Thuban

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Thuban

Th'uban also appears as an enemy in the video game Final Fantasy X
Final Fantasy X

is a console role-playing game developed and published by Square Co. as the tenth installment in the Final Fantasy series. It was released in 2001 for Sony Computer Entertainment's PlayStation 2....
.

Thuban (a Dra / a Draconis / Alpha

Alpha (letter)

Alpha is the first letter of the Greek alphabet. In the system of Greek numerals it has a value of 1. It was derived from the Phoenician alphabet Aleph ....
Draconis) is a star

Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
(or star system) in the constellation

Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
of Draco

Draco (constellation)

Draco is a constellation in the far northern sky. Its name is Latin for dragon. Draco is circumpolar star for many observers in the northern hemisphere....
. A relatively inconspicuous star in the night sky of the Northern Hemisphere

Northern Hemisphere

The Northern Hemisphere is the half of a planet that is north of the equator?the word sphere literally means 'half sphere'. It is also that half of the celestial sphere north of the celestial equator....
, it is historically significant as having been the north pole star

Pole star

A pole star is a visible star, especially a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent position is close to one of the celestial poles, and which lies directly overhead when viewed from the Earth's North Pole or South Pole....
in ancient times.

Even though Thuban carries the Bayer designation

Bayer designation

A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, followed by the genitive case form of its parent constellation's Latin language name....
Alpha Draconis, at apparent magnitude

Apparent magnitude

The apparent magnitude of a celestial body is a measurement of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the Earth's atmosphere....
3.65 it is over a magnitude fainter than the brightest star in the constellation, Gamma Draconis

Gamma Draconis

Gamma Draconis is a star in the constellation Draco . It has the traditional name Eltanin .Eltanin is an orange Giant star of stellar classification K5, lying 148 light years away....
(Etamin), whose apparent magnitude is 2.23.

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Encyclopedia

Thuban (a Dra / a Draconis / Alpha

Alpha (letter)

Alpha is the first letter of the Greek alphabet. In the system of Greek numerals it has a value of 1. It was derived from the Phoenician alphabet Aleph ....
Draconis) is a star

Star

Constellation

Draco (constellation)

Northern Hemisphere

Pole star

Bayer designation

Apparent magnitude

Gamma Draconis

Light pollution

Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light. The International Dark-Sky Association , "The Light Pollution Authority," defines light pollution as: It obscures the stars in the night sky for city dwellers, interferes with astronomy observatory, and, like an...
areas.

Given good viewing conditions, Thuban is relatively easy to spot in the night sky, due to its location in relation to the Big Dipper

Big Dipper

The seven brightest stars of the constellation Ursa Major, the Great Bear, form a well-known asterism that has been recognized as a distinct grouping in many cultures from time immemorial....
asterism

Asterism (astronomy)

In astronomy, an asterism is a pattern of stars seen in Earth's sky which is not an official constellation. Like constellations, they are composed of stars which, while they are in the same general direction, are not physically related, often being at significantly different distances from Earth....
of Ursa Major

Ursa Major

Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. It is dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a useful pointer toward north, and which has mythological significance in numerous world cultures....
. While it is well known that the two outer stars of the 'dipper' point to the modern-day pole star

Pole star

Polaris

Polaris is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole , making it the current northern pole star....
, it is less well known that the two inner stars, Phecda

Gamma Ursae Majoris

Gamma Ursae Majoris is a star in the constellation Ursa Major. It also has the traditional names Phecda, Phekda or Phad and comes from the Arabic word ??? fakhdh [fax?], "thigh" ....
and Megrez

Delta Ursae Majoris

Delta Ursae Majoris is a star in the constellation Ursa Major. It also has the traditional name Megrez .Megrez has an apparent magnitude of +3.32 making it the dimmest of the seven stars in the Big Dipper....
, point to Thuban, just seven and a half degrees of arc from Megrez.

Use as pole star

Due to the precession of Earth

Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
's rotational axis, Thuban was the naked-eye star closest to the north pole

North Pole

The North Pole, also known as the Geographic North Pole or Terrestrial North Pole is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets the Earth's surface....
from 3942 BC, when it moved farther north than Theta Boötis

Theta Boötis

Theta Bo?tis is a star in the constellation Bo?tes. It also has the traditional name Asellus Primus and the Flamsteed designation 23 Bo?tis....
, until 1793 BC, when it was superseded by Kappa Draconis

Kappa Draconis

Kappa Draconis is a blue giant star located in the constellation Draco . Its rarely used traditional name Ketu , meaning the Dragon's Tail, refers to the south lunar node according to the Jyotisha lunar cycle....
. It was closest to the pole in 2787 BC, when it was less than two and a half arc-minutes away from the pole. It remained within one degree of true north for nearly 200 years afterwards, and even 900 years after its closest approach, was just five degrees off the pole. Thuban was considered the pole star until about 1900 BC, when the much brighter Kochab

Beta Ursae Minoris

Beta Ursae Minoris is the second brightest star in the bowl of the "Little Dipper,"the constellation Ursa Minor. It also has the traditional name Kochab....
began to approach the pole as well.

Having gradually drifted away from the pole over the last 4,800 years, Thuban is now seen in the night sky at a declination

Declination

In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle....
of 64° 20' 45.6", RA

Right ascension

Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system....
14h 04m 33.58s. After moving nearly 47 degrees off the pole by 10000 AD, Thuban will gradually move back toward the north celestial pole. In 20346 AD, it will again be the pole star, that year reaching a maximum declination of 88° 43' 17.3", RA 19h 08m 54.17s.

Classification

Thuban has a spectral class

Stellar classification

In astronomy, stellar classification is a classification of stars based on its spectrum characteristics. The spectral class of a star, is a designation of a class to a star describing the ionization of its chromosphere, what atomic excited states are most prominent in the light, giving an objective measure of the temperature in this chr...
of A0III, indicating its similarity to Vega

Vega

Vega is the brightest star in the constellation Lyra, the list of brightest stars in the night sky and the second brightest star in the northern Celestial sphere, after Arcturus....
in temperature and spectrum

Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible electromagnetic radiation frequencies. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation from that particular object....
, but more powerful and more massive. Thuban is not a main sequence

Main sequence

The main sequence is a continuous and distinctive band of stars that appear on plots of stellar Color index versus brightness. These color-absolute magnitude plots are known as Hertzsprung-Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell....
star; it has now ceased hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
fusion

Nuclear fusion

In nuclear physics and nuclear chemistry, nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus....
in its core and is fusing helium

Helium

Helium is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas group in the periodic table and whose atomic number is 2....
. That makes it a white giant star, being 250 times more powerful than our Sun

Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
but over 300 light-year

Light-year

A light-year or light year is a Units of measurement of length, equal to just under ten orders_of_magnitude_%28numbers%29#1012 kilometres....
s distant.

Thuban has no real anomalies other than it's quite rare to have a giant star in the A class, A being usually reserved for main sequence and the occasional supergiant. This indicates that Thuban has not been a giant star for very long and is likely still in the process of expanding, probably to eventually become a K class red-orange giant of the Aldebaran

Aldebaran

Aldebaran is the brightest star in the constellation Taurus and list of brightest stars in the nighttime sky. Because of its location in the head of Taurus, it has historically been called the Bull's Eye....
sort. It may also mean that it has recently run out of helium to fuse and is contracting before starting to burn carbon

Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, in which case it may end up a blue giant

Blue giant

In astronomy, a blue giant is a star with a spectral type of O or B and a luminosity class of III . In the standard Hertzsprung-Russell diagram, blue giants are found in the upper left corner, due to their high luminosity and early spectral type....
such as Beta Centauri

Beta Centauri

Beta Centauri , also known as Hadar or Agena, is the second brightest star in the constellation Centaurus and the list of brightest stars in the night sky....
.

Thuban is a binary star

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star or secondary....
, with a companion star in a 51-day orbit. The companion has not been directly imaged and from its mass is likely a red dwarf

Red Dwarf

Red Dwarf is a United Kingdom science fiction television situation comedy Media franchise, primarily comprising eight series of a television sitcom that ran on BBC Two between 1988 and 1999 and gained a cult following....
or a low mass white dwarf

White dwarf

A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. Because a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth, it is very density....
.

The name comes from the Arabic ????? (?u‘ban, "the basilisk

Basilisk

In European bestiary and legends, a basilisk is a legendary reptile reputed to be king of Serpent and said to have the power to cause death with a single glance....
"), the Arabic name for the constellation Draco.