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Theta Boötis
 
 
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Theta Boötis (? Boo / ? Boötis) 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....
 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....
 Boötes
Boötes

Bo?tes Bo?tes was one of the 48 constellations described by the 1st century astronomer Ptolemy and is now one of the 88 modern constellations. It contains the List of brightest stars in the night sky, Arcturus....
. It also has the traditional name Asellus Primus (Latin for "first donkey
Donkey

The 'donkey' or 'ass', Equus africanus asinus, is a Domestication member of the Equidae or horse family, and an Odd-toed ungulates. The wild ancestor of the donkey is the Wild Ass, E....
 colt") and the Flamsteed designation
Flamsteed designation

Flamsteed designations for stars are similar to Bayer designations, except that they use numbers instead of Greek letters. Each star is assigned a number and the Latin genitive of the constellation it lies in ....
 23 Boötis.

Theta Boötis has 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....
 +4.04 and belongs to the 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...
 F7V. It is approximately 47 light years from 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...
. From about 4300 BC until 3942 BC, it was the closest star to the celestial 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....
 visible to the naked eye, although it was still too far away and too dim to be regarded as a 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....
.

There is a nearby 11th magnitude companion star about 70 arcseconds away.






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Theta Boötis (? Boo / ? Boötis) 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....
 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....
 Boötes
Boötes

Bo?tes Bo?tes was one of the 48 constellations described by the 1st century astronomer Ptolemy and is now one of the 88 modern constellations. It contains the List of brightest stars in the night sky, Arcturus....
. It also has the traditional name Asellus Primus (Latin for "first donkey
Donkey

The 'donkey' or 'ass', Equus africanus asinus, is a Domestication member of the Equidae or horse family, and an Odd-toed ungulates. The wild ancestor of the donkey is the Wild Ass, E....
 colt") and the Flamsteed designation
Flamsteed designation

Flamsteed designations for stars are similar to Bayer designations, except that they use numbers instead of Greek letters. Each star is assigned a number and the Latin genitive of the constellation it lies in ....
 23 Boötis.

Theta Boötis has 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....
 +4.04 and belongs to the 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...
 F7V. It is approximately 47 light years from 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...
. From about 4300 BC until 3942 BC, it was the closest star to the celestial 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....
 visible to the naked eye, although it was still too far away and too dim to be regarded as a 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....
.

There is a nearby 11th magnitude companion star about 70 arcseconds away. This is a class M2.5 dwarf that is separated by approximately 1,000 AUs
Astronomical unit

An astronomical unit is a unit of length based on the mean distance from the Earth to the Sun. The precise value of the AU is currently accepted as 149,597,870,691 Plus-minus sign 6 metres ....
. It is uncertain whether they are gravitationally-bound, but they do have a common motion through space and so the two stars likely share a common origin.

Reference




External links


  • by Professor Jim Kaler.


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