Astronomers Discover Sun's Twin at McDonald Observatory (Forwarded)
Andrew Yee
University of Texas
Contact: Rebecca Johnson
ph: 512-475-6763 fax: 512-471-5060
09 November 2007
Astronomers Discover Sun's Twin at McDonald Observatory
FORT DAVIS, Texas -- Peruvian astronomers Jorge Melendez of The Australian
National University and Ivan Ramirez of The University of Texas at Austin
have discovered the best "solar twin" to date, using the 2.7-meter Harlan J.
Smith Telescope at McDonald Observatory. Their findings suggest that the
Sun's chemical composition is not unique, as some previously thought.
The star, HIP 56948, is more like the Sun than any yet seen, and is 200
light-years away in the constellation Draco, the dragon. The star may be a
billion years older than the Sun.
Only three solar twins were previously known: 18 Scorpius, HD 98618, and HIP
100963. But while they were all like the Sun in many ways, there was one
major difference: the amount of lithium they contained. They all had several
times more than the Sun. Astronomers wondered if the Sun was unique in its
low amount of lithium.
The discovery of this new solar twin puts that question to rest: it has the
same low lithium content as the Sun. The study turned up another solar twin,
HIP 73815, that contains a similarly low amount of lithium.
The question of chemical peculiarities in the Sun is related to the
"anthropic principle" -- is there something special about the Sun that has
allowed life to spring up in our solar system? Their findings don't answer
that completely, but they do show that when it comes to the Sun's chemical
composition, the answer is an emphatic "no."
Melendez' and Ramirez' findings suggest the opposite, so-called "Copernican"
view: It is possible that life is common elsewhere in the universe. They
suggest that stars like HIP 56948 would be good targets for SETI (Search for
Extra-Terrestrial Intelligence) researchers.
The star already has been studied by the McDonald Observatory Planet Search
led by University of Texas at Austin astronomer Bill Cochran. His team found
that, like our Sun, HIP 56948 does not host any "hot Jupiter" planets, those
massive, short-period planets orbiting close to their parent stars, so
common among the more than 200 stars found to date that host one or more
planets.
Searches for "solar twins" are important because astronomers use the Sun as
a baseline for many other types of studies. But they cannot study the Sun
the same way they do the distant stars. It's too close, and too bright.
The solar twins discovered at McDonald will be useful for many areas of
astrophysics. In particular, they will help astronomers who study the
chemical compositions of stars, as well as validate theoretical models of
stars' interiors, and theoretical models of stellar evolution.
IMAGE CAPTIONS:
[Image 1:
http://mcdonaldobservatory.org/news/gallery/image.php?id=113]
Finder chart for HIP 56948. The star is located 200 light-years away in
Draco, the dragon. It's too dim to see with the unaided eye. (Tim
Jones/McDonald Obs./UT-Austin)
[Image 2:
http://mcdonaldobservatory.org/news/gallery/image.php?id=36]
The 2.7-meter Harlan J. Smith Telescope at McDonald Observatory. (Marty
Harris/McDonald Obs./UT-Austin)