Mini-Throughput: Supernova 35 Years And Running

On the night of February 24, 1987, astronomer Ian Shelton was working on the 10-inch astrograph at Las Campanas Observatory in Chile. His initial test plate was of the Large Magellanic Cloud — a small galaxy that orbits our own. After developing the plate, he noticed a bright star where he didn’t expect one. He then stepped out into the night and looked up at the LMC, which is visible to the naked eye.

At the same night, staff member Oscar Dulhade was doing his rounds of the domes, making sure everything was functioning. As he stepped out of one of the domes, he glanced up at the sky. He too noticed a bright star in the LMC where none had been before.

While the story was told to me second-hand, the version I heard was this: Oscar went back into the dome to tell the astronomers what he’d seen. But the telescope operator asked him to repeat a funny story he’d told earlier. As he was doing so, Shelton came in with his plate and said he thought a supernova had gone off in the LMC. Eventually, astronomers went down to La Serena and sent out a circular to the community:

SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD

W. Kunkel and B. Madore, Las Campanas Observatory, report the
discovery by Ian Shelton, University of Toronto Las Campanas
Station, of a mag 5 object, ostensibly a supernova, in the Large
Magellanic Cloud at R.A. = 5h35m.4, Decl. = -69 16′ (equinox 1987.2), 18′
west and 10′ south of 30 Dor and possibly involved with the
association NGC 2044. The discovery was made around Feb. 24.23 UT on
a 3-hr exposure with a 0.25-m astrograph beginning on Feb. 24.06,
and the object had evidently brightened by at least about 8 mag since
the previous night. An independent suspected sighting was made
visually by Oscar Duhalde, also at Las Campanas, around Feb. 24.2.
The object had brightened to about mag 4.5 by Feb. 24.33.

F. M. Bateson, Royal Astronomical Society of New Zealand,
informs us that the object was discovered independently by Albert
Jones, Nelson, on Feb. 24.37 UT (position R.A. = 5h35m.8, Decl. = -69 18′,
equinox 1950.0) at mag 6.5-7.0 (in clouds); he estimated mv = 5.1
on Feb. 24.46. B. Moreno and S. Walker, Auckland Observatory,
obtained V = 4.81, B-V = +0.085, U-B = -0.836 on Feb. 24.454 UT.

Supernovae are among the most violent events in the universe, caused when a massive star runs out of its core fuel. The interior implodes down to a neutron star and the outer layers crash down, creating a shock wave that blows the star apart. At its peak, a supernova can outshine galaxies.

But these explosions are rare. Only stars that start out eight times the mass of the Sun will go supernova and such stars are extremely rare. Moreover, the burn out very quickly, lasting only 10 millions years, a thousandth of the lifetime of a star like the Sun. One goes off in the nearby universe maybe once a century. They have been critical, though. Two supernovae — Tycho’s supernova in 1572 and Kepler’s in 1604 — occurred in the midst of a debate over the nature of the universe and helped challenge the idea that the heavens were perfect and unchanging. And ancient records from around the world have recorded other supernovae over the centuries — most famously the one that created the Crab Nebula back in 1054. That event was visible during the day at its peak and persisted in the sky for two years.

SN 1987A — the designation was from being first supernova discovered in 1987 — would continue to brighten for the next three months. The intense light of the supernova would light up rings of cold dust that had been blown out by the blue supergiant progenitor. Analysis would show that neutrinos — tiny subatomic particles thought to be produced in supernovae — were detected three hours before the light reached us. Over the ensuing 35 years, we would continue to study the shattered remnants of the star, learning more about supernovae than we’d learned int he previous 35 centuries. Now, of course, supernovae are routine. SN 1987A was the first discovered in 1987; now it would be the several hundredth.

Astronomy deals with epic scales in both space and time. We are used to things taking millions or billions of years to happen. But, occasionally, things happen on a human time-scale. The detonation of a star is one of those. I was 15 when SN 1987A exploded but I didn’t get to see it; it was too far South. But I keep hoping that I’ll live long enough to see another one go off.