FK Comae Berenices is a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

that varies in

apparent 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 li ...

between 8.14 and 8.33 over a period of 2.4 days. It is the prototype for the

FK Comae Berenices FK Comae Berenices is a variable star that varies in apparent magnitude between 8.14 and 8.33 over a period of 2.4 days. It is the prototype for the FK Comae Berenices (FK Com) class of variable stars. The variability of FK Com stars may ...

(FK Com) class of variable stars. The variability of FK Com stars may be caused by large, cool spots on the rotating surfaces of the stars. This star is thought to be the result of a recent binary merger, resulting in a high rate of both spin and

magnetic activity A stellar magnetic field is a magnetic field generated by the motion of conductive plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material. A localized magn ...

. The spectral class of FK Comae Berenices is G4 III, although it is considered unusual in having very broad

absorption line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s as well as some

emission line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s. The broadened spectral lines are due to rapid rotation. The rotation rate of FK Comae Berenices is unusually fast for a cool

giant star A giant star is a star with substantially larger radius and luminosity than a main sequence, main-sequence (or ''dwarf'') star of the same effective temperature, surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moo ...

. It is speculated that this is due to the merger of a contact binary pair of stars into a single star. The rotation produces extremely strong magnetic fields which are expected to

brake A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background ...

the star to a slower rotation rate. Analysis of variability due to star spots on the surface show that the star rotates at different speeds at different latitudes. FK Comae Berenices is listed as a companion to the slightly brighter HD 117567. The two are not thought to be physically associated, with HD 117567 being a much closer F2

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 ...

star.

References

External links

FK Coma Berenices
{{DEFAULTSORT:FK Comae Berenices Coma Berenices 117555 Comae Berenices, FK G-type bright giants FK Comae Berenices variables 065915 Durchmusterung objects