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Alpha Ursae Minoris
Polaris alpha ursae minoris.jpg
Polaris as seen by the Hubble Space Telescope.
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Minor
Right ascension 02h 31m 48.7s
Declination +89° 15′ 51″
Apparent magnitude (V) 1.97
Characteristics
Spectral type F7 Ib-II SB
U-B color index 0.38
B-V color index 0.60
Variable type Cepheid variable
Astrometry
Radial velocity (Rv) -17 km/s
Proper motion (μ) RA: 44.22 mas/yr
Dec.: -11.74 mas/yr
Parallax (π) 7.56 ± 0.48 mas
Distance 430 ± 30 ly
(132 ± 8 pc)
Absolute magnitude (MV) -3.63±0.14[1]
Details
Mass 7.54±0.6[1][2] M
Radius 30 R
Luminosity 2200 L
Temperature 7200 K
Metallicity 112% solar[3]
Rotation ~17 km/s
Age ? years
Other designations
Polaris, Cynosura, Alruccabah, Phoenice,

Navigatoria, Star of Arcady, Yilduz, Mismar,

Поля́рная звезда́ (Polyarnaya zvyezda), 1 Ursae Minoris, HR 424,

BD +88°8, HD 8890, SAO 308, FK5 907,

GC 2243, ADS 1477, CCDM 02319+8915, HIP 11767.

Polaris (α UMi / α Ursae Minoris / Alpha Ursae Minoris, commonly North(ern) Star or Pole Star, or Dhruva Tara and sometimes Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole (42′ away as of 2006[citation needed]), making it the current northern pole star.

Polaris is about 430 light-years from Earth. It is a multiple star. α UMi A is a six solar mass[4] F7 bright giant (II) or supergiant (Ib). The two smaller companions are: α UMi B, a 1.5 solar mass[4] F3V main sequence star orbiting at a distance of 2400 AU, and α UMi Ab, a very close dwarf with an 18.5 AU radius orbit. There are also two distant components α UMi C and α UMi D.[5] Recent observations show that Polaris may be part of a loose open cluster of type A and F stars.

Polaris B can be seen even with a modest telescope and was first noticed by William Herschel in 1780. In 1929, it was discovered by examining the spectrum of Polaris A that it had another very close dwarf companion (variously α UMi P, α UMi a 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, directly showing all three members of the Polaris ternary system. The nearer dwarf star is in an orbit of only 18.5 AU (2.8 billion km;[6] about the distance from our Sun to Uranus) from Polaris A, explaining why its light is swamped by its close and much brighter companion.[7]

Polaris is a classic Population I Cepheid variable (although it was once thought to be Population II due to its high galactic latitude). Since Cepheids are an important standard candle for determining distance, Polaris (as the closest such star) is heavily studied. Around 1900, the star luminosity varied ±8% from its average (0.15 magnitudes in total) with a 3.97 day period; however the stars heat is a at a low level. Over the same period, the star has brightened by 15% (on average), and the period has lengthened by about 8 seconds each year.

Recent research reported in Science suggests that Polaris is 2.5 times brighter today than when Ptolemy observed it (now 2mag, antiquity 3mag). Astronomer Edward Guinan considers this to be a remarkable rate of 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."

Contents

Pole Star

An artist's concept of Polaris's system

Because in the current era[8] α UMi lies nearly in a direct line with the axis of the Earth's rotation "above" the North Pole — the north celestial pole — Polaris stands almost motionless on 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 antiquity of its use is attested by the fact that it is found represented on the earliest known Assyrian tablets.[citation needed] In more recent history it was referenced in Nathaniel Bowditch's 1802 book, The American Practical Navigator, where it is listed as one of the navigational stars.[9] At present, Polaris is 0.7° away from the pole of rotation (1.4 times the Moon disc) and hence revolves around the pole in a small circle 1½° in diameter. Only twice during every sidereal day does Polaris accurately define the true north azimuth; the rest of the time it is only an approximation and must be corrected using tables or a rough rule of thumb.

Due to the precession of the equinoxes, Polaris will not always be the pole star. Over tens of thousands of years, perturbations to the Earth's axis of rotation will cause it to point to other regions of the sky, tracing out a circle over 25,800 years.[8] Other stars along this circle would have served as the pole star in the past and will again in the future, including Beta Ursae Minoris from 1500 BC to 500 AD, Thuban around 2500 BC and Vega 12000 BC.[8]

Other names for Polaris

Polaris has numerous traditional names: Alruccabah, Cynosura, Phoenice, Tramontana, Angel Stern, Navigatoria, Star of Arcady, Yilduz, Mismar, Gwiazda Polarna, Polyarnaya. Cynosūra is from the Greek κυνόσουρα "the dog’s tail" and is the source of the English word "cynosure."[10] Yilduz is from the Turkish word for "star" (see Yildun).

Cultural significance

  • To the Bedouin people of the Negev and Sinai, Polaris is known as الجديّ al-jadiyy, "the billy goat". It and Suhail (= Canopus, α Car) are the two principal stars used for nomadic wandering at night. Because it was circumpolar and hence always visible from the Northern Hemisphere, it became associated with a steadfast nature, as opposed to Suhail, which disappears below the horizon and hence 'flees'.[11]
  • A monkey's head is the emblem of the Mayan god of the pole star.
  • In Finnish mythology, Polaris (Pohjantähti) was called Taivaanneula, (Heaven's Needle), indicating the pillar which supported the heavens above Earth.

See also

Notes

  1. ^ a b Wieland page 9: Table 5 gives mass of component A as 6.0 ±0.5 and P as 1.54 ±0.25 solar masses
  2. ^ "Polaris: Mass and Multiplicity". http://arxiv.org/abs/astro-ph/0609759. Retrieved 2009-04-13.  (URL for full PDF) (Evans et al support Wieland's prediction: "preliminary mass of 5.0 ± 1.5 M⊙ for the Cepheid and 1.38 ± 0.61 M⊙ for the close companion.)
  3. ^ Cayrel de Strobel, G.; Soubiran, C.; Ralite, N. (2001). " Catalogue of [Fe/H] determinations for FGK stars: 2001 edition ". A&A 373: 159–163. doi:10.1051/0004-6361:20010525. http://adsabs.harvard.edu/abs/2001A%26A...373..159C. 
  4. ^ a b Wieland page 3: masses of A and P ... (6.0+1.54M⊙)
  5. ^ Wieland page 2
  6. ^ There's More to the North Star Than Meets the Eye
  7. ^ Evans, N. R.; Schaefer, G.; Bond, H.; Bono, G.; Karovska, M.; Nelan, E.; Sasselov, D. (January 9, 2006). "Direct detection of the close companion of Polaris with the Hubble Space Telescope". American Astronomical Society 207th Meeting. http://www.aas.org/publications/baas/v37n4/aas207/1130.htm. 
  8. ^ a b c Norton, Arthur P. (1973). Norton's Star Atlas. Edinburgh: Sky Publishing. p. 10. ISBN 0-85248-900-5. "4500 years ago it was Thuban (α Draconis); 8000 years hence it will be Deneb" 
  9. ^ Nathaniel Bowditch: The American Practical Navigator, 2002 Bicentennial Ed., Chapter 15 Navigational Astronomy, page 248, Figure 1530a. Navigational stars and the planets
  10. ^ Wikisource-logo.svg "Cynosure". Encyclopædia Britannica (11th ed.). 1911. 
  11. ^ Bailey, Clinton (1974). (abstract) "Bedouin Star-Lore in Sinai and the Negev". Bulletin of the School of Oriental and African Studies, University of London 37 (3): 580–96. doi:10.1017/S0041977X00127491. http://links.jstor.org/sici?sici=0041-977X%281974%2937%3A3%3C580%3ABSISAT%3E2.0.CO%3B2-Q (abstract). Retrieved 2008-01-14. 
  12. ^ Smith, Robert W. (1943) The Last Days: Scriptural and Secular Prophecies Pertaining to the Last Days. Salt Lake City: Pyramid Press, p. 218
  13. ^ A 1987 Sunstone Magazine cartoon shows someone emerging from a flying saucer that has just landed proclaiming “We’re from the Ten Lost Tribes and we want to see Disney World!”

References

External links

Preceded by
Kochab & Pherkad
Pole Star
500–3000
Succeeded by
Alrai

Coordinates: Sky map 02h 31m 48.7s, +89° 15′ 51″

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Source material

Up to date as of January 22, 2010

From Wikisource

Polaris
by Howard Phillips Lovecraft
Written c. May 1918 (Published December 1920 in The Philosopher, 1, No. 1 , 3-5.)
Listen to this text, read by jpontoli (4.9MB, help | file info or download)

     Into the north window of my chamber glows the Pole Star with uncanny light. All through the long hellish hours of blackness it shines there. And in the autumn of the year, when the winds from the north curse and whine, and the red-leaved trees of the swamp mutter things to one another in the small hours of the morning under the horned waning moon, I sit by the easement and watch that star. Down from the heights reels the glittering Cassiopeia as the hours wear on, while Charles’ Wain lumbers up from behind the vapour-soaked swamp trees that sway in the night-wind. Just before dawn Arcturus winks ruddily from above the cemetery on the low hillock, and Coma Berenices shimmers weirdly afar off in the mysterious east; but still the Pole Star leers down from the same place in the black vault, winking hideously like an insane watching eye which strives to convey some strange message, yet recalls nothing save that it once had a message to convey. Sometimes, when it is cloudy, I can sleep.

     Well do I remember the night of the great Aurora, when over the swamp played the shocking coruscations of the daemon-light. After the beams came clouds, and then I slept.

     And it was under a horned waning moon that I saw the city for the first time. Still and somnolent did it lie, on a strange plateau in a hollow betwixt strange peaks. Of ghastly marble were its walls and its towers, its columns, domes, and pavements. In the marble streets were marble pillars, the upper parts of which were carven into the images of grave bearded men. The air was warm and stirred not. And overhead, scarce ten degrees from the zenith, glowed that watching Pole Star. Long did I gaze on the city, but the day came not. When the red Aldebaran, which blinked low in the sky but never set, had crawled a quarter of the way around the horizon, I saw light and motion in the houses and the streets. Forms strangely robed, but at once noble and familiar, walked abroad, and under the horned waning moon men talked wisdom in a tongue which I understood, though it was unlike any language I had ever known. And when the red Aldebaran had crawled more than half way around the horizon, there were again darkness and silence.

     When I awaked, I was not as I had been. Upon my memory was graven the vision of the city, and within my soul had arisen another and vaguer recollection, of whose nature I was not then certain. Thereafter, on the cloudy nights when I could sleep, I saw the city often; sometimes under that horned waning moon, and sometimes under the hot yellow rays of a sun which did not set, but which wheeled low around the horizon. And on the clear nights the Pole Star leered as never before.

     Gradually I came to wonder what might be my place in that city on the strange plateau betwixt strange peaks. At first content to view the scene as an all-observant uncorporeal presence, I now desired to define my relation to it, and to speak my mind amongst the grave men who conversed each day in the public squares. I said to myself, “This is no dream, for by what means can I prove the greater reality of that other life in the house of stone and brick south of the sinister swamp and the cemetery on the low hillock, where the Pole Star peers into my north window each night?”

     One night as I listened to the discourse in the large square containing many statues, I felt a change; and perceived that I had at last a bodily form. Nor was I a stranger in the streets of Olathoë, which lies on the plateau of Sarkis, betwixt the peaks Noton and Kadiphonek. It was my friend Alos who spoke, and his speech was one that pleased my soul, for it was the speech of a true man and patriot. That night had the news come of Daikos’ fall, and of the advance of the Inutos; squat, hellish, yellow fiends who five years ago appeared out of the unknown west to ravage the confines of our kingdom, and finally to besiege our towns. Having taken the fortified places at the foot of the mountains, their way now lay open to the plateau, unless every citizen could resist with the strength of ten men. For the squat creatures were mighty in the arts of war, and knew not the scruples of honour which held back our tall, grey-eyed men of Lomar from ruthless conquest.

     Alos, my friend, was commander of all the forces of the plateau, and in him lay the last hope of our country. On this occasion he spoke of the perils to be faced, and exhorted the men of Olathoë, bravest of the Lomarians, to sustain the traditions of their ancestors, who when forced to move southward from Zobna before the advance of the great ice-sheet (even as our descendants must some day flee from the land of Lomar), valiantly and victoriously swept aside the hairy, long-armed, cannibal Gnophkehs that stood in their way. To me Alos denied a warrior’s part, for I was feeble and given to strange faintings when subjected to stress and hardships. But my eyes were the keenest in the city, despite the long hours I gave each day to the study of the Pnakotic manuscripts and the wisdom of the Zobnarian Fathers; so my friend, desiring not to doom me to inaction, rewarded me with that duty which was second nothing in importance. To the watch-tower of Thapnen he sent me, there to serve as the eyes of our army. Should the Inutos attempt to gain the citadel by the narrow pass behind the peak Noton, and thereby surprise the garrison, I was to give the signal of fire which would warn the waiting soldiers and save the town from immediate disaster.

     Alone I mounted the tower, for every man of stout body was needed in the passes below. My brain was sore dazed with excitement and fatigue, for I had not slept in many days; yet was my purpose firm, for I loved my native land of Lomar, and the marble city of Olathoë that lies betwixt the peaks of Noton and Kadiphonek.

     But as I stood in the tower’s topmost chamber, I beheld the horned waning moon, red and sinister, quivering through the vapours that hovered over the distant valley of Banof. And through an opening in the roof glittered the pale Pole Star, fluttering as if alive, and leering like a fiend and tempter. Methought its spirit whispered evil counsel, soothing me to traitorous somnolence with a damnable rhythmical promise which it repeated over and over:

”Slumber, watcher, till the spheres
Six and twenty thousand years
Have revolv’d, and I return
To the spot where now I burn.
Other stars anon shall rise
To the axis of the skies;
Stars that soothe and stars that bless
With a sweet forgetfulness:
Only when my round is o’er
Shall the past disturb thy door.”

Vainly did I struggle with my drowsiness, seeking to connect these strange words with some lore of the skies which I had learnt from the Pnakotic manuscripts. My head, heavy and reeling, drooped to my breast, and when next I looked up it was in a dream; with the Pole Star grinning at me through a window from over the horrible swaying trees of a dream-swamp. And I am still dreaming.

     In my shame and despair I sometimes scream frantically, begging the dream-creatures around me to waken me ere the Inutos steal up the pass behind the peak Noton and take the citadel by surprise; but these creatures are daemons, for they laugh at me and tell me I am not dreaming. They mock me whilst I sleep, and whilst the squat yellow foe may be creeping silently upon us. I have failed in my duty and betrayed the marble city of Olathoë; I have proven false to Alos, my friend and commander. But still these shadows of my dream deride me. They say there is no land of Lomar, save in my nocturnal imaginings; that in those realms where the Pole Star shines high and red Aldebaran crawls low around the horizon, there has been naught save ice and snow for thousands of years, and never a man save squat yellow creatures, blighted by the cold, whom they call “Esquimaux”.

     And as I writhe in my guilty agony, frantic to save the city whose peril every moment grows, and vainly striving to shake off this unnatural dream of a house of stone and brick south of a sinister swamp and a cemetery on a low hillock; the Pole Star, even and monstrous, leers down from the black vault, winking hideously like an insane watching eye which strives to convey some strange message, yet recalls nothing save that it once had a message to convey.

PD-icon.svg This work is in the public domain in the United States because it was published before January 1, 1923. It may be copyrighted outside the U.S. (see Help:Public domain). Flag of the United States.svg

Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also polaris

Contents

English

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Wikipedia

Etymology

From Latin Stella polaris, "pole star"

Pronunciation

  • IPA: /pɔʊˈlɑrɪs/

Proper noun

Singular
Polaris

Plural
-

Polaris

  1. (astronomy) The pole star, a trinary star in the constellation Ursa Minor that currently lies close to the north celestial pole; Alpha (α) Ursae Minoris
  2. A type of U.S. ballistic missile, capable of carrying a nuclear warhead and designed to be launched from a submarine.

Translations

Synonyms


Gaming

Up to date as of February 01, 2010

From Wikia Gaming, your source for walkthroughs, games, guides, and more!

Polaris

Developer(s) Taito
Publisher(s) Tigervision
Release date Atari 2600:
1981 (NA)
Genre Fixed Shooter Shoot 'em up
Mode(s) Single player
1-2 players alternating
Age rating(s) N/A
Atari 2600
Platform(s) Atari 2600
Input Atari 2600 Joystick
Credits | Soundtrack | Codes | Walkthrough



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