M stars within 100 light-years |
Home | Stars | Habitability | Life | |
© 2006 Sol Company
Larger map.
Red "M" dwarf stars are
more common than brighter
OBAFGK stars but none are
visible in Earth's night
due their dimness.
Summary
Around two thousand stars (1,026+) of spectral type "M" have been tentatively identified and located within 100 light-years (ly) or (or 30.7 parsecs) of Sol, due to the difficulty of observing red dwarf stars and determining their distance. Of those two thousand some M-type stars, astronomers believe that none evolved out of the main sequence into giant stars, although one high-mass star has evolved into a red giant (more on nearby giants and subgiants). Far more luminous than their main-sequence counterparts, M-type, giant stars, such as ?, are relatively common (for giant stars) in nearby space.
NASA -- larger image
Most nearby stars are very dim red dwarfs
-- like Gliese 623 A (M2.5V) and B (M5.8Ve)
at lower right -- invisible to the unaided
Human eye in Earth's night sky.
Compared to hotter and brighter OBAFGK type stars, M type stars radiate more light towards the infrared end of the spectrum. For M-type stars, their spectral lines are characterized by the presence of molecular metallic lines (such as Titanium Oxide) and neutral metals. Main-sequence M stars have surface temperatures of 2,000 to 3,500 K and around 0.1 to 9 percent of Sol's luminosity. M-type dwarf stars appear to have between 0.75 to 0.64 Solar-masses, which indicates in theory that these stars may spend from over a trillion to as few as 17 billion years in the main sequence fusing core hydrogen (more from CSIRO Australia).
NASA
Observatorium
Main-sequence M stars like
Barnard's Star are all
cooler, dimmer, and redder
than other main sequence
stars (OBAFGK).
See a discussion of
the
"main
sequence"
as part of
stellar
evolution and death.
Main sequence stars have internal zones which are either convective or radiative. Massive stars (with "several" Solar masses) are convective deep in their cores, and are radiative in their outer layers. By comparison, low mass stars (Sol-type F, G, K, and M and cooler stars) have convective outer layers and radiative cores. Intermediate mass stars (i.e., spectral type A) may be radiative throughout. (More discussion on the internal structure of main sequence stars is available from NASA's Goddard Space Flight Center.)
Nearby M Stars by Distance
The following celestial objects are located within 30.7 parsecs, 100 light-years (ly), of Sol.
Other Information
Summary information on brighter and larger, blue-white B, bluish white A, yellowish F, and yellow-orange G stars within 100 light-years are also available.
Try Professor James Kaler's Stars site for more discussion of spectral classification as well as information on individual yellow-orange stars.
Up-to-date technical summaries on some stars can be found at: NASA's NStar Database, the Astronomiches Rechen-Institut at Heidelberg's ARCNS, Centre de Données astronomiques de Strasbourg's SIMBAD, and www.alcyone.de's bright star catalogue search. Additional information may be available at Roger Wilcox's Internet Stellar Database.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
© 2006 Sol Company. All Rights Reserved. |