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18-Apr-2014

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N° 47–1994: Hubble finds one of smallest stars in the Universe

16 December 1994

This picture taken by the European Space Agency's faint object camera on-board the Hubble Space Telescope(*) resolves, for the first time, one of the smallest stars in our Milky Way galaxy. Called G1623b 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 only be eight times brighter than the Full Moon).

Located 25 light years away, in the constellation Hercules, G1623b 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 300 million Km). The small star completes one orbit about its larger companion every four years.

G1623b was first detected, indirectly, from previous astrometric observations that measured the wobble of the primary star due to the gravitational pull of its smaller, invisible 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 G1623b. 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 Galaxy. However, recent Hubble observations show that these low mass stars are surprisingly rare

(*)The Hubble Space Telescope is a project of international cooperatio between NASA and ESA (the European Space Agency).


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