Pole star

A pole star or polar star is a star, preferably bright, closely aligned to the axis of rotation of an astronomical object.

Currently, Earth's pole stars are Polaris (Alpha Ursae Minoris), a magnitude 2 star aligned approximately with its northern axis, and a pre-eminent star in celestial navigation, and Polaris Australis (Sigma Octantis), a much dimmer star. A couple thousand years ago, Kochab and Pherkad were twin northern pole stars, though neither was as close to the pole as Polaris is now.

Sterneamwalberla2
A long exposure (45 min.) photo of Polaris and neighbouring stars, taken at Ehrenbürg (Franconia), 2001.

History

Precession N
The path of the north celestial pole amongst the stars due to the effect of precession, with dates shown
Precession S
The path of the south Celestial pole amongst the stars due to the effect of precession

In classical antiquity, Beta Ursae Minoris (Kochab) was closer to the celestial north pole than Alpha Ursae Minoris. While there was no naked-eye star close to the pole, the midpoint between Alpha and Beta Ursae Minoris was reasonably close to the pole, and it appears that the entire constellation of Ursa Minor, in antiquity known as Cynosura (Greek Κυνοσούρα "dog's tail") was used as indicating the northern direction for the purposes of navigation by the Phoenicians.[1] The ancient name of Ursa Minor, anglicized as cynosure, has since itself become a term for "guiding principle" after the constellation's use in navigation.

Alpha Ursae Minoris (Polaris) was described as ἀειφανής "always visible" by Stobaeus in the 5th century, when it was still removed from the celestial pole by about 8°. It was known as scip-steorra ("ship-star") in 10th-century Anglo-Saxon England, reflecting its use in navigation. In the Hindu Puranas, it is personified under the name Dhruva ("immovable, fixed").

In the medieval period, Polaris was also known as stella maris "star of the sea" (from its use for navigation at sea), as in e.g. Bartholomeus Anglicus (d. 1272), in the translation of John Trevisa (1397):

"by the place of this sterre place and stedes and boundes of the other sterres and of cercles of heven ben knowen: therefore astronomers beholde mooste this sterre. Then this ster is dyscryved of the moste shorte cercle; for he is ferre from the place that we ben in; he hydeth the hugenesse of his quantite for unmevablenes of his place, and he doth cerfifie men moste certenly, that beholde and take hede therof; and therfore he is called stella maris, the sterre of the see, for he ledeth in the see men that saylle and have shyppemannes crafte."[2]

Polaris was associated with Marian veneration from an early time, Our Lady, Star of the Sea being a title of the Blessed Virgin. This tradition goes back to a misreading of Saint Jerome's translation of Eusebius' Onomasticon, De nominibus hebraicis (written ca. 390). Jerome gave stilla maris "drop of the sea" as a (false) Hebrew etymology of the name Maria. This stilla maris was later misread as stella maris; the misreading is also found in the manuscript tradition of Isidore's Etymologiae (7th century);[3] it probably arises in the Carolingian era; a late 9th-century manuscript of Jerome's text still has stilla, not stella,[4] but Paschasius Radbertus, also writing in the 9th century, makes an explicit reference to the "Star of the Sea" metaphor, saying that Mary is the "Star of the Sea" to be followed on the way to Christ, "lest we capsize amid the storm-tossed waves of the sea."[5]

The name stella polaris was coined in the Renaissance, even though at that time it was well recognized that it was several degrees away from the celestial pole; Gemma Frisius in the year 1547 determined this distance as 3°7'.[6] An explicit identification of Mary as stella maris with the North Star (Polaris) becomes 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.

Precession of the equinoxes

Earth precession
Precession of Earth's rotational axis

As of October 2012, Polaris had the declination +89°19′8″ (at epoch J2000 it was +89°15′51.2″). Therefore, it always appears due north in the sky to a precision better than one degree, and the angle it makes with respect to the true horizon (after correcting for refraction and other factors) is equal to the latitude of the observer to better than one degree. The celestial pole will be nearest Polaris in 2100 and will thereafter become more distant.[7][8]

Due to the precession of the equinoxes (as well as the stars' proper motions), the role of North Star has passed (and will pass) from one star to another in the remote past (and in the remote future). In 3000 BC, the faint star Thuban in the constellation Draco was the North Star, aligning within 0.1° distance from the celestial pole, the closest of any of the visible pole stars.[9][10] However, at magnitude 3.67 (fourth magnitude) it is only one-fifth as bright as Polaris, and today it is invisible in light-polluted urban skies.

During the 1st millennium BC, Beta Ursae Minoris ("Kochab") was the bright star closest to the celestial pole, but it was never close enough to be taken as marking the pole, and the Greek navigator Pytheas in ca. 320 BC described the celestial pole as devoid of stars.[7][11] In the Roman era, the celestial pole was about equally distant between Polaris and Kochab.

The precession of the equinoxes takes about 25,770 years to complete a cycle. Polaris' mean position (taking account of precession and proper motion) will reach a maximum declination of +89°32'23", which translates to 1657" (or 0.4603°) from the celestial north pole, in February 2102. Its maximum apparent declination (taking account of nutation and aberration) will be +89°32'50.62", which is 1629" (or 0.4526°) from the celestial north pole, on 24 March 2100.[8]

Precession will next point the north celestial pole at stars in the northern constellation Cepheus. The pole will drift to space equidistant between Polaris and Gamma Cephei ("Errai") by 3000 AD, with Errai reaching its closest alignment with the northern celestial pole around 4200 AD.[12][13] Iota Cephei and Beta Cephei will stand on either side of the northern celestial pole some time around 5200 AD, before moving to closer alignment with the brighter star Alpha Cephei ("Alderamin") around 7500 AD.[12][14]

Precession will then point the north celestial pole at stars in the northern constellation Cygnus. Like Beta Ursae Minoris during the 1st millennium BC, the bright star closest to the celestial pole in the 10th millennium AD, first-magnitude Deneb, will be a distant 7° from the pole, never close enough to be taken as marking the pole,[9] while third-magnitude Delta Cygni will be a more helpful pole star, at a distance of 3° from celestial north, around 11,500 AD.[12] Precession will then point the north celestial pole nearer the constellation Lyra, where the second brightest star in the northern celestial hemisphere, Vega, will be a pole star around 13,700 AD, though at a distance of 5° from celestial north.[12]

Precession will eventually point the north celestial pole nearer the stars in the constellation Hercules, pointing towards Tau Herculis around 18,400 AD.[15] The celestial pole will then return to the stars in constellation Draco (Thuban, mentioned above) before returning to the current constellation, Ursa Minor. When Polaris becomes the North Star again around 27,800 AD, due to its proper motion it then will be farther away from the pole than it is now, while in 23,600 BC it was closer to the pole.

Over the course of Earth's 26,000-year axial precession cycle, a series of bright naked eye stars (an apparent magnitude up to +6; a full moon is −12.9) in the northern hemisphere will hold the transitory title of North Star.[12] While other stars might line up with the north celestial pole during the 26,000 year cycle, they do not necessarily meet the naked eye limit needed to serve as a useful indicator of north to an Earth-based observer, resulting in periods of time during the cycle when there is no clearly defined North Star. There will also be periods during the cycle when bright stars give only an approximate guide to "north", as they may be greater than 5° of angular diameter removed from direct alignment with the north celestial pole.[13]

The 26,000 year cycle of North Stars, starting with the current star, with stars that will be "near-north" indicators when no North Star exists during the cycle, including each star's average brightness and closest alignment to the north celestial pole during the cycle:[7][8][9][10][12][13][14][15]

Bayer Traditional V Constellation Alignment notes
Alpha Ursae Minoris Polaris 1.98 Ursa Minor within 0.5° current North Star
Gamma Cephei Errai 3.21 Cepheus within 3° binary star system
Iota Cephei 3.51 Cepheus within 5° shares timing with Beta Cephei
Beta Cephei Alfirk 3.51 Cepheus within 5° shares timing with Iota Cephei
Alpha Cephei Alderamin 2.51 Cepheus within 3°
Alpha Cygni Deneb 1.25 Cygnus within 7° a near-north star
Delta Cygni Fawaris 2.87 Cygnus within 3°
Alpha Lyrae Vega 0.026 Lyra within 5° brightest North Star
Iota Herculis 3.75 Hercules within 4°
Tau Herculis 3.89 Hercules within 1°
Iota Draconis Edasich 3.29 Draco within 5°
Alpha Draconis Thuban 3.65 Draco within 0.2° closest to celestial pole when North Star
Kappa Draconis 3.82 Draco within 6° a near-north star, shares timing with Kochab
Beta Ursae Minoris Kochab 2.08 Ursa Minor within 7° a near-north star, shares timing with κ Draconis

Southern pole star (South Star)

Series of shots showing the rotation of the Earth's axis relative to the south celestial pole. The Magellanic Clouds and Southern Cross are clearly visible. Near the end of the video, the rise of the moon illuminates the scene.

Currently, there is no South Star as useful as Polaris. Sigma Octantis is the closest naked-eye star to the south Celestial pole, but at apparent magnitude 5.45 it is barely visible on a clear night, making it unusable for navigational purposes.[16] It is a yellow giant 275 light years from Earth. Its angular separation from the pole is about 1° (as of 2000). The Southern Cross constellation functions as an approximate southern pole constellation, by pointing to where a southern pole star would be.

At the equator, it is possible to see both Polaris and the Southern Cross.[17][18] The Celestial south pole is moving toward the Southern Cross, which has pointed to the south pole for the last 2000 years or so. As a consequence, the constellation is no longer visible from subtropical northern latitudes, as it was in the time of the ancient Greeks.

Around 200 BC, the star Beta Hydri was the nearest bright star to the Celestial south pole. Around 2800 BC, Achernar was only 8 degrees from the south pole.

In the next 7500 years, the south Celestial pole will pass close to the stars Gamma Chamaeleontis (4200 AD), I Carinae, Omega Carinae (5800 AD), Upsilon Carinae, Iota Carinae (Aspidiske, 8100 AD) and Delta Velorum (Alsephina, 9200 AD).[19] From the eightieth to the ninetieth centuries, the south Celestial pole will travel through the False Cross. Around 14,000 AD, when Vega is only 4° from the North Pole, Canopus will be only 8° from the South Pole and thus circumpolar on the latitude of Bali (8°S).[20]

Sirius will take its turn as the South Pole Star in the year 66,270 AD. In fact, Sirius will come to within 1.6 degree of the south celestial pole in 66,270 AD. Later, in the year 93,830 AD, Sirius will miss aligning with the south celestial pole by only 2.3 degrees.[21]

Other planets

Pole stars of other planets are defined analogously: they are stars (brighter than 6th magnitude, i.e., visible to the naked eye under ideal conditions) that most closely coincide with the projection of the planet's axis of rotation onto the Celestial sphere. Different planets have different pole stars because their axes are oriented differently. (See Poles of astronomical bodies.)

See also

References

  1. ^ implied by Johannes Kepler (cynosurae septem stellas consideravit quibus cursum navigationis dirigebant Phoenices): "Notae ad Scaligeri Diatribam de Aequinoctiis" in Kepleri Opera Omnia ed. Ch. Frisch, vol. 8.1 (1870) p. 290
  2. ^ cited after J. O. Halliwell, (ed.), The Works of William Shakespeare vol. 5 (1856), p. 40.]
  3. ^ Conversations-Lexicon Für Bildende Kunst vol. 7 (1857), 141f.
  4. ^ A. Maas,"The Name of Mary", The Catholic Encyclopedia (1912)
  5. ^ stella maris, sive illuminatrix Maria, inter fluctivagas undas pelagi, fide ac moribus sequenda est, ne mergamur undis diluvii PL vol. 120, p. 94.
  6. ^ Gemmae Frisii de astrolabo catholico liber: quo latissime patentis instrumenti multiplex usus explicatur, & quicquid uspiam rerum mathematicarum tradi possit continetur, Steelsius (1556), p. 20
  7. ^ a b c Ridpath, Ian (1988). "Chapter Three: The celestial eighty-eight – Ursa Minor". Star Tales. Cambridge: The Lutterworth Press. ISBN 978-0-7188-2695-6. ...in the early 16th century ... Polaris was still around three and a half degrees from the celestial pole ...will reach its closest to the north celestial pole around AD 2100, when the separation will be less than half a degree
  8. ^ a b c Jean Meeus, Mathematical Astronomy Morsels Ch. 50; Willmann-Bell 1997
  9. ^ a b c Ridpath, Ian, ed. (2004). Norton's Star Atlas. New York: Pearson Education. p. 5. ISBN 0-13-145164-2. 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°
  10. ^ a b Moore, Patrick (2005). The Observer's Year: 366 Nights in the Universe. p. 283.
  11. ^ Kaler, James B., "KOCHAB (Beta Ursae Minoris)", Stars, University of Illinois, retrieved 2018-04-28
  12. ^ a b c d e f Our Monthly, 4, Presbyterian Magazine Company, 1871, p. 53.
  13. ^ a b c McClure, Bruce; Deborah, Byrd (2017-09-29). "Gamma Cephei: A future Pole Star". EarthSky. Retrieved 2018-04-25.
  14. ^ a b Kaler, James B., "ALDERAMIN (Alpha Cephei)", Stars, University of Illinois, retrieved 2018-04-28
  15. ^ a b Kaler, James B., "TAU HER (Tau Herculis)", Stars, University of Illinois, retrieved 2018-04-27
  16. ^ "Sigma Octantis". Jumk.De. 6 August 2013.
  17. ^ "The North Star: Polaris". Space.com. May 7, 2012. Retrieved 6 August 2013.
  18. ^ Hobbs, Trace (May 21, 2013). "Night Sky Near the Equator". Wordpress. Retrieved 6 August 2013.
  19. ^ "Precession". moonkmft.co.uk. Retrieved 24 September 2018.
  20. ^ Kieron Taylor (1 March 1994). "Precession". Sheffield Astronomical Society. Retrieved 2018-09-24.
  21. ^ Bruce McClure. "Sirius, future South Pole Star". EarthSky. Retrieved 2018-01-03.
  22. ^ 2004. Starry Night Pro, Version 5.8.4. Imaginova. ISBN 978-0-07-333666-4. www.starrynight.com
  23. ^ Archinal, Brent A.; A'Hearn, Michael F.; Bowell, Edward G.; Conrad, Albert R.; Consolmagno, Guy J.; et al. (2010). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009" (PDF). Celestial Mechanics and Dynamical Astronomy. 109 (2): 101–135. Bibcode:2011CeMDA.109..101A. doi:10.1007/s10569-010-9320-4.
  24. ^ note: due to axial precession, the lunar pole describes a small circle on the celestial sphere every 18.6 years. Patrick Moore (1983), The Guinness Book of Astronomy Facts & Feats, p. 29, In 1968 the north pole star of the Moon was Omega Draconis; by 1977 it was 36 Draconis. The south pole star is Delta Doradus.
  25. ^ http://www.eknent.com/etc/mars_np.png

External links

van Leeuwen, F. (2007). "HIP 11767". Hipparcos, the New Reduction. Retrieved 2011-03-01.

Alpha Cephei

Alpha Cephei (α Cephei, abbreviated Alpha Cep, α Cep), officially named Alderamin , is a second magnitude star in the constellation of Cepheus near the northern pole. The star is relatively close to Earth at 49 light years (ly).

Beta Ursae Minoris

Beta Ursae Minoris (β Ursae Minoris, abbreviated Beta UMi, β UMi), formally named Kochab , is the brightest star in the bowl of the Little Dipper asterism (which is part of the constellation of Ursa Minor), 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 (40.1 parsecs).Amateur astronomers can use Kochab as a very precise guide for setting up a telescope, as the celestial north pole is located 43 arcminutes away from Polaris, very close to the line connecting Polaris with Kochab.

Big Dipper

The Big Dipper (US, Canada) or the Plough (UK, Ireland) is a large asterism consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez (δ), of third magnitude. Four define a "bowl" or "body" and three define a "handle" or "head". It is recognized as a distinct grouping in many cultures.

The North Star (Polaris), the current northern pole star and the tip of the handle of the Little Dipper (Little Bear), can be located by extending an imaginary line through the front two stars of the asterism, Merak (β) and Dubhe (α). This makes it useful in celestial navigation.

Delta Cygni

Delta Cygni (δ Cygni, abbreviated Delta Cyg, δ Cyg) is a binary star of a combined third-magnitude in the constellation of Cygnus. It is also part of the Northern Cross asterism whose brightest star is Deneb. Based upon parallax measurements obtained during the Hipparcos mission, Delta Cygni is located roughly 165 light-years (51 parsecs) distant from the Sun.Delta Cygni's two components are designated Delta Cygni A (officially named Fawaris ) and B. More widely separated is a faint third component, a 12th magnitude star that is moving along with the others. Together they form a triple star system.

Delta Doradus

δ Doradus (often Latinised to Delta Doradus, abbreviated to δ Dor or delta Dor) 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.This is an A-type main sequence star with a stellar classification of A7 V. The star is spinning rapidly with a projected rotational velocity of 172 km/s. This is giving the star an oblate shape with an equatorial bulge that is 12% larger than the polar radius. Although A-type stars are not expected to harbor a magnetic dynamo needed to power X-ray emission, an X-ray flux of 3.6×1027 erg/s has been detected at these coordinates. This may indicate that the star has an unseen companion. δ Doradus displays an infrared excess suggesting it may be a Vega-like star with an orbiting debris disk.Currently this star is the Moon's south pole star, which occurs once every 18.6 years. The pole star status changes periodically, because of the precession of the Moon's rotational axis. When δ Doradus is the pole star, it is better aligned than Earth's Polaris (α Ursae Minoris), but much fainter. It is also the south pole star of Jupiter.

Delta Octantis

δ Octantis, Latinised as Delta Octantis, has the distinction of being Saturn's southern pole star. An orange giant of class K2III, it has 1.2 times the mass of the Sun and about 25 times the Sun's radius. This star is about 4.3 billion years old, which is similar to the age of the Sun.

Deneb

Deneb is a first-magnitude star in the constellation of Cygnus, the swan. Deneb is one of the vertices of the asterism known as the Summer Triangle and the "head" of the Northern Cross. It is the brightest star in Cygnus and the 19th brightest star in the night sky, with an average apparent magnitude of 1.25. A blue-white supergiant, Deneb rivals Rigel as the most luminous first magnitude star. However its distance, and hence luminosity, is poorly known; its luminosity is somewhere between 55,000 and 196,000 times that of the Sun. Its Bayer designation is α Cygni which is Latinised to Alpha Cygni, abbreviated to Alpha Cyg or α Cyg.

Dhruva reactor

The Dhruva reactor is India's largest nuclear research reactor. Located in the Mumbai (Bombay) suburb of Trombay at the Bhabha Atomic Research Centre (BARC), it is India's primary generator of weapons-grade plutonium-bearing spent fuel for its nuclear weapons program. Originally named the R-5, this pool-type reactor first went critical on 8 August 1985 after 10 years of construction. However, the unit did not attain full power until 1988. The reactor experienced at least one serious accident when 4MT (four metric tons) of heavy water overflowed from the reactor core in 1985 following vibration problems.Designed as a larger version of the CIRUS reactor, Dhruva was an Indian designed project built to provide an independent source of weapons-grade plutonium free from safeguards. The Dhruva project cost 950 million rupees. The reactor uses heavy water (deuterium) as a moderator and coolant. Aluminum clad fuel rods containing natural uranium are used to obtain a maximum power output of 100MW. According to conservative estimates, the reactor produces an average of 16–26 kilograms (35–57 lb) of weapons-grade plutonium per year in its spent fuel, while former Indian Atomic Energy Commission (AEC) Chairman P.K. Iyengar said the unit could produce up to 30 kilograms (66 lb) of weapons-grade plutonium each year.

Dhruva, in Indian mythology, is a prince blessed to eternal existence and glory as the Pole Star (Dhruva Nakshatra in Sanskrit) by Lord Vishnu. It can also mean simply the Pole Star or 'ultimate' in Sanskrit.

Egyptian astronomy

Egyptian astronomy begins in prehistoric times, in the Predynastic Period. In the 5th millennium BCE, the stone circles at Nabta Playa may have made use of astronomical alignments. By the time the historical Dynastic Period began in the 3rd millennium BCE, the 365-day period of the Egyptian calendar was already in use, and the observation of stars was important in determining the annual flooding of the Nile.

The Egyptian pyramids were carefully aligned towards the pole star, and the temple of Amun-Re at Karnak was aligned on the rising of the midwinter Sun. Astronomy played a considerable part in fixing the dates of religious festivals and determining the hours of night, and temple astrologers were especially adept at watching the stars and observing the conjunctions and risings of the Sun, Moon, and planets, as well as the lunar phases.

In Ptolemaic Egypt, the Egyptian tradition merged with Greek astronomy and Babylonian astronomy, with the city of Alexandria in Lower Egypt becoming the centre of scientific activity across the Hellenistic world. Roman Egypt produced the greatest astronomer of the era, Ptolemy (90–168 CE). His works on astronomy, including the Almagest, became the most influential books in the history of Western astronomy. Following the Muslim conquest of Egypt, the region came to be dominated by Arabic culture and Islamic astronomy.

The astronomer Ibn Yunus (c. 950–1009) observed the Sun's position for many years using a large astrolabe, and his observations on eclipses were still used centuries later. In 1006, Ali ibn Ridwan observed the SN 1006, a supernova regarded as the brightest stellar event in recorded history, and left the most detailed description of it. In the 14th century, Najm al-Din al-Misri wrote a treatise describing over 100 different types of scientific and astronomical instruments, many of which he invented himself.

FT PGB

FT PGB is an abbreviation for a family of Chinese built precision guided munitions named To-Fly Precision Guided Bomb (Fei-Teng Jing-Que Zhi-Dao Zha-Dan, 飞腾精确制导炸弹), developed by China Academy of Launch Vehicle Technology (CALT), a subsidiary of China Aerospace Science and Technology Corporation (CASC).

FT PGB is actually an upgrade kit to modernize gravity bombs with precision guidance. The kit consists of two modules, the inertial guidance module and the satellite guidance module. The primary guidance system is the satellite guidance module, a technology reportedly to be reverse engineered from unexploded Joint Direct Attack Munition (JDAM) ordnance in the NATO bombing of the People's Republic of China embassy in Belgrade, according to many Chinese military enthusiasts. A variety of satellite guidance can be used, such as GPS and GLONASS, as well as Chinese system Beidou navigation system, which will be usable in Asia-Pacific region in 2012. When satellite guidance is not available, the inertial guidance system is used, though the two systems are generally used together, complimenting each other.Chinese media have shown photographs of FT PGB being dropped from helicopters such as Chinese Naval Ka-28, in addition to the fixed winged platforms. FT series PGB is also used as a component for a subfamily of another Chinese PGM, LS PGB, a family of gliding precision guided bomb. FT series PGB was first revealed to public at the 7th Zhuhai Airshow held in November 2006 with two models of the family FT-1 and FT-3, and the family of this weapon is built to Chinese GJV289A standard, the Chinese equivalent of MIL-STD-1553B. The adaptation of such military standard means that the weapon can be readily deployed on any western platforms.There are 10 bombs in the FT family:

FT-1: satellite guided 500 kg / 1000 lb bombs

FT-2: satellite guided 500 kg / 1000 lb glide bombs

FT-3: satellite guided 250 kg / 500 lb bombs

FT-4: satellite guided 250 kg / 500 lb bombs with planar wing kit

FT-5: small diameter 100 kg bombs

FT-6: satellited guided 250 kg / 500 lb bombs with planar wing kit

FT-7: small 130 kg bomb with planar wing

FT-9: small 50 kg weapon for drones

FT-10: small 25 kg weapon

FT-12: large 500 kg glide bomb unit. A rocket booster can be attached to extend its range to 150 km, provided a release velocity of 600–1000 km/h.

TD500-ER: At the 9th Zhuhai Airshow held in November 2012, it was revealed that a family of satellite guided bombs (SGB) utilizing FT PGB upgrade kit was designated as Tiangang (or Tian Gang, 天罡 in Chinese, which is the ancient Chinese name for Pole star). Produced by the subsidiary of Norinco, the Harbin Jiancheng Group (哈尔滨建成集团有限公司), Polar star 500 was shown to the public at the airshow, named after 500 kg gravity bomb used. However, the developer confirmed that gravity bombs of other different sizes are available upon customer's requests. The marketing of Pole star series SGBs suggests that the FT PGB upgrade conversion kit, as well as the bombs armed with such conversion upgrade kits, the Pole star series, are both available for export.Pole star series SGB have rather unusual Pinyin abbreviation as TD, because when its Chinese name, Tian Gang is Romanized, the abbreviation is TG, which is the same as the abbreviation of another Chinese precision guided bomb (PGB), Tian Ge (or Tiange, 天戈 in Chinese, the ancient Chinese name for Boötes), which is a laser guided PGB developed by the same company reveal at the same airshow. Since the Pinyin abbreviation TG is already taken by Boötes (Tian Ge) series PGB, Pole star (Tian Gang) series PGB is named as TD series instead. The ER suffix is the English abbreviation for Extended Range, because the bomb also incorporates the gliding components of LS PGB to increase its range so that it can be launched further away from targets.

Finnish neopaganism

Finnish Neopaganism, or the Finnish native faith (Finnish: Suomenusko: "Finnish Religion") is the contemporary Neopagan revival of Finnish paganism, the pre-Christian polytheistic ethnic religion of the Finns. A precursor movement was the Ukonusko ("Ukko's Faith", revolving around the god Ukko) of the early 20th century. The main problem in the revival of Finnish paganism is the nature of pre-Christian Finnish culture, which relied on oral tradition and of which very little is left. The primary sources concerning Finnish native culture are written by latter-era Christians.

There are two main organisations of the religion, the "Association of Finnish Native Religion" (Suomalaisen kansanuskon yhdistys ry) based in Helsinki and officially registered since 2002, and the "Pole Star Association" (Taivaannaula ry) headquartered in Turku with branches in many cities, founded and officially registered in 2007. The Association of Finnish Native Religion also caters to Karelians and is a member of the Uralic Communion.

Iota Herculis

Iota Herculis (ι Herculis, ι Her) is a fourth-magnitude variable star system in the constellation Hercules, consisting of at least four stars all about 139 parsecs (450 ly) away. The brightest is a β Cephei variable, a pulsating star.

Octans

Octans is a faint constellation located in the deep southern sky. Its name is Latin for the eighth part of a circle, but it is named after the octant, a navigational instrument. The constellation was devised by French astronomer Nicolas Louis de Lacaille in 1752, and it remains one of the 88 modern constellations.

Order of the Polar Star

The Order of the Polar Star (Swedish: Nordstjärneorden) is a Swedish order of chivalry created by King Frederick I on 23 February 1748, together with the Order of the Sword and the Order of the Seraphim.

The Order of the Polar Star was until 1975 intended as a reward for Swedish and foreign "civic merits, for devotion to duty, for science, literary, learned and useful works and for new and beneficial institutions".

Its motto is, as seen on the blue enameled centre of the badge, Nescit Occasum, a Latin phrase meaning "It knows no decline". This is to represent that Sweden is as constant as a never setting star. The Order's colour is black. This was chosen so that when wearing the black sash, the white, blue and golden cross would stand out and shine as the light of enlightenment from the black surface. The choice of black for the Order's ribbon may also have been inspired by the black ribbon of the French Order of St. Michael, which at the time the Order of the Polar Star was instituted was also awarded to meritorious civil servants. At present, the ribbon of the Order is blue with yellow stripes near the edges (i.e., the national colors, but the reverse of the Order of the Sword's yellow tibbon with blue stripes near the edges). Women and clergy men are not called knight or commander but simply as Member (Ledamot).

After the reorganization of the orders in 1975 the order is only awarded to foreigners and members of the royal family. It is often awarded to foreign office holders (such as prime and senior ministers) during Swedish state visits. It is also awarded to junior members of royal families who would not qualify for the more prestigious Royal Order of the Seraphim.

Polaris

Polaris , designated α Ursae Minoris (Alpha Ursae Minoris, abbreviated Alpha UMi, α UMi), commonly the North Star or Pole Star, is the brightest star in the constellation of 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 other methods derive distances around 30% closer.

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). 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.

Polaris (short story)

"Polaris" is a fantasy short story by American author H. P. Lovecraft, written in 1918 and first published in the December 1920 issue of the amateur journal The Philosopher. It is the story that introduces Lovecraft's fictional Pnakotic Manuscripts, the first of his arcane tomes.In the story, an unnamed narrator describes his nightly obsession with the Pole star, and his recurring dreams of a city under siege. The narrator struggles with determining whether his reality is real, or if his dream is the true reality. Critics have noted autobiographical elements in the story, and have connected it with Lovecraft's experiences of uselessness during World War I.

Sigma Octantis

Sigma Octantis (σ Octantis, abbreviated Sig Oct, σ Oct), officially named Polaris Australis , is the current South Star. Its position near the southern celestial pole makes it the southern hemisphere's pole star. This is a solitary star in the southern circumpolar constellation of Octans. Located approximately 281 light-years from Earth, it is classified as a giant star with a spectral type of F0 III. Sigma Octantis is a Delta Scuti variable, with its average magnitude of 5.47 varying by about 0.03 magnitudes every 2.33 hours.

Tau Herculis

Tau Herculis, Latinized from τ Herculis, is a fourth-magnitude star in the constellation Hercules. It is a blue subgiant star, seven hundred times more luminous than the Sun.

Thuban

Thuban , designation Alpha Draconis (α Draconis, abbreviated Alpha Dra, α Dra), is a star (or star system) in the constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star from the 4th to 2nd millennium BC.

Even though Johann Bayer gave Thuban the designation Alpha, its apparent magnitude of 3.65 means it is 3.7 times fainter than the brightest star in the constellation, Gamma Draconis (Eltanin), whose apparent magnitude is 2.24.

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