θ Carinae, Latinized as Theta Carinae, is a

spectroscopic binary A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

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 southern

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 ...

Carina Carina may refer to: Places Australia * Carina, Queensland, a suburb in Brisbane * Carina Heights, Queensland, a suburb in Brisbane * Carina, Victoria, a locality in Mildura Serbia * Carina, Osečina, a village in the Kolubara District ...

. With an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...

of 2.76, it is the brightest star in the

open star 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 ...

IC 2602 IC 2602 (also known as the Southern Pleiades, Theta Carinae Cluster, or Caldwell 102) is an open cluster in the constellation Carina (constellation), Carina. Discovered by Abbe Lacaille in 1751 from South Africa, the cluster is easily visible to t ...

. It marks the northeastern end of the Diamond Cross asterism.

Parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

measurements from 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 ...

mission place this star at a distance of about from Earth.

Properties

The MKK stellar classification of this star is B0.5 Vp, which indicates this

B-type main sequence star A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type stars ...

generates energy through the

nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...

of hydrogen in its core. The 'p' suffix designates peculiar spectral features, which have been observed in both optical and ultraviolet wavelengths. Theta Carinae is a single-lined spectroscopic binary with a 2.2 day period; the shortest known orbital period among massive stars, suggesting earlier mass transfer between the two components, possibly explaining the spectral peculiarities. In this spectroscopic system, the primary star is a

blue straggler A blue straggler is a type of star that is more luminous and bluer than expected. Typically identified in a stellar cluster, they have a higher effective temperature than the main sequence turnoff point for the cluster, where ordinary stars b ...

, which is an unusual type of star created by merging or the interaction between two or more stars. The source of the mass transfer is likely to be the less massive secondary companion, and what is now the primary star was probably originally the less massive component. The estimated age of the pair is 4 million years, and it appears much younger than the surrounding IC 2602 cluster. The primary star is about and . Theta Carinae has an intensely hot outer radiating envelope with an effective surface temperature of . Once the primary reaches around 11 million years old, the star will expand and will begin to transferring its outer surface mass back to its companion. Little is known about the companion star, but it is likely an

F-type star 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 ...

with a luminosity less than 1% of the primary.

Etymology

In Chinese, (), meaning '' Southern Boat'', refers to an asterism consisting of θ Carinae, V337 Carinae, PP Carinae, β Carinae and ω Carinae. Consequently, θ Carinae itself is known as (, ).AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 28 日

Apparent location

In most versions of its asterism, the neighbouring bright stars, thus plotted along the imaginary hull forming Carina are Omega Carinae which is approximately 120 light years closer and PP (also known as p) Carinae, of a similar distance to Theta.

Notes

References

External links

Southern Sky Photos
{{DEFAULTSORT:Theta Carinae B-type main-sequence stars Blue stragglers Carinae, Theta Carina (constellation) 4199 093030 052419 Durchmusterung objects IC 2602 Spectroscopic binaries