SETI bioastro: Giant magnetic bubble discovered in nearby galaxy M82

From: Larry Klaes (lklaes@bbn.com)
Date: Tue Apr 18 2000 - 15:28:13 PDT


Subject: Giant magnetic bubble discovered in nearby galaxy (Forwarded)
Date: Tue, 18 Apr 2000 12:31:21 -0400
From: Andrew Yee <ayee@nova.astro.utoronto.ca>
Organization: UTCC Campus Access
To: SEDSNEWS@LISTSERV.TAMU.EDU

------------------
Joint Astronomy Centre

Contact numbers:

Jane Greaves (JAC)
email: j.greaves@jach.hawaii.edu
phone/voicemail (USA): (808) 969 6562
fax (USA): (808) 961 6516
Note Hawaii time is 6 hours behind the US East Coast and 11 hours behind
the United Kingdom.

Thursday 13th April 2000

GIANT MAGNETIC BUBBLE DISCOVERED IN NEARBY GALAXY

HILO, HAWAII -- A team of astronomers from the Joint Astronomy Centre
(JAC) in Hawaii today announced the first image of a magnetic field in
star-formation regions of another galaxy. M82 is one of the closest
'starburst' galaxies, with dozens of very active sites around the
nucleus where stars are being born. The new discovery shows a giant
magnetic 'bubble' 3000 light years across, apparantly blown outwards
by the superwind from the galaxy's stars and supernovae.

"This is the first time we've been able to see right into the heart of
the star-forming activity and image the magnetic structure", said JAC
astronomer Jane Greaves, who led the research team. By observing at
short radio wavelengths of about a millimetre, they can probe through
obscuring interstellar dust clouds that block out the nucleus in
traditional optical images.

The team was surprised to see the huge 'bubble' outlined in the image.
The most likely explanation is that enormously energetic winds --
outflows of interstellar gas powered by stars and supernovae -- are
forcing the magnetic field out into the halo of the galaxy.

"One of the most exciting things", said team member Wayne Holland,
"is that we see some field lines pointing right into the nucleus".
"Magnetic fields can help gas clouds fall inwards, so we may have
a clue to why this galaxy has such a condensation of star-forming
activity near the centre."

The astronomers used a new technique that detects tiny differences in
emission from interstellar dust, by looking at different angles on the
sky. The dust grains are lined up by local magnetic fields, just like
iron filings around an ordinary magnet. The differencing technique,
millimetre-wavelength polarimetry, has never before been used to look
at another galaxy.

M82 is one of our closer galaxy neighbours, at a distance of about 11
million light years. It is object number 82 in the famous catalogue
of 'fuzzy objects' compiled by Messier in 18th century. The starburst
activity was most likely triggered by a close flyby of the neighbour
galaxy M81, which can be seen in the Image Gallery at the website of
the Chandra X-ray Observatory at this URL:

http://xrtpub.harvard.edu/photo/0094/what.html

How was the new image obtained?

The new image was obtained using the 15-metre James Clerk Maxwell
Telescope at the Mauna Kea Observatory in Hawaii. The JCMT is the
world's largest telescope dedicated to the study of light at
'submillimetre' wavelengths. The team of astronomers used a
revolutionary new camera called SCUBA (Submillimetre Common User
Bolometer Array), which was built by the Royal Observatory in
Edinburgh (now the UK Astronomical Technology Centre). The
Polarimeter was built by Queen Mary and Westfield College in
London, and funded by a joint science initiative of the UK and
Japan.

SCUBA uses detectors cooled to a tenth of a degree above absolute zero
(-273 degrees Celsius) to measure the tiny amounts of heat emission
from small dust particles at a wavelength close to one millimetre.
SCUBA by itself detects both of the two perpendicular waves ('planes
of polarization') of which light of any wavelength is made up. The
Polarimeter uses a very fine (6 micron spacing) grid that passes only
one plane, and a bi-refringent quartz plate that rotates the source
polarization. Together these produce slightly different images every
30 seconds, that are analysed to measure the magnetic field directions.

The JCMT is operated by the Joint Astronomy Centre, on behalf of the UK
Particle Physics and Astronomy Research Council, the Netherlands
Organisation for Scientific Research, and the National Research Council
of Canada.

Information and images are available on the World Wide Web at

   http://www.jach.hawaii.edu/~jsg/m82_press.html

Full-size images are also available:

* M82 GIF image

  http://www.jach.hawaii.edu/~jsg/m82_pr_annot_2.gif

* M82 JPEG image

  http://www.jach.hawaii.edu/~jsg/m82_pr_annot_2.jpg

IMAGE CAPTION:

Image of the emission from M82 at a wavelength of 0.45 mm, and
polarization results at 0.85 mm wavelength. The red and blue arrows
show the observed magnetic field directions and the white dashed
curves outline the magnetic bubble structure. The long white arrows
depict the direction of the wind from the centre of the galaxy.

PAPER:

"The first image of magnetic fields in a star-forming galaxy nucleus"
by Jane S. Greaves, Wayne S. Holland, Tim Jenness, Tim G. Hawarden.
Appearing in Nature on April 13th 2000.

Related links:

* Joint Astronomy Centre

  http://www.jach.hawaii.edu/

* James Clerk Maxwell Telescope

  http://www.jach.hawaii.edu/JCMT/

* Submillimetre Common-User Bolometer Array (SCUBA)

  http://www.jach.hawaii.edu/JCMT/scuba

Author information:

* Jane Greaves, JCMT astronomer

  http://www.jach.hawaii.edu/~jsg/life.html

* Wayne Holland (JCMT)

  http://www.jach.hawaii.edu/~wsh/wayne/wayne.html

* Tim Jenness (JCMT)

  http://www.jach.hawaii.edu/~timj

* Tim Hawarden (UKIRT)

  http://www.jach.hawaii.edu/~hawarden/

*****

Particle Physics and Astronomy Research Council
Swindon, U.K.

Contacts:

Charlotte Allen
PPARC press office
Tel: 01793 442012
Mobile 07881 654121
E-mail: c.allen@pparc.ac.uk

Jane Greaves
JCMT Astronomer
Tel: 00 1 808 969 6562 (Hawaii is 11 hours behind BST)
E-mail: j.greaves@jach.hawaii.edu

18 April 2000

Giant magnetic bubble discovered in nearby galaxy

A giant magnetic 'bubble' measuring 3000 light years [18 trillion miles]
across has been discovered in a nearby galaxy by a team of astronomers
in Hawaii. Nothing similar has ever been seen before and it sheds new light
on our understanding of how "starburst" galaxies evolve.

The astronomers from the Joint Astronomy Centre were mapping the
magnetic structure of galaxy M82 in order to see stars being born in the
smouldering gas clouds at the very heart of this active starburst region
when they detected the magnetic bubble.

"We were really surprised to see the huge bubble," said British
astronomer Jane Greaves," this is a new feature of galaxies that we
didn't know about before and could show how magnetic fields help
shape the evolution of starburst regions.

"The most likely explanation for the bubble is that enormously energetic
winds -- outflows of interstellar gas powered by stars and supernovae --
are forcing the magnetic field out into the halo of the galaxy.

Galaxy M82 makes up to fifty times more stars than other galaxies, but
the reason for this remains unexplained. "One of the most exciting
things," said team member Wayne Holland, "is that we see some magnetic
field lines pointing right into the nucleus of the galaxy, and since
the [ionised] particles in gas clouds tend to flow along the lines of
magnetic force, then we may have a clue as to why this galaxy has
such a predominance of star-forming activity at its centre."

The team used the 15 metre James Clerk Maxwell Telescope equipped with
a revolutionary new camera SCUBA, which was built by the Royal
Observatory Edinburgh, now the UK Astronomy Technology Centre. The
polarimeter used was built by Queen Mary and Westfield College, London.
The scientists used a new technique that detects tiny differences in
emission from interstellar dust. They discovered that the dust grains
are lined up around local magnetic fields, just like iron filings
around an ordinary magnet.

The next step will be to use this 'sub-millimetre' technique to look
at other galaxies, to see whether M82 is a freak or if other nearby
starburst galaxies show the same thing.

Professor Ian Halliday, Chief executive of the Particle Physics and
Astronomy Research Council, PPARC, said ''British scientists are
leading the field of sub-millimetre astronomy. The JCMT/SCUBA
combination represents the largest telescope in the world dedicated
to this type of observation.

The UK is continuing its commitment to this field by investing in
the new ALMA submillimetre array in the Atacama Desert. ALMA, which
begins construction in 2002, will enable scientists to see 10 times
more clearly at this wavelength and will take our understanding of
galaxy formation to a new level."

Images:

http://www.jach.hawaii.edu/~jsg/m82_press.html

Note to editors

A starburst galaxy is a galaxy in which there is thought to be an
exceptionally high rate of star formation. Starburst galaxies are
characterised by excessive emission of infrared radiation.

Galaxy M82 is one of our nearest galaxy neighbours at a distance of
about 11 million light years. It is an active star forming region.
M82 is so named because it is object number 82 in Messier's 18th
century catalogue of 'fuzzy objects'. A star explodes about every
10 years in M82. These violent explosions heat up the surrounding
gas to produce an expanding hot bubble.

PPARC

The Particle Physics and Astronomy Research Council (PPARC) is the UK's
strategic science investment agency. It funds research, education and
public understanding in four broad areas of science -- particle physics,
astronomy, cosmology, and space science.

PPARC is government funded and provides research grants and studentships
to scientists in British universities, gives researchers access to
world-class facilities and funds the UK membership of international
bodies such as the European Laboratory for Particle Physics, CERN,
and the European Space Agency. It also contributes money for the UK
telescopes overseas on La Palma, Hawaii, Australia and in Chile, the
UK Astronomy Technology Centre at the Royal Observatory, Edinburgh
and the MERLIN/VLBI National Facility.

PPARC's Public Understanding of Science and Technology Awards Scheme
provides funding to both small local projects and national initiatives
aimed at improving public understanding of its areas of science.

---
Andrew Yee
ayee@nova.astro.utoronto.ca



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