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M82
press release: 21/5/04 |
University College London press release
For immediate use
Friday 21 May 2004
STARBURST GALAXY SHOWERS THE UNIVERSE
When a galaxy known as M82 had a near-miss with its neighbour,
it set off an explosive burst of star formation that sent plumes of hot
gas tens of thousands of light years into space. Now a team of UK and
American astronomers has discovered that these gas clouds are like the
jets from a high pressure shower head.
M82 – which astronomers call a “starburst galaxy” -
is located at a distance of a bit more than 10 million light years from
our own Milky Way. Dr. Linda Smith, from the Department of Physics and
Astronomy, University College London, explains: "M82 shows intense
star formation packed in dense star clusters. This powers plumes of hot
gas that extend for tens of thousands of light years above and below the
starry plane of the galaxy. This cosmic hurricane is travelling at more
than a million miles an hour into intergalactic space.”
Dr. Smith and her postgraduate student Mark Westmoquette, together with
Jay Gallagher from the University of Wisconsin-Madison, have combined
images taken with the ground-based WIYN Telescope on Kitt Peak, Arizona,
and pictures from the Hubble Space Telescope in near Earth orbit. This
enabled them to produce a unique view of M82. "This approach allows
us to combine the strength of WIYN to measure very faint diffuse emission
with the superb sharpness of Hubble to obtain a full picture of the superwind
emerging from M82," says Professor Gallagher.
"Our problem was how to visualize data covering a huge range in brightness
and spatial scale," explains Westmoquette. "We solved this by
overlaying the sharp images from the Hubble that cover the inner part
of the galaxy, where resolving key details is critical, on top of WIYN
data that show the extended wind."
As a result, Dr. Smith and her colleagues can trace the outer wind back
to the point in the centre of the galaxy where it is being produced, like
following the cloud of smoke from a power plant back to the individual
chimney that produced it. Many of the stars that are formed in the M82
starburst end their short lives with a supernova explosion. That means
the winds they produce are laden with chemicals known as heavy elements.
“Our goal here is to understand the structure of the wind’s
plumes, which are key factors in the evolution of this galaxy and the
eventual pollution of nearby intergalactic space with new chemical elements,"
says Dr. Smith.
A HIGH RESOLUTION IMAGE IS AVALIABLE via the web (see
above) or ftp:
It can be downloaded from http://www.star.ucl.ac.uk/~msw/M82_pr
ftp ftp.star.ucl.ac.uk, username: anonymous, password: your email address;
then type “cd pub/msw” and “get M82_WIYN_and_HST_large.tif.
-ends-
For further information please contact:
Judith H Moore
Media Relations Manager
University College London
Tel: +44 (0)20 7679 7678
Mobile: +44 (0)77333 07596
Email: judith.moore@ucl.ac.uk
Dr Linda J. Smith
Department of Physics and Astronomy
University College London
Tel: 020 7679 7760
Mobile: 07766 564808
Email: ljs@star.ucl.ac.uk
Mark Westmoquette
Department of Physics and Astronomy
University College London
Tel: 020 7679 3410
Mobile: 07974 919732
Email: msw@star.ucl.ac.uk
Notes to editors
Figure caption: Colour-coded image of
the starburst galaxy M82 oriented to show its supergalactic wind running
left-right (north-south) and the nearly vertical disk of stars. Broad
blue, green and red filters were used to render the relatively smooth
stellar disk. Purple represents emission from hydrogen.
Image credits: Mark Westmoquette (UCL),
Jay Gallagher (University of Wisconsin-Madison), Linda Smith (UCL), WIYN/NSF,
NASA/ESA.
Acronyms:
The WIYN 3.5 m telescope is a joint facility of the University of Wisconsin-Madison,
Indiana University, Yale University and the National Optical Astronomy
Observatories.
NSF – National Science Foundation (USA)
NASA – National Aeronautics and Space Administration
ESA – European Space Agency
Facts about M82
The galaxy was discovered on 31 December 1774 by the German astronomer
Johann Elert Bode.
It is located in the northern hemisphere near the constellation Ursa Major
(The Plough) at a distance of just over 10 million light years.
It is the brightest galaxy in the sky when viewed using infrared light
and can be seen in visible light with a small telescope (visual magnitude=8.4).
M82 sits in a galaxy group that includes M81, M82, NGC 3077 and NGC 2976.
It is a small dwarf galaxy around one-quarter of the size of our Milky
Way.
A close encounter with the giant spiral galaxy M81 some 300 million years
ago set off the starburst event that we now see in the centre of M82.
Huge quantities of gas were funnelled into the centre by gravitational
forces. Eventually when this gas settled, large numbers of dense star
clusters were formed which produce the burst of star formation we see
today. We believe the starburst and the resulting superwind are around
10 million years old. Today, M81 and M82 are safely separated by 120,000
thousand light years.
There are three main classes of galaxy in the universe (as classified
by Hubble): spiral, elliptical and irregular. M82 is classified as a peculiar
galaxy because it does not fit into this standard classification scheme.
Peculiar galaxies constitute between 5% and 10% of the known galaxy population,
although most ‘normal’ galaxies will show peculiar features
if examined carefully. The terms ‘peculiar galaxy’ and ‘interacting
galaxy’ are now virtually synonymous. These objects provided the
first clear evidence that a galaxy’s environment can profoundly
affect its evolution.
Starburst galaxies account for only a few per cent of the galaxies in
our local universe but were much more common in the distant past when
the universe was smaller and galaxies were closer together.
About University College London
UCL has been consistently rated amongst the top three multi-faculty
universities in the UK. With an international reputation for excellence
and innovation in teaching and learning, UCL has occupied a pioneering
role in higher education since its inception. As well as being the first
English university established after Oxford and Cambridge, UCL was the
first university to offer undergraduate teaching in physics, chemistry
and engineering. Visit the website at: http://www.ucl.ac.uk/
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