Massive-star supernovae found to be major space dust factories
9th June 2006
An unaccounted for source of space dust which spawns life in the universe has been identified by an international team of scientists including Professor Albert A. Zijlstra of Manchester University's School of Physics and Astronomy.
Their paper in Science Express reports that the dust is formed when a massive star comes to the end of its life and releases its cataclysmic energy in what is called a Type II supernova.
Planets such as the Earth form out of small particles called 'dust', composed of elements such as carbon, silicon, magnesium, iron and oxygen. Until recently, it was thought that this dust was mainly formed by large, cool surfaced, stars known as red giants - the end of the life cycle of stars similar to our Sun. But the amount of dust found in young galaxies in the early universe makes this unlikely, as such stars are found only in older galaxies - at least a billion years after the galaxy's origin.
Supernovae produced by short-lived massive stars have long been suspected as the dust factories but they are fairly rare events that only happen approximately once every hundred years in a galaxy, making it harder for researchers to find and analyse whether dust is formed in their aftermath.
The Manchester Astrophysics Group has been heavily involved in the search for the origins of cosmic dust. Professor Zijlstra explains: "we now have, for the first time, detected an amount of newly formed dust in a supernova, which comes close to the amount needed to produce the dust seen in the Universe. This is a major discovery, affecting the origin of the Earth - and, indirectly, life."
The astronomers used NASA's Spitzer and Hubble Space Telescopes and the Gemini North Telescope atop Mauna Kea in Hawaii to observe a supernova, discovered in 2003, in the spiral galaxy Messier 74, approximately 30 million light-years away. Their results suggest for the first time that dust can form efficiently in supernovae, using up about five per cent of the heavy elements available.
The two images are 4 arcmin by 4 arcmin fields of view of part of the Spiral Galaxy M74, taken with the IRAC camera on the Spitzer Space Telescope on 28 July 2004 (left) and 15 Jan 2005 (right). The blue objects are hot stars (1000's of degrees K), whilst the reddish regions (200-300 K) are warm dust. The location of supernova SN 2003gd is in the centre of each frame just to the left of the "x". In July 2004 it appeared bright and green, meaning it was warm (~500 K), but by January 2005 it had completely disappeared: the energy of the supernova explosion having dissipated into space so its remnant would have been both cooler and less bright. Click image for a hi-res version.
Although researchers have detected many supernovae in the past at visible wavelengths, supernova 2003gd is only one of three in the universe that, at infrared wavelengths, have been seen producing dust. Supernovae dim and expand into space fairly quickly, so scientists require extremely sensitive telescopes to study them even a few months after the initial explosion. While astronomers have suspected that most supernovae do produce dust, their ability to study this dust production in the past has been limited by technology.
"One of the difficulties in trying to detect infrared emissions from distant galaxies is the extreme sensitivity of the detectors to heat from other sources," explains Professor Mike Barlow of University College London's Department of Physics and Astronomy.
"Infrared is primarily heat radiation, so the Spitzer Space Telescope must be cooled to near absolute zero (-273 degrees Celsius) so that it can observe infrared signals from space without interference from the telescope's own heat."
Infrared measurements of supernova 2003gd made 500-700 days after the outburst revealed emission consistent with newly formed cooling dust. Sophisticated modelling of the observed infrared emission and of the measured obscuration at visible wavelengths implied that solid dust particles equivalent to up to seven thousand Earth masses had formed.
Dr Ben Sugerman, of the Space Telescope Science Institute in Baltimore who led the research, says: "People have suspected for 40 years that supernovae could be producers of dust, but the technology to confirm this has only recently become available. The advantage of using Spitzer is that we can actually see the warm dust as it forms."
Team member Professor Robert Kennicutt, of the University of Cambridge's Institute of Astronomy, added: "These results provide an impressive demonstration of how Spitzer observations of supernovae can provide unique new insights into the processes that produce dust in the universe."
Notes to editors
The paper, 'Massive-Star Supernovae as Major Dust Factories' is in the June 8 Science Express edition of the journal Science.
Ben E. K. Sugerman (1), Barbara Ercolano (2), Michael J. Barlow (2), Alexander. G. G. M. Tielens (3), Geoffrey C. Clayton (4), Albert A. Zijlstra (5) Margaret Meixner (1), Angela Speck (6), Tim M. Gledhill (7), Nino Panagia (1), Martin Cohen (8), Karl D. Gordon (9) , Martin Meyer (1), Joanna Fabbri (2), Janet. E. Bowey (2) Douglas L. Welch (10), Michael W. Regan (1), Robert C. Kennicutt, Jr.(11)
(1) Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
(2 ) Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
(3)Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, Netherlands
(4)Dept. of Physics & Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA
(5)School of Physics and Astronomy, University of Manchester, P.O. Box 88, Manchester M60 1QD, UK
(6)Dept. of Physics & Astronomy, University of Missouri, 316 Physics, Columbia, MO 65211,USA
(7) Dept. of Physics, Astronomy, and Maths, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
(8) Monterey Institute for Research in Astronomy, 200 Eighth Street, Marina, CA 93933, USA
(9) Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721,USA
(10) Dept. of Physics and Astronomy,McMaster University, Hamilton, Ontario L8S 4M1, Canada
(11) Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
For further information, please contact:
Prof. Albert Zijlstra
School of Physics and Astronomy
The University of Manchester
P.O. Box 88
Manchester M60 1QD
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology. JPL is a division of Caltech.