(This press release from December
21, 1994, is reproduced courtesy of the Space Telescope Science Institute.)
This NASA Hubble Space Telescope picture resolves, for the first time,
one of the smallest stars in our Milky Way Galaxy. Called Gliese 623b or
Gl623b, the diminutive star (right of center) is ten times less massive than
the Sun and 60,000 times fainter. (If it were as far away as the Sun, it
would be only eight times brighter than the full Moon).
Located 25 light-years away in the constellation Hercules, Gl623b is the
smaller component of a double star system, where the separation between
the two members is only twice the distance between Earth and the Sun
(approximately 200 million miles). The small star completes one orbit
about its larger companion every four years.
Gl623b was first detected, indirectly, from astrometric observations
that measured the wobble of the primary star due to the gravitational
pull of its smaller, unseen companion. However, the star is too dim
and too close to its companion star to be seen by ground-based
telescopes. Hubble s view is sharp enough to separate the small
star from its companion.
The new Hubble observations will allow astronomers to measure the
intrinsic brightness and mass of Gl623b. This will lead to a better
understanding of the formation and evolution of the smallest stars
currently known. Red dwarf stars were once thought to be the most
abundant stars in the Milky Way, and thus possibly a solution to the
mystery of the Galaxys dark matter. However, recent Hubble
observations show that these low mass stars are surprisingly rare.
The image was taken in visible light on June 11, 1994, with the
European Space Agency s Faint Object Camera.
Credit: C. Barbieri (Univ. of Padua), and NASA/ESA