.99;[95] only about 13% of the star's radiant energy is emitted as visible light. If human eyes were sensitive to radiation at all wavelengths, Betelgeuse would appear as the brightest star in the night sky.[34]
Catalogues list up to nine faint visual companions to Betelgeuse. They are at distances of about one to four arc-minutes and all are fainter than 10thmagnitude.[96][97]
Star system
Betelgeuse is generally considered to be a single isolated star and a runaway star, not currently associated with any cluster or star-forming region, although its birthplace is unclear.[98]
Two spectroscopic companions to Betelgeuse have been proposed. Analysis of polarization data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1years, and by using speckle interferometry, the team concluded that the closer of the two companions was located at 0.06″±0.01″ (≈9AU) from the main star with a position angle of 273°, an orbit that would potentially place it within the star's chromosphere. The more distant companion was at 0.51″±0.01″ (≈77AU) with a position angle of 278°.[99][100] Further studies have found no evidence for these companions or have actively refuted their existence,[101] but the possibility of a close companion contributing to the overall flux has never been fully ruled out.[102] High-resolution interferometry of Betelgeuse and its vicinity, far beyond the technology of the 1980s and 1990s, has not detected any companions.[61][103]
A more recent study found that a not yet directly-observed, dust-modulating stellar-mass companion of 1.17±0.7M☉ would be the most likely solution for Betelgeuse's 2170-day secondary periodicity, fluctuating radial velocity, moderate radius and low variation in effective temperature. The candidate companion would have a semi-major axis of 8.60±0.33AU.[104]
Parallax is the apparent change of the position of an object, measured in seconds of arc, caused by the change of position of the observer of that object. As the Earth orbits the Sun, every star is seen to shift by a fraction of an arc second, which measure, combined with the baseline provided by the Earth's orbit gives the distance to that star. Since the first successful parallax measurement by Friedrich Bessel in 1838, astronomers have been puzzled by Betelgeuse's apparent distance. Knowledge of the star's distance improves the accuracy of other stellar parameters, such as luminosity that, when combined with an angular diameter, can be used to calculate the physical radius and effective temperature; luminosity and isotopic abundances can also be used to estimate the stellar age and mass.[105]
When the first interferometric studies were performed on the star's diameter in 1920, the assumed parallax was 0.0180″. This equated to a distance of 56pc or roughly 180ly, producing not only an inaccurate radius for the star but every other stellar characteristic. Since then, there has been ongoing work to measure the distance of Betelgeuse, with proposed distances as high as 400pc or about 1,300ly.[105]
Before the publication of the Hipparcos Catalogue (1997), there were two slightly conflicting parallax measurements for Betelgeuse. The first, in 1991, gave a parallax of 9.8±4.7mas, yielding a distance of roughly 102pc or 330ly.[106] The second was the Hipparcos Input Catalogue (1993) with a trigonometric parallax of 5±4mas, a distance of 200pc or 650ly.[107] Given this uncertainty, researchers were adopting a wide range of distance estimates, leading to significant variances in the calculation of the star's attributes.[105]
The results from the Hipparcos mission were released in 1997. The measured parallax of Betelgeuse was 7.63±1.64mas, which equated to a distance of roughly 131pc or 427ly, and had a smaller reported error than previous measurements.[108] However, later evaluation of the Hipparcos parallax measurements for variable stars like Betelgeuse found that the uncertainty of these measurements had been underestimated.[109] In 2007, an improved figure of 6.55±0.83 was calculated, hence a much tighter error factor yielding a distance of roughly 152±20pc or 500±65ly.[3]
In 2008, measurements using the Very Large Array (VLA) produced a radio solution of 5.07±1.10mas, equaling a distance of 197±45pc or 643±146ly.[105] As the researcher, Harper, points out: "The revised Hipparcos parallax leads to a larger distance (152±20pc) than the original; however, the astrometric solution still requires a significant cosmic noise of 2.4 mas. Given these results it is clear that the Hipparcos data still contain systematic errors of unknown origin." Although the radio data also have systematic errors, the Harper solution combines the datasets in the hope of mitigating such errors.[105] An updated result from further observations with ALMA and e-Merlin gives a parallax of 4.51±0.8 mas and a distance of 222+34 −48 pc or 724+111 −156 ly.[10]
In 2020, new observational data from the space-based Solar Mass Ejection Imager aboard the Coriolis satellite and three different modeling techniques produced a refined parallax of 5.95+0.58 −0.85 mas, a radius of 764+116 −62R☉, and a distance of 168.1+27.5 −14.4 pc or 548+90 −49 ly, which, if accurate, would mean Betelgeuse is nearly 25% smaller and 25% closer to Earth than previously thought.[11]
Although the European Space Agency's current Gaia mission was not expected to produce good results for stars brighter than the approximately V=6 saturation limit of the mission's instruments,[110] actual operation has shown good performance on objects to about magnitude +3. Forced observations of brighter stars mean that final results should be available for all bright stars and a parallax for Betelgeuse will be published an order of magnitude more accurate than currently available.[111] There is no data on Betelgeuse in Gaia Data Release 2, which was released in 2018.[112]
Variability
AAVSOV-bandlight curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002Orion, with Betelgeuse at its usual magnitude (left) and during the unusually deep minimum in early 2020 (right)
Betelgeuse is classified as a semiregular variable star, indicating that some periodicity is noticeable in the brightness changes, but amplitudes may vary, cycles may have different lengths, and there may be standstills or periods of irregularity. It is placed in subgroup SRc; these are pulsating red supergiants with amplitudes around one magnitude and periods from tens to hundreds of days.[8]
Betelgeuse typically shows only small brightness changes near to magnitude +0.5, although at its extremes it can become as bright as magnitude 0.0 or as faint as magnitude +1.6. Betelgeuse is listed in the General Catalogue of Variable Stars with a possible period of 2,335 days.[8] More detailed analyses have shown a main period near 400 days, a short period of 185 days,[11] and a longer secondary period around 2,100 days.[103][113] The lowest reliably-recorded V-band magnitude of +1.614 was reported in February 2020.
Radial pulsations of red supergiants are well-modelled and show that periods of a few hundred days are typically due to fundamental and first overtone pulsation.[114]Lines in the spectrum of Betelgeuse show doppler shifts indicating radial velocity changes corresponding, very roughly, to the brightness changes. This demonstrates the nature of the pulsations in size, although corresponding temperature and spectral variations are not clearly seen.[115] Variations in the diameter of Betelgeuse have also been measured directly.[59]First overtone pulsations of 185 days have been observed, and the ratio of the fundamental to overtone periods gives valuable information about the internal structure of the star and its age.[11]
The source of the long secondary periods is unknown, but they cannot be explained by radial pulsations.[113] Interferometric observations of Betelgeuse have shown hotspots that are thought to be created by massive convection cells, a significant fraction of the diameter of the star and each emitting 5–10% of the total light of the star.[102][103] One theory to explain long secondary periods is that they are caused by the evolution of such cells combined with the rotation of the star.[113] Other theories include close binary interactions, chromospheric magnetic activity influencing mass loss, or non-radial pulsations such as g-modes.[116]
In addition to the discrete dominant periods, small-amplitude stochastic variations are seen. It is proposed that this is due to granulation, similar to the same effect on the sun but on a much larger scale.[113]
On 13 December 1920, Betelgeuse became the first star outside the Solar System to have the angular size of its photosphere measured.[37] Although interferometry was still in its infancy, the experiment proved a success. The researchers, using a uniform disk model, determined that Betelgeuse had a diameter of 0.047″, although the stellar disk was likely 17% larger due to the limb darkening, resulting in an estimate for its angular diameter of about 0.055".[37][58] Since then, other studies have produced angular diameters that range from 0.042 to 0.069″.[41][56][118] Combining these data with historical distance estimates of 180 to 815ly yields a projected radius of the stellar disk of anywhere from 1.2 to 8.9AU. Using the Solar System for comparison, the orbit of Mars is about 1.5AU, Ceres in the asteroid belt2.7AU, Jupiter5.5AU—so, assuming Betelgeuse occupying the place of the Sun, its photosphere might extend beyond the Jovian orbit, not quite reaching Saturn at 9.5AU.
Radio image from 1998 showing the size of Betelgeuse's photosphere (circle) and the effect of convective forces on the star's atmosphere
The precise diameter has been hard to define for several reasons:
Betelgeuse is a pulsating star, so its diameter changes with time;
The star has no definable "edge" as limb darkening causes the optical emissions to vary in color and decrease the farther one extends out from the center;
Betelgeuse is surrounded by a circumstellar envelope composed of matter ejected from the star—matter which absorbs and emits light—making it difficult to define the photosphere of the star;[57]
Measurements can be taken at varying wavelengths within the electromagnetic spectrum and the difference in reported diameters can be as much as 30–35%, yet comparing one finding with another is difficult as the star's apparent size differs depending on the wavelength used.[57] Studies have shown that the measured angular diameter is considerably larger at ultraviolet wavelengths, decreases through the visible to a minimum in the near-infrared, and increase again in the mid-infrared spectrum;[52][119][120]
Atmospheric twinkling limits the resolution obtainable from ground-based telescopes since turbulence degrades angular resolution.[47]
The generally reported radii of large cool stars are Rosseland radii, defined as the radius of the photosphere at a specific optical depth of two-thirds. This corresponds to the radius calculated from the effective temperature and bolometric luminosity. The Rosseland radius differs from directly measured radii, with corrections for limb darkening and the observation wavelength.[121] For example, a measured angular diameter of 55.6 mas would correspond to a Rosseland mean diameter of 56.2 mas, while further corrections for the existence of surrounding dust and gas shells would give a diameter of 41.9mas.[18]
To overcome these challenges, researchers have employed various solutions. Astronomical interferometry, first conceived by Hippolyte Fizeau in 1868, was the seminal concept that has enabled major improvements in modern telescopy and led to the creation of the Michelson interferometer in the 1880s, and the first successful measurement of Betelgeuse.[122] Just as human depth perception increases when two eyes instead of one perceive an object, Fizeau proposed the observation of stars through two apertures instead of one to obtain interferences that would furnish information on the star's spatial intensity distribution. The science evolved quickly and multiple-aperture interferometers are now used to capture speckled images, which are synthesized using Fourier analysis to produce a portrait of high resolution.[123] It was this methodology that identified the hotspots on Betelgeuse in the 1990s.[124] Other technological breakthroughs include adaptive optics,[125]space observatories like Hipparcos, Hubble and Spitzer,[52][126] and the Astronomical Multi-BEam Recombiner (AMBER), which combines the beams of three telescopes simultaneously, allowing researchers to achieve milliarcsecond spatial resolution.[127][128]
Observations in different regions of the electromagnetic spectrum—the visible, near-infrared (NIR), mid-infrared (MIR), or radio—produce very different angular measurements. In 1996, Betelgeuse was shown to have a uniform disk of 56.6±1.0mas. In 2000, a Space Sciences Laboratory team measured a diameter of 54.7±0.3mas, ignoring any possible contribution from hotspots, which are less noticeable in the mid-infrared.[56] Also included was a theoretical allowance for limb darkening, yielding a diameter of 55.2±0.5mas. The earlier estimate equates to a radius of roughly 5.6AU or 1,200R☉, assuming the 2008 Harper distance of 197.0±45pc,[129] a figure roughly the size of the Jovian orbit of 5.5AU.[130][131]
In 2004, a team of astronomers working in the near-infrared announced that the more accurate photospheric measurement was 43.33±0.04mas. The study also put forth an explanation as to why varying wavelengths from the visible to mid-infrared produce different diameters: the star is seen through a thick, warm extended atmosphere. At short wavelengths (the visible spectrum) the atmosphere scatters light, thus slightly increasing the star's diameter. At near-infrared wavelengths (K and L bands), the scattering is negligible, so the classical photosphere can be directly seen; in the mid-infrared the scattering increases once more, causing the thermal emission of the warm atmosphere to increase the apparent diameter.[119]
Studies with the IOTA and VLTI published in 2009 brought strong support to the idea of dust shells and a molecular shell (MOLsphere) around Betelgeuse, and yielded diameters ranging from 42.57 to 44.28mas with comparatively insignificant margins of error.[102][132] In 2011, a third estimate in the near-infrared corroborating the 2009 numbers, this time showing a limb-darkened disk diameter of 42.49±0.06mas.[133] The near-infrared photospheric diameter of 43.33mas at the Hipparcos distance of 152±20pc equates to about 3.4AU or 730R☉.[134] A 2014 paper derives an angular diameter of 42.28mas (equivalent to a 41.01mas uniform disc) using H and K band observations made with the VLTI AMBER instrument.[135]
In 2009 it was announced that the radius of Betelgeuse had shrunk from 1993 to 2009 by 15%, with the 2008 angular measurement equal to 47.0mas.[58][136] Unlike most earlier papers, this study used measurements at one specific wavelength over 15 years. The diminution in Betelgeuse's apparent size equates to a range of values between 56.0±0.1mas seen in 1993 to 47.0±0.1mas seen in 2008—a contraction of almost 0.9AU in 15years.[58] The observed contraction is generally believed to be a variation in just a portion of the extended atmosphere around Betelgeuse, and observations at other wavelengths have shown an increase in diameter over a similar period.[135]
The latest models of Betelgeuse adopt a photospheric angular diameter of around 43mas, with multiple shells out to 50–60mas.[17] Assuming a distance of 197pc, this means a stellar diameter of 887±203R☉.[18]
Once considered as having the largest angular diameter of any star in the sky after the Sun, Betelgeuse lost that distinction in 1997 when a group of astronomers measured R Doradus with a diameter of 57.0±0.5mas, although R Doradus, being much closer to Earth at about 200ly, has a linear diameter roughly one-third that of Betelgeuse.[137]
Betelgeuse is too far from the ecliptic to be occulted by the major planets, but those by some asteroids (which are more wide-ranging and much more numerous) occur frequently. A partial occultation by the 19th magnitude asteroid (147857) 2005 UW381 occurred on 2 January 2012. It was partial because the angular diameter of the star was larger than that of the asteroid; the brightness of Betelgeuse dropped by only about 0.01 magnitudes.[138][139]
The 14th magnitude asteroid 319 Leona was predicted to occult on 12 December 2023, 01:12 UTC.[140] Totality was at first uncertain, and the occulation was projected to only last approximately twelve seconds (visible on a narrow path on Earth's surface, the exact width and location of which was initially uncertain due to lack of precise knowledge of the size and path of the asteroid).[141] Projections were later refined as more data were analyzed for[142] a totality ("ring of fire") of approximately five seconds and a 60km wide path stretching from Tajikistan, Armenia, Turkey, Greece, Italy, Spain, the Atlantic Ocean, Miami, Florida and the Florida Keys to parts of Mexico.[143] (The serendiptous event would also afford detailed observations of 319 Leona itself.)[144] Among other programmes 80 amateur astronomers in Europe alone have been coordinated by astrophysicist Miguel Montargès, et al. of the Paris Observatory for the event.[145]
Physical characteristics
(July 2008, outdated). Relative sizes of the planets in the Solar System and several stars, including Betelgeuse:
Betelgeuse is a very large, luminous but cool star classified as an M1-2 Ia-ab red supergiant. The letter "M" in this designation means that it is a red star belonging to the M spectral class and therefore has a relatively low photospheric temperature; the "Ia-ab" suffix luminosity class indicates that it is an intermediate-luminosity supergiant, with properties partway between a normal supergiant and a luminous supergiant. Since 1943, the spectrum of Betelgeuse has served as one of the stable anchor points by which other stars are classified.[146]
Uncertainty in the star's surface temperature, diameter, and distance make it difficult to achieve a precise measurement of Betelgeuse's luminosity, but research from 2012 quotes a luminosity of around 126,000L☉, assuming a distance of 200pc.[147] Studies since 2001 report effective temperatures ranging from 3,250 to 3,690 K. Values outside this range have previously been reported, and much of the variation is believed to be real, due to pulsations in the atmosphere.[18] The star is also a slow rotator and the most recent velocity recorded was 5.45km/s[17]—much slower than Antares which has a rotational velocity of 20km/s.[148] The rotation period depends on Betelgeuse's size and orientation to Earth, but it has been calculated to take 36years to turn on its axis, inclined at an angle of around 60° to Earth.[17]
In 2004, astronomers using computer simulations speculated that even if Betelgeuse is not rotating it might exhibit large-scale magnetic activity in its extended atmosphere, a factor where even moderately strong fields could have a meaningful influence over the star's dust, wind and mass-loss properties.[149] A series of spectropolarimetric observations obtained in 2010 with the Bernard Lyot Telescope at Pic du Midi Observatory revealed the presence of a weak magnetic field at the surface of Betelgeuse, suggesting that the giant convective motions of supergiant stars are able to trigger the onset of a small-scale dynamo effect.[150]
Mass
Betelgeuse has no known orbital companions, so its mass cannot be calculated by that direct method. Modern mass estimates from theoretical modelling have produced values of 9.5–21M☉,[151] with values of 5M☉–30M☉ from older studies.[152] It has been calculated that Betelgeuse began its life as a star of 15–20M☉, based on a solar luminosity of 90,000–150,000.[129] A novel method of determining the supergiant's mass was proposed in 2011, arguing for a current stellar mass of 11.6M☉ with an upper limit of 16.6 and lower of 7.7M☉, based on observations of the star's intensity profile from narrow H-band interferometry and using a photospheric measurement of roughly 4.3AU or 955±217R☉.[151] A probablystic age prior analysis give a current mass of 16.5–19M☉ and an initial mass of 18–21M☉.[11]
Betelgeuse's mass can also be estimated based on its position on the color‑magnitude‑diagram(CMD). Betelgeuse's color may have changed from yellow (or possibly orange; i.e. a yellow supergiant) to red in the last few thousand years, based on a 2022 review of historical records. This color change combined with the CMD suggest a mass of 14M☉ and age of 14Myr, and a distance from 125 to 150 parsecs (~400 to 500 light years).[12]
Motion
Map showing the Orion OB1 association, which contains the blue supergiants of Orion's Belt and the Orion Nebula. Betelgeuse is believed to be a runaway star that was ejected from the Orion OB1 association.
The kinematics of Betelgeuse are complex. The age of Class M supergiants with an initial mass of 20M☉ is roughly 10million years.[105][153] Starting from its present position and motion, a projection back in time would place Betelgeuse around 290parsecs farther from the galactic plane—an implausible location, as there is no star formationregion there. Moreover, Betelgeuse's projected pathway does not appear to intersect with the 25 Orisubassociation or the far younger Orion Nebula Cluster (ONC, also known as Ori OB1d), particularly since Very Long Baseline Array astrometry yields a distance from Betelgeuse to the ONC of between 389 and 414parsecs. Consequently, it is likely that Betelgeuse has not always had its current motion through space but has changed course at one time or another, possibly the result of a nearby stellar explosion.[105][154] An observation by the Herschel Space Observatory in January 2013 revealed that the star's winds are crashing against the surrounding interstellar medium.[155]
The most likely star-formation scenario for Betelgeuse is that it is a runaway star from the Orion OB1 association. Originally a member of a high-mass multiple system within Ori OB1a, Betelgeuse was probably formed about 10–12million years ago,[156] but has evolved rapidly due to its high mass.[105] H. Bouy and J. Alves suggested in 2015 that Betelgeuse may instead be a member of the newly discovered Taurion OB association.[157]
Circumstellar dynamics
Image from ESO's Very Large Telescope showing the stellar disk and an extended atmosphere with a previously unknown plume of surrounding gas
In the late phase of stellar evolution, massive stars like Betelgeuse exhibit high rates of mass loss, possibly as much as oneM☉ every 10,000years, resulting in a complex circumstellar environment that is constantly in flux. In a 2009 paper, stellar mass loss was cited as the "key to understanding the evolution of the universe from the earliest cosmological times to the current epoch, and of planet formation and the formation of life itself".[158] However, the physical mechanism is not well understood.[134] When Martin Schwarzschild first proposed his theory of huge convection cells, he argued it was the likely cause of mass loss in evolved supergiants like Betelgeuse.[51] Recent work has corroborated this hypothesis, yet there are still uncertainties about the structure of their convection, the mechanism of their mass loss, the way dust forms in their extended atmosphere, and the conditions which precipitate their dramatic finale as a type II supernova.[134] In 2001, Graham Harper estimated a stellar wind at 0.03M☉ every 10,000years,[159] but research since 2009 has provided evidence of episodic mass loss making any total figure for Betelgeuse uncertain.[160] Current observations suggest that a star like Betelgeuse may spend a portion of its lifetime as a red supergiant, but then cross back across the H–R diagram, pass once again through a brief yellow supergiant phase and then explode as a blue supergiant or Wolf–Rayet star.[29]
Artist's rendering from ESO showing Betelgeuse with a gigantic bubble boiling on its surface and a radiant plume of gas being ejected to six photospheric radii or roughly the orbit of Neptune
Astronomers may be close to solving this mystery. They noticed a large plume of gas extending at least six times its stellar radius indicating that Betelgeuse is not shedding matter evenly in all directions.[61] The plume's presence implies that the spherical symmetry of the star's photosphere, often observed in the infrared, is not preserved in its close environment. Asymmetries on the stellar disk had been reported at different wavelengths. However, due to the refined capabilities of the NACO adaptive optics on the VLT, these asymmetries have come into focus. The two mechanisms that could cause such asymmetrical mass loss, were large-scale convection cells or polar mass loss, possibly due to rotation.[61] Probing deeper with ESO's AMBER, gas in the supergiant's extended atmosphere has been observed vigorously moving up and down, creating bubbles as large as the supergiant itself, leading his team to conclude that such stellar upheaval is behind the massive plume ejection observed by Kervella.[160]
Asymmetric shells
In addition to the photosphere, six other components of Betelgeuse's atmosphere have now been identified. They are a molecular environment otherwise known as the MOLsphere, a gaseous envelope, a chromosphere, a dust environment and two outer shells (S1 and S2) composed of carbon monoxide (CO). Some of these elements are known to be asymmetric while others overlap.[102]
Exterior view of ESO's Very Large Telescope (VLT) in Paranal, Chile
At about 0.45 stellar radii (~2–3AU) above the photosphere, there may lie a molecular layer known as the MOLsphere or molecular environment. Studies show it to be composed of water vapor and carbon monoxide with an effective temperature of about 1,500±500K.[102][161] Water vapor had been originally detected in the supergiant's spectrum in the 1960s with the two Stratoscope projects but had been ignored for decades. The MOLsphere may also contain SiO and Al2O3—molecules which could explain the formation of dust particles.
Interior view of one of the four 8.2-meter Unit Telescopes at ESO's VLT
Another cooler region, the asymmetric gaseous envelope, extends for several radii (~10–40AU) from the photosphere. It is enriched in oxygen and especially in nitrogen relative to carbon. These composition anomalies are likely caused by contamination by CNO-processed material from the inside of Betelgeuse.[102][162]
Radio-telescope images taken in 1998 confirm that Betelgeuse has a highly complex atmosphere,[163] with a temperature of 3,450±850K, similar to that recorded on the star's surface but much lower than surrounding gas in the same region.[163][164] The VLA images also show this lower-temperature gas progressively cools as it extends outward. Although unexpected, it turns out to be the most abundant constituent of Betelgeuse's atmosphere. "This alters our basic understanding of red-supergiant star atmospheres", explained Jeremy Lim, the team's leader. "Instead of the star's atmosphere expanding uniformly due to gas heated to high temperatures near its surface, it now appears that several giant convection cells propel gas from the star's surface into its atmosphere."[163] This is the same region in which Kervella's 2009 finding of a bright plume, possibly containing carbon and nitrogen and extending at least six photospheric radii in the southwest direction of the star, is believed to exist.[102]
The chromosphere was directly imaged by the Faint Object Camera on board the Hubble Space Telescope in ultraviolet wavelengths. The images also revealed a bright area in the southwest quadrant of the disk.[165] The average radius of the chromosphere in 1996 was about 2.2 times the optical disk (~10AU) and was reported to have a temperature no higher than 5,500K.[102][166] However, in 2004 observations with the STIS, Hubble's high-precision spectrometer, pointed to the existence of warm chromospheric plasma at least one arcsecond away from the star. At a distance of 197pc, the size of the chromosphere could be up to 200AU.[165] The observations have conclusively demonstrated that the warm chromospheric plasma spatially overlaps and co-exists with cool gas in Betelgeuse's gaseous envelope as well as with the dust in its circumstellar dust shells.[102][165]
This infrared image from the ESO's VLT shows complex shells of gas and dust around Betelgeuse – the tiny red circle in the middle is the size of the photosphere.
The first claim of a dust shell surrounding Betelgeuse was put forth in 1977 when it was noted that dust shells around mature stars often emit large amounts of radiation in excess of the photospheric contribution. Using heterodyne interferometry, it was concluded that the red supergiant emits most of its excess radiation from positions beyond 12 stellar radii or roughly the distance of the Kuiper belt at 50 to 60 AU, which depends on the assumed stellar radius.[42][102] Since then, there have been studies done of this dust envelope at varying wavelengths yielding decidedly different results. Studies from the 1990s have estimated the inner radius of the dust shell anywhere from 0.5 to 1.0arcseconds, or 100 to 200AU.[167][168] These studies point out that the dust environment surrounding Betelgeuse is not static. In 1994, it was reported that Betelgeuse undergoes sporadic decades-long dust production, followed by inactivity. In 1997, significant changes in the dust shell's morphology in one year were noted, suggesting that the shell is asymmetrically illuminated by a stellar radiation field strongly affected by the existence of photospheric hotspots.[167] The 1984 report of a giant asymmetric dust shell 1pc (206,265AU) has not been corroborated by recent studies, although another published the same year said that three dust shells were found extending four light-years from one side of the decaying star, suggesting that Betelgeuse sheds its outer layers as it moves.[169][170]
Although the exact size of the two outer CO shells remains elusive, preliminary estimates suggest that one shell extends from about 1.5 to 4.0 arcseconds and the other expands as far as 7.0 arcseconds.[171] Assuming the Jovian orbit of 5.5AU as the star radius, the inner shell would extend roughly 50 to 150 stellar radii (~300 to 800AU) with the outer one as far as 250 stellar radii (~1,400AU). The Sun's heliopause is estimated at 100 AU, so the size of this outer shell would be almost fourteen times the size of the Solar System.
Supersonic bow shock
Betelgeuse is travelling supersonically through the interstellar medium at a speed of 30km/s (i.e. ~6.3AU/a) creating a bow shock.[172][173] The shock is not created by the star, but by its powerful stellar wind as it ejects vast amounts of gas into the interstellar medium at a speed of 17km/s, heating the material surrounding the star, thereby making it visible in infrared light.[174] Because Betelgeuse is so bright, it was only in 1997 that the bow shock was first imaged. The cometary structure is estimated to be at least one parsec wide, assuming a distance of 643 light-years.[175]
Hydrodynamic simulations of the bow shock made in 2012 indicate that it is very young—less than 30,000 years old—suggesting two possibilities: that Betelgeuse moved into a region of the interstellar medium with different properties only recently or that Betelgeuse has undergone a significant transformation producing a changed stellar wind.[176] A 2012 paper, proposed that this phenomenon was caused by Betelgeuse transitioning from a blue supergiant (BSG) to a red supergiant (RSG). There is evidence that in the late evolutionary stage of a star like Betelgeuse, such stars "may undergo rapid transitions from red to blue and vice versa on the Hertzsprung–Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks."[172][177] Moreover, if future research bears out this hypothesis, Betelgeuse may prove to have traveled close to 200,000 AU as a red supergiant scattering as much as 3M☉ along its trajectory.
Life phases
Betelgeuse is a red supergiant that has evolved from an O-type main-sequence star. After core hydrogen exhaustion, Betelgeuse evolved into a blue supergiant before evolving into its current red supergiant form.[98] Its core will eventually collapse, producing a supernova explosion and leaving behind a compact remnant. The details depend on the exact initial mass and other physical properties of that main sequence star.
The initial mass of Betelgeuse can only be estimated by testing different stellar evolutionary models to match its current observed properties. The unknowns of both the models and the current properties mean that there is considerable uncertainty in Betelgeuse's initial appearance, but its mass is usually estimated to have been in the range of 10–25M☉, with modern models finding values of 15–20M☉. Its chemical makeup can be reasonably assumed to have been around 70% hydrogen, 28% helium, and 2.4% heavy elements, slightly more metal-rich than the Sun but otherwise similar. The initial rotation rate is more uncertain, but models with slow to moderate initial rotation rates produce the best matches to Betelgeuse's current properties.[18][98][178] That main sequence version of Betelgeuse would have been a hot luminous star with a spectral type such as O9V.[147]
A 15M☉ star would take between 11.5 and 15million years to reach the red supergiant stage, with more rapidly-rotating stars taking the longest.[178] Rapidly-rotating 20M☉ stars take 9.3million years to reach the red supergiant stage, while 20M☉ stars with slow rotation take only 8.1million years.[98] These are the best estimates of Betelgeuse's current age, as the time since its zero age main sequence stage is estimated to be 8.0–8.5million years as a 20M☉ star with no rotation.[18]
After core hydrogen exhaustion
Betelgeuse's time spent as a red supergiant can be estimated by comparing mass loss rates to the observed circumstellar material, as well as the abundances of heavy elements at the surface. Estimates range from 10,000years to a maximum of 140,000years. Betelgeuse appears to undergo short periods of heavy mass loss and is a runaway star moving rapidly through space, so comparisons of its current mass loss to the total lost mass are difficult.[18][98]
This is what Betelgeuse may have looked like up until about 1 million years ago, when it was a main-sequence star.
The surface of Betelgeuse shows enhancement of nitrogen, relatively low levels of carbon, and a high proportion of 13C relative to 12C, all indicative of a star that has experienced the first dredge-up. However, the first dredge-up occurs soon after a star reaches the red supergiant phase and so this only means that Betelgeuse has been a red supergiant for at least a few thousand years. The best prediction is that Betelgeuse has already spent around 40,000years as a red supergiant,[18] having left the main sequence perhaps one million years ago.[178]
The current mass can be estimated from evolutionary models from the initial mass and the expected mass lost so far. For Betelgeuse, the total mass lost is predicted to be no more than about oneM☉, giving a current mass of 19.4–19.7M☉, considerably higher than estimated by other means such as pulsational properties or limb-darkening models.[18]
Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which could be brighter than the supernova that exploded in 1006 (SN 1006)
All stars more massive than about 10M☉ are expected to end their lives when their cores collapse, typically producing a supernova explosion. Up to about 15M☉, a typeII-P supernova is always produced from the red supergiant stage.[178]
More massive stars can lose mass quickly enough that they evolve towards higher temperatures before their cores can collapse, particularly for rotating stars and models with especially high mass loss rates. These stars can produce typeII-L or typeIIb supernovae from yellow or blue supergiants, or type Ib/c supernovae from Wolf–Rayet stars.[179] Models of rotating 20M☉ stars predict a peculiar typeII supernova similar to SN 1987A from a blue supergiant progenitor.[178] On the other hand, non-rotating 20M☉ models predict a typeII-P supernova from a red supergiant progenitor.[18]
The time until Betelgeuse explodes depends on the predicted initial conditions and on the estimate of the time already spent as a red supergiant. The total lifetime from the start of the red supergiant phase to core collapse varies from about 300,000years for a rotating 25M☉ star, 550,000years for a rotating 20M☉ star, and up to a million years for a non-rotating 15M☉ star. Given the estimated time since Betelgeuse became a red supergiant, estimates of its remaining lifetime range from a "best guess" of under 100,000years for a non-rotating 20M☉ model to far longer for rotating models or lower-mass stars.[18][178] Betelgeuse's suspected birthplace in the Orion OB1 association is the location of several previous supernovae. It is believed that runaway stars may be caused by supernovae, and there is strong evidence that OB starsμColumbae, AE Aurigae, and 53 Arietis all originated from such explosions in OriOB1 2.2, 2.7, and 4.9million years ago.[154]
A typical typeII-P supernova emits 2×1046J of neutrinos and produces an explosion with a kinetic energy of 2×1044J. As seen from Earth, Betelgeuse as a typeIIP supernova would have a peak apparent magnitude somewhere in the range −8 to −12.[180] This would be easily visible in daylight, with a possible brightness up to a significant fraction of the full moon, though likely not exceeding it. This type of supernova would remain at roughly constant brightness for 2–3months before rapidly dimming. The visible light is produced mainly by the radioactive decay of cobalt, and sustains its brightness due to the increasing transparency of the cooling hydrogen ejected by the supernova.[181]
Media reporting
Due to misunderstandings caused by the 2009 publication of the star's 15% contraction, apparently of its outer atmosphere,[57][130] Betelgeuse has frequently been the subject of scare stories and rumors suggesting that it will explode within a year, and leading to exaggerated claims about the consequences of such an event.[182][183] The timing and prevalence of these rumors have been linked to broader misconceptions of astronomy, particularly to doomsday predictions relating to the Mayan calendrical apocalypse.[184][185] Betelgeuse is not likely to produce a gamma-ray burst and is not close enough for its X-rays, ultraviolet radiation, or ejected material to cause significant effects on Earth.[18][186]
Following the dimming of Betelgeuse in December2019,[187][62] reports appeared in the science and mainstream media that again included speculation that the star might be about to explode as a supernova – even in the face of scientific research that a supernova is not expected for perhaps 100,000years.[188] Some outlets reported the magnitude as faint as +1.3 as an unusual and interesting phenomenon, like Astronomy magazine,[68] the National Geographic,[71] and the Smithsonian.[189]
Some mainstream media, like The Washington Post,[72]ABC News in Australia,[73] and Popular Science,[190] reported that a supernova was possible but unlikely, whilst other outlets falsely portrayed a supernova as an imminent realistic possibility. CNN, for example, chose the headline "A giant red star is acting weird and scientists think it may be about to explode",[191] while the New York Post declared Betelgeuse as "due for explosive supernova".[74]
Phil Plait, in his Bad Astronomy blog, noting that Betelgeuse's recent behaviour, "[w]hile unusual . . . isn't unprecedented," argued that the star is not likely to explode "for a long, long time."[192]Dennis Overbye of The New York Times agreed that an explosion was not imminent but added that "astronomers are having fun thinking about it."[193]
Following the eventual supernova, a small dense remnant will be left behind, either a neutron star or black hole. Betelgeuse does not seem to have a core massive enough for a black hole, so the remnant will probably be a neutron star of approximately 1.5M☉.[18]
Ethnological attributes
Spelling and pronunciation
Betelgeuse has also been spelled Betelgeux[1] and, in German, Beteigeuze[lower-alpha 2] (according to Bode).[194][195]Betelgeux and Betelgeuze were used until the early 20th century, when the spelling Betelgeuse became universal.[196] Consensus on its pronunciation is weak and is as varied as its spellings:
The -urz pronunciations are attempts to render the French eu sound; they only work in r-dropping accents.
Etymology
An illustration of Orion (horizontally reversed) in al-Sufi's Book of Fixed Stars. Betelgeuze is annotated as Yad al-Jauzā ("Hand of Orion"), one of the proposed etymological origins of its modern name, and also as Mankib al Jauzā' ("Shoulder of Orion").
Betelgeuse is often mistranslated as "armpit of the central one".[198] In his 1899 work Star-Names and Their Meanings, American amateur naturalist Richard Hinckley Allen stated the derivation was from the ابط الجوزاءIbṭ al-Jauzah, which he claimed degenerated into a number of forms, including Bed Elgueze, Beit Algueze, Bet El-gueze, and Beteigeuze, to the forms Betelgeuse, Betelguese, Betelgueze and Betelgeux. The star was named Beldengeuze in the Alfonsine Tables,[199] and Italian Jesuit priest and astronomer Giovanni Battista Riccioli had called it Bectelgeuze or Bedalgeuze.[26]
Paul Kunitzsch, Professor of Arabic Studies at the University of Munich, refuted Allen's derivation and instead proposed that the full name is a corruption of the Arabic يد الجوزاءYad al-Jauzā', meaning "the Hand of al-Jauzā'"; i.e., Orion.[200] European mistransliteration into medieval Latin led to the first character y (ﻴ, with two dots underneath) being misread as a b (ﺒ, with only one dot underneath). During the Renaissance, the star's name was written as بيت الجوزاءBait al-Jauzā' ("house of Orion") or بط الجوزاءBaţ al-Jauzā', incorrectly thought to mean "armpit of Orion" (a true translation of "armpit" would be ابط, transliterated as Ibţ). This led to the modern rendering as Betelgeuse.[201] Other writers have since accepted Kunitzsch's explanation.[35]
The last part of the name, "-elgeuse", comes from the Arabic الجوزاءal-Jauzā', a historical Arabic name of the constellation Orion, a feminine name in old Arabian legend, and of uncertain meaning. Because جوزj-w-z, the root of jauzā', means "middle", al-Jauzā' roughly means "the Central One". The modern Arabic name for Orion is الجبارal-Jabbār ("the Giant"), although the use of الجوزاءal-Jauzā' in the star's name has continued.[201] The 17th-century English translator Edmund Chilmead gave it the name Ied Algeuze ("Orion's Hand"), from Christmannus.[26] Other Arabic names recorded include اليد اليمنىAl Yad al Yamnā ("the Right Hand"), الذراعAl Dhira ("the Arm"), and المنكبAl Mankib ("the Shoulder"), all of al-Jauzā, Orion,[26] as منكب الجوزاءMankib al Jauzā'.
Dunhuang Star Chart, circa AD 700, showing 參宿四Shēnxiùsì (Betelgeuse), the Fourth Star of the constellation of Three Stars
Other names
Other names for Betelgeuse included the Persian Bašn "the Arm", and CopticKlaria "an Armlet".[26]Bahu was its Sanskrit name, as part of a Hindu understanding of the constellation as a running antelope or stag.[26] In traditional Chinese astronomy, the name for Betelgeuse is 参宿四 (Shēnxiùsì, the Fourth Star of the constellation of Three Stars)[202] as the Chinese constellation参宿 originally referred to the three stars in Orion's Belt. This constellation was ultimately expanded to ten stars, but the earlier name stuck.[203] In Japan, the Taira, or Heike, clan adopted Betelgeuse and its red color as its symbol, calling the star Heike-boshi, (平家星), while the Minamoto, or Genji, clan chose Rigel and its white color. The two powerful families fought a legendary war in Japanese history, the stars seen as facing each other off and only kept apart by the Belt.[204][205]
In Tahitian lore, Betelgeuse was one of the pillars propping up the sky, known as Anâ-varu, the pillar to sit by. It was also called Ta'urua-nui-o-Mere "Great festivity in parental yearnings".[206] A Hawaiian term for it was Kaulua-koko ("brilliant red star").[207] The Lacandon people of Central America knew it as chäk tulix ("red butterfly").[208]
Astronomy writer Robert Burnham Jr. proposed the term padparadaschah, which denotes a rare orange sapphire in India, for the star.[196]
Mythology
With the history of astronomy intimately associated with mythology and astrology before the scientific revolution, the red star, like the planet Mars that derives its name from a Roman war god, has been closely associated with the martial archetype of conquest for millennia, and by extension, the motif of death and rebirth.[26] Other cultures have produced different myths. Stephen R. Wilk has proposed the constellation of Orion could have represented the Greek mythological figure Pelops, who had an artificial shoulder of ivory made for him, with Betelgeuse as the shoulder, its color reminiscent of the reddish yellow sheen of ivory.[32]
Aboriginal people from the Great Victoria Desert of South Australia incorporated Betelgeuse into their oral traditions as the club of Nyeeruna (Orion), which fills with fire-magic and dissipates before returning. This has been interpreted as showing that early Aboriginal observers were aware of the brightness variations of Betelgeuse.[209][210] The Wardaman people of northern Australia knew the star as Ya-jungin ("Owl Eyes Flicking"), its variable light signifying its intermittent watching of ceremonies led by the Red Kangaroo Leader Rigel.[211] In South African mythology, Betelgeuse was perceived as a lion casting a predatory gaze toward the three zebras represented by Orion's Belt.[212]
In the Americas, Betelgeuse signifies a severed limb of a man-figure (Orion)—the Taulipang of Brazil know the constellation as Zililkawai, a hero whose leg was cut off by his wife, with the variable light of Betelgeuse linked to the severing of the limb. Similarly, the Lakota people of North America see it as a chief whose arm has been severed.[32]
A Sanskrit name for Betelgeuse is ārdrā ("the moist one"), eponymous of the Ardralunar mansion in Hindu astrology.[213] The Rigvedic God of storms Rudra presided over the star; this association was linked by 19th-century star enthusiast Richard Hinckley Allen to Orion's stormy nature.[26] The constellations in Macedonian folklore represented agricultural items and animals, reflecting their way of life. To them, Betelgeuse was Orach ("the ploughman"), alongside the rest of Orion, which depicted a plough with oxen. The rising of Betelgeuse at around 3a.m. in late summer and autumn signified the time for village men to go to the fields and plough.[214] To the Inuit, the appearance of Betelgeuse and Bellatrix high in the southern sky after sunset marked the beginning of spring and lengthening days in late February and early March. The two stars were known as Akuttujuuk ("those [two] placed far apart"), referring to the distance between them, mainly to people from North Baffin Island and Melville Peninsula.[36]
The opposed locations of Orion and Scorpius, with their corresponding bright red variable stars Betelgeuse and Antares, were noted by ancient cultures around the world. The setting of Orion and rising of Scorpius signify the death of Orion by the scorpion. In China they signify brothers and rivals Shen and Shang.[32] The Batak of Sumatra marked their New Year with the first new moon after the sinking of Orion's Belt below the horizon, at which point Betelgeuse remained "like the tail of a rooster". The positions of Betelgeuse and Antares at opposite ends of the celestial sky were considered significant, and their constellations were seen as a pair of scorpions. Scorpion days marked as nights that both constellations could be seen.[215]
In popular culture
As one of the brightest and best-known stars, Betelgeuse has featured in many works of fiction. The star's unusual name inspired the title of the 1988 film Beetlejuice, referring to its titular antagonist, and script writer Michael McDowell was impressed by how many people made the connection.[196] In the popular science fiction series The Hitchhiker's Guide to the Galaxy by Douglas Adams, Ford Prefect was from "a small planet somewhere in the vicinity of Betelgeuse."[216]
Two American navy ships were named after the star, both of them World War II vessels, the USSBetelgeuse(AKA-11) launched in 1939 and USSBetelgeuse(AK-260) launched in 1944. In 1979, the French supertanker Betelgeuse was moored off Whiddy Island, discharging oil when it exploded, killing 50 people in one of the worst disasters in Ireland's history.[217]
Sang the drunken boatswain; / Farther than Betelgeuse, / More brilliant than Orion / Or the planets Venus and Mars, / The star flames on the ocean; / 'A woman has ten claws,' /
This table provides a non-exhaustive list of angular measurements conducted since 1920. Also included is a column providing a current range of radii for each study based on Betelgeuse's most recent distance estimate (Harper et al.) of 197±45pc.
Also noteworthy, Harper et al. in the conclusion of their paper make the following remark: "In a sense, the derived distance of 200pc is a balance between the 131pc (425ly) Hipparcos distance and the radio which tends towards 250pc (815ly)"—hence establishing ± 815ly as the outside distance for the star.
↑ Stella lucida in umero dextro, quae ad rubedinem vergit.[26]
"Bright star in right shoulder, which inclines to ruddiness."
↑ Likely the result of mistaking the l for an i. Ultimately, this led to the modern "Betelgeuse".
↑ The final year of observations, unless otherwise noted
↑ Uniform disk measurement, unless otherwise noted
↑ Radii calculations use the same methodology as outlined in Note No. 2 below ‡Limb darkened measurement
Related Research Articles
Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinised to Alpha Scorpii. Often referred to as "the heart of the scorpion", Antares is flanked by σ Scorpii and τ Scorpii near the center of the constellation. Distinctly reddish when viewed with the naked eye, Antares is a slow irregular variable star that ranges in brightness from an apparent visual magnitude of +0.6 down to +1.6. It is on average the fifteenth-brightest star in the night sky. Antares is the brightest and most evolved stellar member of the Scorpius–Centaurus association, the nearest OB association to the Sun. It is located about 170 parsecs (550 ly) from Earth at the rim of the Upper Scorpius subgroup, and is illuminating the Rho Ophiuchi cloud complex in its foreground.
Rigel is a blue supergiant star in the constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori. Rigel is the brightest and most massive component – and the eponym – of a star system of at least four stars that appear as a single blue-white point of light to the naked eye. This system is located at a distance of approximately 860 light-years (260 pc) from the Sun.
Scutum is a small constellation. Its name is Latin for shield, and it was originally named Scutum Sobiescianum by Johannes Hevelius in 1684. Located just south of the celestial equator, its four brightest stars form a narrow diamond shape. It is one of the 88 IAU designated constellations defined in 1922.
Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K.
Saiph, designation Kappa Orionis and 53 Orionis, is a blue supergiant star and the sixth-brightest star in the constellation of Orion. Of the four bright stars that compose Orion's main quadrangle, it is the star at the south-eastern corner. A northern-hemisphere observer facing south would see it at the lower left of Orion, and a southern-hemisphere observer facing north would see it at the upper right. Parallax measurements yield an estimated distance of 650 light-years from the Sun. It is smaller, less luminous but hotter at its surface than Rigel with an apparent visual magnitude of 2.1. The luminosity of this star changes slightly, varying by 0.04 magnitudes.
Red supergiants (RSGs) are stars with a supergiant luminosity class and a stellar classification K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares A are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.
A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blue supergiants.
Alnilam is the central star of Orion's Belt in the equatorial constellation of Orion. It has the Bayer designation ε Orionis, which is Latinised to Epsilon Orionis and abbreviated Epsilon Ori or ε Ori. This is a massive, blue supergiant star some 1,200 light-years distant. It is estimated to be 419,600 times as luminous as the Sun, and 40 times as massive.
Bellatrix is the third-brightest star in the constellation of Orion, positioned 5° west of the red supergiant Betelgeuse. It has the Bayer designation γ Orionis, which is Latinized to Gamma Orionis. With a slightly variable magnitude of around 1.6, it is typically the 25th-brightest star in the night sky. Located at a distance of 250±10 light-years from the Sun, it is a blue giant star around 7.7 times as massive as the sun with 5.75 times its diameter.
Alnitak is a triple star system in the constellation of Orion. It has the designations ζ Orionis, which is Latinised to Zeta Orionis and abbreviated Zeta Ori or ζ Ori, and 50 Orionis, abbreviated 50 Ori. The system is located at a distance of several hundred parsecs from the Sun and is one of the three main stars of Orion's Belt along with Alnilam and Mintaka.
Mu Cephei, also known as Herschel's Garnet Star, Erakis, or HD 206936, is a red supergiant or hypergiant star in the constellation Cepheus. It appears garnet red and is located at the edge of the IC 1396 nebula. Since 1943, the spectrum of this star has served as a spectral standard by which other stars are classified.
119 Tauri is a red supergiant star in the constellation Taurus. It is a semiregular variable and its angular diameter has been measured at about 10 mas. It is a similar star to Betelgeuse although redder and more distant.
A yellow supergiant (YSG) is a star, generally of spectral type F or G, having a supergiant luminosity class. They are stars that have evolved away from the main sequence, expanding and becoming more luminous.
RW Cephei is a K-type hypergiant and a semirregular variable star in the constellation Cepheus, at the edge of the Sharpless 132 H II region and close to the small open cluster Berkeley 94. It is among the largest stars known with a radius of 1,100 times that of the Sun (R☉), nearly as large as the orbit of Jupiter.
VY Canis Majoris is an extreme oxygen-rich red hypergiant or red supergiant and pulsating variable star 1.2 kiloparsecs from the Solar System in the slightly southern constellation of Canis Major. It is one of the largest known stars, one of the most luminous and massive red supergiants, and one of the most luminous stars in the Milky Way.
A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially star formation, stability, and their expected demise as supernovae. Notable examples of hypergiants include the Pistol Star, a blue hypergiant located close to the Galactic Center and one of the most luminous stars known; Rho Cassiopeiae, a yellow hypergiant that is one of the brightest to the naked eye; and Mu Cephei (Herschel's "Garnet Star"), one of the largest and brightest stars known.
25 Orionis, less commonly known by its Bayer designation Psi1 Orionis is a fifth-magnitude star in the constellation Orion. It lies among a dense cluster of low-mass pre-main-sequence stars in the Orion OB1a.
Nu Orionis is a binary star system in the northeastern part of the constellation Orion. It should not be confused with the variable star NU Orionis. Nu Orionis has an apparent visual magnitude of 4.42, which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 0.00632 arcseconds, the distance to this system is roughly 520 light years.
UY Scuti (BD-12°5055) is a red supergiant star, located 5,900 light-years away in the constellation Scutum. It is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56, which is too dim for naked-eye visibility. It is considered to be one of the largest known stars, with a radius estimated at 909 solar radii, thus a volume of 750 million times that of the Sun. This estimate implies if it were placed at the center of the Solar System, its photosphere would extend past the orbit of Mars or even the asteroid belt.
BC Cygni is a red supergiant and pulsating variable star of spectral type M3.5Ia in the constellation Cygnus.
1 2 3 Nicolet, B. (1978). "Catalogue of Homogeneous Data in the UBV Photoelectric Photometric System". Astronomy & Astrophysics. 34: 1–49. Bibcode:1978A&AS...34....1N.
1 2 Ducati, J.R. (2002). "VizieR online data catalog: Catalogue of stellar photometry in Johnson's 11color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
1 2 3 Samus, N.N.; Durlevich, O.V.; etal. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-Line Data Catalog: B/gcvs. 1: 1. Bibcode:2009yCat....102025S. Originally published in Bibcode:2009yCat....102025S
↑ Ramírez, Solange V.; Sellgren, K.; Carr, John S.; Balachandran, Suchitra C.; Blum, Robert; Terndrup, Donald M.; Steed, Adam (July 2000). "Stellar Iron Abundances at the Galactic Center". The Astrophysical Journal. 537 (1): 205–20. arXiv:astro-ph/0002062. Bibcode:2000ApJ...537..205R. doi:10.1086/309022. S2CID14713550.
1 2 3 4 5 Kervella, Pierre; Decin, Leen; Richards, Anita M.S.; Harper, Graham M.; McDonald, Iain; O'Gorman, Eamon; Montargès, Miguel; Homan, Ward; Ohnaka, Keiichi (2018). "The close circumstellar environment of Betelgeuse. V. Rotation velocity and molecular envelope properties from ALMA". Astronomy and Astrophysics. 609: A67. arXiv:1711.07983. Bibcode:2018A&A...609A..67K. doi:10.1051/0004-6361/201731761. S2CID54670700.
↑ Brück, H. A. (11–15 July 1978). "P. Angelo Secchi, S.J. 1818–1878". In McCarthy, M.F.; Philip, A.G.D.; Coyne, G.V. (eds.). Proceedings of the IAU Colloquium47. Spectral Classification of the Future. Vatican City, IT (published 1979). pp.7–20. Bibcode:1979RA......9....7B.
1 2 Levesque, E. M. (June 2010). The Physical Properties of Red Supergiants. Hot and Cool: Bridging Gaps in Massive Star Evolution ASP Conference Series. Astronomical Society of the Pacific. Vol.425. p.103. arXiv:0911.4720. Bibcode:2010ASPC..425..103L.
1 2 3 4 Wilk, Stephen R. (1999). "Further Mythological Evidence for Ancient Knowledge of Variable Stars". The Journal of the American Association of Variable Star Observers. 27 (2): 171–74. Bibcode:1999JAVSO..27..171W.
1 2 Ravi, V.; Wishnow, E.; Lockwood, S.; Townes, C. (December 2011). "The many faces of Betelgeuse". Astronomical Society of the Pacific. 448: 1025. arXiv:1012.0377. Bibcode:2011ASPC..448.1025R.
↑ Karovska, M.; Noyes, R.W.; Roddier, F.; Nisenson, P.; Stachnik, R.V. (1985). "On a possible close companion to αOri". Bulletin of the American Astronomical Society. 17: 598. Bibcode:1985BAAS...17..598K.
1 2 3 Montargès, M.; Kervella, P.; Perrin, G.; Chiavassa, A.; Le Bouquin, J.-B.; Aurière, M.; López Ariste, A.; Mathias, P.; Ridgway, S. T.; Lacour, S.; Haubois, X.; Berger, J.-P. (2016). "The close circumstellar environment of Betelgeuse. IV. VLTI/PIONIER interferometric monitoring of the photosphere". Astronomy & Astrophysics. 588: A130. arXiv:1602.05108. Bibcode:2016A&A...588A.130M. doi:10.1051/0004-6361/201527028. S2CID53404211.
↑ Goldberg, Jared A.; Joyce, Meridith; Molnár, László (17 August 2024). "A Buddy for Betelgeuse: Binarity as the Origin of the Long Secondary Period in α Orionis". arXiv:2408.09089 [astro-ph.SR].
↑ Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (August 2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. ISSN0004-637X.
1 2 Balega, Iu.; Blazit, A.; Bonneau, D.; Koechlin, L.; Labeyrie, A.; Foy, R.. (November 1982). "The angular diameter of Betelgeuse". Astronomy and Astrophysics. 115 (2): 253–56. Bibcode:1982A&A...115..253B.
1 2 3 Perrin, G.; Ridgway, S.T.; Coudé du Foresto, V.; Mennesson, B.; Traub, W.A.; Lacasse, M.G. (2004). "Interferometric Observations of the Supergiant Stars α Orionis and α Herculis with FLUOR at IOTA". Astronomy and Astrophysics. 418 (2): 675–685. arXiv:astro-ph/0402099. Bibcode:2004A&A...418..675P. doi:10.1051/0004-6361:20040052. S2CID119065851. Assuming a distance of 197±45pc, an angular distance of 43.33±0.04mas would equate to a radius of 4.3AU or 920R☉
↑ Nemiroff, R.; Bonnell, J., eds. (21 April 2012). "3 ATs". Astronomy Picture of the Day. NASA. Retrieved 17 August 2012. Photograph showing three of the four enclosures which house 1.8 meter Auxiliary Telescopes (ATs) at the Paranal Observatory in the Atacama Desert region of Chile.
↑ Roddier, F. (1999). "Ground-Based Interferometry with Adaptive Optics". Working on the Fringe: Optical and IR Interferometry from Ground and Space. Proceedings from ASP Conference. Vol.194. p.318. Bibcode:1999ASPC..194..318R. ISBN978-1-58381-020-0.{{cite book}}: |journal= ignored (help)
1 2 Ohnaka, K.; Weigelt, G.; Millour, F.; Hofmann, K.-H.; Driebe, T.; Schertl, D.; Chelli, A.; Massi, F.; Petrov, R.; Stee, Ph. (2011). "Imaging the dynamical atmosphere of the red supergiant Betelgeuse in the CO first overtone lines with VLTI/AMBER". Astronomy & Astrophysics. 529: A163. arXiv:1104.0958. Bibcode:2011A&A...529A.163O. doi:10.1051/0004-6361/201016279. S2CID56281923. We derive a uniform-disk diameter of 42.05±0.05mas and a power-law-type limb-darkened disk diameter of 42.49±0.06mas and a limb-darkening parameter of (9.7±0.5)×10−2
1 2 3 Kervella, P.; Perrin, G.; Chiavassa, A.; Ridgway, S. T.; Cami, J.; Haubois, X.; Verhoelst, T. (2011). "The close circumstellar environment of Betelgeuse". Astronomy & Astrophysics. 531: A117. arXiv:1106.5041. doi:10.1051/0004-6361/201116962. S2CID119190969.
↑ Cowen, Ron (10 June 2009). "Betelgeuse Shrinks: The Red Supergiant has Lost 15 Percent of its Size". Archived from the original on 29 June 2011. Retrieved 11 June 2009. The shrinkage corresponds to the star contracting by a distance equal to that between Venus and the Sun, researchers reported June 9 at an American Astronomical Society meeting and in the June 1 Astrophysical Journal Letters.
1 2 Neilson, H. R.; Lester, J. B.; Haubois, X. (December 2011). Weighing Betelgeuse: Measuring the Mass of α Orionis from Stellar Limb-darkening. 9th Pacific Rim Conference on Stellar Astrophysics. Proceedings of a conference held at Lijiang, China in 14–20 April 2011. ASP Conference Series. Astronomical Society of the Pacific. Vol.451. p.117. arXiv:1109.4562. Bibcode:2011ASPC..451..117N.
↑ Posson-Brown, Jennifer; Kashyap, Vinay L.; Pease, Deron O.; Drake, Jeremy J. (2006). "Dark Supergiant: Chandra's Limits on X-rays from Betelgeuse". arXiv:astro-ph/0606387.
↑ Maeder, André; Meynet, Georges (2003). "The Role of Rotation and Mass Loss in the Evolution of Massive Stars". Proceedings of IAU Symposium. 212: 267. Bibcode:2003IAUS..212..267M.
1 2 Reynolds, R.J.; Ogden, P.M. (1979). "Optical evidence for a very large, expanding shell associated with the I Orion OB association, Barnard's loop, and the high galactic latitude H-alpha filaments in Eridanus". The Astrophysical Journal. 229: 942. Bibcode:1979ApJ...229..942R. doi:10.1086/157028.
↑ Decin, L.; Cox, N.L.J.; Royer, P.; Van Marle, A.J.; Vandenbussche, B.; Ladjal, D.; Kerschbaum, F.; Ottensamer, R.; Barlow, M.J.; Blommaert, J.A.D.L.; Gomez, H.L.; Groenewegen, M.A.T.; Lim, T.; Swinyard, B.M.; Waelkens, C.; Tielens, A.G.G.M. (2012). "The enigmatic nature of the circumstellar envelope and bow shock surrounding Betelgeuse as revealed by Herschel. I. Evidence of clumps, multiple arcs, and a linear bar-like structure". Astronomy & Astrophysics. 548: A113. arXiv:1212.4870. Bibcode:2012A&A...548A.113D. doi:10.1051/0004-6361/201219792. S2CID53534124.
↑ Lambert, D. L.; Brown, J. A.; Hinkle, K. H.; Johnson, H. R. (1984). "Carbon, Nitrogen, and Oxygen Abundances in Betelgeuse". Astrophysical Journal. 284: 223–37. Bibcode:1984ApJ...284..223L. doi:10.1086/162401.
↑ Lim, Jeremy; Carilli, Chris L.; White, Stephen M.; Beasley, Anthony J.; Marson, Ralph G. (1998). "Large Convection Cells as the Source of Betelgeuse's Extended Atmosphere". Nature. 392 (6676): 575–77. Bibcode:1998Natur.392..575L. doi:10.1038/33352. S2CID4431516.
1 2 3 Lobel, A.; Aufdenberg, J.; Dupree, A. K.; Kurucz, R. L.; Stefanik, R. P.; Torres, G. (2004). "Spatially Resolved STIS Spectroscopy of Betelgeuse's Outer Atmosphere". Proceedings of the 219th Symposium of the IAU. 219: 641. arXiv:astro-ph/0312076. Bibcode:2004IAUS..219..641L. doi:10.1017/s0074180900182671. S2CID15868906. In the article, Lobel et al. equate 1 arcsecond to approximately 40 stellar radii, a calculation which in 2004 likely assumed a Hipparcos distance of 131 pc (430 ly) and a photospheric diameter of 0.0552" from Weiner et al.
↑ Dupree, Andrea K.; Gilliland, Ronald L. (December 1995). "HST Direct Image of Betelgeuse". Bulletin of the American Astronomical Society. 27: 1328. Bibcode:1995AAS...187.3201D. Such a major single feature is distinctly different from scattered smaller regions of activity typically found on the Sun although the strong ultraviolet flux enhancement is characteristic of stellar magnetic activity. This inhomogeneity may be caused by a large scale convection cell or result from global pulsations and shock structures that heat the chromosphere."
↑ Danchi, W. C.; Bester, M.; Degiacomi, C. G.; Greenhill, L. J.; Townes, C. H. (1994). "Characteristics of Dust Shells around 13 Late-type Stars". The Astronomical Journal. 107 (4): 1469–1513. Bibcode:1994AJ....107.1469D. doi:10.1086/116960.
↑ Baud, B.; Waters, R.; De Vries, J.; Van Albada, G. D.; etal. (January 1984). "A Giant Asymmetric Dust Shell around Betelgeuse". Bulletin of the American Astronomical Society. 16: 405. Bibcode:1984BAAS...16..405B.
↑ Harper, Graham M.; Carpenter, Kenneth G.; Ryde, Nils; Smith, Nathan; Brown, Joanna; etal. (2009). "UV, IR, and mm Studies of CO Surrounding the Red Supergiant α Orionis (M2 Iab)". AIP Conference Proceedings. 1094: 868–71. Bibcode:2009AIPC.1094..868H. doi:10.1063/1.3099254.
↑ Noriega-Crespo, Alberto; van Buren, Dave; Cao, Yu; Dgani, Ruth (1997). "A Parsec-Size Bow Shock around Betelgeuse". Astronomical Journal. 114: 837–40. Bibcode:1997AJ....114..837N. doi:10.1086/118517. Noriega in 1997 estimated the size to be 0.8 parsecs, having assumed the earlier distance estimate of 400 ly. With a current distance estimate of 643 ly, the bow shock would measure ~1.28 parsecs or over 4 ly
↑ Plait, Phil (21 January 2011). "Betelgeuse and 2012". Bad Astronomy. Discovery. Archived from the original on 3 November 2012. Retrieved 14 September 2012.
↑ Bode, Johann Elert, (ed.). (1782) Vorstellung der Gestirne: auf XXXIV Kupfertafeln nach der Parisier Ausgabe des Flamsteadschen Himmelsatlas, Gottlieb August Lange, Berlin / Stralsund, pl. XXIV.
↑ Bode, Johann Elert, (ed.) (1801). Uranographia: sive Astrorum Descriptio, Fridericus de Harn, Berlin, pl. XII.
↑ "天文教育資訊網 2006 年 5 月 25 日"[Astronomy Education Information Network 25 May 2006]. aeea.nmns.edu.tw. AEEA (Activities of Exhibition and Education in Astronomy). 25 May 2006. Archived from the original on 16 July 2011. Retrieved 26 June 2012.
↑ Steve Renshaw & Saori Ihara. "Yowatashi Boshi; Stars that Pass in the Night". Archived from the original on 4 June 2016. Retrieved 25 June 2012.{{cite web}}: CS1 maint: unfit URL (link) Other Versions: "Yowatashi Boshi; Stars that Pass in the Night". Griffith Observer. Vol.63, no.10. October 1999. pp.2–17. and "Yowatashi Boshi; Stars that Pass in the Night". The Kyoto Journal. No.48. July 2000.
↑ Harney, Bill Yidumduma; Cairns, Hugh C. (2004) [2003]. Dark Sparklers (Reviseded.). Merimbula, New South Wales: Hugh C. Cairns. pp.139–40. ISBN978-0-9750908-0-0.
↑ Motz, Lloyd; Nathanson, Carol (1991). The Constellations: An Enthusiast's Guide to the Night Sky. London, United Kingdom: Aurum Press. p.85. ISBN978-1-85410-088-7.
↑ Cenev, Gjore (2008). "Macedonian Folk Constellations". Publications of the Astronomical Observatory of Belgrade. 85: 97–109. Bibcode:2008POBeo..85...97C.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
