Supernova 1987a
1987A supernova remnant near the center
SN 1987A was a supernova in the Large Magellanic Cloud, a nearby dwarf galaxy. It
occurred approximately 50 kiloparsecs from Earth, the closest supernova since SN 1604, which occurred in the
Milky Way itself. The light from the supernova reached Earth on February 23, 1987. As the first supernova
discovered in 1987, it was labeled "1987A". Its brightness peaked in May with a apparent magnitude of about 3 and slowly declined in the following months. It was modern astronomers' first opportunity to see a supernova up close.
Since 50 kiloparsecs is approximately 164,000 light-years, the cosmic event
itself happened approximately 164,000 years ago.
Model studies indicate that 99% of the energy radiated by supernovae is in the form of neutrinos.
Approximately three hours before the visible light from SN 1987A reached the Earth, a burst of neutrinos was observed at three
separate neutrino observatories (Kamiokande II, IMB and Baksan). At 7:35am Universal time, Kamiokande II detected 11 neutrinos, IMB 8 neutrinos and Baksan 5 neutrinos, in a
burst lasting less than 13 seconds. Although the actual neutrino count was only 24, it was a significant rise from the
previously-observed background level. This was the first time neutrinos emitted from a supernova had been observed directly, and
the observations were consistent with theoretical supernova models in which most of the energy of the collapse is radiated away
in neutrinos. The observations are also consistent with the models' estimates of a total neutrino count of 1058 with a total energy of 1046 joules.
SN 1987A
Observation Data
(Epoch B1950.0) |
| Type |
II unusual |
| Host |
Large Magellanic Cloud |
| Right
Ascension |
05h 35m 49.942s (1950) |
| Declination |
−69° 17′ 57.60″ (1950) |
| Discovery |
1987/02/24.23 UTC [1] (http://cfa-www.harvard.edu/iauc/04300/04316.html) |
| Peak
Magnitude (V) |
+3 |
| Physical Characteristics |
| Progenitor |
Sanduleak −69° 202 a |
| Progenitor Type |
B3 supergiant |
| Colour (B-V) |
+0.085 |
| Notable Features |
The closest recorded sn.
since invention of telescope |
One highly significant result was obtained from the data however. It appears that the neutrinos and antineutrinos both took the same time to arrive at earth, about 164,000 years, and from general relativity one would expect gravity to increase the travel time
by about five months. The difference in their arrival times was less than 12 seconds. This is the first empirical evidence that
matter and antimatter react similarly to gravitational fields, which was widely
predicted but not previously tested directly.
Sanduleak, the precursor to SN 1987A was a blue supergiant
presumed to have a mass of about 20 solar masses. This required some revisions
to models of high mass stellar evolution, which had suggested
that supernovae would result from red supergiants.
The supernova remnant formed by debris from SN 1987A is one of
the most-studied astronomical objects today.
External links
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