Updated Message From The Committee Chairman

For more information contact Committee Chairperson Robert O. Evans (bobevans@pnc.com.au)

Update of AAVSO Supernova Search Committee Web page
November, 1999
by the Rev. Robert Evans (Committee Chair.)

The text of the Supernova Search Manual is naturally dated, but it contains much basic information about how to conduct a supernova search, and how to verify and report any supernovae which are found in such a search. The other documents on the web page are now mainly of historical interest, but do give some insights into the whole research program.

When the Supernova Search Manual was written, and first printed, in 1993, visual searching was the main option open to amateurs. Professional astronomers had only just begun to succeed in operating computerised searches using CCDs. The task of devising and perfecting these automatic or semi-automatic searches had taken the best part of ten years, and had cost many millions of dollars of research funds. The Berkeley group led by Carl. Pennypacker and Richard Muller were the first ones to master the art.

Over the last eight years, computers and CCDs have become much cheaper. Even small computers are now much more powerful, and much faster, than the ones that Pennypacker et al had to use in devising the first successful automatic search.

As a result, a number of other professional groups have now become involved in the search for supernovae, and have had a considerable degree of success.

Also, a considerable number of amateurs have purchased the equipment needed to computerise a telescope, and use a CCD, in searching for supernovae. They have been able to produce CCD pictures of galaxies on their computer screens, and find supernovae, by comparing the picture with a file picture.

Today, several amateurs have also been able to build systems to make fully automatic searches. Thus they can compete directly with the professional groups in searching for supernovae which are brighter than about magnitude 18. This is a pleasing development which becomes apparent when looking at the lists of supernovae which have been found this year, and in the last year or two.

No doubt this trend will continue, and increase. The sad thing about it is that people who cannot afford the equipment, or who have a different scale of values in the way they spend their money, cannot compete very well in finding supernovae. However, it is good for science, because it means that supernovae are being found earlier, and that there is a better coverage in finding all the supernovae in galaxies which are within easy distances from the Milky Way.

Despite this almost overpowering competition, however, visual observers should never give up, but should concentrate their attention especially on the brightest and nearest galaxies where the brightest supernovae will appear. These are the supernovae which are of the most importance in supernova research, because they can be studied in the most detail, and they provide the basic information which enables us to understand all the other more distant supernovae which are being found now. There are even a few nearby galaxies that cover a larger area of sky than is covered by the CCDs used by professional searches.

Also, visual observers should be careful to cover all types of galaxies. There is no guarantee that CCD searchers do this. Many search programs only cover those galaxies which are assumed to possess the best chances of producing a supernova. Other galaxies are often ignored, and this is bad science.

In the last year or so, groups of professional astronomers have used supernova studies in researching some of the basic questions of cosmology, relating to the age and destiny of the universe, and in refining our knowledge of the distances of the remotest galaxies.

This is one of the main factors which drive the desire by groups of professional astronomers to find as many supernovae as they can.

Last year, the two groups which are searching for, and studying very distant supernovae announced they had found that the expansion of the universe is accelerating. This discovery shocked and surprised many scientists, and it will need to be researched much further, in order to eliminate the possibility that errors have crept into their calculations.

Since 1983, and over the ten years that followed, a number of refinements have taken place in our understanding of Type 1a supernovae. These refinements have enabled astronomers to use these supernovae as standard candles, to measure remote distances in the universe, and to calculate whether the expansion of the universe is accelerating, is static, or is slowing down. These refinements have all depended directly upon the detailed study of bright supernovae which were first found by amateurs using backyard telescopes. Many of these supernovae were found visually.

Supernovae in the range of brightness between 15th and 18th magnitude, which are now being found in large numbers by CCD observers, both professional and amateur, are of relatively little scientific use, unless they are found before maximum light.

Astronomers who use spectrographs and photometers on the large telescopes are not inclined to use their precious observing time on fainter supernovae unless they already know that the stars are pre-maximum. Those searching for supernovae should therefore make repeated observations of a smaller number of galaxies. If observations of a galaxy have been made only a few weeks apart, there is more likelihood that a new supernova will still be pre-maximum. The time lapse since the last time the galaxy was observed should always be reported with the discovery details.

So, observe fewer galaxies more often, instead of spreading out over many galaxies which can only be observed on scattered occasions.