Supernova 1987A shines brightly near the center of this photo, taken
March 2, 1987. The wispy gas clouds of the Tarantula Nebula lie to
the supernova’s left. Marcelo Bass/CTIO/NOAO/AURA/NSF
It was 20 years ago today,
A shock wave started 87A,
Its behavior was pretty wild,
Left a core of a dozen miles,
So let me introduce to you,
A star that launched a million cheers,
(Lennon-McCartney-Talcott [with apologies to the first two])
In the predawn hours of February 23, 1987, a few alert observers in the Southern Hemisphere noticed a star shining next to the Tarantula Nebula. Of course, billions of stars lie near the Tarantula Nebula, a huge star-forming region in the Large Magellanic Cloud (LMC), a satellite galaxy to the Milky Way. But this one was visible to the naked eye — no mean feat from 160,000 light-years away.
It was an exploding star — a supernova — and it would advance our knowledge of these stellar bombs like none before. Although its light was the first thing we saw, it wasn't the first signal to arrive at Earth. At 2:35 A.M. EST (7h35m Universal Time), a thousand trillion trillion neutrinos created in the collapse of the supernova's progenitor star ripped through Earth. About two dozen of them were stopped dead in their tracks by neutrino detectors located in Ohio, Japan, and the Soviet Union. (Unfortunately, these detectors recorded the interactions, and no one knew of the discovery until days later.) The neutrinos confirmed, for the first time, that supernovae create neutron stars.
Even though the explosion was seen in late February, it was the first supernova discovered in 1987. As such, it was christened supernova 1987A. A good gauge of how much telescopes and technology have improved over the past 20 years: Yesterday astronomers discovered supernova 2007ae — this year's 31st supernova. 87A may have provided a quantum leap to our knowledge of how stars explode, but the unprecedented number of supernovae found these past few years has helped astronomers decipher how the universe works.
Today at the "Supernova 1987A: 20 Years After" workshop in Aspen, Colorado, the assembled astronomers reminisced about where they were when they heard the news. (At least the ones who were out of grade school did.) Many were in their offices and heard about it from colleagues — the same way I heard. The Internet wasn't around to the extent it is today, and information didn't travel worldwide instantaneously.
Will we live to see the next naked-eye supernova? It's hard to say. Supernovae should go off a couple of times a century in our galaxy, and we haven't seen one since 1604. But a Milky Way supernova could lie behind light-years of dust and never reach naked-eye visibility. We'll have to wait, and hope. And in the meantime, make a toast to a singular event that happened 20 years ago today.