SDSS J102915+172927
SDSS J102915+172927 |
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© ESO,
Digitized Sky Survey 2
Larger and
jumbo images.
Located around 4,140 light-years away in
the galactic halo,
SDSS J102915+172927
is an ancient star that may be over 13
billion years old
(more).
One of the Most Metal-poor Stars Known
On August 31, 2011, a team of astronomers using the European Southern Observatory's Very Large Telescope (VLT) announced their discovery of one of the most metal-poor stars known in the Milky Way's galactic halo. Designated SDSS J102915+172927, the star has been measured to be made of almost purely hydrogen and helium, with only extremely small amounts of heavier elements ("metals"). The star is located over 4,140 +/- 490 light-years away (1,270 +/- 150 parsecs) from our Sun, Sol, in Constellation Leo, the Lion (10:29:15.15+17:29:28 J2000). SDSS J102915+172927 is believed to be one of several stars which have been found recently to have the lowest amount of elements heavier than helium of all stars yet studied. With a mass smaller than that of the Sun (at around 0.8 Solar-masses), the star is probably more than 13 billion years old (ESO science release; Caffau et al, 2011; Lisa Grossman, New Scientist, September 1, 2011; Nancy Atkinson, Universe Today, September 1, 2011; and Astronomy Picture of the Day).
© ESO,
Akira Fujii,
Digitized Sky Survey 2
Larger and
jumbo illustrations
(source).
SDSS J102915+172927 is a very faint star
located around 4,140 light-years away from
our Sun, Sol, in
Constellation
Leo
(more).
The proportion of elements heavier than helium in SDSS J102915+172927 is more than 20,000 times less than that found in Sol. According to widely accepted cosmological theory, only the lightest chemical elements, hydrogen and helium as well as a little lithium was created after the Big Bang. Almost all heavier elements were formed later by stars or in supernova explosions, which dispersed into and enriched the interstellar medium, so that later stars formed with higher amounts of metals in their composition than older stars. As a result, the proportion of metals in a star indirectly provides a gauge of its age. As SDSS J102915+172927 is extremely metal-poor, it most be "very primitive" and possibly one of the oldest stars ever found.
© ESO,
Digitized Sky Survey 2
Larger and
jumbo illustrations
(source).
SDSS J102915+172927 has been measured
to have less than 7 / 100,000th of a percent
of the elements heavier than hydrogen and
helium that our Sun, Sol,
is composed of
(more).
Another unexpected finding was the lack of lithium in SDSS J102915+172927. Although such an old star should have a relative lithium composition similar to that of the Universe theorized to have soon after the Big Bang, the astronomers found that the proportion of lithium in the star was at least fifty times less than expected. Given existing theories, the astronomers were unable to explain how the lithium that formed just after the Big Bang could have been destroyed within the star.
© ESO
Like HE 1523-0901, which
is also located thousands
light-years away in the galactic
halo, SDSS J102915+172927 is
probably more than 13 billion
years old
(more).
a
Other Information
Up-to-date technical summaries on this star may become available at: NASA's ADS Abstract Service for the Astrophysics Data System; and the SIMBAD Astronomical Database mirrored from CDS, which may require an account to access.
The Constellation Leo represents the Lion that Hercules (also a constellation) had to kill as one of his 12 tasks. For more information and an illustration of the constellation, go to Christine Kronberg's Leo. For another illustration, see David Haworth's Leo.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
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