AB Doradus Moving Group is a group of about 30 associated stars that are moving through space together with the star
AB Doradus. 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 ...
is distinguished by its members having about the same age, composition (or
metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
) and motion through space. Hence they most likely formed in the same location.
This group is located about 20
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...
s from the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
and is the closest known co-moving group. The average
space velocity
of this group has components of U = −8, V = −27 and W = −14 km/s. About 10 of these stars form a nuclear group within a volume roughly 10
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...
s
across.
[
]
The proximity of this moving group makes it useful for studies of shared stellar properties, as well as detection of companions through direct imaging. These can be used for refinement of young stellar models, for example.
Age
The age of the AB Dor Moving Group has been somewhat controversial, with quoted ages in the range of ~50 to ~150
Myr; recent work, however, seems
to have converged on an age similar to that of the Pleiades (130 ± 20 Myr).
Zuckerman & Song (2004)
estimated an age of ~50 Myr for the AB Dor Moving Group, however this was only
via comparison of age indicators to a single other group (the ~30 Myr-old Tucana group, which itself
has a poorly determined age).
Luhman, Stauffer, & Mamajek (2005)
demonstrated that the AB Dor Moving Group
and Pleiades open cluster have a similar pattern of Lithium depletion and color-magnitude
diagram positions amongst
their low-mass members, suggesting that the two groups were of similar age (~100-125 Myr).
They also proposed that the similarity in space motions between the AB Dor group and
Pleiades
The Pleiades (), also known as The Seven Sisters, Messier 45 and other names by different cultures, is an asterism and an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance of ...
(within 2 km/s) hinted that the AB Dor group may have formed in the same star-forming complex
that spawned the
Pleiades
The Pleiades (), also known as The Seven Sisters, Messier 45 and other names by different cultures, is an asterism and an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance of ...
cluster.
Ortega et al. (2007)
integrated the past Galactic orbits of the AB Dor Moving Group and the
Pleiades
The Pleiades (), also known as The Seven Sisters, Messier 45 and other names by different cultures, is an asterism and an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance of ...
cluster, and concluded that they were in close proximity 119 ± 20 Myr ago. The similarity of this kinematic age with the modern age of the Pleiades determined from the Lithium-depletion boundary method (130 ± 20 Myr),
led these investigators to conclude that AB Dor Moving Group and Pleiades likely formed around the same time in the same star-forming complex.
In 2013, a color-magnitude analysis of the low-mass stars in the group by Barenfeld et al. (2013)
[
] found that the members of
spectral type
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...
K6 and hotter appeared to be on the
main sequence
In astronomy, 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 Her ...
, whereas the cooler
M-type stars Type M or M type may refer to:
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* Type M, a name for the 15 amp BS 546 electrical plug
* Vaio Type M, a kind of Vaio computer from Sony
* M-type asteroid
* m-type filter, an electronic filter
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are pre-main sequence - consistent with a lower limit on the age of the AB Dor Moving Group of >110 Myr. The latter study also concluded that some members of the moving group outside of the nucleus do not share a common chemical composition, implying that they are unrelated interlopers.
Substellar members
*
AB Doradus, the main star of the namesake moving group is suspected to contain 2 brown dwarfs namely AB Doradus Ca/Cb
*Bowler et al. (2012)
[
] discovered a ~30 Jupiter mass L0-type companion to the AB Dor Moving Group member 1RXS J235133.3+312720.
*In 2011, a
brown dwarf
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...
with mass 31 was discovered orbiting around the star
CD−35 2722.
*In 2012, a group of astronomers announced the discovery of
CFBDSIR 2149−0403
CFBDSIR 2149-0403 (full designation CFBDSIR J214947.2-040308.9) is a free-floating planetary-mass object or possibly a high- metallicity, low-mass brown dwarf in the constellation Aquarius. Originally, it was thought to be part of the AB Doradu ...
, a purported "free-floating planet" between 4 and 7 times the mass of
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
that appeared to be part of the moving group. At the time of its discovery, it was the closest known
rogue planet
A rogue planet (also termed a free-floating planet (FFP), interstellar, nomad, orphan, starless, unbound or wandering planet) is an interstellar object of planetary-mass, therefore smaller than fusors (stars and brown dwarfs) and without a h ...
; there are a few other previously detected objects which might also be rogue planets, but astronomers are uncertain as to whether they are
planet
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
s or
brown dwarf
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...
s because their ages are unknown. These previous discoveries were discussed in the research paper in which CFBDSIR 2149-0403 was announced.
At this time, however, there is no evidence that CFBDSIR 2149−0403 formed like a planet, and its status as a low-mass brown dwarf appears to be uncontroversial.
*In 2013, a
superjovian
A super-Jupiter is a gas giant exoplanet that is more massive than the planet Jupiter. For example, companions at the planet–brown dwarf borderline have been called super-Jupiters, such as around the star Kappa Andromedae.
By 2011 there were ...
planet was found orbiting a red dwarf
2MASS J01225093-2439505
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
.
*In 2014, exoplanet
GU Piscium b
GU Piscium b (GU Psc b) is a directly imaged planetary-mass companion orbiting the star GU Piscium, with an extremely large orbit of , and an apparent angular separation of 42 arc seconds. The planet is located at right ascension declinatio ...
was discovered orbiting
GU Piscium
GU Piscium is a star in the constellation Pisces. An RS Canum Venaticorum variable, it ranges from magnitude 12.96 to 13.24 over 1.04 days. It is 48 Parsecs (155 light-years) distant from Earth. This star is also believed to be a member ...
at a distance of 2000 AU and period of 80,000 years.
*In 2016,
superjovian
A super-Jupiter is a gas giant exoplanet that is more massive than the planet Jupiter. For example, companions at the planet–brown dwarf borderline have been called super-Jupiters, such as around the star Kappa Andromedae.
By 2011 there were ...
planet was discovered orbiting
2MASS J22362452+4751425
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
.
See also
*
List of nearby stellar associations and moving groups
This is a list of nearby stellar associations and moving groups. A stellar association is a very loose star cluster, looser than an open cluster. A moving group is the remnant of such a stellar association. Members of stellar associations an ...
*
β Pictoris moving Group
*
TW Hydrae association The TW Hydrae association is a group of very young low-mass stars and substellar objects located approximately 25–75 parsecs (80–240 light years) from Earth. They share a common motion and appear to all be roughly the same age, 10±3 million yea ...
*
Ursa Major Moving Group
References
{{DEFAULTSORT:Ab Doradus Moving Group
Moving groups