81 Ceti 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 ...

located approximately 331

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 away from the Sun in the

equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator ** equatorial orbit **equatorial coordinate system ** equatorial mount, of telescopes * equatorial ...

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 ...

of Cetus. ''81 Ceti'' is the Flamsteed designation for this object. It is visible to the naked eye as a dim, yellow-hued point of light with an apparent visual magnitude of 5.65. The star is drifting further away from the Earth with a heliocentric

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

of +9 km/s. This is an aging K-type giant star with a

stellar classification 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 ...

of K0III, having exhausted the supply of hydrogen at its core and expanded to 11 times the Sun's radius. It is a red clump giant, which indicates it is on the

horizontal branch The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red-giant branch in stars whose masses are similar to the Sun's. Horizontal-branch stars are powered by helium fusion in the core (via the triple-alpha process) ...

and is generating energy from core helium fusion. The star is now 2.5 billion years old with 1.6 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

. It is radiating 60 times the luminosity of the Sun from its enlarged

photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...

at an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of 4,825 K.

Planetary system

In July 2008, the planet

81 Ceti b 81 Ceti b (abbreviated 81 Cet b) is an extrasolar planet approximately 331 light years away in the constellation of Cetus. It is estimated to be 5.3 times the mass of Jupiter which also makes it a gas giant. It orbits the G-type giant star ...

was announced by Sato and collaborators, along with 14 Andromedae b and

6 Lyncis b 6 Lyncis b (abbreviated 6 Lyn b) is an extrasolar planet orbiting the K-type subgiant star 6 Lyncis which is approximately 182 light years away in the Lynx constellation. The planet has a minimum mass . The orbital period for this planet is 8 ...

. The planet was found to be a super-Jupiter, with 5.3 times the mass of Jupiter. It takes 953 days for it to complete its orbit around the star.

References

External links

* {{DEFAULTSORT:81 Ceti K-type giants Horizontal-branch stars Planetary systems with one confirmed planet Cetus (constellation) Ceti, 81 Durchmusterung objects 016400 012247 0771

Planetary system

See also

References

External links