Massive Old Star Reveals Secrets On Deathbed (Forwarded)

Gemini Observatory
Hilo, HI

Media Contacts:

Peter Michaud
Gemini Observatory, Hilo, HI
Phone: 808/974-2510
E-mail:

Science Contacts:

Stephen Smartt
University of Cambridge
Phone: +44 (0)1223 766 651
E-mail:

Justyn R. Maund
University of Cambridge
Phone: +44 (0)1223 337544
E-mail:

Seppo Mattila
Stockholm Observatory
Phone: +46 (0)8 5537 8557
E-mail:

FOR IMMEDIATE RELEASE: January 26, 2004

Massive Old Star Reveals Secrets On Deathbed

Like a doctor trying to understand an elderly patient's sudden demise,
astronomers have obtained the most detailed observations ever of an old but
otherwise normal massive star just before and after its life ended in a
spectacular supernova explosion.

Imaged by the Gemini Observatory and Hubble Space Telescope (HST) less than a
year prior to the gigantic explosion, the star is located in the nearby galaxy
M-74 in the constellation of Pisces. These observations allowed a team of
European astronomers led by Dr. Stephen Smartt of the University of Cambridge,
England to verify theoretical models showing how a star like this can meet such
a violent fate.

The results were published in the January 23, 2004 issue of the journal Science.
This work provides the first confirmation of the long-held theory that some of
the most massive (yet normal) old stars in the Universe end their lives in
violent supernova explosions.

"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. I like to think that
finding the superb Gemini and HST data for this star is a vindication of our
prediction that one day we had to find one of these stars in the immense data
archives that now exist." Click here for more details on Dr. Smartt's ongoing
supernova program.

During the last few years, 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 these galaxies will
some day explode as a supernova. In this case, the renowned Australian amateur
supernova hunter, Reverend Robert Evans, made the initial discovery of the
explosion (identified as SN203gd) while scanning galaxies with a 12-inch (31cm)
backyard telescope from his home in New South Wales, Australia in June, 2003.

Following Evans' discovery, Dr. Smartt's team quickly followed up with detailed
observations using the Hubble Space Telescope. These observations verified the
exact position of the original or "progenitor" star. Using this positional data,
Smartt and his team dug through data archives and discovered that observations
by the Gemini Observatory and HST contained the combination of data necessary to
reveal the nature of the progenitor.

The Gemini data was obtained during the commissioning of the Gemini Multi-Object
Spectrograph (GMOS) on Mauna Kea, Hawaii in 2001. These data were also used to
produce a stunning high-resolution image of the galaxy that clearly shows the
red progenitor star.

Armed with the earlier Gemini and HST observations Smartt's team was able to
demonstrate that the progenitor star was what astronomers classify as a normal
red supergiant. Prior to exploding, this star appeared to have a mass about 10
times greater, and a diameter about 500 times greater than that of our Sun. If
our sun were the size of the progenitor it would engulf the entire inner solar
system out to about the planet Mars.

Red supergiant stars are quite common in the universe and an excellent example
can be easily spotted during January from almost anywhere on the Earth by
looking at Betelgeuse, the bright red shoulder star in the constellation of
Orion. Like SN2003gd, it is believed that Betelgeuse could meet the same
explosive fate at any time from next week to thousands of years from now.

After SN2003gd exploded, the team observed its gradually fading light for
several months using the Isaac Newton Group of telescopes on La Palma. These
observations demonstrated that this was a normal type II supernova, which means
that the ejected material from the explosion is rich in hydrogen. Computer
models developed by astronomers have long predicted that red supergiants with
extended, thick atmospheres of hydrogen would produce these type II supernovae
but until now have not had the observational evidence to back up their theories.
However, the fantastic resolution and depth of the Gemini and Hubble images
allowed the Smartt team to estimate the temperature, luminosity, radius and mass
of this progenitor star and reveal that it was a normal large, old star. "The
bottom-line is that 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.

This is only the third time astronomers have actually seen the progenitor of a
confirmed supernova explosion. The others were peculiar type II supernovae: SN
1987A, which had a blue supergiant progenitor, and SN 1993J, which emerged from
a massive interacting binary star system
[http://hubble.esa.int/science-e/www/...bjectid=34455].

Dr. Smartt concludes, "Supernova explosions produce and distribute the chemical
elements that make up everything in the visible Universe -- especially life. It
is critical that we know what type of stars produce these building blocks if we
are to understand our origins."

Archived Gemini and HST data was critical to the success of this project. "This
discovery is a perfect example of archival data's immense value to new
scientific projects," said Dr. Colin Aspin who is the Gemini Scientist
responsible for the development of the Gemini Science Archive (GSA). He
continued, "this discovery demonstrates the spectacular results that can be
realized by using archival data and stresses the importance of developing the
GSA for future generations of astronomers."

The Gemini Multi-Object Spectrograph used to make the Gemini observations are
twin instruments built as a joint partnership between Gemini, the Dominion
Astrophysical Observatory, Canada, the UK Astronomy Technology Centre and Durham
University, UK. Separately, the U.S. National Optical Astronomy Observatory
provided the detector subsystem and related software. GMOS is primarily designed
for spectroscopic studies where several hundred simultaneous spectra are
required, such as when observing star and galaxy clusters. GMOS also has the
ability to focus astronomical images on its array of over 28 million pixels.

The Isaac Newton Group of Telescopes (ING) is an establishment of the Particle
Physics and Astronomy Research Council (PPARC) of the United Kingdom, the
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands
and the Instituto de Astrofísica de Canarias (IAC) in Spain. The ING operates
the 4.2 metre William Herschel Telescope, the 2.5 metre Isaac Newton Telescope,
and the 1.0 metre Jacobus Kapteyn Telescope. The telescopes are located in the
Spanish Roque de Los Muchachos Observatory on La Palma which is operated by the
Instituto de Astrofísica de Canarias (IAC).

Background Information:

Supernovae are among the most energetic phenomena observed in the entire
Universe. When a star of more than about eight times the mass of our Sun reaches
the end of its nuclear fuel reserve, its core is no longer stable from
collapsing under its own immense weight. As the core of the star collapses, the
outer layers are ejected in a fast-moving shock wave. This huge energy release
results in a supernova that is about one billion times brighter than our Sun,
and is comparable to the brightness of an entire galaxy. After destroying
itself, the core of the star becomes either a neutron star or a black hole.

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

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.

[NOTE: Images supporting this release are available at
http://www.gemini.edu/media/images_2004-2.html ]

In message , Andrew Yee
writes

Massive Old Star Reveals Secrets On Deathbed




Red supergiant stars are quite common in the universe and an excellent
example can be easily spotted during January from almost anywhere on
the Earth by looking at Betelgeuse, the bright red shoulder star in the
constellation of Orion. Like SN2003gd, it is believed that Betelgeuse
could meet the same explosive fate at any time from next week to
thousands of years from now.

I suspect this has been asked before, but does anyone know what changes
occur in a red supergiant just before it explodes - in the last year, or
last 500 years?
In other words, could Betelgeuse have gone already (whatever that means)
and the news hasn't reached us yet?
--
Save the Hubble Space Telescope!
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