A team of scientists including University of Hawaii
astronomers have found the nearest example of a young
planet-forming star.
Using the telescopes on Mauna Kea, Hawaii, they have
discovered a spectacular circumstellar dust disk with
indirect evidence for newly formed planets around the
star AU Microscopium (AU Mic). At a distance of only
33 light years, this is the nearest star with a visible
disk, enabling astronomers to directly observe the
primordial material for making planets.
“We know that extrasolar planets are common, but
understanding how they form is an outstanding question.
Because AU Mic is so near to Earth, it provides us a
special opportunity to examine planet formation in great
detail,” said team member Dr. Michael Liu, an astronomer
at the University of Hawaii Institute for Astronomy.
The results will be published in this week’s online
AU Mic is a dim red star, with only half the mass and
“Unfortunately, we can’t go back in time and observe
The team used the James Clerk Maxwell Telescope on
By analyzing the radiation, the team deduced that
“The dust missing from the inner regions of AU Mic
The team’s visible light images of AU Mic reveal a
The images were obtained with an instrument known as
“This fascinating system shows how the exceptional
“AU Mic is a common red dwarf star, which comprise 85%
Images of disks around nearby stars are very rare, and
AU Mic is close enough that future imaging with the
“We’re waiting for the next observing season to go
“Astronomers will be studying AU Mic for many years
This work was supported by the National Science
The Institute for Astronomy at the University of Hawaii
Note to Editors:
Color images are available at:
Image Caption: Visible light image of the circumstellar
Science Express
March print edition of Science, and an upcoming issue
of the Astrophysical Journal. The authors are
Drs. Michael C. Liu and Jonathan P. Williams of the
University of Hawaii, and Drs. Paul G. Kalas and Brenda C.
Matthews of the University of California, Berkeley.
one-tenth the energy output as the Sun. Previous studies
had shown that AU Mic is about 12 million years old. In
comparison, our Sun is about 4.6 billion years old.
our own Solar System. But by studying these very
young stars, we can examine how planets are forming
around them, and thus indirectly learn about the
origin of our own Solar System,” said Liu.
Mauna Kea, Hawaii to study the sub-millimeter
radiation from AU Mic. This radiation, which is
invisible to the naked eye, comes from very cold
dust grains orbiting the star in the form of a disk.
Such disks are believed to be the nurseries for
forming planets.
dust particles only existed at large distances from
the star, and were missing inside a radius of about
17 AU. This would be slightly inside the orbit of
Uranus in our own Solar System.
is the telltale sign of an orbiting planet. The
planet sweeps away any dust in the inner regions,
keeping the dust in the outer region at bay,” said
Liu.
spectacular edge-on disk, extending out to at least
210 Astronomical Units (AU), or about 20 billion
miles. In comparison, the known edge of our Solar
System is about 50 AU, or four times smaller.
AU Mic’s disk is visible due to small dust particles
which reflect the light of the central star.
a coronagraph deployed on the with the University of
Hawaii’s 2.2-meter telescope. The coronagraph blocked
out the bright glare of the central star, allowing
detection of the faint edge-on disk.
clarity, darkness, and transparency of the Mauna Kea
skies allows Hawaii astronomers to make frontier
discoveries,” said Dr. Rolf Kudritzki, Director of the
Institute for Astronomy.
for all stars. By studying this nearby system, we
might learn about how the majority of planetary
systems can form,” said team member Dr. Paul Kalas,
an astronomer at the University of California,
Berkeley and a Ph.D. recipient from the University
of Hawaii.
AU Mic is the closest dust disk found since the
discovery 20 years ago of a disk around beta Pictoris,
a star about 2.5 times the mass of the sun and 65 light
years away. Though the two stars are far apart on the
sky, they appear to have been formed at the same time
and are traveling together through the galaxy.
Hubble Space Telescope or ground-based telescopes
using adaptive optics can study the detailed
structure of the disk and perhaps directly image
the light from any planets.
back and study the physical properties of the disk.
But we expect other teams to do the same thing – there
will be lots of follow-up,” said Kalas.
to come,” said Liu.
Foundation and the NASA Astronomical Search for
Origins program.
conducts research into galaxies, cosmology, stars,
planets, and the sun. Its faculty and staff are also
involved in astronomy education, deep space missions,
and in the development and management of the
observatories on Haleakala and Mauna Kea. Refer to
http://www.ifa.hawaii.edu/for more information about
the Institute.
http://www.ifa.hawaii.edu/info/press-releases/AU_Mic_images.html
disk around the nearby young star AU Mic discovered
with the University of Hawaii 2.2-meter telescope.
The disk is seen edge-on, revealed by starlight
scattering off of small dust grains. The outer extent
is about 210 Astronomical Units. The bright light
from the star is blocked by an opaque mask and its
supporting crosshairs, allowing detection of the very
faint disk. Analysis of the radiation from AU Mic
shows that the inner disk is cleared of material,
indirect evidence for newly formed planets in the
inner regions.
