Astronomers
at the University of Michigan have found what
are believed to be some of the youngest solar
systems yet detected.
The systems are around the young stars UX Tau
A and LkCa 15, located in the Taurus star
formation region just 450 light years away.
Using a telescope that measures levels of
infrared radiation, the researchers noticed gaps
in the protoplanetary disks of gas and dust
surrounding these stars. They say those gaps are
most likely caused by infant planets sweeping
those areas clear of debris.
A paper on the findings by
astronomy doctoral student Catherine Espaillat,
professor Nuria Calvet, and their colleagues is
published in the Dec. 1 issue of Astrophysical
Journal Letters.
"Previously, astronomers were seeing
holes at the centers of protoplanetary disks and
one of the theories was that the star could be
photoevaporating that material," said Espaillat,
first author of the paper.
Photoevaporation refers to the process
of heating up the dust and gas in the
surrounding cloud until it evaporates and
dissipates.
"We found that in some
stars, including these two, instead of a hole,
there's a gap," Espaillat said. "It's more like
a lane has been cleared within the disk. That is
not consistent with photoevaporation. The
existence of planets is the most probable theory
that can explain this structure."
The
researchers used NASA's Spitzer Space Telescope
for this study. The infrared orbiting telescope
observes energy at wavelengths invisible to
optical telescopes. That allowed astronomers to
study these "pre-main sequence stars" in a
deeper way.
A main sequence star is an
average adult star, like the sun, which burns by
converting hydrogen into helium. Pre-main
sequence stars like UX Tau A and LkCa 15 haven't
yet established this conversion process. They
derive energy from gravitational contraction. UX
Tau A and LkCa 15 are both about 1 million years
old.
"They're baby stars," Calvet said.
The sun, for comparison, is a middle-aged star
at 4.5 billion years old.
Calvet said
this research adds new insights to the study of
solar systems.
"We are looking for our
history," Calvet said. "We are looking for the
history of solar systems, trying to understand
how they form."
The paper is called "On
the Diversity of the Taurus Transitional Disks:
UX Tau A & LkCa 15."
Source:-University of
Michigan
Published on
the 30th November 2007
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