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1996 - A Record Year For Supernovae
By Greg Bryant
 

Published in the April 1997 issue of Universe
 



You may not have read it in the headlines recently, but 1996 was a record year for supernovae. A total of 83 supernovae have received designations indicating that the discovery either occurred in 1996 or was seen on an image first taken in 1996.

This total surpasses the previous record of 73, set in 1992. The below table lists the years in which records have been set, going back to the first official supernova designation in 1885. Since then, over 1000 supernovae have been recorded.

Year    Last Designation        Actual Number 
1885    SN 1885A                1
1895    SN 1895B                2
1921    SN 1921C                3
1937    SN 1937F                6
1950    SN 1950O                14 (*)
1954    SN 1954ad               30
1989    SN 1989ae               31
1990    SN 1990ak               37
1991    SN 1991bl               64
1992    SN 1992bu               73
1996    SN 1996ce               83
* : 15 designations were given, but SN 1950E turned out to be minor planet (2093) Genichesk

This does not mean, however, that stars are exploding at a greater frequency. Rather, the limiting magnitude for detections is growing fainter, and more equipment and time is being devoted to their discoveries, leading to greater numbers of supernovae being detected.

While 1996 was a record year, it wasn't necessarily a "super" year. The brightest supernova in 1996 was SN 1996X in NGC 5061, which was independently discovered at 13th magnitude on 12th April by both ASNSW member Reverend Robert Evans (the world's leading amateur discoverer) and Kesao Takamizawa. Evans' discovery was visual, while Takamizawa's method was photographic. There were only four other supernovae discovered during the year that there were brighter than 15th magnitude at the time of the discovery. At the other end of the scale, 31 supernovae (37% of the year's total) were discovered at a brightness of 20th magnitude or fainter, with the faintest being SN 1996az at magnitude 24.0.

The last supernova that was discovered at a brightness greater than 10th magnitude and was visible from New South Wales, other than the naked-eye supernova SN 1987A in the Large Magellanic Clouds ten years ago, was SN 1972E in the galaxy M83 at magnitude 8.5. Bright supernovae are not a common occurrence.

Once again, the register failed to record any discoveries from Bowen or Ilford, whether they be supernovae, novae, minor planets, comets, or even new variable stars. The challenge is there for our members. Astrophotographers - check your photographs. Your galaxy images may record a supernova tucked in among the spiral arms, while a faint comet could easily show up. Edward Szczepanski, an American amateur with the Houston Astronomical Society, discovered a 10th magnitude comet on a 50 minute exposure he took of the galaxy M101 and its surrounds on 27th January 1996. Comet C/1996 B1 (Szczepanski) subsequently was estimated to be 8th magnitude by visual observers during February before fading.

Already, more than 60 supernovae have been recorded during the first three months of 1997, though none have been notable, while it has been nearly eight months since a visual discovery of a comet was made, the last being comet Tabur in August last year.

What special discoveries will be in store for 1997?