Infrared observations of supernova 1987A show a bright ring around the supernova that is apparently an infrared echo of it. The recently completed analysis of those observations, which were made Aug. 6 at the European Southern Observatory European Southern Observatory (ESO), an intergovernmental organization for astronomical research with headquarters in Garching, near Munich, Germany. The ESO began in 1962 as a consortium among Belgium, Denmark, France, Germany, the Netherlands, and Sweden. in La Silla, Chile, were reported in "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 4481' by A. Chalabaev of the Observatoire de Haute Provence at St.-Michel-l'Observatoire, France, and C. Perrier and J.M. Mariotti of the Observatoire de Lyon (France).
At the same time, in the Dec. 1 ASTROPHYSICAL JOURNAL The Astrophysical Journal, often abbreviated to ApJ, is a scientific journal covering astronomy and astrophysics. It was founded in 1895 by George Ellery Hale and James E. Keeler. It currently (October 2006) publishes three issues per month, with 500 pages per issue. LETTERS, Bradley E. Schaefer Dr. Bradley E. Schaefer is a professor of physics at LSU. He received his PhD from MIT in 1983.
His research interests include the use of photometry of exploding objects to get results of interest for cosmology. of the NASA/Goddard Space Flight Center in Greenbelt, Md., predicts the appearance of an echo in visible light. This visible echo should in fact already be there, he says, although it is indistinguishable because of the brightness of the supernova itself. Later, as the supernova dims, the echo should become more dominant. By a year after the supernova explosion--around March 1988--the echo should be a ring of about 10th magnitude, visible in small telescopes and maybe binoculars. It should persist for decades. "After the supernova itself has faded, the light-echo nebula nebula (nĕb`ylə) [Lat.,=mist], in astronomy, observed manifestation of a collection of highly rarefied gas and dust in interstellar space. will remain visible like the Cheshire Cat's smile,' Schaefer writes.
On earth, the first indication of a supernova is light coming directly from the exploding star. However, the exploding star is surrounded by diffuse interstellar matter interstellar matter, matter in a galaxy between the stars, known also as the interstellar medium. Distribution of Interstellar Matter
Compared to the size of an entire galaxy, stars are virtually points, so that the region occupied by the and may also have a somewhat denser circumstellar cir·cum·stel·lar
Revolving around or surrounding a star. shell of material that sometime in the past came off the star itself. Light going out in all directions from such an explosion will be reflected off this matter, and some of the reflected light will eventually come to earth. This reflection, the "echo,' will first appear sometime after the supernova itself, as the light takes times to go out and get reflected. The geometry of the situation is such that at any particular time, a ring of matter at a particular distance and angle from the supernova will reflect the light seen on earth as the echo, accounting for the ring shape.
The echo is interesting not only as an optical phenomenon but also as a probe of the nature of the matter surrounding the supernova. Terrestrial telescopes cannot resolve the light echoes of distant supernovas, says Schaefer, but two fairly close novas have exhibited the effect, Nova Persei 1901 and Nova Sagittarii 1936.