The Beta Pictoris Moving Group is a young

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 ...

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s located relatively near

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 ...

. A moving group, 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 ...

, is a group of stars that share a common motion through space as well as a common origin. This moving group is named for Beta Pictoris. The Beta Pictoris Moving Group is an important object for astronomical study as it is the closest youthful group of stars to the Earth. The star Beta Pictoris is known to have a large disk of gas and dust, possibly a

protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, be ...

. There is also evidence of a young

gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...

planet around the star. A

free-floating 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 ...

has also been found in the moving group, PSO J318.5-22. The age and distance of the group makes it a candidate for directly imaging

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

Constituents

The Beta Pictoris Moving Group consists of 17 stellar systems, comprising a total of 28 individual component stars, including identified

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. The core of the group is located some 115

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from Earth, and has an average estimated age of between 20 and 26 million years. The majority of the group is made up of cool, dim K and M

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

stars. Most are not visible to the naked eye. The members that are visible to the naked eye are: * Beta Pictoris * Eta Telescopii * 51 Eridani * HD 203 * HD 146624 *

HD 165189 HD 165189 and HD 165190 are components of a visual binary star system located 145 light years away in the southern constellation of Corona Australis. It is visible to the naked eye with the primary having an apparent visual magnit ...

HD 172555 HD 172555 is a white-hot A7V star located relatively close by, 95 light years from Earth in the direction of the constellation Pavo (constellation), Pavo. Spectrographic evidence indicates a relatively recent collision between two planet ...

Beta Trianguli Australis Beta Trianguli Australis, Latinisation of names, Latinized from β Trianguli Australis, is a double star in the southern constellation of Triangulum Australe. It is approximately from Earth and has an apparent visual magnitude of +2.85. ...

(potential member) The group covers a region of space for the most part visible only in the Southern Hemisphere, as shown in the map below.

Discovery

An early estimated age for the star Beta Pictoris at about 10 million years proved problematic due to the star's apparent isolation in space. According to current theory regarding

stellar evolution Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is cons ...

, extremely young stars of this age should be located near other young stars that formed from the same region in space. It is not until significantly later that gravitational interactions with other stars causes stellar 'siblings' to disperse. In 1999 the situation was resolved by the discovery of a pair of dim

red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

stars that were found to have a similar velocity and age to β Pictoris, lending credence to the estimated age of the star. Further work published in 2001 identified a total of 17 stellar systems with a similar motion and age as the Beta Pictoris moving group, named for the primary member of the association.

Origin

The movements of the group were tracked to the positions they occupied 11.5Myr ago, where they occupied a space 3 times smaller than their current distribution (24pc, versus 72pc today) situated in between two regions of the Scorpius-Centaurus OB star group, and it was suggested that they originated there when a supernova from either OB region of Scorpius-Centaurus OB would have been close enough to trigger stellar formation.

References

{{Reflist, refs= {{cite journal , title=On the age of the beta Pictoris moving group , last1=Mamajek , first1=Eric E. , last2=Bell , first2=Cameron P. M. , journal=Monthly Notices of the Royal Astronomical Society , volume=445 , issue=3 , pages=2169–2180 , year=2014 , arxiv=1409.2737 , bibcode=2014MNRAS.445.2169M , doi=10.1093/mnras/stu1894 Moving groups

Constituents

Discovery

Origin

See also

References