In
astronomy
Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...
, the Arcturus moving group or Arcturus stream is a
moving group
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.
Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well a ...
or
stellar stream
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.
Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as t ...
, discovered by
Olin J. Eggen (1971), comprising 53 stars moving at 275,000 miles per hour, which includes the nearby bright star
Arcturus
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, Note (category: variability): , , H and K emission vary.
Arcturus is the brightest star in the northern constellation of Boötes. With an apparent visual magnitude of −0.05, it is the third-brightest of th ...
. It comprises many stars which share similar
proper motion
Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...
and so appear to be physically associated.
This group of stars is not in the plane of the
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
galaxy, and has been proposed as a remnant of an ancient dwarf
satellite galaxy
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents are bound ...
, long since disrupted and assimilated into the Milky Way. It consists of old stars deficient in heavy elements.
However, Bensby and colleagues, in analysing chemical composition of F and G dwarf stars in the solar neighbourhood, found there was no difference in chemical makeup of stars from the stream, suggesting an intragalactic rather than extragalactic origin.
One possibility is that the stream appeared in a manner similar to the
Hercules group, which is hypothesized to have formed due to
Outer Lindblad Resonance with the
Galactic bar. However, it is unclear how this could produce an overdensity of stars in the thick disk.
Research from the
RAdial Velocity Experiment (RAVE) at the
Australian Astronomical Observatory, headed by Quentin Parker, was the first to quantify the nature of the group, though astronomers had known of its existence for some time. It was first discovered in 1971.
Other members include the
red giant
A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...
Kappa Gruis and the M-class stars
27 Cancri
27 Cancri is a single star in the zodiac constellation of Cancer, located around 990 light-years away from the Sun. It is visible to the naked eye as a faint, red-hued star with a typical apparent visual magnitude of around +5.5 ...
,
Alpha Vulpeculae
Alpha Vulpeculae (α Vulpeculae, abbreviated Alpha Vul, α Vul), officially named Anser , is the brightest star in the constellation of Vulpecula. It is approximately 291 light-years from Earth. It forms a wide optical binary wit ...
and
RT Hydrae.
See also
*
List of stellar streams
This is a list of stellar streams. A stellar stream is an association of stars orbiting a galaxy that was once a globular cluster or dwarf galaxy that has now been torn apart and stretched out along its orbit by tidal forces. An exception in the ...
References
External links
*{{cite news, url=http://www.abc.net.au/science/news/stories/s1568599.htm , title=Sucked in! Our galaxy eats neighbour, work=ABC News in Science, author=Skatssoon, Judy, date=February 14, 2006
Stellar streams
Boötes
Milky Way