Mr. Galaxy's Supernovae

Observing Supernovae

A light curve, along with spectral analysis, define the nature of a supernova. Shown at left is a light curve for SN 1991T plotted from independent visual observations by Mr. Galaxy and Stephen Knight, co-discoverers of SN1991T. The observed data shows a good fit to the light curve of a slow type I supernova illustrated by Thompson & Bryan in their book, The Supernova Search Charts. Click here to see a larger image (640x498).

Frequently Asked Questions (FAQ) About Observing Supernovae

• Telescope.  As a general idea a telescope with an 8-inch aperture can be used visually for supernova searching down to about 13th magnitude. You can scale from there, a 6-inch telescope will be good for detecting SNe down to about 12th magnitude and a 10-inch will be good for about 14th magnitude, etc. Also, relatively high magnification (~30x/inch) is used to examine the galaxy after locating it with low power. The high magnification increases the contrast with the background, making it easier to spot stellar images superimposed on the hazy galaxy.

• CCD Camera.  A CCD imaging camera that mounts on the telescope greatly increases the magnitude limit you can search. An 8-inch telescope can now be used reliably to hunt for 16th magnitude supernovae.

• Personal Computer.   A personal computer (PC) with plenty of disk space (1 to 2 G-byte minimum) is a great tool if available, especially if CCD images are to be stored. Software is needed to perform the following tasks:
  1. Position the telescope (if it has that capability, though not a requirement)
  2. Record/store CCD images
  3. Process the image for visual enhancement (especially for reducing the galaxy's nuclear brightness)
  4. Compare with previously stored images.

• Galaxy Charts and Reference Images.  Galaxy locating charts are helpful. However, it is important for you to get reference images using your own setup so that you can readily compare images to see whether anything has changed.

Supernovae are easier to detect and, hence, are more often found in bigger, brighter, and older galaxies than in smaller, less luminous, and younger galaxies. Spiral galaxies statistically produce more supernovae than do elliptical galaxies. Also, galaxies having the following morphological types are more likely to contain supernovae: Sc, Sb, S, Sa, and E.

The only absolutely sure way to confirm your discovery is to have it confirmed through spectroscopy at one of the university or professional observatories. But before you do that, there are some preliminary confirmation steps that need to be taken, as follows:

1. Compare your galaxy/supernova image with as many reference images as you can find. For example, the Space Telescope Science Institute (STScI) Digitized Sky Survey (DSS) is an excellent on-line source. Vickers' two-volume CCD atlas is a great hardcopy reference.

2. Check for movement by taking several images (using a CCD camera at least over one hour) to confirm that what you are seeing is not an asteroid, a hot pixel or a variable star.

3. Confirm discovery with one or more independent expert observations from SunSEARCH or the International Supernovae Network ( ISN) which has contacts world-wide.

4. Refer to the ISN web page for additional information and guidance on verifying supernovae.

1. Confirm that you have found a supernova by performing the steps mentioned above.

2. When you are as sure as you can be or do not have any other alternative, report your findings to the International Astronomical Union (IAU) by sending an e-mail to the Central Bureau for Astronomical Telegrams (CBAT). This should be done very cautiously! They have long memories if you report a false alarm. The CBAT has a Web page entitiled "How to Report a Discovery" here.

3. Plot your light curve as often as possible for as long as you can. See the graph at the top of this section for an example of a light curve. Sometimes the AAVSO will provide charts with reference stars for some of the brighter supernovae. The ISN is starting to provide some magnitude information for field stars where possible.