Supernova 1987A

On February 23, 1987, a supernova was detected in the Large Magellanic Cloud about 160,000 light years from Earth. The first supernova to be discovered that year, it was designated 1987A.

Reaching an apparent magnitude of about 3, it could easily be seen with the naked eye, the brightest such event since 1604. Since its distance from the Earth is known, its absolute magnitude could be calculated. Further discussion 进一步讨论 Neutrinos observed 观测到的中微子 达到视星等约3等，可以轻易用肉眼看到，这是自1604年以来最亮的此类事件。由于其与地球的距离已知，其绝对星等可以计算出来。

Supernova 1987A Neutrinos

Ten neutrino events were detected in a deep mine neutrino detection facility in Japan which coincided with the observation of Supernova 1987A. They were detected within a time interval of about 15 seconds against a background of lower energy neutrino events. A similar facility, IMB in Ohio detected 8 neutrino events in 6 seconds. These observations were made 18 hours before the first optical sighting of the supernova.

Supernova 1987A

The discovery of Supernova 1987A was a great opportunity for detailed observation of the dynamics of a supernova. This supernova was unusual in that it did not rise abruptly to its maximum brightness, but paused briefly before increasing its luminosity by another factor of ten. It increased for about 85 days and then began a gradual decline which was more characteristic of other observed supernovae.

Another unique feature about this supernova is that the star which exploded had been observed and named Sk-69202. It was a blue supergiant presumed to have a mass of about 20 solar masses.

Almost coincident with the observation of the supernova, a burst of neutrinos were observed on the Earth, providing further information for modeling supernovae and providing another test for the mass of the neutrino.

This image of the remnant of Supernova 1987a was taken by the Hubble Space Telescope (Picture credit ESA/Hubble & NASA). The image was taken in December 2006 with Hubble's Advanced Camera for Surveys. The field of view is about 25x25 arcseconds. Note the two glowing loops and the inner circle of glowing material. ESA suggests that the loops and rings are probably material ejected from the star earlier in its history that is now being illuminated by the supernova and its shockwave. A neutron star is expected as a remnant of the supernova, but it has not been detected.

"The pink object in the centre of the ring is debris from the supernova blast. The glowing debris is being heated by radioactive elements, principally titanium 44, created in the explosion. The debris will continue to glow for many decades."

Reference: Hubble website