Kangaroos, Elephant Trunks, and
Stars
Astronomers Discover Menagerie
of Hot Molecules
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Media Release - School of Physics
- The University of New South Wales
Monday 21st September 1998
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A new instrument on the Anglo-Australia Telescope is helping astronomers
peer deep into star-forming clouds in our Galaxy. According to Dr.
Lori Allen, an astronomer at the University of New South Wales, stars
form deep in clouds of gas and dust. The very material that form the
stars also hide the birthing process from view by conventional instruments.
However, by looking at infrared light
from these regions, astronomers can see what is happening inside
the stellar nurseries. "That's because infrared light penetrates
the dusty gas clouds, while visible light is scattered and absorbed
by the dust particles'', says Allen. The star-forming clouds are
composed primarily of molecular hydrogen, with some heavier elements
and dust mixed in.
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Image Right :
A Close-up of the dust lanes within the star forming region
Messier 16, the Eagle Nebula, as seen with the Anglo Australian
Telescope. The red colour is due to the emission from fluorescent
hydrogen gas.
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The new instrument, developed at the
University of New South Wales (UNSWIRF, or UNSW Infrared Fabry-Perot)
enables Allen and her colleagues to make images of molecular clouds
at very high spectral and spatial resolution, i.e., to isolate the
light of a very specific wavelength, and investigate the small-scale
structure of these clouds. Specifically, they are investigating
the ways in which young, hot stars affect the surrounding gas that
is left over after their formation, and what implications these
interactions may have for future generations of stars. "If the newly
formed star is extremely hot and bright, it can destroy all the
molecular gas in its vicinity, thus preventing any more stars from
forming nearby. But if the energy it emits is just right, it can
actually compress the surrounding gas, inducing subsequent star
formation'' Allen said.
Investigations have focused on the M16
star forming region (also known as the "Eagle Nebula''), which is
famous for its striking elephant trunk--shaped columns of molecular
gas. This cloud material, left over from the formation of a large
cluster of massive stars about 2 million years ago, is now being
heated by those stars, and images made by the UNSW group reveal
that the gas within the trunks is not uniformly distributed. Instead,
it is clumpy, and shows large variations in its density. This discovery
has important implications for the theories of how stars form. Another
region featured in the study is a kangaroo-shaped nebula in the
constellation Carina. The newly discovered "Roo nebula'' was one
of the first images made with the powerful new instrument.
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Image Right :
Close up of the dust lanes, or "Elephant Trunks", within the
Eagle Nebula, seen with the Hubble Space Telescope. The colours
represent a change in the excitation of the gas from low (red)
to high (blue); red shows emission from singly-ionized sulphur
atoms, green the emission from fluorescent hydrogen gas, and
blue from doubly-ionized oxygen atoms. The dark pillars are
full of gas and dust and are invisible at optical wavelengths.
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Allen works with Dr. Michael Burton,
a senior lecturer at the University of New South Wales, Department
of Astrophysics. Collaborators include UNSW astronomers Professor
John Storey and Dr. Michael Ashley, the designers of UNSWIRF, and
Dr. Stuart Ryder of the Joint Centre for Astronomy in Hawaii. Allen
worked as an undergraduate on particle physics experiments at the
Stanford Linear Accelerator, and later on SETI, the Search for Extraterrestrial
Intelligence, at NASA.
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Further Information
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