One of these, called the Groombridge 1830 group, consists of a number
of subdwarfs and the star RR Lyrae, after which the RR Lyrae variables were named.
Not exact matches
The stars may be passing through a stage
of stellar evolution that lasts no more than a few tens
of thousands
of years, the scientists say — a phase between red giants (about 30 or 40 times the size
of our sun) and blue
subdwarfs (stars about one - fifth the size
of our sun but seven times hotter and 70 times brighter).
We analyze the kinematics
of ultracool dwarfs in our catalog and find evidence that bluer but otherwise generic late - M and L field dwarfs (i.e., not
subdwarfs) tend to have higher tangential velocities compared to typical field objects.
The star may even be suspected
of being a dim
subdwarf (sd / VI)-- like Groombridge 1830 or Kapteyn's Star — rather than a main - sequence dwarf star (V).
Known as
subdwarfs, these stars are also fusing hydrogen in their core and so they mark the lower edge
of the main sequence's fuzziness resulting from chemical composition.
The central star
of M27 is quite bright at mag 13.5, and an extremely hot blueish
subdwarf dwarf at about 85,000 K (so the spectral type is given as O7 in the Sky Catalog 2000).
Unusually faint for its spectral type, Groombridge 1830 is a yellow - orange halo
subdwarf star
of spectral and luminosity type sdG8p / VI.
Kapteyn's Star is a dim red
subdwarf or main sequence (sdM0 - 1.5 or V), halo star (John E. Gizis, 1997, page 809; and NASA Star and Exoplanet Database), which is thought to be originally a member
of the Milky Way galaxy's luminous halo.