16 June 2006

The Astronomical Research Institute's National Supernova Search Program for Amateurs

Bob Holmes, Astronomical Research Institute, Charleston, Illinois

Harlan Devore, Cape Fear High School, Fayetteville, North Carolina 

J. Patrick Miller, James Cook University, Townsville, Australia

Introduction

A star with a mass that is more than 8 to 10 times that of the Sun dies a fiery death in an incredible explosion called a supernova (Type II) (see Fig. 1). For weeks, this event emits as much light as combined in the billions of stars that make up its host galaxy. As a result, these events can be seen millions, if not billions, of light years across the universe.

A binary system consists of two stars orbiting one another. A binary system with a mass less than 8 times that of the Sun can also produce a supernova (see Fig. 2).

The more massive of the two stars passes more quickly through a star's evolutionary cycle, first growing in size to an enormous red giant and then shrinking into a tiny white dwarf. As the less massive star catches up and grows into a red giant, the white dwarf captures material from its expanding companion. This can lead to the supernova explosion of the white dwarf (Type I).

The physics of a Type I supernova explosion is well understood, and the amount of light emitted is a known quantity. This means that such an event can be used as a “standard candle.” Or in other words, it can be used to calculate the distance that the host galaxy is from Earth.

As a result, supernovae are used to determine the three dimensional map of the universe. This information is used to understand the structure of the universe and the nature of its expansion. Therefore, astronomers have a keen interest in finding these events in distant galaxies.


Amateur Astronomers Find Supernovae

Using today's affordable small telescopes coupled with equally-affordable digital camera technology it is possible for amateur astronomers to seek and find supernovae in these distant galaxies. Each year approximately 400 supernovae are discovered, and many are original discoveries by amateurs.

The assembly shown in Fig. 3 is a telescope with a CCD (charge-coupled device) located at the Astronomical Research Observatory (ARO) maintained by the Astronomical Research Institute (ARI, Charleston , Illinois). This assembly is used in an on-going program by amateurs to search for supernovae.

Figure 4 shows two images of an anonymous galaxy in the cluster Abell 1656b. Both images were made by the ARO 16” Meade telescope shown in Fig. 3. The first image was made on January 26, 2006. The second, which was made on May 19, 2006, shows the presence of a supernova in the outer regions of that galaxy.

This is a Type I supernova designated as SN 2006bz by the International Astronomical Union (IAU), reported on May 4, 2006. Unfortunately, this was not an original discovery by amateurs (a fact not known at the time of its detection but later determined in a literature search). However, original discoveries have been made.

Figure 5 shows two images of a galaxy in the cluster Abell 1831 taken at the Astronomical Research Observatory. The first image was taken February 24, 2006, and the second March 27, 2006. The change in brightness of the galaxy is noticeable, as a supernova will emit as much light as combined in the billions of stars that make up its host galaxy.

The supernova is an unknown type. It was an original discovery by amateurs and is designated SN 2006bi by the IAU.

To confirm that a supernova was present a subtraction was performed on the two images. After subtraction, the extra light from one image appears (residual light) as shown in Fig. 6. The subtraction method was the one developed by Christoph Alard (1999) and was performed by Patrick Miller as part of his doctoral thesis with James Cook University (Townsville, Australia).

In Fig. 7 is another supernova (Type I) in a distant galaxy. Using the ARO 16” Meade telescope, this was an original discovery by amateurs. It is designated as SN 2006al by the International Astronomical Union. Figure Fig. 8 shows the subtraction of these two images.

The image in Fig. 9 is from the same Abell 1066 galaxy cluster. It shows an image of the galaxy NGC 3326 taken on January 26, 2006, and a subtraction of this galaxy on February 19, 2006.

Residual light is shown toward the center or core of the galaxy. This light may originate from a supernova or an active galactic nucleus (AGN). An AGN is a large black hole with a mass millions of times that of the Sun. When an object comes within a certain distance of the black hole (the event horizon) it is trapped and perhaps forever lost from the universe. However, in the process it emits tremendous amounts of light that causes the core of a galaxy to flare up and become visible at great distances.

There are a number of ways to distinguish between the two events. One way that amateurs use is to monitor the amount of light coming from the event over time (i.e., produce a light curve as shown in Fig. 10). The nature of this curve can identify an AGN. It can also identify supernovae (Type I or II).


What Does The Future Hold?

The Astronomical Research Institute is in the process of completing its Astronomical Research Observatory equipping it with a 32-inch telescope. This telescope will be capable of reaching magnitude 22 in a 5-minute exposure. It has the light-gathering capability of 16,384 times that of the human eye.

This telescope will be used to search for a variety of objects, including supernovae. Images from this instrument will be made available real-time (i.e., the following day) to amateurs around the nation and even the world. Amateurs can analyze the images and make original discoveries of these important astronomical events, which are then reported to the professional organizations that maintain official records.

Some teachers have successfully included the ARI search programs as part of their science classroom activities for their students. Students at Cape Fear High School in Fayetteville, North Carolina, have participated in the ARI search programs (see Fig. 12) and discovered several supernovae. Students from Hardin-Simmons University in Abilene, Texas, and Jackson State University in Jackson, Mississippi, analyzed ARI images as part of an upper division science course (see Fig. 13) and discovered a supernova and an active galactic nucleus.

If you are an amateur astronomer or an interested student or teacher, you are invited to volunteer your time to help the Astronomical Research Institute conduct its searches. For more information on how you can participate, visit the ARI home page at http://www.astro-research.org/ . The ARI mission and contact information is there along with a complete description of the various searches being conducted.


Acknowledgements

Students at Cape Fear High School (Fayetteville , North Carolina) have participated in the ARI search programs and discovered several supernovae. Brian Graves, a Cape Fear student, is credited with the discovery of 2006bu, a Type Ia supernova. At 1.23 billion light years from Earth, it is believed to be the most distant supernova ever discovered by an amateur.

Dr. Graeme L. White (Centre for Astronomy, James Cook University; Townsville, Australia) and Dr. Carlton R. Pennypacker (University of California, Berkeley; James Cook University ) provided invaluable technical assistance in the image subtractions.

The Aladin Sky Atlas was used to create many of the images in this article. For additional information see 2000A&AS..143...33B.

 
Figure 1. Remnants from a Type II supernova explosion in our own Milky Way Galaxy. It was observed in 1054 AD and remains visible today in amateur telescopes. Courtesy NASA, ESA, J. Hester and A. Loll (ASU).
 
Figure 2. Artist's rendition of material from a red giant falling onto its white dwarf companion just prior to the Type II supernova explosion of the white dwarf. Courtesy of Don Dixon.
 
Figure 3. Astronomical Research Institute telescopes. Courtesy of and copyright by ARI 2006.
 
Figure 4. Anonymous galaxy in the cluster Abell 1656b. Courtesy of and copyright by ARI 2006.
 
Figure 5. Anonymous galaxy in the cluster Abell 1831. Courtesy of and copyright by ARI 2006.
 
Figure 6. Subtracting the two images of the anonymous galaxy in Abell 1831 yields the residual light from the supernova. Courtesy of and copyright by ARI 2006.
 
Figure 7. Anonymous galaxy in the cluster Abell 1066. Courtesy of and copyright by ARI 2006.
 
Figure 8. Subtracting the two images of the anonymous galaxy in Abell 1066 yields the residual light from the supernova. Courtesy of and copyright by ARI 2006.
 
Figure 9. NGC 3326 in the cluster Abell 1066 (left panel) and subtraction of NGC 3326. Courtesy of and copyright by ARI 2006.
 
Figure 10. Example of a supernova light curve. Curves like this are used to distinguish between a supernova and an active galactic nucleus. Courtesy of Nicole Stewart, Cape Fear High School, Fayetteville, North Carolina.
 
Figure 11. Installation of the 32-inch telescope at the Astronomical Research Observatory of the Astronomical Research Institute. First light is scheduled for this month (June 2006). Courtesy of and copyright by ARI 2006.
 
Figure 12. Harlan Devore, a science teacher at Cape Fear High School in Fayetteville, North Carolina, with his students in the background analyzing ARI images. Courtesy of Andrew Craft of Fayetteville Online.
 
Figure 13. Students from Hardin-Simmons University in Abilene, Texas, and Jackson State University in Jackson, Mississippi, analyzing ARI images at the Lawrence Berkeley National Laboratory. Courtesy of Holly Ann Fidler, Hardin-Simmons University.
   
Copyright 2005 by Society for Amateur Scientists