Somewhere
out there, astronomers knew the sun had another long-lost relative aimlessly
drifting through the Milky Way. Now they've found it.
Although a
happy reunion is unlikely, as the star HIP 56948 is about 200 light-years away,
it is now considered to be the best "solar twin" out of four known
candidates.
The wayward
star challenges the idea that our backyard star has a unique composition, as it
has a similarly low quantity of the element lithium--a lightweight byproduct of
the fusion reactions that power stars.
Astronomers
Jorge Melendez of the Australian National University and Ivan Ramirez of the University of Texas at Austin discovered the new star with a telescope at the McDonald
Observatory in Texas. The mid-sized star is one of many in the Draco the
dragon constellation and may be a billion years older than the sun, which
is middle-aged at 4.6 billion years.
Three other
solar twins were previously proposed: 18 Scorpius, HD 98618 and HIP 100963. While
similar to the sun in many ways, spectrographic analysis revealed that their
lithium contents are dramatically higher.
Because of
those observations, astronomers wondered if the sun's low
amount of lithium was unique. The newfound twin now shows that it isn't.
Searches
for solar twins are important, the astronomers said, because the sun is used as
a baseline for many other types of studies. But our own solar power plant is
too close and too bright to study like distant stars.
The solar
twins discovered at McDonald should help astronomers study the chemical
compositions of stars and back theoretical models of our sun's stellar insides
and evolution with real observations.
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