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INTERNATIONAL ASTRONOMY TEAM BRINGS STORY OF EXPLODING STAR TO THE SCREEN JANUARY 14, 1997: An international team led by a York University astronomer and his American colleague released a mini-movie depicting in the greatest detail ever the death of a star -- a supernova. York University astronomy professor Norbert Bartel and Michael Rupen of the National Radio Astronomy Observatory in Socorro, New Mexico are the principal investigators involved in the three-year project illustrating the evolution of a supernova -- the most energetic single process in the universe after the Big Bang. As a star dies, it becomes a supernova, increasing greatly in brightness from an explosion ejecting most of its mass. This research will shed more light on the effects of a star's explosion and help in determining cosmological distances and the age of the universe. The movie was released today at the 189th conference of the American Astronomical Society (AAS) being held at Toronto's Westin Harbour Castle Conference Centre from Jan. 12 to 16. It can be seen throughout the conference at the York University booth. Bartel will expound on the team's research in a talk at 10 a.m. today titled "VLBI Imaging of SN1993J in M81." This is the first time that supernova images of such quality have been made and assembled into a movie. The team monitored the supernova expansion from a fixed reference point, showing, with unique precision, detailed information on the effect of the explosion to a degree never before seen. "It's fascinating to actually watch how a star explodes and what the effect is on the environment," said Bartel. "So much material spills out from the explosion, at such speed, that it sweeps away everything in its path and probably evaporates any planetary system that might have existed around the original star." The movie shows the supernova changing its structure, revealing images of the star's expanding debris as the star explodes. The images for the movie were taken from May 1993 to December 1995. The seven images chosen show various phases in the life of a supernova. The team members filled in the gaps through computer enhancement to provide a smooth, complete picture of the supernova's evolution. The movie, which was produced in five- and ten-second versions, reveals what a supernova looks like as it expands. The naked eye cannot see a supernova with this level of detail, so the research team used radio waves to obtain the images. The supernova in the movie, SN1993J, was discovered in 1993 by an amateur astronomer in Spain. It is located in the galaxy M81 in the constellation Ursa Major, about 12 million light years away from Earth. In the first frame, the supernova appears very compact. It reveals the very early stages of a huge shock wave travelling out spherically from the explosion centre of the star at 60 million kilometres per hour, sweeping through the thin circumstellar gas left over from the millions of years of evolution that led to the star's demise. Subsequent frames in the movie follow this expansion. Bright segments in the expanding shell may reflect areas with a high density of material in the shock front (the first wave of the explosion) or in the gaseous environment. The last frame in the movie is a complex image showing the interaction of the shock front with the surrounding thin medium of gas into which the shock front expands. In addition to the shell structure from the shock front, there now appears a bright spot in an inner area of the picture. This might indicate the existence inside the shell of a neutron star, an extremely condensed object only 10 kilometres wide, formed at the very beginning of the explosion. The enormous magnetic field of the neutron star could cause a bright source of radiation in the neutron star's vicinity. By now, the supernova is 250 times larger than our entire solar system. Eighteen radio telescopes around the globe were used to simultaneously record data for subsequent synthesis to get a detailed, magnified picture that would otherwise require a telescope the size of the Earth itself. The team used a technique called "very-long-baseline interferometry", which enables radio astronomers to zoom in on celestial objects with a resolution 100 times higher than that of the Hubble telescope, and 1,000 times higher than that of any optical telescope on Earth. "This supernova is a unique event for radio astronomers, and we plan to continue studying it for decades to come," said Bartel. The international research team is also comprised of: York University researcher Michael Bietenholz; Tony Beasley of the National Radio Astronomy in New Mexico; David Graham of the Max-Planck-Institut fur Radioastronomie in Bonn, Germany; Tiziana Venturi and Grazia Umana of the Instituto di Radioastronomia in Italy; Antonio Rius of the Centre d'Estudis Avancats in Blanes, Spain, Valery Altunin and Dayton Jones of the Jet Propulsion Laboratory in Pasadena, CA, U.S.A.; and John Conway of the Joint Institute for VLBI in Europe and the Onsala Space Observatory in Sweden.
For more information, call:
Prof. Norbert Bartel
Dr. Michael Rupen
Mary Ann Horgan
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