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The Ursa Major Moving Group, also known as Collinder 285, is the closest moving group
Moving group

In astronomy, it is widely accepted that most stars are born within molecular clouds known as molecular cloud. The stars formed within such a cloud compose open clusters containing dozens to thousands of members....
 to 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...
, that is, a set of stars with common velocities in space, thought to have a common origin. Its core is located roughly 80 light years away. It is rich in bright stars, including most of the stars of 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....
.

stars in the Ursa Major Moving Group are in roughly the same location in the Milky Way Galaxy, are moving in roughly the same direction at roughly the same speed, contain roughly the same mix of metal
Metallicity

In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium....
s, and, based on stellar theory, appear to be roughly the same age.






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The Ursa Major Moving Group, also known as Collinder 285, is the closest moving group
Moving group

In astronomy, it is widely accepted that most stars are born within molecular clouds known as molecular cloud. The stars formed within such a cloud compose open clusters containing dozens to thousands of members....
 to 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...
, that is, a set of stars with common velocities in space, thought to have a common origin. Its core is located roughly 80 light years away. It is rich in bright stars, including most of the stars of 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....
.

Discovery and constituents

All stars in the Ursa Major Moving Group are in roughly the same location in the Milky Way Galaxy, are moving in roughly the same direction at roughly the same speed, contain roughly the same mix of metal
Metallicity

In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium....
s, and, based on stellar theory, appear to be roughly the same age. This evidence suggests to astronomers that the stars in the group share a common origin.

Based on the ages of its constituent stars, the Ursa Major Moving Group is believed to have once been an open cluster
Open cluster

An open cluster is a star cluster of up to a few thousand stars that were formed from the same giant molecular cloud, and are still loosely gravity to each other....
, having formed from a protostellar nebula
Nebula

A nebula is an interstellar cloud of cosmic dust, hydrogen gas and Plasma . Originally nebula was a general name for any extended astronomy astronomical object, including galaxy beyond the Milky Way ....
 approximately 500 million years ago, which is fairly young. Since that distant time in the past, the sparse group has been scattered over a region about 30 by 18 light-years, whose center is currently some 80 light-years away, making it the closest cluster-like object
Star cluster

Star clusters or star clouds are groups of stars which are gravity bound. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars, while open clusters generally contain less than a few hundred members, and are often very young....
 to the 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...
.

The Ursa Major Moving Group was discovered in 1869 by Richard A. Proctor, who noticed that, except for Dubhe and Alkaid, the stars of 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....
 all have proper motion
Proper motion

The proper motion of a star is its angular change in position over time as seen from the Sun, as inferred after improper motions are accounted for....
s heading towards a common point in Sagittarius
Sagittarius (constellation)

Sagittarius is one of the constellations of the zodiac. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow....
. Thus, the Big Dipper, unlike most constellations or asterisms, is actually largely composed of related stars.

Some of the brighter stream members include Alpha Coronae Borealis
Alpha Coronae Borealis

Alpha Coronae Borealis is a binary star in the constellation Corona Borealis. It also has the traditional names Gemma or Alphekka or Alphecca....
 (a CrB or Alphecca or Gemma), Beta Aurigae
Beta Aurigae

Beta Aurigae , traditionally named Menkalinan , is a Subgiant star star system star system approximately 85 light-years away in the constellation Auriga ....
 (ß Aur), Delta Aquarii
Delta Aquarii

Delta Aquarii is the third-brightest star in the constellation Aquarius . It also has the traditional name Skat or Scheat, which can also refer to Beta Pegasi....
 (d Aqr), Gamma Leporis
Gamma Leporis

Gamma Leporis is a multiple star system which is located at a distance of about 29 light-years from Earth and consists of 2 or 3 stars: Gamma Leporis A, Gamma Leporis B and possibly Gamma Leporis C....
 (? Lep) and Beta Serpentis
Beta Serpentis

Beta Serpentis is a star system in the constellation Serpens, in its head . It also has the traditional name Chow, from the Mandarin ?, zhou, referring to the Zhou Dynasty....
 (ß Ser). More bright and moderately bright stars which are currently believed to be members of the group are listed in two sections below: Core stars and Stream stars.

Group members

Current criteria for membership in the moving group is based on the stars' motion in space. This motion can be determined from the proper motions and parallax
Parallax

Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines....
 (or distance) to the stars and radial velocities
Radial velocity

Radial velocity is the velocity of an object in the direction of the line of sight . The light of an object with a substantial radial velocity will be subject to Doppler effect, so the frequency of the light decreases for receding objects and increases for approaching objects ....
. The Hipparcos
Hipparcos

Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to astrometry, the accurate measurement of star positions, parallaxes, and proper motions....
 satellite has recently greatly improved both the proper motion and parallax estimates of nearby bright stars, refining the study of this and other moving groups .

Based on their distances (measured with Hipparcos) and 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....
, the absolute magnitude
Absolute magnitude

In astronomy, absolute magnitude measures a celestial object's intrinsic brightness. To derive the absolute magnitude from the observed apparent magnitude of a celestial object its value is corrected for distance to the observer....
 can be used to estimate the age of the stars. The stars in the moving group appear to have a common age of about 500 million years.

Core stars

The core of the moving group consists of 14 stars, of which 13 are in the 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....
 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....
 and the other is in the neighboring constellation of Canes Venatici
Canes Venatici

Canes Venatici is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is Latin for hunting dogs and it represents the mythological dogs Chara and Asterion being held on a leash by Bo?tes the herdsman, a neighboring constellation....
.

The following are members of the moving group closest to its center. These stars are all in 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....
 except where indicated.

  • 37 Ursae Majoris (HD 91480)
  • Beta Ursae Majoris
    Beta Ursae Majoris

    Beta Ursae Majoris is a star in the constellation of Ursa Major. It also has the traditional name Merak.It is more familiar to northern hemisphere observers as one of the "pointer stars" in the Big Dipper, and a line connecting it with nearby Alpha Ursae Majoris extends to Polaris, the north star....
     (Merak) (HD 95418)
  • Gamma Ursae Majoris
    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" ....
     (Phecda) (HD 103287)
  • Delta Ursae Majoris
    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....
     (Megrez) (HD 106591)
  • HD 109011
  • HD 109647 (in Canes Venatici
    Canes Venatici

    Canes Venatici is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is Latin for hunting dogs and it represents the mythological dogs Chara and Asterion being held on a leash by Bo?tes the herdsman, a neighboring constellation....
    )
  • HD 110463
  • Epsilon Ursae Majoris
    Epsilon Ursae Majoris

    Epsilon Ursae Majoris is the brightest star in the constellation Ursa Major , and at apparent magnitude 1.76 is the list of brightest stars in the sky....
     (Alioth) (HD 112185)
  • 78 Ursae Majoris A (HD 113139A)
  • Gliese 503.2 (HD 115043)
  • Zeta Ursae Majoris (Mizar) A (HD 116656)
  • Zeta Ursae Majoris (Mizar) B (HD 116657)
  • 80 Ursae Majoris (Alcor) (HD 116842)


Stream stars

There is also a "stream" of stars which are likely members of the Ursa Major Moving Group, scattered more widely across the sky (from Cepheus
Cepheus (constellation)

Cepheus is a constellation in the northern sky. It is named after Cepheus, King of Aethiopia in Greek mythology, and is considered to represent a king....
 to Triangulum Australe
Triangulum Australe

Triangulum Australe is a small constellation in the southern sky, created in the sixteenth century. Its name is Latin for 'the southern triangle', which distinguishes it from Triangulum in the northern sky....
). Only stars with 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....
s or 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 ....
s are listed here.

  • Delta Aquarii
    Delta Aquarii

    Delta Aquarii is the third-brightest star in the constellation Aquarius . It also has the traditional name Skat or Scheat, which can also refer to Beta Pegasi....
  • Beta Aurigae
    Beta Aurigae

    Beta Aurigae , traditionally named Menkalinan , is a Subgiant star star system star system approximately 85 light-years away in the constellation Auriga ....
     (Menkalinan)
  • Zeta Boötis
    Zeta Boötis

    Zeta Bo?tis is a bright speckle interferometry in the constellation of Bo?tes. It also has the Flamsteed designation 30 Bo?tis. It is approximately 181 light years from Earth and has a combined apparent magnitude of +3.78....
  • 18 Boötis
    18 Boötis

    18 Bo?tis is a star in the constellation Bo?tes about 85 light years away from Earth. Its apparent magnitude is 5.40 and its absolute magnitude is 3.3....
  • Chi Ceti
  • Zeta Crateris
  • 29 Comae Berenices
  • Alpha Coronae Borealis
    Alpha Coronae Borealis

    Alpha Coronae Borealis is a binary star in the constellation Corona Borealis. It also has the traditional names Gemma or Alphekka or Alphecca....
     (Alphecca or Gemma)
  • 59 Draconis
  • 21 Leonis Minoris
  • Gamma Leporis
    Gamma Leporis

    Gamma Leporis is a multiple star system which is located at a distance of about 29 light-years from Earth and consists of 2 or 3 stars: Gamma Leporis A, Gamma Leporis B and possibly Gamma Leporis C....
  • 16 Lyrae
    16 Lyrae

    16 Lyrae is a 5th apparent magnitude star in the constellation Lyra , approximately 128 light years away from Earth. It is a white star of the spectral type A7V, meaning it has a surface temperature of 7,500 to 11,000 kelvins....
  • Gamma Microscopii
    Gamma Microscopii

    Gamma Microscopii is the brightest star in the constellation of Microscopium . It is a G-type star giant star with an apparent visual magnitude of approximately 4.677, around 220 light-years from the Sun....
  • Chi1 Orionis
    Chi1 Orionis

    Chi1 Orionis is a star about 32 light years away. It is in the constellation Orion .?1 Ori is a main sequence dwarf star of spectral type G0V....
  • 89 Piscium
  • Beta Serpentis
    Beta Serpentis

    Beta Serpentis is a star system in the constellation Serpens, in its head . It also has the traditional name Chow, from the Mandarin ?, zhou, referring to the Zhou Dynasty....
  • Tau6 Serpentis
    Tau6 Serpentis

    Tau6 Serpentis is a G-type star giant star star in the constellation of Serpens , approximately 450 light-years from the Earth....
  • Omega Serpentis
    Omega Serpentis

    Omega Serpentis is a star in the constellation Serpens.Omega Serpentis is a yellow stellar classification giant star with an apparent magnitude of +5.21....
  • 6 Sextantis
  • 66 Tauri
  • Zeta Trianguli Australis
    Zeta Trianguli Australis

    Zeta Trianguli Australis is a spectroscopic binary in the constellation Triangulum Australe. It is approximately 39.5 light years from Earth....
  • Pi1 Ursae Majoris
    Pi1 Ursae Majoris

    pi1 Ursae Majoris is a yellow stellar classification main sequence with a mean apparent magnitude of +5.63. It is approximately 46.5 light years from Earth....
  • 41 Virginis


Non-members

The bright, nearby star Sirius
Sirius

Sirius is the list of brightest stars in the night sky with a visual apparent magnitude of −1.46, almost twice as bright as Canopus, the next brightest star....
 was long believed to be a member of the group, but may not be, according to research in 2003 by Jeremy King et al. at Clemson University
Clemson University

Clemson University is a state university , coeducational, Land-grant_university, research university located in Clemson, South Carolina, South Carolina, United States....
. This research seems to indicate that it is too young to be a member.

Our Solar System
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
 is in the outskirts of this stream, but is not a member, being about 10 times older. 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....
 merely drifted in along its 250 million year galactic orbit, and 40 million years ago was nowhere near these stars.

External links

  • Arizona University website
  • Ken Croswell
    Ken Croswell

    Ken Croswell is an astronomer and author living in Berkeley, California. His first degree mixed science and wider interests, Academic major in physics and minoring in English literature....
    's astronomy website.
  • LeDrew, Glenn (1998). . Retrieved July 28, 2005.
  • - D. Montes, UCM
  • J.R.King et al 2003 Astronomical Journal paper classifying group members based on Hipparcos data.