Chi¹ Orionis (χ¹ Ori, χ¹ Orionis) is 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 ...

about 28 light years away. It is 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 origins of the e ...

Orion, where it can be seen in the tip of the hunter's upraised club. Chi1OriLightCurve

χ¹ Ori is a G0V star. It is listed in the

General Catalog of Variable Stars The General Catalogue of Variable Stars (GCVS) is a list of variable stars. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR and edited by B. V. Kukarkin and P. P. Parenago. Second and thi ...

as an

RS Canum Venaticorum variable An RS Canum Venaticorum variable is a type of variable star. The variable type consists of close binary stars having active chromospheres which can cause large stellar spots. These spots are believed to cause variations in their observed luminosi ...

, varying between

visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

4.38 and 4.41. Stępień and Geyer measured its period to be 5.5 days. χ¹ Ori has a faint companion with a mass estimated at about 15 % of the mass of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, and an

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

al period of 14.1

year A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hou ...

s. The companion orbits an average distance of 6.1 AU from the primary, but has a fairly high orbital

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

, ranging from 3.3 AU out to 8.9 AU from the primary. Because of this

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 ...

companion, the likelihood of habitable

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 in this system is low. It is thought that the companion is a

still contracting towards 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 ...

. A necessary condition for the existence of a planet in this system are stable zones where the object can remain in orbit for long intervals. For hypothetical planets in a circular orbit around the individual members of this star system, this maximum orbital radius is computed to be 1.01 AU for the primary and 0.41 AU for the secondary. (Note that the orbit of the Earth is 1 AU from the Sun.) A planet orbiting outside of both stars would need to be at least 18.4 AU distant. χ¹ Ori is a candidate stream star member of the Ursa Major Moving Group, although there is some evidence to the contrary.

References

External links

Chi-1 Orionis
by Professor Jim Kaler.

at SolStation. {{DEFAULTSORT:Chi1 Orionis G-type main-sequence stars M-type main-sequence stars Orionis, 54 Binary stars Ursa Major Moving Group Orion (constellation) Orionis, Chi BD+20 1162 Orionis, 54 0222 039587 027913 2047

See also

References

External links