25 Orionis, less commonly known by its

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

Psi¹ Orionis (ψ¹ Orionis, ψ¹ Ori) is a fifth-magnitude

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Orion Orion may refer to: Common meanings * Orion (constellation), named after the mythical hunter * Orion (mythology), a hunter in Greek mythology Arts and media Fictional entities Characters and species * Orion (character), a DC Comics c ...

. It lies among a dense

cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Cluster II (spacecraft), a European Space Agency mission to study the magnetosphere * Asteroid cluster, a small ...

of low-mass pre-main-sequence stars in the Orion OB1a.

Stellar group

25 Orionis is the dominant member of a rich low-mass star region, first identified in 2005 in a statistical analysis of 2.5 million stars. It is one of several sub-associations within Orion OB1a, all thought to lie at around the same distance of 338

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. Over 200 members of the 25 Orionis stellar group have been found, mostly

T Tauri star T Tauri stars (TTS) are a class of variable stars that are less than about ten million years old. This class is named after the prototype, T Tauri, a young star in the Taurus Molecular Cloud, Taurus star-forming region. They are found near mo ...

s with spectral types of K and M and masses less than half the sun's. There are also around 60 hotter stars in the region, including the

eruptive variable A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

V346 Tauri. This region is known as Briceño 1.

Properties

Like the star Pleione in the

Pleiades The Pleiades (), also known as Seven Sisters and Messier 45 (M45), is an Asterism (astronomy), asterism of an open cluster, open star cluster containing young Stellar classification#Class B, B-type stars in the northwest of the constellation Tau ...

open cluster An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

, 25 Ori is a

Be star Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer ...

with a gaseous

circumstellar disk A Circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the res ...

. The

SIMBAD SIMBAD (the Set of Identifications, Measurements and Bibliography for Astronomical Data) is an astronomy, astronomical database of objects beyond the Solar System. It is maintained by the Centre de données astronomiques de Strasbourg (CDS), Fr ...

astronomical database lists its

spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

as B1Vn. 25 Orionis is a fast rotator, clocking a rotational velocity of 316 km/s, significantly faster than

Achernar Achernar is the brightest star in the constellation of Eridanus and the ninth-brightest in the night sky. It has the Bayer designation Alpha Eridani, which is Latinized from α Eridani and abbreviated Alpha Eri or α Eri. The name Ac ...

's speed of 251 km/s in the constellation Eridanus. Having a radius of , the star rotates on its axis roughly once every 23 hours. With a mass in excess of , the star is expected to explode as a

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

. 25 Orionis is a

Gamma Cassiopeiae variable A Gamma Cassiopeiae variable (γ Cassiopeiae variable) is a type of variable star, named for its prototype γ Cassiopeiae. Variability γ Cassiopeiae variables show irregular changes in brightness on a timescale of decades. These typically ha ...

star, and has been given the variable star designation V1086 Orionis. The

General Catalog of Variable Stars A general officer is an officer of high rank in the armies, and in some nations' air and space forces, marines or naval infantry. In some usages, the term "general officer" refers to a rank above colonel."general, adj. and n.". OED Online ...

lists its magnitude as varying between magnitude 4.92 and 4.96 in the visual (V) band - an amplitude only 0.04 magnitudes. However photometry by the ''

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of ...

'' satellite, which had a

passband A passband is the range of frequency, frequencies or wavelengths that can pass through a Filter (signal processing), filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all t ...

broader than the V band, showed a 0.145 magnitude range in brightness.

References

External links

*Jim Kaler's Stars, University of Illinois
25 ORI (25 Orionis)
* Philippe Stee's in-depth information on

* Olivier Thizy's in-depth information on
Be Stars
{{Stars of Orion Orion (constellation) B-type main-sequence stars Be stars Orionis, Psi1 Orionis, 25

1789 Events January–March * January – Emmanuel Joseph Sieyès publishes the pamphlet '' What Is the Third Estate?'' ('), influential on the French Revolution. * January 7 – The 1788-89 United States presidential election ...

35439 025302 BD+01 1005 Orionis, V1086

Stellar group

Properties

See also

References

External links