9 Ceti

Stellar classification



  • X -19
  • Y -65
  • Z -3
→ Sol: 68

Object type

  • Variable of BY Dra type
  • Star
  • Double or multiple star
  • Flare Star
  • Infra-Red source
  • High proper-motion Star
  • Rotationally variable Star
  • UV-emission source
  • Variable Star
  • X-ray source
simbad:* 9 Cet


9 Ceti is the Flamsteed designation for a star in the equatorial constellation of Cetus. It has an apparent visual magnitude of 6.39, which is below the limit that can be seen with the naked eye by a typical observer. (According to the Bortle scale, it is possible for some observers to see it from dark rural skies.) Based upon measurements made by the Hipparcos spacecraft, this star is around 68 light years away from the Sun. There is a magnitude 12.57 optical companion at an angular separation of 214 arc seconds along a position angle of 294° (as of 1999), although the pair are not physically associated as they have different proper motions.

This is a solar analog, which is defined as a "Population I dwarf with gross properties not very different from those of the Sun". It is a G-type main sequence star with a stellar classification of G3 V, which means it is generating energy through the fusion of hydrogen into helium at its core. The mass and radius of the star are similar to the Sun, although the abundance of elements other than hydrogen and helium is about 50% greater. It is much younger than the Sun, being an estimated 850 million years of age. The effective temperature of the stellar atmosphere is around 5,807 K, giving it the yellow-hued glow of a G-type star.

In 1980, this was found to be a variable star with a periodicity of 7.655 days, and it was given variable star designation BE Cet. This variation in luminosity was interpreted to be the result of rotational modulation of star spot activity in the photosphere, and hence it is classified as a BY Draconis variable. There is considerable variation in the strength of the surface activity—to the point where it has appeared inactive during some observation runs. The strength of the surface magnetic field was measured to be 450 G. The spectrum of this star includes lines of titanium oxide and calcium hydride, which, for a star of this class, is further evidence of star spot activity. Star spots cover an estimated 3% of the surface.

This star has been examined for evidence of a planetary companion or a debris disk, but as of 2015 none has been found. The age of the star and its motion through space suggest that it is a member of the Hyades stellar kinematic group.

This article uses material from the Wikipedia article "9 Ceti", which is released under the Creative Commons Attribution-Share-Alike License 3.0.