[ASC-media] Media release: Aussie amateur helps confirm star-death idea

Helen.Sim at csiro.au Helen.Sim at csiro.au
Wed Jan 28 12:04:19 EST 2004


Issued by: Helen Sim, CSIRO Australia Telescope National Facility, on behalf
of the Australian Gemini Office (http://www.ausgo.unsw.edu.au/)
Tel: +61-2-9372-4251 (office) +61-419-635-905 (mobile)

Researcher contacts and image URLs at end

28 January 2004

For immediate use							


AUSSIE AMATEUR HELPS CONFIRM STAR-DEATH IDEA


An amateur Aussie astronomer has helped scientists confirm central aspects
of their theory of how stars age and die.

Scientists using the Hubble Space Telescope and the Gemini Observatory in
Hawai'i have pinned down the nature of a star seen exploding last June. The
team, led by Dr Stephen Smartt of the University of Cambridge, reported its
results in Science on 23 January.

The finding confirms astronomers' long-held belief that the most common kind
of stellar explosions, or supernovae, arise from red supergiant stars.

The supernova, SN 2003gd, appeared in the nearby galaxy M 74, in the
constellation of Pisces.

It was first seen by the Reverend Bob Evans of Hazelbrook, NSW, a renowned
amateur supernova sleuth, while he was scanning galaxies with a 31-cm (12")
telescope from his back verandah. 

Mr Evans reported his finding to the world astronomical community through an
alert system run by the International Astronomical Union.

Following Mr Evans' discovery, Dr Smartt's team used the Hubble Space
Telescope to determine the supernova's exact position. 

They then searched through data archives from the HST and the Gemini
Observatory to find images of the star that had exploded.

The images showed the progenitor was a 'red supergiant' - a star ten times
more massive than our Sun and 500 times bigger in diameter. If placed where
the Sun is, it would reach out as far as the orbit of Mars, engulfing Earth
and the inner planets.  

The supernova itself is classified as a type II-P supernova, the most common
type of stellar explosion. Astronomers had long thought that these
supernovae arose from red supergiants. But SN 2003 gd provides the first
proof.

Astronomers have found the progenitors of only two other explosions
identified with certainty as type II supernovae. Both of those explosions
were peculiar, and neither arose from a red supergiant. The star that
exploded as supernova 1987A was a blue supergiant, while supernova 1993J
arose from a massive interacting binary star system.

During the last few years Dr Smartt's research team has been using the most
powerful telescopes both in space and on the ground to image hundreds of
galaxies in the hope that one of the millions of stars in those galaxies
would some day explode.

"It might be argued that a certain amount of luck or serendipity was
involved in this finding," said Dr Smartt. "However, we've been searching
for this sort of normal progenitor star on its deathbed for some time."

The Gemini data on the progenitor of SN 2003gd were obtained during the
commissioning of the Gemini Multi-Object Spectrograph (GMOS) on Mauna Kea,
Hawai'i, in 2001. These data were also used to produce a high-resolution
image of the galaxy that clearly shows the red progenitor star
[http://www.gemini.edu/media/images_2004-2.html].

The resolution and depth of the Gemini and Hubble images allowed the
temperature, luminosity, radius and mass of this progenitor star to be
estimated.

"These observations provide a strong confirmation that the theories for both
stellar evolution and the origins of these cosmic explosions are correct,"
said co-author Seppo Mattila of Stockholm Observatory. 

Red supergiant stars are quite common. A good example is the bright red star
Betelgeuse in the constellation Orion
[http://www.gemini.edu/media/images_2004-2.html , bottom of page].
Astronomers think Betelgeuse could explode as a supernova at any time from
next week to thousands of years from now.

The member countries of the Gemini Observatory partnership are Argentina,
Australia, Brazil, Canada, Chile, the UK and the USA.

Australia's membership of the Gemini partnership is supported by the
Australian Research Council and by the Department of Education, Science and
Training through the Major National Research Facilities component of the
"Backing Australia's Ability" program.  


TEAM MEMBERS
Stephen J. Smartt, Justyn R. Maund, Margaret A. Hendry, Christopher A. Tout,
and Gerald F. Gilmore (all University of Cambridge, UK), Seppo Mattila
(Stockholm Observatory, Sweden), and Chris R. Benn (Isaac Newton Group of
Telescopes, Spain).


CONTACTS
Stephen Smartt, University of Cambridge, UK
Tel: +44 (0)1223 766 651 (office), +44 (0)7754 782 758 (mobile)
E-mail: sjs at ast.cam.ac.uk

Justyn R. Maund, University of Cambridge, UK
Tel: +44 (0)1223 337544
E-mail: jrm at ast.cam.ac.uk

Seppo Mattila, Stockholm Observatory, Sweden
Tel: +46 (0)8 5537 8557
E-mail: seppo at astro.su.se

Bob Evans (in Hazelbrook, NSW, Australia)
Tel: +61-2-4758-9053
bobevans at pnc.com.au

Professor Warrick Couch, UNSW
Australian Gemini Project Scientist and Chair, International Gemini Science
Committee
+61-2-9385-4578 (office), + 61-413-011-371 (mobile)
w.couch at unsw.edu.au


IMAGES
Gemini images of SN 2003gd in the galaxy M 74
http://www.gemini.edu/media/images_2004-2.html

The supernova shortly after its discovery. Photo: Ted Doboscz, Sydney,
Australia.
http://www.ausgo.unsw.edu.au/SN2003gd-M74.jpg


PUBLICATION
Stephen J. Smartt, Justyn R. Maund, Margaret A. Hendry, Christopher A.Tout,
Gerard F. Gilmore, Seppo Mattila, and Chris R. Benn. "Detection of a Red
Supergiant Progenitor Star of a Type II-Plateau Supernova." Science, 303,
499 (2004).


BACKGROUND - THE GEMINI OBSERVATORY
The Gemini Observatory is an international collaboration that has built two
identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is
located on Mauna Kea, Hawai'i (Gemini North), and the Gemini South telescope
is located on Cerro Pachón in central Chile (Gemini South), and hence
provide full coverage of both hemispheres of the sky. Both telescopes
incorporate new technologies that allow large, relatively thin mirrors under
active control to collect and focus both optical and infrared radiation from
space.

The Gemini Observatory provides the astronomical communities in each partner
country with state-of-the-art astronomical facilities that allocate
observing time in proportion to each country's contribution. In addition to
financial support, each country also contributes significant scientific and
technical resources. The national research agencies that form the Gemini
partnership include: the US National Science Foundation (NSF), the UK
Particle Physics and Astronomy Research Council (PPARC), the Canadian
National Research Council (NRC), the Chilean Comisión Nacional de
Investigación Cientifica y Tecnológica (CONICYT), the Australian Research
Council (ARC), the Argentinean Consejo Nacional de Investigaciones
Científicas y Técnicas (CONICET) and the Brazilian Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq). The Observatory is managed
by the Association of Universities for Research in Astronomy, Inc. (AURA)
under a cooperative agreement with the NSF. The NSF also serves as the
executive agency for the international partnership.


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