Stars within 10 light-years

Including Sol itself, only 12 stellar objects (including the white dwarf, stellar remnant known as Sirius B) are currently believed to be located within 10 light-years (ly) of Sol. Except for Lalande 21185, astronomers believe that Sol and its current nearest neighbors were born close to or within the Milky Way's "thin disk." While Lalande 21185 may be substantially older than Sol, Barnard's Star may be even older, born perhaps as much as 10 or more billion years ago. By comparison, Sol is middle-aged at almost 4.6 billion years old, and the Sirius binary system is probably the youngest with perhaps around 300 million years.

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.

Seven of the 12 (58 percent) are very dim red dwarfs, of which six have been identified as flare stars and are likely to be relatively younger. Only Sirius A and Alpha Centauri A are currently brighter, larger, and more massive than Sol. Although Sirius B is now much dimmer and smaller than Sol with about the same mass, it was once brighter, larger, and more massive than even its primary companion.

VLTI, ESO



Larger and jumbo images.



Although the larger bluish white
to orange dwarf stars are roughly
similar to Sol in size, red dwarfs
such as Proxima Centauri are not
much larger than Jupiter (more).

The volume of space lying within 10 light-years of Sol encompasses nearly 4,189 cubic light-years. Within that enormous sphere, astronomers have detected at least 7.38 Solar-masses of visible matter bound up in 11 luminous stars and one weakly glowing white dwarf. Thus, the local density of luminous mass is low, less than 2/1,000 (or 0.00176) of a Solar-mass per cubic light-year -- not even the mass of two Jupiter-sized planets.

NASA


Larger image.


Among Sol's nearest neighbors,
only the Alpha Centauri system
may possibly be capable of
hosting Earth-type planets.

As of early January 2005, astronomers have been able to detect planets in the Solar System and around Lalande 21185 among the nearest 12 stars. Other than Sol itself, however, only Alpha Centauri A and B may possibly be capable of hosting Earth-type planets in stable orbits within their respective circumstellar habitable zones (CHZs). Within a CHZ orbit, liquid water may be possible on a planetary surface without tidal locking and orbital disruption from another celestial object.