Serendipity: supernova in Centaurus A.Serendipity serendipity
happy finding of an unexpected object or solution while searching for something else. : Supernova in Centaurus A
Supernovas--giant stellar explosions --are not particularly rare in the universe. They are a staple item for Astronomical Telegrams, astronomers' system for quick notification of new developments. Highly active galaxies are also fairly numerous. However, the combination --a supernova in an active galaxy--is much rarer. And when the galaxy is the nearest active galaxy to us, Centaurus A, which also happens to be one of the strongest and longest studied celestial sources of radio waves, the combination provides a rather unique excitement for astronomers.
The current supernova, officially designated supernova 1986G, was first reported on May 4 by Robert Evans, an amateur astronomer in Hazelbrook, New South Wales Hazelbrook is a village in New South Wales, Australia (Elevation: 674 metres, Pop.: 4409 (2001)) It is located 93 kilometres west of Sydney and approximately 17 kilometres east of Katoomba in the Blue Mountains on the Great Western Highway. , Australia, and confirmed by observers at the Anglo-Australian Telescope at Siding Spring Mountain in New South Wales New South Wales, state (1991 pop. 5,164,549), 309,443 sq mi (801,457 sq km), SE Australia. It is bounded on the E by the Pacific Ocean. Sydney is the capital. The other principal urban centers are Newcastle, Wagga Wagga, Lismore, Wollongong, and Broken Hill. . Centaurus A, also known as NGC 5128, is visible only from the Southern Hemisphere. Observatories there have been turning toward it: The National Optical Astronomy Observatories say all major telescopes at their Cerro Tololo Inter-American Observatory Cerro Tololo Inter-American Observatory (sā`rō tōlō`lō), astronomical observatory located on Cerro Tololo peak, Chile, with offices in La Serena, about 40 mi (64 km) to the west. Funded by the U.S. near La Serena, Chile La Serena ("the serene one") is the second oldest city in Chile. The city, located 471 km north of Santiago, has a population of 147,815, according to the 2002 census. There are also 12,333 inhabitants of the immediately surrounding countryside. , are observing it, an unusual concentration of resources on a single object for a major observatory.
According to Mark Phillips of Cerro Tololo, the supernova's maximum brightness occurred about a week after it was detected. To better understand how supernovas happen, astronomers want to find them before maximum light, while the explosion is on the way up, but most are not noticed until after maximum. However, in a report on International Astronomical Union “IAU” redirects here. For other uses, see IAU (disambiguation).
The International Astronomical Union (IAU) unites national astronomical societies from around the world. Circular 4216 (May 15), G. Meurer of Mt. Stromlo Observatory in the Australian Capital Territory Australian Capital Territory (1991 pop. 276,468), 939 sq mi (2,432 sq km), SE Australia, an enclave within New South Wales, containing Canberra, capital of Australia. It was called the Federal Capital Territory until 1938. says spectra he took indicate that brightness peaked April 21, well before the first sighting. Two more reports on the same circular indicate that the International Ultraviolet Explorer International Ultraviolet Explorer: see ultraviolet astronomy. satellite has taken ultraviolet spectra.
Spectra will tell which type of supernova this is--Meurer says his show it to be Type I--and track its development. They may also tell something about the nature and dynamics of the "lane' of dust that lies across the center of Centaurus A. As luck would have it, the supernova lies behind the dust. Such dust lanes are features of several galaxies, and astronomers are interested in their nature and their relation to the dynamics and evolution of the galaxies that have them. Spectra and a profile of the supernova's brightness over time will also help refine the figure for the distance to Centaurus A.
Photo: Centaurus A before (left) and after supernova.