February 22, 2006
Some 440 million years ago an explosive extremely high energy event occurred in the distant universe. The initial energy released by the blast sped across the emptiness of space unimpeded until February 18, 2006 when it excited the electronic sensors of the Swift satellite instruments orbiting Earth. Almost immediately thereafter, Swift telemetry streams signaled worldwide alerts to astronomers. Ground-based telescopes swung into action to study the region of space where the signal emerged. Additional alerts were sent to amateur astronomers via the Internet. One of those messages arrived in the inbox of the Cedar Amateur Astronomers (CAA) group. The group "Stellar Commitee" leader issued a call to members to try to observe and possibly image the optical component of an anticipated supernova.
For many years, gamma ray bursts puzzled astronomers. The cause of such extremely high energy levels was mind-boggling. All sorts of theories
emerged to explain them from neutron star mergers to mysterious magnetars.
In his book Extreme Stars, James Kaler refers to gamma ray bursts (GRBs) as "the ultimate violence". The problem astronomers faced
was locating the GRB sources accurately and quickly with as much scientific gear as could be mustered. With the availability of the Swift satellite
astronomers are gathering more data and evolving more definitive theories. This recent gamma ray burst (GRB060218) occurred at 03:34:30.97 Universal Time.
Large ground based telescopes detected a supernova energy signals 3 days later. It was suggested that a dim and "nearby"
object may be detectable with amateur telescopes and CCD cameras. With the CAA Stellar committee chair's call I went to see
what I could find.
My first information source was the American Association of Variable Star Observers (AAVSO) web site. Plenty of information is available in AAVSO Special Notice #8. From the notice I learned the celestial coordinates of the burst and acquired a star chart indicating the precise location of the "optical afterglow". The notice detailed photometric techniques and filter types that would benefit further research. Although I'd like to contribute scientifically valuable data, I'm not yet equipped or experienced enough to do so. My goal was challenging enough: locate a beacon of light energy from the emerging supernova a mere 440 million light years away.
I opened my observatory dome on the evening of February 22 near 9:00pm. By 9:50 I was recording the first frames of the target area. I decided on 5 minute exposures using high resolution. Following the first exposure I performed an image link with the TheSky Version 6 planetarium software. The image link attempts to align the image with precise coordinates of bright catalogued stars. To my surprise the first image link was successful. My telescope was right on target. I then instructed the CCD imaging software to record another 6 images of 5 minutes each. After 4 images were accumulated I began aligning and combining them to learn whether or not an object signal existed at the target location. This is the time when reality sets in. Is a 10" telescope capable of resolving a point source of light 440 million light years distant? Well as a matter of fact yes it can! After only 15 minutes of combined exposure time a faint speck of a star-like image appeared. The trick was to continue imaging until a convincing signal developed above the background sky brightness. After 25 minutes the light source was convincing but I kept going to further increase the signal to noise ratio. After 35 minutes I had my results. To make sure the image quality was optimal I recorded bias and flat frames to substract unwanted electronic noise and dust moats from the final composite. Click on the image to view Supernove 2006aj.
Read AAVSO Special Notice #8 http://www.aavso.org/publications/specialnotice/8.shtml
Read more about the Swift Telescope at http://swift.sonoma.edu/about_swift/instruments
If you'd like to read more about GRB060218 see http://www.dsi-astronomie.de/SN_2006aj_2006-03-02.805.htm
Contact Cedar Amateur Astronomers http://www.cedar-astronomers.org/