PASADENA, CALIF. — Baby stars have at last been
found in the harsh environment at the center of the Milky Way, astronomers said
here this week at the 214th meeting of the American Astronomical Society.
These are
"stars that have just ignited their core and they are just starting to
produce light. So it is a very early phase in the star formation process,"
said team member Solange Ramirez of NASA's Exoplanet Science Institute at
Caltech.
The heart
of our galaxy is an extreme environment, with fierce stellar winds, shock waves
and a core supermassive
black hole all packed into a region 600 light-years across. While this is
but a fraction of the total diameter of the galaxy, which is 100,000
light-years across, the core is stuffed with 10 percent of the gas in the
galaxy and a bounty of stars.
Astronomers
have long known that stars are born in this chaotic environment, as evidenced
by clusters of massive adolescent stars and clouds of charged gas – a sign that
new stars are beginning
to ignite.
But how
they could survive in the region of intense radiation and tremendous
gravitational interactions remains something of a mystery, and direct
observations of newborn stars have been complicated by the dust that enshrouds
them.
"These
stars are like needles in a haystack," Ramirez said. "There's no way
to find them using optical light, because dust gets in the way."
To get
around the obscuring fields of dust, astronomers used NASA's Spitzer
Space Telescope.
Ramirez and
her colleagues scanned Spitzer mosaics of the galactic center, focusing in on
more than 100 candidates of so-called young stellar objects. Viewed from far
away, these stars can look much older than their actual age because both types
of stars are dusty.
"The
old stars and the young stars look pretty much alike," Ramirez said.
"You cannot tell them apart."
Examining
the light signatures of each star can distinguish between baby and elderly
stars. Clouds of certain warm, dense gases are one signature of young stars,
for example.
The stars
are "still embedded in the molecular cloud where they are being
born," Ramirez said.
The three
young stellar objects found by Spitzer in the heart of the galaxy are all less
than about one million years old (our sun is 4.6 billion years old and
considered middle-aged). They are all shrouded in these clouds of gas and dust,
which will supposedly eventually flatten into disks and could form planets.
The team
plans to look for more baby stars in the galactic center in the future, which
could shed light on how these stars manage to form in the intense environment
at the heart of the Milky Way.
"By
studying individual stars in the galactic center, we can better understand how
stars are formed in different interstellar environments," said team member
Deokkeun An, also of Caltech.
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