Special stars: Gliese 105

Gliese 105 A and C
Graphic: Nasa, Hubble Telescope


A small triple system. The C star, a red dwarf, is with 2600 kelvin surface temperature the coolest known main sequence star. Its mass is just enough to start the hydrogen fusion.
The B star is a bigger red dwarf, A is a yellow-orange star.


Constellation: Cetus
Distance: 23.5 light-years
Space between Gliese 105 A and B: 1200 AU
Space between Gliese 105 A and C: 24 AU

Gliese 105 A

Spectral class: K3
Visual magnitude: 5.82
Luminosity: 0.21 * Sun
Mass: 0.81 * Sun
Diameter: 0.85 * Sun


Gliese 105 B

Spectral class: M3.5
Visual magnitude: 12
Luminosity: 0.001 * Sun
Mass: 0.21 * Sun
Diameter: 0.28 * Sun

Gliese 105 C

Spectral class: M7
Luminosity: 0.0000084 * Sun
Mass: 0.082 * Sun


Kappa Ceti:



Photo: ESO Online Digitized Sky Survey

A yellow star of sunlike measures, but with much more raving attributes. It is a superflare star with eruptions a million times heavier than those of our Sun. They are caused by disturbances of the magnetic field from a still undiscovered near companion.

Constellation: Cetus
Age: 800 million years
Distance: 29.87 light-years
Spectral class: G5
Visual magnitude: 4.83
Luminosity: 0.851 * Sun
Mass: 1 * Sun
Diameter: 0.984 * Sun
Radial velocity: 18.9 km/sec