Polaris

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Polaris
Ursa Minor IAU.svg
Red circle.svg
Polaris (α Ursae Minoris, circled in red) in the constellation Ursa Minor (white area)
Observation data
Epoch J2000       Equinox
Constellation Ursa Minor
α UMi Aa
Right ascension 02h 31m 49.09s
Declination +89° 15 50.8
Apparent magnitude (V)1.98 [1] (variable 1.86–2.13)
α UMi Ab
Right ascension
Declination
Apparent magnitude (V)9.2 [1]
α UMi B
Right ascension 02h 30m 41.63s
Declination +89° 15 38.1
Apparent magnitude (V)8.7 [1]
Characteristics
α UMi Aa
Spectral type F7Ib [2]
U−B color index 0.38 [1]
B−V color index 0.60 [1]
Variable type Classical Cepheid [3]
α UMi Ab
Spectral type F6V [1]
α UMi B
Spectral type F3V [1]
U−B color index 0.01 [4]
B−V color index 0.42 [4]
Astrometry
Radial velocity (Rv)−17 km/s
Proper motion (μ)RA: 198.8±0.20  mas/yr
Dec.: -15±0.30  mas/yr
Parallax (π)7.54 ± 0.11 [5]   mas
Distance 323–433 [6]   ly
(99–133 [6]   pc)
Absolute magnitude  (MV)−3.6 (α UMi Aa) [1]
3.6 (α UMi Ab) [1]
3.1 (α UMi B) [1]
Orbit [7]
Primaryα UMi Aa
Companionα UMi Ab
Period (P)29.59 ± 0.02 yr
Semi-major axis (a)0.1204 ± 0.0059″
Eccentricity (e)0.608 ± 0.005
Inclination (i)146.2 ± 10.9°
Longitude of the node (Ω)191.4 ± 4.9°
Periastron epoch (T)1987.66 ± 0.13
Argument of periastron (ω)
(secondary)
123.01 ± 0.75°
Semi-amplitude (K1)
(primary)
3.72 ± 0.03 km/s
Details
α UMi Aa
Mass 5.4 [8]   M
Radius 37.5 [8]   R
Luminosity (bolometric)1,260 [8]   L
Surface gravity (log g)2.2 [9]   cgs
Temperature 6015 [4]   K
Metallicity 112% solar [10]
Rotation 119 days [2]
Rotational velocity (v sin i)14 [2]  km/s
Age 7×107 [11]  years
α UMi Ab
Mass 1.26 [1]   M
Radius 1.04 [1]   R
Luminosity (bolometric)3 [1]   L
Age 7×107 [11]  years
α UMi B
Mass 1.39 [1]   M
Radius 1.38 [4]   R
Luminosity (bolometric)3.9 [4]   L
Surface gravity (log g)4.3 [4]   cgs
Temperature 6900 [4]   K
Rotational velocity (v sin i)110 [4]  km/s
Age 7×107 [11]  years
Position (relative to α UMi Aa)
Componentα UMi Ab
Epoch of observation 2005.5880
Angular distance0.172
Position angle 231.4°
Position (relative to α UMi Aa)
Componentα UMi B
Epoch of observation 2005.5880
Angular distance18.217
Position angle 230.540°
Other designations
Polaris, North Star, 1 Ursae Minoris, HR 424, BD +88° 8, HD 8890, SAO 308, FK5 907, GC  2243, ADS 1477, CCDM J02319+8915, HIP 11767, Cynosura, Alruccabah, Phoenice, Navigatoria, Star of Arcady, Yilduz, Mismar
Database references
SIMBAD α UMi A
α UMi B

Polaris ( /pˈlɛərɪs,pə-,-lær-/ UK: /pəˈlɑːrɪs/ ), [12] designated α Ursae Minoris (Latinized to Alpha Ursae Minoris, abbreviated Alpha UMi, α UMi), commonly the North Star or Pole Star, is the brightest star of the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star. The revised Hipparcos parallax gives a distance to Polaris of about 433 light-years (133 parsecs), while calculations by some other methods derive distances up to 35% closer.

Contents

Polaris is a triple star system, composed of the primary star, Polaris Aa (a yellow supergiant), in orbit with a smaller companion (Polaris Ab); the pair in orbit with Polaris B (discovered in August 1779 by William Herschel).

Stellar system

Polaris components as seen by the Hubble Space Telescope Polaris alpha ursae minoris.jpg
Polaris components as seen by the Hubble Space Telescope

Polaris Aa is a 5.4 solar mass (M) F7 yellow supergiant of spectral type Ib. It is the first classical Cepheid to have a mass determined from its orbit. The two smaller companions are Polaris B, a 1.39 M F3 main-sequence star orbiting at a distance of 2,400  astronomical units (AU), [13] and Polaris Ab (or P), a very close F6 main-sequence star with a mass of 1.26 M.

Polaris B can be seen with a modest telescope. William Herschel discovered the star in August 1779 using a reflecting telescope of his own, one of the best telescopes of the time. By examining the spectrum of Polaris A, it was also discovered in 1929 that it was a very close binary, with the secondary being a dwarf (variously α UMi P, α UMi an or α UMi Ab), which had been theorized in earlier observations (Moore, J. H. and Kholodovsky, E. A.). In January 2006, NASA released images, from the Hubble telescope, that showed the three members of the Polaris ternary system. [14] [15]

There were once thought to be two more distant components—Polaris C and Polaris D—but these have been shown not to be physically associated with the Polaris system. [11] [16]

Observation

Polaris is the brightest star in the constellation of Ursa Minor (upper right). UrsaMinorCC.jpg
Polaris is the brightest star in the constellation of Ursa Minor (upper right).
Big Dipper and Ursa Minor in relation to Polaris Ursa Major - Ursa Minor - Polaris.jpg
Big Dipper and Ursa Minor in relation to Polaris
A typical Northern Hemisphere star trail with Polaris in the center. Star Trail above Beccles - geograph.org.uk - 1855505.jpg
A typical Northern Hemisphere star trail with Polaris in the center.
A view of Polaris in a small telescope. Polaris B is separated by 18 arc seconds from the primary star, Polaris A. Polaris star and companion.jpg
A view of Polaris in a small telescope. Polaris B is separated by 18 arc seconds from the primary star, Polaris A.

Variability

Polaris Aa, the supergiant primary component, is a low-amplitude Population I classical Cepheid variable, although it was once thought to be a type II Cepheid due to its high galactic latitude. Cepheids constitute an important standard candle for determining distance, so Polaris, as the closest such star, is heavily studied. The variability of Polaris had been suspected since 1852; this variation was confirmed by Ejnar Hertzsprung in 1911. [17]

The range of brightness of Polaris is given as 1.86–2.13, [3] but the amplitude has changed since discovery. Prior to 1963, the amplitude was over 0.1 magnitude and was very gradually decreasing. After 1966, it very rapidly decreased until it was less than 0.05 magnitude; since then, it has erratically varied near that range. It has been reported that the amplitude is now increasing again, a reversal not seen in any other Cepheid. [2]

The period, roughly 4 days, has also changed over time. It has steadily increased by around 4.5 seconds per year except for a hiatus in 1963–1965. This was originally thought to be due to secular redward evolution across the Cepheid instability strip, but it may be due to interference between the primary and the first-overtone pulsation modes. [15] [18] [19] Authors disagree on whether Polaris is a fundamental or first-overtone pulsator and on whether it is crossing the instability strip for the first time or not. [8] [19] [20]

The temperature of Polaris varies by only a small amount during its pulsations, but the amount of this variation is variable and unpredictable. The erratic changes of temperature and the amplitude of temperature changes during each cycle, from less than 50  K to at least 170 K, may be related to the orbit with Polaris Ab. [9]

Research reported in Science suggests that Polaris is 2.5 times brighter today than when Ptolemy observed it, changing from third to second magnitude. [21] Astronomer Edward Guinan considers this to be a remarkable change and is on record as saying that "if they are real, these changes are 100 times larger than [those] predicted by current theories of stellar evolution".

Role as pole star

Because Polaris lies nearly in a direct line with the Earth's rotational axis "above" the North Pole—the north celestial pole—Polaris stands almost motionless in the sky, and all the stars of the northern sky appear to rotate around it. Therefore, it makes an excellent fixed point from which to draw measurements for celestial navigation and for astrometry. The moving of Polaris towards and, in the future, away from the celestial pole, is due to the precession of the equinoxes. [22] The celestial pole will move away from α UMi after the 21st century, passing close by Gamma Cephei by about the 41st century, moving towards Deneb by about the 91st century. The celestial pole was close to Thuban around 2750 BC, [22] and during classical antiquity it was slightly closer to Kochab (β UMi) than to Polaris, although still about 10° from either star. [23] It was about the same angular distance from β UMi as to α UMi by the end of late antiquity. The Greek navigator Pytheas in ca. 320 BC described the celestial pole as devoid of stars. However, as one of the brighter stars close to the celestial pole, Polaris was used for navigation at least from late antiquity, and described as ἀεί φανής (aei phanēs) "always visible" by Stobaeus (5th century), and it could reasonably be described as stella polaris from about the High Middle Ages. On his first trans-Atlantic voyage in 1492, Christopher Columbus had to correct for the "circle described by the pole star about the pole". [24] In Shakespeare's play Julius Caesar, written around 1599, Caesar describes himself as being "as constant as the northern star", though in Caesar's time there was no constant northern star.

Polaris was referenced in Nathaniel Bowditch's 1802 book, American Practical Navigator , where it is listed as one of the navigational stars. [25] Twice in each sidereal day Polaris' azimuth is true north; the rest of the time it is displaced eastward or westward, and the bearing must be corrected using tables or a rule of thumb. The best approximation [26] was made using the leading edge of the "Big Dipper" asterism in the constellation Ursa Major. The leading edge (defined by the stars Dubhe and Merak) was referenced to a clock face, and the true azimuth of Polaris worked out for different latitudes.

Names

This artist's concept shows: supergiant Polaris Aa, dwarf Polaris Ab, and the distant dwarf companion Polaris B. Polaris system.jpg
This artist's concept shows: supergiant Polaris Aa, dwarf Polaris Ab, and the distant dwarf companion Polaris B.

The modern name Polaris [27] is shortened from New Latin stella polaris "polar star", coined in the Renaissance when the star had approached the celestial pole to within a few degrees. Gemma Frisius, writing in 1547, referred to it as stella illa quae polaris dicitur ("that star which is called 'polar'"), placing it 3° 8' from the celestial pole. [28]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) [29] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 [30] included a table of the first two batches of names approved by the WGSN; which included Polaris for the star α Ursae Minoris Aa.

In antiquity, Polaris was not yet the closest naked-eye star to the celestial pole, and the entire constellation of Ursa Minor was used for navigation rather than any single star. Polaris moved close enough to the pole to be the closest naked-eye star, even though still at a distance of several degrees, in the early medieval period, and numerous names referring to this characteristic as polar star have been in use since the medieval period. In Old English, it was known as scip-steorra ("ship-star"); In the Old English rune poem, the T-rune is apparently associated with "a circumpolar constellation", compared to the quality of steadfastness or honour. [31]

In the Hindu Puranas, it became personified under the name Dhruva ("immovable, fixed"). [32] In the later medieval period, it became associated with the Marian title of Stella Maris "Star of the Sea" (so in Bartholomeus Anglicus, c. 1270s) [33] An older English name, attested since the 14th century, is lodestar "guiding star", cognate with the Old Norse leiðarstjarna, Middle High German leitsterne. [34]

The ancient name of the constellation Ursa Minor, Cynosura (from the Greek κυνόσουρα "the dog’s tail"), [35] became associated with the pole star in particular by the early modern period. An explicit identification of Mary as stella maris with the polar star (Stella Polaris), as well as the use of Cyonsura as a name of the star, is evident in the title Cynosura seu Mariana Stella Polaris (i.e. "Cynosure, or the Marian Polar Star"), a collection of Marian poetry published by Nicolaus Lucensis (Niccolo Barsotti de Lucca) in 1655. [ citation needed ]

Its name in traditional pre-Islamic Arab astronomy was al-Judayy الجدي ("the kid", in the sense of a juvenile goat ["le Chevreau" in Description des Etoiles fixes), and that name was used in medieval Islamic astronomy as well. [36] [37] In those times, it was not yet as close to the north celestial pole as it is now, and used to rotate around the pole.

It was invoked as a symbol of steadfastness in poetry, as "steadfast star" by Spenser. Shakespeare's sonnet 116 is an example of the symbolism of the north star as a guiding principle: "[Love] is the star to every wandering bark / Whose worth's unknown, although his height be taken." In Julius Caesar , he has Caesar explain his refusal to grant a pardon by saying, "I am as constant as the northern star/Of whose true-fixed and resting quality/There is no fellow in the firmament./The skies are painted with unnumbered sparks,/They are all fire and every one doth shine,/But there’s but one in all doth hold his place;/So in the world" (III, i, 65–71). Of course, Polaris will not "constantly" remain as the north star due to precession, but this is only noticeable over centuries.[ citation needed ]

In Inuit astronomy, Polaris is known as Niqirtsuituq. It is depicted on the flag and coat of arms of the Canadian Inuit territory of Nunavut, as well as on the flag of the U.S. state of Alaska. [38]

In traditional Lakota star knowledge, Polaris is named "Wičháȟpi owáŋžila". This translates to "The Star that Sits Still". This name comes from a Lakota story in which he married Tapun San Win "Red Cheeked Woman". However she fell from the heavens, and in his grief he stared down from "waŋkátu" (the above land) forever.[ citation needed ]

Distance

Stellar parallax is the basis for the parsec, which is the distance from the Sun to an astronomical object which has a parallax angle of one arcsecond. (1 AU and 1 pc are not to scale, 1 pc = about 206265 AU) Stellarparallax parsec1.svg
Stellar parallax is the basis for the parsec, which is the distance from the Sun to an astronomical object which has a parallax angle of one arcsecond. (1 AU and 1 pc are not to scale, 1 pc = about 206265 AU)

Many recent papers calculate the distance to Polaris at about 433 light-years (133 parsecs), [15] based on parallax measurements from the Hipparcos astrometry satellite. Older distance estimates were often slightly less, and research based on high resolution spectral analysis suggests it may be up to 110 light years closer (323 ly/99 pc). [6] Polaris is the closest Cepheid variable to Earth so its physical parameters are of critical importance to the whole astronomical distance scale. [6] It is also the only one with a dynamically measured mass.

Selected distance estimates to Polaris
YearComponentDistance, ly (pc)Notes
2006A330 ly (101 pc)Turner [18]
2007 [A] A433 ly (133 pc)Hipparcos [5]
2008B359 ly (110 pc)Usenko & Klochkova [4]
2013B323 ly (99 pc)Turner, et al. [6]
2014A≥ 385 ly (≥ 118 pc)Neilson [39]
2018B521 ly (160pc)Bond et al. [40]
2018B445.3 ly (136.6 pc) [B] Gaia DR2 [41]
2020B447.6 ly (137.2pc)Gaia EDR3 [42]
A New revision of observations from 1989–1993, first published in 1997
B Statistical distance calculated using a weak distance prior

The Hipparcos spacecraft used stellar parallax to take measurements from 1989 and 1993 with the accuracy of 0.97  milliarcseconds (970 microarcseconds), and it obtained accurate measurements for stellar distances up to 1,000 pc away. [43] The Hipparcos data was examined again with more advanced error correction and statistical techniques. [5] Despite the advantages of Hipparcos astrometry, the uncertainty in its Polaris data has been pointed out and some researchers have questioned the accuracy of Hipparcos when measuring binary Cepheids like Polaris. [6] The Hipparcos reduction specifically for Polaris has been re-examined and reaffirmed but there is still not widespread agreement about the distance. [44]

The next major step in high precision parallax measurements comes from Gaia , a space astrometry mission launched in 2013 and intended to measure stellar parallax to within 25 microarcseconds (μas). [45] Although it was originally planned to limit Gaia's observations to stars fainter than magnitude 5.7, tests carried out during the commissioning phase indicated that Gaia could autonomously identify stars as bright as magnitude 3. When Gaia entered regular scientific operations in July 2014, it was configured to routinely process stars in the magnitude range 3 – 20. [46] Beyond that limit, special procedures are used to download raw scanning data for the remaining 230 stars brighter than magnitude 3; methods to reduce and analyse these data are being developed; and it is expected that there will be "complete sky coverage at the bright end" with standard errors of "a few dozen µas". [47] Gaia Data Release 2 does not include a parallax for Polaris, but a distance inferred from it is 136.6±0.5  pc (445.5 ly) for Polaris B, [41] somewhat further than most previous estimates and several times more accurate. This was further improved to 137.2±0.3  pc (447.6 ly), upon publication of the Gaia Early Data Release 3 catalog on 3 December 2020 which superseded Gaia Data Release 2. [42]

Polaris has long been important for the cosmic distance ladder because, prior to Gaia, it was the only Cepheid variable for which direct distance data existed, which had a ripple effect on distance measurements that use this "ruler". [48]

Observational history

Polaris in stellar catalogues and atlases
SourcePresence
Ptolemy (~169)Yes
Al-Sufi (964)Yes
Al-Biruni (~1030)Yes
Khayyam (~1100)Yes
Nasir al-Din al-Tusi (1272)No
Ulugh Beg (1437)Yes
Copernicus (1543)Yes
Schöner (1551)Yes
Brahe (1598)Yes
Brahe (1602)Yes
Bayer (1603)Yes
De Houtman (1603)No
Kepler (1627)Yes
Schiller (1627)Yes
Halley (1679)No
Hevelius (1690)Yes
Flamsteed (1725)Yes
Flamsteed (1729)Yes
Bode (1801a)Yes
Bode (1801b)Yes

See also

Related Research Articles

Ursa Minor Constellation in the northern celestial hemisphere, containing the northern celestial pole

Ursa Minor, also known as the Little Bear, is a constellation in the Northern Sky. Like the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the North American name, Little Dipper: seven stars with four in its bowl like its partner the Big Dipper. It was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor has traditionally been important for navigation, particularly by mariners, because of Polaris being the north pole star.

Beta Ursae Minoris Star in the constellation Ursa Minor

Beta Ursae Minoris, formally named Kochab, is the brightest star in the bowl of the Little Dipper asterism, and only slightly fainter than Polaris, the northern pole star and brightest star in Ursa Minor. Kochab is 16 degrees from Polaris and has an apparent visual magnitude of 2.08. The distance to this star from the Sun can be deduced from the parallax measurements made during the Hipparcos mission, yielding a value of 130.9 light-years.

Zeta Geminorum Star in the constellation Gemini

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Delta Cephei Binary star system in the constellation Cepheus

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Omega Ursae Majoris Binary system in the constellation Ursa Major

Omega Ursae Majoris is the Bayer designation for a binary star system in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye with an apparent visual magnitude of 4.61. Based upon an annual parallax shift of 13.24 mas, it is roughly 246 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.11 due to interstellar dust.

Delta Ursae Minoris Star in the constellation Ursa Minor

Delta Ursae Minoris, Latinized from δ Ursae Minoris, formally named Yildun, is a white-hued star in the northern circumpolar constellation of Ursa Minor, forming the second star in the bear's tail. It is visible to the naked eye with an apparent visual magnitude of 4.36. Based upon an annual parallax shift of 18.95 mas as seen from Earth, it is located 172 light years from the Sun. The star is moving closer to the Sun with a radial velocity of about −8 km/s.

Pi2 Ursae Minoris, which is Latinized from π2 UMi Ursae Minoris, is a binary star system in the northern circumpolar constellation of Ursa Minor. The pair have a combined apparent visual magnitude of 6.89, which can be viewed with a pair of binoculars. They are located at a distance of approximately 400 light years from the Sun based on parallax, but are drifting closer with a radial velocity of −32 km/s.

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δ Doradus is a star in the southern constellation of Dorado. Based upon an annual parallax shift of 21.80 mas as seen from Earth, it is located around 150 light years from the Sun. The star is visible to the naked eye with an apparent visual magnitude of +4.34.

HD 221525 Star in the constellation Cepheus

HD 221525 is a single star near the north celestial pole in the constellation Cepheus. At an apparent magnitude of 5.56, it can be seen with the naked eye under dark skies. It is about 30 times fainter than the nearby prominent star Polaris. Based upon parallax measurements, HD 221525 is located at a distance of approximately 317 light years from the Sun, but is drifting closer with a radial velocity of −11 km/s.

Nu Ceti Star in the constellation Cetus

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Mu Piscis Austrini Star in the constellation Piscis Austrinus

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HR 4072 is a binary star system in the northern circumpolar constellation of Ursa Major. It has the variable star designation ET Ursae Majoris, abbreviated ET Uma, while HR 4072 is the system's designation from the Bright Star Catalogue. It has a white hue and is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.94. The system is located at a distance of approximately 339 light years from the Sun based on parallax measurements. The radial velocity measurement is poorly constrained, but it appears to be drifting closer to the Sun at the rate of around −3 km/s.

RR Ursae Minoris, abbreviated RR UMi, is a binary star system in the northern circumpolar constellation of Ursa Minor. It can be viewed with the naked eye, typically having an apparent visual magnitude of around 4.710. Based upon an annual parallax shift of 10.0 mas as seen from Earth's orbit, it is located 330 light years away. The system is moving further from the Sun with a heliocentric radial velocity of +6 km/s.

R Muscae is a yellow-white hued variable star in the southern constellation of Musca. It has a nominal apparent visual magnitude of 6.31, which is near the lower limit of visibility to the naked eye. The distance to this star, as determined from its annual parallax shift of 1.00 mas, is around 3,260 light years.

T Vulpeculae is a possible binary star system in the northern constellation of Vulpecula, near the star Zeta Cygni, close to the pair 31 Vulpeculae and 32 Vulpeculae. It is visible to the naked eye with an apparent visual magnitude that ranges around 5.75. The distance to this system is around 1,900 light years, as determined from its annual parallax shift of 1.67 mas.

BG Crucis is a suspected binary star system in the southern constellation of Crux. It is visible to the naked eye as a faint yellow-white hued point of light with an apparent visual magnitude that fluctuates around 5.49. The system is located at a distance of approximately 1,830 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −19 km/s.

R Crucis is a variable star in the southern constellation of Crux. It has a yellow-white hue and is often too faint to see with the naked eye, having an apparent visual magnitude that fluctuates around 6.89. This object is located at a distance of approximately 1,600 light years from the Sun based on parallax, but it is drifting closer with a radial velocity of −13.5 km/s.

AH Velorum Star in the constellation Vela

AH Velorum is a single, yellow-white hued star in the constellation Vela. It has an average apparent visual magnitude of 5.70, which makes it bright enough to be dimly visible to the naked eye in good seeing conditions. The distance to this star can be estimated from its annual parallax shift of 1.217 mas, which yields a separation of roughly 2,700 light years. It is moving further away from the Earth with a heliocentric radial velocity of +26 km/s.

T Ursae Minoris is a star in the constellation Ursa Minor, located 2'30" west-southwest of 3 Ursae Minoris toward the western border of the constellation with Draco.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Evans, N. R.; Schaefer, G. H.; Bond, H. E.; Bono, G.; Karovska, M.; Nelan, E.; Sasselov, D.; Mason, B. D. (2008). "Direct Detection of the Close Companion of Polaris with The Hubble Space Telescope". The Astronomical Journal. 136 (3): 1137. arXiv: 0806.4904 . Bibcode:2008AJ....136.1137E. doi:10.1088/0004-6256/136/3/1137. S2CID   16966094.
  2. 1 2 3 4 Lee, B. C.; Mkrtichian, D. E.; Han, I.; Park, M. G.; Kim, K. M. (2008). "Precise Radial Velocities of Polaris: Detection of Amplitude Growth". The Astronomical Journal. 135 (6): 2240. arXiv: 0804.2793 . Bibcode:2008AJ....135.2240L. doi:10.1088/0004-6256/135/6/2240. S2CID   12176373.
  3. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S.
  4. 1 2 3 4 5 6 7 8 9 Usenko, I. A.; Klochkova, V. G. (2008). "Polaris B, an optical companion of the Polaris (α UMi) system: Atmospheric parameters, chemical composition, distance and mass". Monthly Notices of the Royal Astronomical Society: Letters. 387 (1): L1. arXiv: 0708.0333 . Bibcode:2008MNRAS.387L...1U. doi:10.1111/j.1745-3933.2008.00426.x. S2CID   18848139.
  5. 1 2 3 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: 0708.1752 . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID   18759600.
  6. 1 2 3 4 5 6 Turner, D. G.; Kovtyukh, V. V.; Usenko, I. A.; Gorlova, N. I. (2013). "The Pulsation Mode of the Cepheid Polaris". The Astrophysical Journal Letters. 762 (1): L8. arXiv: 1211.6103 . Bibcode:2013ApJ...762L...8T. doi:10.1088/2041-8205/762/1/L8. S2CID   119245441.
  7. Evans, N. R.; Marovska, M.; Bond, H. E.; Schaefer, G. H.; Sahu, K. C.; Mack, J.; Nelan, E. P.; Gallene, A.; Tingle, E. D. (2018). "The Orbit of the Close Companion of Polaris: Hubble Space Telescope Imaging, 2007 to 2014". The Astrophysical Journal. 863 (2): 187. arXiv: 1807.06115 . Bibcode:2018ApJ...863..187E. doi:10.3847/1538-4357/aad410. S2CID   119392532.
  8. 1 2 3 4 Fadeyev, Y. A. (2015). "Evolutionary status of Polaris". Monthly Notices of the Royal Astronomical Society. 449 (1): 1011–1017. arXiv: 1502.06463 . Bibcode:2015MNRAS.449.1011F. doi:10.1093/mnras/stv412. S2CID   118517157.
  9. 1 2 Usenko, I. A.; Miroshnichenko, A. S.; Klochkova, V. G.; Yushkin, M. V. (2005). "Polaris, the nearest Cepheid in the Galaxy: Atmosphere parameters, reddening and chemical composition". Monthly Notices of the Royal Astronomical Society. 362 (4): 1219. Bibcode:2005MNRAS.362.1219U. doi: 10.1111/j.1365-2966.2005.09353.x .
  10. Cayrel de Strobel, G.; Soubiran, C.; Ralite, N. (2001). "Catalogue of [Fe/H] determinations for FGK stars: 2001 edition". Astronomy and Astrophysics. 373: 159–163. arXiv: astro-ph/0106438 . Bibcode:2001A&A...373..159C. doi:10.1051/0004-6361:20010525. S2CID   17519049.
  11. 1 2 3 4 Wielen, R.; Jahreiß, H.; Dettbarn, C.; Lenhardt, H.; Schwan, H. (2000). "Polaris: Astrometric orbit, position, and proper motion". Astronomy and Astrophysics. 360: 399. arXiv: astro-ph/0002406 . Bibcode:2000A&A...360..399W.
  12. "Polaris | meaning in the Cambridge English Dictionary". Cambridge English Dictionary . Retrieved 11 December 2020.
  13. Jim Kaler. "Polaris (Alpha Ursae Minoris)". Stars. Retrieved 2020-09-09.
  14. "There's More to the North Star Than Meets the Eye". Hubblesite.org. 2006-01-09. Retrieved 2020-02-27.
  15. 1 2 3 Evans, N. R.; Sasselov, D. D.; Short, C. I. (2002). "Polaris: Amplitude, Period Change, and Companions". The Astrophysical Journal. 567 (2): 1121. Bibcode:2002ApJ...567.1121E. doi: 10.1086/338583 .
  16. Evans, Nancy Remage; Guinan, Edward; Engle, Scott; Wolk, Scott J.; Schlegel, Eric; Mason, Brian D.; Karovska, Margarita; Spitzbart, Bradley (2010). "Chandra Observation of Polaris: Census of Low-mass Companions". The Astronomical Journal. 139 (5): 1968. Bibcode:2010AJ....139.1968E. doi: 10.1088/0004-6256/139/5/1968 .
  17. Hertzsprung, Ejnar (August 1911). "Nachweis der Veränderlichkeit von α Ursae Minoris". Astronomische Nachrichten (in German). 189 (6): 89. Bibcode:1911AN....189...89H. doi:10.1002/asna.19111890602.
  18. 1 2 Turner, D. G.; Savoy, J.; Derrah, J.; Abdel‐Sabour Abdel‐Latif, M.; Berdnikov, L. N. (2005). "The Period Changes of Polaris". Publications of the Astronomical Society of the Pacific. 117 (828): 207. Bibcode:2005PASP..117..207T. doi: 10.1086/427838 .
  19. 1 2 Neilson, H. R.; Engle, S. G.; Guinan, E.; Langer, N.; Wasatonic, R. P.; Williams, D. B. (2012). "The Period Change of the Cepheid Polaris Suggests Enhanced Mass Loss". The Astrophysical Journal. 745 (2): L32. arXiv: 1201.0761 . Bibcode:2012ApJ...745L..32N. doi:10.1088/2041-8205/745/2/L32. S2CID   118625176.
  20. Engle, Scott G; Guinan, Edward F; Harmanec, Petr (2018). "Toward Ending the Polaris Parallax Debate: A Precise Distance to Our Nearest Cepheid from Gaia DR2". Research Notes of the AAS. 2 (3): 126. Bibcode:2018RNAAS...2..126E. doi:10.3847/2515-5172/aad2d0.
  21. Irion, R (2004). "American Astronomical Society meeting. As inconstant as the Northern Star". Science. 304 (5678): 1740–1. doi:10.1126/science.304.5678.1740b. PMID   15205508. S2CID   129246155.
  22. 1 2 Ridpath, Ian, ed. (2004). Norton's Star Atlas . New York: Pearson Education. p.  5. ISBN   978-0-13-145164-3. Around 4800 years ago Thuban (α Draconis) lay a mere 0°.1 from the pole. Deneb (α Cygni) will be the brightest star near the pole in about 8000 years' time, at a distance of 7°.5.
  23. "Star Tales – Ursa Minor" . Retrieved 20 August 2016.
  24. The Life of the Admiral Christopher Columbus by His Son Ferdinand. Benjamin Keen (transl.) London: Folio Society, 1960. Page 74.
  25. Nathaniel Bowditch; National Imagery and Mapping Agency (2002). "15 Navigational Astronomy". The American practical navigator : an epitome of navigation. Paradise Cay Publications. p. 248. ISBN   978-0-939837-54-0.
  26. "A visual method to correct a ship's compass using Polaris using Ursa Major as a point of reference" . Retrieved Aug 7, 2016.
  27. IAU Working Group on Star Names "IAU Catalog of Star Names" . Retrieved 28 July 2016.
  28. Gemmae Frisii de astrolabo catholico liber: quo latissime patentis instrumenti multiplex usus explicatur, & quicquid uspiam rerum mathematicarum tradi possit continetur, Steelsius (1556), p. 20; see also Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Publishing. p. 23. ISBN   978-1-931559-44-7.
  29. "International Astronomical Union | IAU". www.iau.org. Retrieved 2019-01-19.
  30. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF).
  31. Bruce Dickins, Runic and heroic poems of the old Teutonic peoples (1915), p. 18; Dickins' "a circumpolar constellation" is attributed to L. Botkine, La Chanson des Runes (1879).
  32. Alain Daniélou. The Myths and Gods of India: The Classic Work on Hindu Polytheism, Princeton/Bollingen (1964) Inner Traditions / Bear & Co, 1991 ISBN   978-0-892-813544 p.186.
  33. J. O. Halliwell, (ed.), The Works of William Shakespeare vol. 5 (1856), p. 40.]
  34. Friedrich Kluge, Alfred Götze, Etymologisches Wörterbuch der deutschen Sprache, Walter de Gruyter 1943 ISBN   978-3-111-67185-7 p.355.
  35. Ian Ridpath (28 June 2018). Star Tales. Lutterworth Press. ISBN   978-0-7188-4782-1.
  36. Al-Sufi, AbdulRahman (964). "Book Of Fixed Stars".
  37. Schjellerup, Hans (1874). Description des Etoiles fixes. p. 45.
  38. Legistative Assembly of Nunavut, The Coat of Arms of Nunavut. (n.d.) https://assembly.nu.ca/about-legislative-assembly/coat-arms-nunavut
  39. Neilson, H. R. (2014). "Revisiting the fundamental properties of the Cepheid Polaris using detailed stellar evolution models". Astronomy & Astrophysics. 563: A48. arXiv: 1402.1177 . Bibcode:2014A&A...563A..48N. doi:10.1051/0004-6361/201423482. S2CID   119252434.
  40. Bond, Howard E; Nelan, Edmund P; Remage Evans, Nancy; Schaefer, Gail H; Harmer, Dianne (2018). "Hubble Space Telescope Trigonometric Parallax of Polaris B, Companion of the Nearest Cepheid". The Astrophysical Journal. 853 (1): 55. arXiv: 1712.08139 . Bibcode:2018ApJ...853...55B. doi:10.3847/1538-4357/aaa3f9. S2CID   118875464.
  41. 1 2 Bailer-Jones, C. A. L; Rybizki, J; Fouesneau, M; Mantelet, G; Andrae, R (2018). "Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2". The Astronomical Journal. 156 (2): 58. arXiv: 1804.10121 . Bibcode:2018AJ....156...58B. doi:10.3847/1538-3881/aacb21. S2CID   119289017.
  42. 1 2 "Gaia EDR3". Gaia Collaboration. 2020. Retrieved 4 December 2020.
  43. Van Leeuwen, F. (1997). "The Hipparcos Mission". Space Science Reviews. 81 (3/4): 201–409. Bibcode:1997SSRv...81..201V. doi:10.1023/A:1005081918325.
  44. Van Leeuwen, F. (2013). "The HIPPARCOS parallax for Polaris". Astronomy & Astrophysics. 550: L3. arXiv: 1301.0890 . Bibcode:2013A&A...550L...3V. doi:10.1051/0004-6361/201220871. S2CID   119284268.
  45. Liu, C.; Bailer-Jones, C. A. L.; Sordo, R.; Vallenari, A.; et al. (2012). "The expected performance of stellar parametrization with Gaia spectrophotometry". Monthly Notices of the Royal Astronomical Society. 426 (3): 2463. arXiv: 1207.6005 . Bibcode:2012MNRAS.426.2463L. doi:10.1111/j.1365-2966.2012.21797.x. S2CID   1841271.
  46. Martín-Fleitas, J.; Mora, A.; Sahlmann, J.; Kohley, R.; Massart, B.; et al. (2 August 2014), "Enabling Gaia observations of naked-eye stars", in Oschmann, Jacobus M.; Clampin, Mark; Fazio, Giovanni G.; MacEwen, Howard A. (eds.), Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, Proc. SPIE, 9143, pp. 91430Y, arXiv: 1408.3039v1 , doi:10.1117/12.2056325, S2CID   119112009
  47. T. Prusti; et al. (GAIA Collaboration) (2016), "The Gaia mission" (PDF), Astronomy and Astrophysics (forthcoming article), 595: A1, arXiv: 1609.04153 , Bibcode:2016A&A...595A...1G, doi:10.1051/0004-6361/201629272, S2CID   9271090 , retrieved 21 September 2016
  48. Subramanian, Smitha; Marengo, Massimo; Bhardwaj, Anupam; Huang, Yang; Inno, Laura; Nakagawa, Akiharu; Storm, Jesper (2017). "Young and Intermediate-Age Distance Indicators". Space Science Reviews. 212 (3–4): 1817. arXiv: 1709.07265 . Bibcode:2017SSRv..212.1817S. doi:10.1007/s11214-017-0427-8. S2CID   119064315.

Coordinates: Jupiter and moon.png 02h 31m 48.7s, +89° 15′ 51″

Preceded by
Kochab & Pherkad
Pole star
5003000
Succeeded by
Gamma Cephei