Alpha Ursae Majoris
Encyclopedia
Alpha Ursae Majoris (α UMa, α Ursae Majoris) is the second-brightest star
in the constellation
of Ursa Major
(despite its Bayer designation
of "alpha"). It has the traditional name Dubhe, and a rarer name Ak.
It forms part of the Big Dipper
(also known as the Plough or the Great Bear), and is the northern of the 'pointers' (or 'guards'), the two stars of Ursa Major which point towards Polaris
, the North Star. Dubhe is about 124 light years away and is typical of a red giant
, an evolved helium
-burning star. It is also a multiple star
, orbited by a main sequence
companion, Dubhe B, at a distance of about 23 astronomical unit
s (AU), as well as a close pair
, Dubhe C, at a distance of about 8000 AU.
However, it is not part of the Ursa Major Moving Group
.
The traditional name comes from the Arabic for "bear", , from the phrase "the back of the Greater Bear".
It is known as (the First Star of the Northern Dipper) or (the Celestial Pivot) in Chinese.
Dubhe is the official state star of the State of Utah.
navy ship.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Ursa Major
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...
(despite its Bayer designation
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...
of "alpha"). It has the traditional name Dubhe, and a rarer name Ak.
It forms part of the Big Dipper
Big Dipper
The Plough, also known as the Big Dipper or the Saptarishi , is an asterism of seven stars that has been recognized as a distinct grouping in many cultures from time immemorial...
(also known as the Plough or the Great Bear), and is the northern of the 'pointers' (or 'guards'), the two stars of Ursa Major which point towards Polaris
Polaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) 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....
, the North Star. Dubhe is about 124 light years away and is typical of a red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
, an evolved helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
-burning star. It is also a multiple star
Multiple star
A multiple star consists of three or more stars which appear from the Earth to be close to one another in the sky. This may result from the stars being physically close and gravitationally bound to each other, in which case it is physical, or this closeness may be merely apparent, in which case...
, orbited by a main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
companion, Dubhe B, at a distance of about 23 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s (AU), as well as a close pair
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, comes, or secondary...
, Dubhe C, at a distance of about 8000 AU.
However, it is not part of the Ursa Major Moving Group
Ursa Major Moving Group
The Ursa Major Moving Group, also known as Collinder 285 or Ursa Major association, is a nearby stellar moving group, a set of stars with common velocities in space and thought to have a common origin. Its core is located roughly 80 light years away...
.
The traditional name comes from the Arabic for "bear", , from the phrase "the back of the Greater Bear".
It is known as (the First Star of the Northern Dipper) or (the Celestial Pivot) in Chinese.
Dubhe is the official state star of the State of Utah.
Dubhe in Military
USS Dubhe (ID-2562) is once of United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
navy ship.