The story of Supernova 1987 A

Ocurred in Large Magellanic Cloud, 170 thousand light years from us.

Progenitor star: Sanduleak -69^o 202, a blue supergiant.

Discovery

24 February, 1987
in Tarantula Nebula in Large Magellanic cloud,
by Ian Shelton, University of Toronto,
at Las Campanas Observatory, Chile.

Is the theory right?

At the core of the theory, so to speak, is the production of vast numbers of neutrinos.

Neutrino detectors available at the time.

Prediction: each detector should see 10 or so neutrinos from SN 1987A in a space of about 10 seconds.

Results.

Timing (times in Universal Time)

7:36, 23 February, neutrinos observed
9:30, 23 February
- Albert Jones, amateur astronomer, observes Tarantula Nebula in LMC
- He sees nothing unusual
10:30, 23 February
- Robert McNaught photographs LMC
- When plate is developed, SN1987A is there.
Some 20 hours later, Ian Shelton's discovery.

Conclusion:

It took between two and three hours for the shock wave to get to the surface of the star.
This agrees with the model prediction.

One surprise:

It was thought that type II supernovae came from red supergiant stars, but the star SK -69 202 was a blue supergiant (~ 20 times smaller than a red supergiant.)
It took some thinking to conclude that some very evolved stars could have a smaller size with higher surface temperatures.
SN 1987A was not as bright as moster type II supernovae. This was explained based on its smaller initial size.
- Initially, because it was small, there was not so much surface area to be radiating. Also, it was so hot it radiated mostly in the ultraviolet, not the visible so some of the radiation was not seen.
- After it expanded greatly, it was cool enough to be radiating mostly in the visible.
- But by then a lot of its energy had been expended in the expansion.

What do we see now?

The remnant from Supernova 1987A has been expanding since 1987. Here is what it looked like in 1994, using th Hubble Space Telescope. The inner ring is about 1.3 ly in diameter. The rings are presumably parts of shells of gas ejected by the star long before the explosion.

SN 1987A's remnant

SN 1987A's remnant, enhanced version

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu