Proxima Centauri b

Last updated

Proxima Centauri b
Artist's impression of Proxima Centauri b shown hypothetically as an arid rocky super-earth.jpg
Artist's conception of Proxima Centauri b as a rocky-like exoplanet, with Proxima Centauri and the Alpha Centauri binary system in the background. The actual appearance of the planet is unknown.
Discovery
Discovered by Anglada-Escudé (ca) et al.
Discovery site European Southern Observatory
Discovery date24 August 2016
Doppler spectroscopy
Orbital characteristics
0.0485+0.0041
−0.0051
AU
Eccentricity <0.35 [1]
11.186+0.001
−0.002
[1] d
310 (± 50) [1]
Semi-amplitude 1.38 (± 0.21) [1]
Star Proxima Centauri
Physical characteristics
Mean radius
0.8–1.5 [2] R
Temperature 234 K (−39 °C; −38 °F)

    Proxima Centauri b (also called Proxima b [3] [4] or Alpha Centauri Cb) is an exoplanet orbiting in the habitable zone of the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of a triple star system. [5] [6] It is located about 4.2 light-years (1.3 parsecs, 40 trillion km, or 25 trillion miles) from Earth in the constellation of Centaurus, making it the closest known exoplanet to the Solar System.

    Exoplanet Any planet beyond the Solar System

    An exoplanet or extrasolar planet is a planet outside the Solar System. The first evidence of an exoplanet was noted in 1917, but was not recognized as such. The first scientific detection of an exoplanet was in 1988; it was confirmed to be an exoplanet in 2012. The first confirmed detection occurred in 1992. As of 1 April 2019, there are 4,023 confirmed planets in 3,005 systems, with 656 systems having more than one planet.

    Red dwarf An informal category of small, cool stars on the main sequence

    A red dwarf is a small and cool star on the main sequence, of M spectral type. Red dwarfs range in mass from about 0.075 to about 0.50 solar mass and have a surface temperature of less than 4,000 K. Sometimes K-type main-sequence stars, with masses between 0.50-0.8 solar mass, are also included.

    Star An astronomical object consisting of a luminous spheroid of plasma held together by its own gravity

    A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the estimated 300 sextillion (3×1023) stars in the Universe are invisible to the naked eye from Earth, including all stars outside our galaxy, the Milky Way.

    Contents

    Proxima Centauri b orbits the star at a distance of roughly 0.05 AU (7,500,000 km; 4,600,000 mi) with an orbital period of approximately 11.2 Earth days, and has an estimated mass of at least 1.3 times that of the Earth. Its habitability has not been established, though it is unlikely to be habitable since the planet is subject to stellar wind pressures of more than 2,000 times those experienced by Earth from the solar wind. [7] [8] [9]

    Planetary habitability Extent to which a planet is suitable for life as we know it

    Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and maintain environments hospitable to life. Life may be generated directly on a planet or satellite endogenously or be transferred to it from another body, a hypothetical process known as panspermia. Environments do not need to contain life to be considered habitable nor are accepted habitable zones the only areas in which life might arise.

    Stellar wind gas flow from the stars

    A stellar wind is a flow of gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.

    Earth Third planet from the Sun in the Solar System

    Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.

    The discovery of the planet was announced in August 2016 by the European Southern Observatory. [1] [5] The planet was found using the radial velocity method, where periodic Doppler shifts of spectral lines of the host star suggest an orbiting object. From these readings, the radial velocity of the parent star relative to the Earth is varying with an amplitude of about 1.4 metres (4.5 feet) per second. [1] According to Guillem Anglada‐Escudé, its proximity to Earth offers an opportunity for robotic exploration of the planet with the Starshot project [5] [6] or, at least, "in the coming centuries". [6]

    European Southern Observatory intergovernmental research organization for ground-based astronomy

    The European Southern Observatory (ESO), formally the European Organisation for Astronomical Research in the Southern Hemisphere, is a 16-nation intergovernmental research organization for ground-based astronomy. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky. The organisation employs about 730 staff members and receives annual member state contributions of approximately €162 million. Its observatories are located in northern Chile.

    Doppler spectroscopy

    Doppler spectroscopy is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star.

    Spectral line optical phenomenon

    A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules. These "fingerprints" can be compared to the previously collected "fingerprints" of atoms and molecules, and are thus used to identify the atomic and molecular components of stars and planets, which would otherwise be impossible.

    Without the inclination of its orbit known, the exact mass of Proxima Centauri b is unknown. If its orbit is nearly edge-on, it would have a mass of 1.27+0.19
    −0.17
    Earth masses. Statistically, there is a roughly 90% chance that the planet's mass is less than 8.1+1.2
    −1.0
    Earth masses.

    Earth mass Unit of mass equal to that of Earth

    Earth mass (ME or M, where ⊕ is the standard astronomical symbol for planet Earth) is the unit of mass equal to that of Earth. The current best estimate for Earth mass is M = 5.9722×1024 kg, with a standard uncertainty of 6×1020 kg (relative uncertainty 10−4). It is equivalent to an average density of 5515 kg⋅m−3.

    Physical characteristics

    Mass, radius, and temperature

    The apparent inclination of Proxima Centauri b's orbit has not yet been measured. The minimum mass of Proxima b is 1.27  M, which would be the actual mass if its orbit were seen edge on from the Earth. [1] Once its orbital inclination is known, the mass will be calculable. More tilted orientations imply a higher mass, with 90% of possible orientations implying a mass below 3 M. [10] The planet's exact radius is unknown. If it has a rocky composition and a density equal to that of the Earth, then its radius is at least 1.1  R. It could be larger if it has a lower density than the Earth, or a mass higher than the minimum mass. [11] Like many super-Earth sized planets, Proxima Centauri b could have an icy composition like Neptune, with a thick layer of hydrogen on its surface; the likelihood that this is the case has been calculated to be greater than 10%. [2] The planet has an equilibrium temperature of 234 K (−39 °C; −38 °F). [1]

    Orbital inclination angle between a reference plane and the plane of an orbit

    Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object.

    In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes.

    Terrestrial planet planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars

    A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars. The terms "terrestrial planet" and "telluric planet" are derived from Latin words for Earth, as these planets are, in terms of structure, "Earth-like". These planets are located between the Sun and the Asteroid Belt.

    Host star

    The planet orbits an M-type red dwarf named Proxima Centauri. The star has a mass of 0.12  M and a radius of 0.14  R. [1] It has a surface temperature of 3042 K [12] and is 4.85 billion years old. [13] In comparison, the Sun is 4.6 billion years old [14] and has a surface temperature of 5778 K. [15] Proxima Centauri rotates once roughly every 83 days, [16] and has a luminosity about 0.0015  L. [1] Like the two larger stars in the triple star system, Proxima Centauri is rich in metals compared with the Sun, something not normally found in low-mass stars like Proxima. Its metallicity ([Fe/H]) is 0.21, or 1.62 times the amount found in the Sun's atmosphere. [17] [note 1]

    Proxima Centauri star in Centaurus constellation

    Proxima Centauri, or Alpha Centauri C, is a red dwarf, a small low-mass star, about 4.244 light-years (1.301 pc) from the Sun in the constellation of Centaurus. It was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. With a quiescent apparent magnitude of 11.13, it is too faint to be seen with the naked eye. Proxima Centauri forms a third component of the Alpha Centauri system, currently with a separation of about 12,950 AU (1.94 trillion km) and an orbital period of 550,000 years. At present Proxima is 2.18° to the southwest of Alpha Centauri.

    Solar mass standard unit of mass in astronomy

    The solar mass (M) is a standard unit of mass in astronomy, equal to approximately 2×1030 kg. It is used to indicate the masses of other stars, as well as clusters, nebulae, and galaxies. It is equal to the mass of the Sun (denoted by the solar symbol ⊙︎). This equates to about two nonillion (two quintillion in the long scale) kilograms:

    Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3:

    Even though Proxima Centauri is the closest star to the Sun, it is not visible to the unaided eye from Earth because of its low luminosity (average apparent magnitude of 11.13 [18] ).

    Proxima Centauri is a flare star. [19] This means that it undergoes occasional dramatic increases in brightness and high-energy emissions because of magnetic activity that would create large solar storms. On 18 March 2016 a superflare was observed with an energy of 10^33.5 erg. [20] The surface irradiation was estimated to be 100 times what is required to kill even UV-hardy microorganisms. Based on the rate of observed flares, total ozone depletion of an Earth-like atmosphere would occur within several hundred thousand years.

    Orbit

    Proxima Centauri b orbits its host star every 11.186 days at a semi-major axis distance of approximately 0.05 astronomical unit s (7,000,000 km; 5,000,000 mi), which means the distance from the exoplanet to its host star is one-twentieth of the distance from the Earth to the Sun. [1] Comparatively, Mercury, the closest planet to the Sun, has a semi-major axis distance of 0.39 AU. Proxima Centauri b receives about 65% of the amount of radiative flux from its host star that the Earth receives from the Sun – for comparison Mars receives about 43%. Most of the radiative flux from Proxima Centauri is in the infrared spectrum. In the visible spectrum the exoplanet receives only ~3% of the PAR (400–700 nm) of Earth irradiance – for comparison Jupiter receives 3.7% and Saturn 1.1%. [21] So it would usually not get much brighter than twilight anywhere on Proxima Centauri b's surface. The maximum illumination of horizontal ground by twilight at sunrise is about 400 lux, [22] while the illumination of Proxima b is about 2700 lux with quiet Proxima. Also, Proxima has flares. The brightest flare observed till 2016 had increased the visual brightness of Proxima about 8 times, which would be a large change from the previous level but, at about 17% the illumination of Earth, not very strong sunlight. [note 2] However, because of its tight orbit, Proxima Centauri b receives about 400 times more X-ray radiation than the Earth does. [1] According to a yet-to-be-published article, a March 2016 flare reached about 68 times usual level, thus a little brighter than the Sun. [23]

    Habitability

    Artist's conception of the surface of Proxima Centauri b. The Alpha Centauri binary system can be seen in the background, to the upper right of Proxima Artist's impression of the planet orbiting Proxima Centauri.jpg
    Artist's conception of the surface of Proxima Centauri b. The Alpha Centauri binary system can be seen in the background, to the upper right of Proxima

    The habitability of Proxima Centauri b has not been established, [7] [8] since the planet is subject to stellar wind pressures of more than 2,000 times those experienced by Earth from the solar wind. [7] [24] This radiation and the stellar winds would likely blow any atmosphere away, leaving the undersurface as the only potentially habitable location on that planet. [25]

    The exoplanet is orbiting within the habitable zone of Proxima Centauri, the region where, with the correct planetary conditions and atmospheric properties, liquid water may exist on the surface of the planet. The host star, with about an eighth of the mass of the Sun, has a habitable zone between ∼0.0423–0.0816 AU. [1] In October 2016, researchers at France's CNRS research institute stated that there is a considerable chance of the planet harboring surface oceans and having a thin atmosphere. [26] However, unless the planet transits in front of its star from the perspective of Earth, it is difficult to test these hypotheses.

    Even though Proxima Centauri b is in the habitable zone, the planet's habitability has been questioned because of several potentially hazardous physical conditions. The exoplanet is close enough to its host star that it might be tidally locked. [27] In this case, it is expected that any habitable areas would be confined to the border region between the two extreme sides, generally referred to as the terminator line, since it is only here that temperatures might be suitable for liquid water to exist. [28] If the planet's orbital eccentricity is 0, this could result in synchronous rotation, with one hot side permanently facing towards the star, while the opposite side is in permanent darkness and freezing cold. [29] [30] However, Proxima Centauri b's orbital eccentricity is not known with certainty, only that it is below 0.35—potentially high enough for it to have a significant chance of being captured into a 3:2 spin-orbit resonance similar to that of Mercury, where Proxima b would rotate around its axis approximately every 7.5 Earth days with about 22.4 Earth days elapsing between one sunrise and the next. [9] [31] [32] Resonances as high as 2:1 are also possible. [9] [32] Another problem is that the flares released by Proxima Centauri could have eroded the atmosphere of the exoplanet. However, according to The Exoplanets Channel, if Proxima b had a strong magnetic field, the flare activity of its parent star would not be a problem. [33] [ better source needed ]

    The European Southern Observatory estimates that if water and an atmosphere are present, a far more hospitable environment would result. Assuming an atmospheric N2 pressure of 1 bar and ∼0.01 bar of CO2, in a world including oceans with average temperatures similar to those on Earth, a wide equatorial belt (non-synchronous rotation), or the majority of the sunlit side (synchronous rotation), would be permanently ice-free. [34] [32] A large portion of the planet may be habitable if it has an atmosphere thick enough to transfer heat to the side facing away from the star. [28] If it has an atmosphere, simulations suggest that the planet could have lost about as much as the amount of water that Earth has due to the early irradiation in the first 100–200 million years after the planet's formation. Liquid water may be present only in the sunniest regions of the planet's surface in pools either in an area in the hemisphere of the planet facing the star or—if the planet is in a 3:2 resonance rotation—diurnally in the equatorial belt. [9] [32] All in all, astrophysicists consider the ability of Proxima Centauri b to retain water from its formation as the most crucial point in evaluating the planet's present habitability. [35] The planet may be within reach of telescopes and techniques that could reveal more about its composition and atmosphere, if it has any. [7]

    View from Proxima Centauri b

    Looking towards the sky around Orion from Alpha Centauri with Sirius near Betelgeuse, Procyon in Gemini, and the Sun between Perseus and Cassiopeia generated by Celestia Sky-from-alpha-centauri.jpg
    Looking towards the sky around Orion from Alpha Centauri with Sirius near Betelgeuse, Procyon in Gemini, and the Sun between Perseus and Cassiopeia generated by Celestia

    Viewed from near the Alpha Centauri system, the sky would appear much as it does for an observer on Earth, except that Centaurus would be missing its brightest star. The Sun would be a yellow star of an apparent magnitude of +0.5 in eastern Cassiopeia, at the antipodal point of Alpha Centauri's current right ascension and declination, at  02h 39m 35s+60° 50 (2000). This place is close to the 3.4-magnitude star ε Cassiopeiae. Because of the placement of the Sun, an interstellar or alien observer would find the \/\/ of Cassiopeia had become a /\/\/ shape [note 3] nearly in front of the Heart Nebula in Cassiopeia. Sirius lies less than a degree from Betelgeuse in the otherwise unmodified Orion and with a magnitude of −1.2 is a little fainter than from Earth but still the brightest star in the Alpha Centauri sky. Procyon is also displaced into the middle of Gemini, outshining Pollux, whereas both Vega and Altair are shifted northwestward relative to Deneb (which barely moves, due to its great distance), giving the Summer Triangle a more equilateral appearance.

    From Proxima Centauri b, Alpha Centauri AB would appear like two close bright stars with the combined apparent magnitude of −6.8. Depending on the binary's orbital position, the bright stars would appear noticeably divisible to the naked eye, or occasionally, but briefly, as a single unresolved star. Based on the calculated absolute magnitudes, the apparent magnitudes of Alpha Centauri A and B would be −6.5 and −5.2, respectively. [36]

    Formation

    It is unlikely that Proxima Centauri b originally formed in its current orbit since disk models for small stars like Proxima Centauri would contain less than one Earth mass M of matter within the central one AU at the time of their formation. This implies that either Proxima Centauri b was formed elsewhere in a manner still to be determined, or the current disc models for stellar formation are in need of revision. [1]

    Discovery

    The first indications of the exoplanet were found in 2013 by Mikko Tuomi of the University of Hertfordshire from archival observation data. [16] [37] To confirm the possible discovery, the European Southern Observatory launched the Pale Red Dot [note 4] project in January 2016. [38] On 24 August 2016 the team of 31 scientists from all around the world, [39] led by Guillem Anglada-Escudé of Queen Mary University of London, confirmed the existence of Proxima Centauri b [13] through their research, published in a peer-reviewed article in Nature . [40] [1] [27] [41] [42] [43]

    The measurements were done using two spectrographs, HARPS on the ESO 3.6 m Telescope at La Silla Observatory and UVES on the 8-metre Very Large Telescope. [1] The peak radial velocity of the host star combined with the orbital period allowed for the minimum mass of the exoplanet to be calculated. The chance of a false positive detection is less than one in ten million. [16]

    Observational complications of the system still leave theoretical room for additional large planets to orbit Proxima Centauri. Calculations suggest that another super-Earth planet around the star cannot be ruled out and that its presence would not destabilize the orbit of Proxima Centauri b. [1]

    Future observations

    The Very Large Telescope and the star system Alpha Centauri. The Very Large Telescope and the star system Alpha Centauri.jpg
    The Very Large Telescope and the star system Alpha Centauri.

    A team of scientists think they can image Proxima Centauri b and probe the planet's atmosphere for signs of oxygen, water vapor, and methane, combining ESPRESSO and SPHERE on the VLT. [45] The James Webb Space Telescope may be able to characterize the atmosphere of Proxima Centauri b, [46] but there is no conclusive evidence for transits combining MOST and HATSouth photometry, giving it less than a 1 percent chance of being a transiting planet. [47] Future telescopes (the Extremely Large Telescope, the Giant Magellan Telescope, and the Thirty Meter Telescope) could have the capability to characterize Proxima Centauri b.

    The discovery of Proxima b was significant to Breakthrough Starshot, a proof of concept project aiming to send a fleet of miniature probes to the Alpha Centauri system. [48] The project is led by research company Breakthrough Initiatives, and plans to develop and launch a fleet of miniature unmanned spacecraft called StarChips, [49] which could travel at up to 20% of the speed of light, [50] [51] arriving at the system in roughly 20 years with notification reaching Earth a little over 4 years later. [5]

    2069 Alpha Centauri mission

    In 2017, Breakthrough Initiatives and the European Southern Observatory (ESO) entered a collaboration to enable and implement a search for habitable planets in the nearby star system, Alpha Centauri. The agreement involves Breakthrough Initiatives providing funding for an upgrade to the VISIR (VLT Imager and Spectrometer for mid-Infrared) instrument on ESO's Very Large Telescope (VLT) in Chile. [44]

    Videos

    See also

    Notes

    1. Taken from 100.21, which gives 1.62 times the metallicity of the Sun
    2. From knowing the absolute visual magnitude of Proxima Centauri, , and the absolute visual magnitude of the Sun, , the visual luminosity of Proxima Centauri can be calculated: = 4.92×10−5. Proxima Centauri b orbits at 0.0485 AU and so therefore, through use of the inverse-square law, the visual luminosity—intensity at the planet's distance—can be calculated:
    3. The coordinates of the Sun would be diametrically opposite Alpha Centauri AB, at α= 02h 39m 36.4951s, δ=+60° 50 02.308
    4. Pale Red Dot is a reference to Pale Blue Dot—a distant photo of Earth taken by Voyager 1.

    Related Research Articles

    Alpha Centauri Star system

    Alpha Centauri is the closest star system and closest planetary system to the Solar System at 4.37 light-years (1.34 pc) from the Sun. It is a triple star system, consisting of three stars: α Centauri A, α Centauri B, and α Centauri C.

    Barnards Star Low mass red dwarf star about 6 light-years from Earth

    Barnard's Star is a very-low-mass red dwarf about 6 light-years away from Earth in the constellation of Ophiuchus. It is the fourth nearest known individual star to the Sun and the closest star in the Northern Celestial Hemisphere. Despite its proximity, the star has a dim apparent magnitude of +9.5 and is invisible to the unaided eye; it is much brighter in the infrared than in visible light.

    Circumstellar habitable zone Zone around a star with strong possibilities for stable liquid water on a suitable planet

    In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. The bounds of the CHZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the CHZ and the objects within it may be instrumental in determining the scope and distribution of Earth-like extraterrestrial life and intelligence.

    Super-Earth An extrasolar planet with a mass higher than Earths, but substantially lower than the Solar Systems ice giants

    A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 15 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, as suggested by MIT professor Sara Seager, although "mini-Neptunes" is a more common term.

    Exoplanetology, or exoplanetary science, is an integrated field of astronomical science dedicated to the search for and study of exoplanets. It employs an interdisciplinary approach which includes astrobiology, astrophysics, astronomy, astrochemistry, astrogeology, geochemistry, and planetary science.

    Discoveries of exoplanets is a planet located outside the Solar System

    An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such. However, the first scientific detection of an exoplanet began in 1988. Shortly afterwards, the first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 1 April 2019, there are 4,023 confirmed planets in 3,005 systems, with 656 systems having more than one planet. This is a list of the most notable discoveries.

    HD 85512 b extrasolar planet

    HD 85512 b is an exoplanet orbiting HD 85512, a K-type main-sequence star approximately 36 light-years from Earth in the constellation of Vela.

    Luhman 16 Binary brown dwarf, third closest star system.

    Luhman 16 is a binary brown-dwarf system in the southern constellation Vela at a distance of approximately 6.5 light-years from the Sun. These are the closest-known brown dwarfs and the closest system found since the measurement of the proper motion of Barnard's Star in 1916, and the third-closest-known system to the Sun. The primary is of spectral type L7.5 and the secondary of type T0.5 ± 1. The masses of Luhman 16 A and B are 33.5 and 28.6 Jupiter masses, respectively, and their ages are estimated to be 600–800 million years. Luhman 16 A and B orbit each other at a distance of about 3.5 astronomical units with an orbital period of approximately 27 years.

    Habitability of red dwarf systems star

    The habitability of red dwarf systems is determined by a large number of factors from a variety of sources. Although the low stellar flux, high probability of tidal locking, small circumstellar habitable zones, and high stellar variation experienced by planets of red dwarf stars are impediments to their planetary habitability, the ubiquity and longevity of red dwarfs are positive factors. Determining how the interactions between these factors affect habitability may help to reveal the frequency of extraterrestrial life and intelligence.

    Gliese 832 c Extrasolar planet

    Gliese 832 c is an extrasolar planet located approximately 16 light-years away in the constellation of Grus, orbiting the star Gliese 832, a red dwarf. It is in its star's habitable zone and a big reason for its high rating is it receives the same amount of solar flux as the earth in the habitable exoplanets catalog. The planet has a mass of 5.2 Earth's masses and an estimated radius of >1.5 Earth radii.

    Kepler-438b extrasolar planet

    Kepler-438b is a confirmed near-Earth-sized exoplanet. It is likely rocky. It orbits on the inner edge of the habitable zone of a red dwarf, Kepler-438, about 640 light-years from Earth in the constellation Lyra. It receives 1.4 times our solar flux. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the confirmation of the exoplanet on 6 January 2015.

    Wolf 1061c extrasolar planet

    Wolf 1061c or WL 1061c is an exoplanet orbiting within the habitable zone of the red dwarf star Wolf 1061 in the constellation Ophiuchus, about 13.8 light years from Earth, making it the fifth closest known, potentially habitable, and confirmed exoplanet to Earth, yielding interest from astronomers. It is the second planet in order from its host star in a triple planetary system, and has an orbital period of 17.9 days. Wolf 1061c is classified as a super-Earth exoplanet as its estimated radius is greater than 1.5 R.

    Breakthrough Starshot research and engineering project by Breakthrough Initiatives

    Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail spacecraft named StarChip, to be capable of making the journey to the Alpha Centauri star system 4.37 light-years away.

    TRAPPIST-1 Ultra-cool dwarf star

    TRAPPIST-1, also designated 2MASS J23062928-0502285, is an ultra-cool red dwarf star that is slightly larger, but much more massive, than the planet Jupiter; it is located 39.6 light-years (12.1 pc) from the Sun in the constellation Aquarius. Seven temperate terrestrial planets have been detected orbiting the star, a larger number than detected in any other planetary system. A study released in May 2017 suggests that the stability of the system is not particularly surprising if one considers how the planets migrated to their present orbits through a protoplanetary disk.

    Mikko Tuomi is a Finnish astronomer from the University of Hertfordshire, most known for his contributions to the discovery of a number of exoplanets, among them the Proxima Centauri b which orbits the closest star to the Sun. Mikko Tuomi was the first to find indications of the existence of Proxima Centauri b in archival observation data. Other exoplanets to whose discovery or study Tuomi has contributed include HD 40307, HD 154857 c, Kapteyn c, Gliese 682 c, HD 154857, Gliese 221, Gliese 581 g and the planetary system orbiting Tau Ceti. He has led the development of new data analysis techniques for distinguishing observations caused by natural activity of the star and those caused by planets orbiting them.

    Ross 128 b exoplanet

    Ross 128 b is a confirmed Earth-sized exoplanet, likely rocky, orbiting within the inner habitable zone of the red dwarf Ross 128, at a distance of about 11 light-years from Earth. The exoplanet was found using a decade's worth of radial velocity data using the European Southern Observatory's HARPS spectrograph at the La Silla Observatory in Chile. Ross 128 b is the nearest exoplanet around a quiet red dwarf, and is considered one of the best candidates for habitability. The planet is only 35% more massive than Earth, receives only 38% more sunlight, and is expected to be a temperature suitable for liquid water to exist on the surface, if it has an atmosphere.

    References

    1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Anglada-Escudé, G.; Amado, P. J.; Barnes, J.; Berdiñas, Z. M.; Butler, R. P.; Coleman, G. A. L.; de la Cueva, I.; Dreizler, S.; Endl, M.; Giesers, B.; Jeffers, S. V.; Jenkins, J. S.; Jones, H. R. A.; Kiraga, M.; Kürster, M.; López-González, M. J.; Marvin, C. J.; Morales, N.; Morin, J.; Nelson, R. P.; Ortiz, J. L.; Ofir, A.; Paardekooper, S.-J.; Reiners, A.; Rodríguez, E.; Rodrίguez-López, C.; Sarmiento, L. F.; Strachan, J. P.; Tsapras, Y.; Tuomi, M.; Zechmeister, M. (25 August 2016). "A terrestrial planet candidate in a temperate orbit around Proxima Centauri" (PDF). Nature. 536 (7617): 437–440. arXiv: 1609.03449 . Bibcode:2016Natur.536..437A. doi:10.1038/nature19106. ISSN   0028-0836. PMID   27558064.
    2. 1 2 Bixel, A.; Apai, D. (21 February 2017). "Probabilistic Constraints on the Mass and Composition of Proxima b". The Astrophysical Journal Letters. 836 (2): L31. Bibcode:2017ApJ...836L..31W. doi:10.3847/2041-8213/aa5f51. ISSN   2041-8205.
    3. "Earth-like planet discovered orbiting sun's neighbor". CNN. 24 August 2016. Retrieved 24 August 2016. A planet named Proxima b has been discovered orbiting the closest star to our sun.
    4. Davis, Nicola (24 August 2016). "Discovery of potentially Earth-like planet Proxima b raises hopes for life". The Guardian . Retrieved 24 August 2016.
    5. 1 2 3 4 Chang, Kenneth (24 August 2016). "One Star Over, a Planet That Might Be Another Earth". New York Times . Retrieved 24 August 2016.
    6. 1 2 3 Strickland, Ashley (24 August 2016). "Closest potentially habitable planet to our solar system found". CNN Health. Retrieved 25 August 2016.
    7. 1 2 3 4 Clery, Daniel (26 August 2016). "The exoplanet next door". Science News. Retrieved 28 August 2016. Researchers have already found hundreds of similarly sized planets, and many appear to be far better candidates for hosting life than the one around Proxima Centauri, called Proxima b.
    8. 1 2 Amos, Jonathan (24 August 2016). "Neighbouring star Proxima Centauri has Earth-sized planet". BBC News. Retrieved 25 August 2016. Just how "habitable" this particular planet really is, one has to say is pure speculation for the time being.
    9. 1 2 3 4 Ribas, Ignasi; Bolmont, Emeline; Selsis, Franck; et al. (25 August 2016). "The habitability of Proxima Centauri b: I. Irradiation, rotation and volatile inventory from formation to the present". Astronomy & Astrophysics. 596: A111. arXiv: 1608.06813 . Bibcode:2016A&A...596A.111R. doi:10.1051/0004-6361/201629576.
    10. Marchis, Franck (24 August 2016). "Proxima Centauri b: Have we just found Earth's cousin right on our doorstep?". The Planetary Society . Retrieved 24 August 2016.
    11. A Potentially Habitable World in Our Nearest Star. Planetary Habitability Laboratory. 24 August 2016.
    12. Ségransan, D.; Kervella, P.; Forveille, T.; Queloz, D. (2003). "First radius measurements of very low mass stars with the VLTI". Astronomy and Astrophysics. 397 (3): L5–L8. arXiv: astro-ph/0211647 . Bibcode:2003A&A...397L...5S. doi:10.1051/0004-6361:20021714.
    13. 1 2 Mathewson, Samantha (24 August 2016). "Proxima b By the Numbers: Possibly Earth-Like World at the Next Star Over". Space.com. Retrieved 25 August 2016.
    14. Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
    15. Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
    16. 1 2 3 "Proxima b is our neighbor ... better get used to it!". Pale Red Dot. 24 August 2016. Retrieved 24 August 2016.
    17. Schlaufman, K. C.; Laughlin, G. (September 2010). "A physically-motivated photometric calibration of M dwarf metallicity". Astronomy and Astrophysics. 519: A105. arXiv: 1006.2850 . Bibcode:2010A&A...519A.105S. doi:10.1051/0004-6361/201015016.
    18. Jao, Wei-Chun; Henry, Todd J.; Subasavage, John P.; Winters, Jennifer G.; Gies, Douglas R.; Riedel, Adric R.; Ianna, Philip A. (2014). "The Solar Neighborhood. XXXI. Discovery of an Unusual Red+White Dwarf Binary at ~25 pc via Astrometry and UV Imaging". The Astronomical Journal. 147 (1): 21. arXiv: 1310.4746 . Bibcode:2014AJ....147...21J. doi:10.1088/0004-6256/147/1/21. ISSN   0004-6256.
    19. Christian, D. J.; Mathioudakis, M.; Bloomfield, D. S.; Dupuis, J.; Keenan, F. P. (2004). "A Detailed Study of Opacity in the Upper Atmosphere of Proxima Centauri" (PDF). The Astrophysical Journal. 612 (2): 1140–1146. Bibcode:2004ApJ...612.1140C. doi:10.1086/422803.
    20. Williams, Matt (2018-04-10). "Proxima Centauri Just Released a Flare so Powerful it was Visible to the Unaided Eye. Planets There Would Get Scorched". Universe Today. Retrieved 2019-01-17.
    21. Ritchie, Raymond J.; Larkum, Anthony W. D.; Ribas, Ignasi (April 2018). "Could photosynthesis function on Proxima Centauri b?". International Journal of Astrobiology . 17 (2): 147–176. Bibcode:2018IJAsB..17..147R. doi:10.1017/S1473550417000167 . Retrieved 2018-09-10.
    22. Schlyter, Paul (2017-03-05). "Radiometry and photometry in astronomy". stjarnhimlen.se. Stockholm, Sweden. 10: How bright are natural light sources?. Retrieved 2017-06-21.
    23. Howard, Ward S; Tilley, Matt A; Corbett, Hank; Youngblood, Allison; Parke Loyd, R. O; Ratzloff, Jeffrey K; Fors, Octavi; Daniel del Ser; Shkolnik, Evgenya L; Ziegler, Carl; Goeke, Erin E; Pietraallo, Aaron D; Haislip, Joshua; Law, Nicholas M (2018). "The First Naked-Eye Superflare Detected from Proxima Centauri". arXiv: 1804.02001 .
    24. Garraffo, Cecilia; Drake, Jeremy J.; Cohen, Ofer (28 September 2016). "The Space Weather of Proxima Centauri b". The Astrophysical Journal. 833: L4. arXiv: 1609.09076 . Bibcode:2016ApJ...833L...4G. doi:10.3847/2041-8205/833/1/L4.
    25. O'Neill, Ian (7 October 2016). "Eyeballing Proxima b: Probably Not a Second Earth". Discovery News. Space.com. Retrieved 2016-10-10.
    26. "Planet in star system nearest our Sun 'may have oceans'", Phys.org, Retrieved 6 October 2016
    27. 1 2 Witze, Alexandra (24 August 2016). "Earth-sized planet around nearby star is astronomy dream come true". Nature. pp. 381–382. Bibcode:2016Natur.536..381W. doi:10.1038/nature.2016.20445 . Retrieved 24 August 2016.
    28. 1 2 Singal, Ashok K. (2014). "Life on a tidally-locked planet". Planex Newsletter. 4 (2): 8. arXiv: 1405.1025 . Bibcode:2014arXiv1405.1025S.
    29. Barnes, Rory, ed. (2010), Formation and Evolution of Exoplanets, John Wiley & Sons, p. 248, ISBN   3527408967.
    30. Heller, R.; Leconte, J.; Barnes, R. (April 2011). "Tidal obliquity evolution of potentially habitable planets". Astronomy & Astrophysics. 528: 16. arXiv: 1101.2156 . Bibcode:2011A&A...528A..27H. doi:10.1051/0004-6361/201015809. A27.
    31. Makarov, Valeri V. (June 2012), "Conditions of Passage and Entrapment of Terrestrial Planets in Spin-orbit Resonances", The Astrophysical Journal, 752 (1): 8, arXiv: 1110.2658 , Bibcode:2012ApJ...752...73M, doi:10.1088/0004-637X/752/1/73, 73.
    32. 1 2 3 4 The habitability of Proxima Centauri b – II. Possible climates and observability. Retrieved 25 August 2016.
    33. Does the exoplanet Proxima b host intelligent life? on YouTube (2017), from The Exoplanets Channel's channel on YouTube
    34. "Numerical simulation of possible surface temperatures on Proxima b (synchronous rotation)". ESO. 2016. Retrieved 24 August 2016.
    35. Barnes, Rory (24 August 2016). "The Habitability of Proxima Centauri b I: Evolutionary Scenarios". Astrobiology. 1608: 62. arXiv: 1608.06919 . Bibcode:2016arXiv160806919B.
    36. Computed; using in solar terms: 1.1 M and 0.92 M, luminosities 1.57 and 0.51 L*/L, Sun magnitude −26.73(v), 11.2 to 35.6 AU orbit. The minimum luminosity adds the planet's orbital radius to the A–B distance (max) (conjunction). The maximum luminosity subtracts the planet's orbital radius to the A–B distance (min) (opposition).
    37. Aron, Jacob. 24 August 2016. Proxima b: Closest Earth-like planet discovered right next door. New Scientist. Retrieved 24 August 2016.
    38. "Follow a Live Planet Hunt!". European Southern Observatory. 15 January 2016. Retrieved 24 August 2016.
    39. Feltman, Rachel (24 August 2016). "Scientists say they've found a planet orbiting Proxima Centauri, our closest neighbor". The Washington Post via GALE.
    40. "Planet Found in Habitable Zone Around Nearest Star – Pale Red Dot campaign reveals Earth-mass world in orbit around Proxima Centauri". www.eso.org. Retrieved 10 January 2017.
    41. "Planet Found in Habitable Zone Around Nearest Star". European Southern Observatory. 24 August 2016.
    42. "Found! Potentially Earth-Like Planet at Proxima Centauri Is Closest Ever". Space.com. 24 August 2016.
    43. Knapton, Sarah (24 August 2016). "Proxima b: Alien life could exist on 'second Earth' found orbiting our nearest star in Alpha Centauri system". The Telegraph . Telegraph Media Group . Retrieved 24 August 2016.
    44. 1 2 "VLT to Search for Planets in Alpha Centauri System - ESO Signs Agreement with Breakthrough Initiatives". www.eso.org. Retrieved 10 January 2017.
    45. Lovis, C.; Snellen, I.; Mouillet, D.; Pepe, F.; Wildi, F.; Astudillo-Defru, N.; Beuzit, J. -L.; Bonfils, X.; Cheetham, A.; Conod, U.; Delfosse, X.; Ehrenreich, D.; Figueira, P.; Forveille, T.; Martins, J. H. C.; Quanz, S.; Santos, N. C.; Schmid, H. -M.; Ségransan, D.; Udry, S. (2016). "Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph". Astronomy & Astrophysics. 599: A16. arXiv: 1609.03082 . Bibcode:2017A&A...599A..16L. doi:10.1051/0004-6361/201629682.
    46. Kreidberg, Laura; Loeb, Abraham (2016). "Prospects for Characterizing the Atmosphere of Proxima Centauri b". The Astrophysical Journal. 832: L12. arXiv: 1608.07345 . Bibcode:2016ApJ...832L..12K. doi:10.3847/2041-8205/832/1/L12.
    47. Kipping, David M.; et al. (2017). "No Conclusive Evidence for Transits of Proxima b in MOST photometry". The Astronomical Journal. 153 (3): 93. arXiv: 1609.08718 . Bibcode:2017AJ....153...93K. doi:10.3847/1538-3881/153/3/93.
    48. Staff (12 April 2016). "Starshot". Breakthrough Initiatives . Retrieved 12 April 2016.
    49. Gilster, Paul (12 April 2016). "Breakthrough Starshot: Mission to Alpha Centauri". Centauri Dreams. Retrieved 14 April 2016.
    50. Overbye, Dennis (12 April 2016). "Reaching for the Stars, Across 4.37 Light-Years; A Visionary Project Aims for Alpha Centauri, a Star 4.37 Light-Years Away". New York Times . Retrieved 12 April 2016.
    51. Stone, Maddie (12 April 2016). "Stephen Hawking and a Russian Billionaire Want to Build an Interstellar Starship". Gizmodo. Retrieved 12 April 2016.

    Further reading

    Coordinates: Celestia.png 14h 29m 42.9487s, −62° 40′ 46.141″