Massive Old Star Reveals Secrets On Deathbed
January 26, 2004
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.
Composite by Richard Sword, IoA/Gemini Observatory GMOS images, except right inset by Isaac Newton Telescope
The star was imaged by the Gemini Observatory and Hubble Space Telescope (HST) less than a year prior to the gigantic explosion, and 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.
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.
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 (31-cm)
backyard telescope from his home in New South Wales, Australia in June
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.
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.
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.
supergiant stars are quite common in the universe. 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
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.
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.
Click here for more details.
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."
Gemini and HST data were 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 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."
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.
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).
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.
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).
Gemini Observatory, Hilo, HI
University of Cambridge
Phone: +44 (0)1223 766 651
Cell: +44 (0)7754 782 758
Justyn R. Maund
Phone: +46 (0)8 5537 8557
High-resolution TIFF (16 MB)
PDF (3 MB)
AI (48 MB)
GMOS image of M-74 (NGC 628) with inset (left) showing pre-explosion
star (enhanced) from Gemini image and (right) SN2003gd after it
exploded from Isaac Newton Telescope when the supernova was 6 months
old. Full resolution images and individual images available below.
Credit: Composite by Richard Sword, Institute of Astronomy, University of Cambridge/Gemini Observatory/Isaac Newton Telescope
Medium-resolution JPEG (35 KB)
North GMOS image of M-74 (NGC 628) used with HST data to determine
nature of progenitor of SN2003gd. Full technical caption here.
Credit: Gemini Observatory: GMOS Commissioning Team`
Medium-resolution JPEG (18 KB)
High-resolution TIFF (7 MB)
|Blow-up of region around SN2003gd progenitor star, with star enhanced for visibility. From Gemini North GMOS image.
Credit: Gemini Observatory: GMOS Commissioning Team
Medium-resolution JPEG (6 KB)
High-resolution TIFF (3 MB)
from the Isaac Newton Telescope with the Wide Field Camera taken on
25th August 2003 by Jonathan Irwin (IoA). It shows the position of the
fading supernova which by then was some six months old.
Credit: Isaac Newton Telescope, Jonathan Irwin
Medium-resolution GIF (7 KB)
|Sky-map showing location of Betelgeuse which is a red supergiant like the progenitor to SN2003gd described in this release.
Credit: Diagram courtesy of Eleanor Gilchrist, Royal Observatory of Edinburgh UK.