Press Release

Backyard Astronomers Unite to Solve Mysteries of Stellar Explosions

Sometimes the little things in life count the most, especially when it comes to backyard stargazers making major contributions to the field of professional astronomy.

Dr. Janet A. Mattei, director of the American Association of Variable Star Observers (AAVSO), discusses some exciting examples of the results that have been obtained thanks to the networking of dedicated amateur astronomers and their collective collaboration with professional astronomers in variable star astronomy in her talk, "Networking and Internationalization in the Amateur Variable Star Community," on February 18 at the 2001 Annual Meeting of the American Association for the Advancement of Science (AAAS) in San Francisco.

In an era of 10-meter mountaintop telescopes and massive earth-orbiting observatories, amateur astronomers with modest telescopes continue to provide professional astronomers with critical data on star explosions and flares too numerous and random to track. These data are used often to point a satellite to those objects during these rare behaviors.

"Amateurs make crucial contributions when it comes to pointing a satellite like the Hubble Space Telescope (HST) to one of these bright exploding objects. Observations from amateurs help HST staff to determine if the object is too bright to be observed safely with a specific instrument aboard the satellite," said Mattei. "Often amateurs' observations drive the way the professionals plan observations with big telescopes or orbiting observatories."

"The AAVSO supports professional astronomers in scheduling observations with satellites and in providing follow-up optical data on cosmic events, as well as notification of bursting star systems," Mattei said.

SS Cygni, a close binary system in the constellation of Cygnus (the Swan), is a favorite of both professional and amateur astronomers, and many times amateurs' alerts to an outburst of this system have led to very important scientific results that could not have been determined without the amateurs' contributions.

What are these systems like SS Cygni that are so interesting to amateurs and professionals? These close binary star systems contain a red dwarf star and a white dwarf. A red dwarf is a star a little cooler than the Sun. A white dwarf was once as large as the sun but subsequently ran out of fuel, blew its outer shell into space, and collapsed to form a white-hot ember. The dense white dwarf, with its strong gravitational potential, pulls a stream of gas off of its companion star. This transferred gas collects in a disk, called an accretion disk, around the white dwarf.

The dramatic brightening by many orders of magnitude in this system is the result of an instability in the disk which forces the disk material to drain down onto the surface of the white dwarf, causing a titanic energy release equivalent to that of billions of atomic bombs exploding every second. These stellar outbursts, which often occur without warning and rarely last more than one or two weeks, serve as floodlights that brighten a dim star system for scientists to study.

In the past 5 months, SS Cygni was the target of two collaborative research programs involving amateur and professional astronomers and three NASA satellites - the Chandra X-Ray Observatory, Rossi X-Ray Timing Explorer (RXTE), and Extreme Ultraviolet Explorer (EUVE).

Amateur astronomers in Europe and North America kept a patient vigil on SS Cygni and alerted the AAVSO as soon as they saw the system begin to brighten in outburst, first in September and then in January. Both times Mattei coordinated the observations and communicated with the professional astronomers waiting anxiously for news so they could trigger multiple satellite observations, in September with EUVE and RXTE, and in January with RXTE and Chandra.

It was crucial to trigger the satellite observations at just the right times because the astronomers wanted to study certain behaviors that SS Cygni exhibits only at very specific times at or near the start of an outburst. Without the amateurs' alerts and ongoing observations, determining the right times for the satellites would have been impossible.

Thanks to everyone's dedicated efforts during both campaigns, all three satellites acquired excellent observations. The EUVE/RXTE/optical observations yielded ground-breaking information about exactly where in SS Cygni's disk an outburst starts and how the activity in the optical, extreme ultraviolet, and X-ray wavelengths are related. The RXTE/Chandra/optical observations are being analyzed, and they promise to fill in the missing pieces of the puzzle of SS Cygni's X-ray behavior during outburst and to further understanding of the accretion disk boundary layer.

Answers for SS Cygni may lead to answers for other astronomical objects: Active Galactic Nuclei (AGNs) are enigmatic objects that show some of the same behavior in extreme ultraviolet and X-ray that SS Cygni does in its disk during outburst. Understanding SS Cygni may help solve this AGN mystery.

Recently, amateur astronomers have embarked on yet another observing challenge: to catch the optical counterparts to gamma-ray bursts (GRBs), the most powerful events known in the Universe. The bursts occur randomly from all directions and typically last only for a few hours. It is difficult to obtain good optical data on the bursts without dedicated all-sky - and immediate - monitoring. The AAVSO has formed a worldwide GRB Network in which its observers are alerted via pagers so they can be immediately informed of these bursts and right away make the crucial observations with their backyard telescopes. Already several amateurs have successfully imaged optical counterparts of GRBs.

Ground-based variable star observers around the world have also successfully collaborated on the alphabet soup of NASA and European Space Agency missions, such as HEAO-1 and -2, IUE, Voyager, ASTRO-1 and -2, ROSAT, HIPPARCOS, ISO, ORFEUS, CGRO, HST, FUSE, and Chandra.

The AAVSO was founded in 1911 at Harvard College Observatory to coordinate variable star observations made largely by amateur astronomers and became an independent, non-profit organization in 1954. Today, AAVSO has members in over 45 countries and maintains the world's largest computer-readable variable star data archive, with over 10 million observations, and growing by almost half a million yearly. The AAVSO headquarters are in Cambridge, Massachusetts.

For more information, refer to the AAVSO website at http://www.aavso.org/. Mattei's talk will be held Sunday, February 18; AM; Track - Looking Beyond Earth; Symposium - A Telescope the Size of the Earth: Global Astronomy Networks; Hilton San Francisco & Towers.