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SN1993J in the spiral galaxy M81. CCD image taken with clear filter, 120 sec exposure with the University of Iowa’s ATF Observatory.

Best Observing Season: Any Level: Introductory Learning Goals: The student will search for undiscovered supernovae. Terminology: supernova Software: MaxIm                          Archive Image Directory: snsearch Archive Image List: Selection from over 800 NGC Galaxies in the supernova archives. References: Sky and Telescope; December, 1993

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Background and Theory

The first supernova detection in an external galaxy was the result of visual observations  of the nearby spiral M31, the Great Andromeda Galaxy in the year 1885. On average, a supernova (SN) occurs in a typical galaxy once every ~100 years, although a few galaxies appear to have significantly greater rates, e.g. M83 and NGC6946 have been producing SN about once every ten years. The prompt discovery of a supernova within hours or at most a few days of the explosion is extremely important for modeling the supernova outburst.

Since it is impossible for professional astronomers to devote a large amount of observing time on large apertures instruments for SN searches, amateurs astronomers have played an important role in the discovery of many historical SN. A number of serious amateurs have a regular surveillance program to monitor the brightest galaxies. The record for amateur discoveries is probably the Reverend R. Evans who discovered three supernovae in a single year! Recently there have been several professional automated observatories set up to search for new SN. The most successful automated search system is probably Berkeley’s Automatic Imaging Telescope (BAIT) which have resulted in several SN discoveries in past year [1] ^.

In the event you think that there is no real chance of detecting a new SN, the following tale will suffice. In late March 1993, a new supernova was discovered in the nearby spiral M81 by the amateur astronomer M. Garcia. The SN (known as SN1993J)  generated great interest, particularly since it was close enough that the precursor star could be seen on historical photos of M81. Professional astronomers around the world have been studying this enigmatic SN ever since discovery [2] . This event could have been easily discovered by students in this lab: The discovery magnitude was V~13.

By observing a number of galaxies periodically over the course of a semester, there is a significant chance to discover you own SN. The technique is quite simple: you must carefully compare each galaxy image with an older image. Good luck!        

Procedure

Observing

1.      The number of galaxies searched should be sufficient to ensure some chance of success but not so large as to exceed either observing time of the telescope or the observer’s ability to inspect the images. A reasonable number per session might be 20-40. Select from the list of galaxies in the file cand-s96.lis (directory supernova) suitable for observing during the spring semester.

2.      Make a schedule file with the chosen galaxies.  Most of the galaxies in the list are sufficiently close that a SN will be V~15 or brighter at maximum.  Use a clear filter with an exposure time of 60 seconds.

3.      Plan to observe the galaxy list at least once per week for several weeks. It is important to examine the images promptly because you don’t want to be scooped in your first astronomical discovery!

Image Analysis

1.      Use the program MaxIm to display each image.  Then click on View/Blink to bring up the Blink window.  Add your image with the reference image, click OK, then press play.  Compare your image with an archival image taken by the Automated Telescope Facility to see if there are any changes.