Pulsar mystery ends: the TV camera did it.

Pulsar mystery ends: The TV camera did it

Oops! Forget that dramatic report last year of a rapidly spinning pulsar at the heart of supernova 1987A -- the fastest pulsar ever described. "It was a television signal," says John Middleditch of the Los Alamos (N.M.) National Laboratory.

Middleditch, a member of the team that reported discovering the pulsar rotating 1,968 times a second (SN: 2/18/89, p.100), retracted the finding in New Orleans this week at the American Association for the Advancement of Science meeting. Many researchers studying the supernova had been notified of the embarrassing development a few days before.

"We didn't expect a television camera to be this coherent, but it was," Middleditch says. "You can't tell the difference between this [signal] and a pulsar."

Since supernova 1987A temporarily brightened the Southern Hemisphere's night sky three years ago, astronomers have expected eventually to find a pulsar there -- a dense, spinning sphere of neutrons left after the cataclysmic collapse of a large star. On Jan. 18, 1989, astronomers recording the supernova's visible and infrared light at the Cerro Tololo Inter-American Observatory in Chile got nearly seven hours' worth of data. The observations seemed to reveal pulsations about 0.5 milliseconds apart, with variations in the pulsar's spin frequency that suggested the presence of an orbiting companion with the mass of Jupiter, and perhaps a second companion with the mass of Neptune.

No one ever confirmed the pulsar sighting. Theorists offered suggestions for why the pulsar might have appeared and then disappeared from view, as well as models for its composition (perhaps pure quarks) and why it rotated so rapidly.

Then, on Feb. 8 of this year, as the team prepared for new observations of supernova 1987A, they pointed the Cerro Tololo telescope at the Crab nebula, site of a well-studied pulsar, and recorded the identical pulse rate reported for supernova's pulsar. "So obviously the universe is pulsed or the signal has nothing to do with the pulsar," Middleditch says.

He says the spurious signal apparently came from one of two television cameras used to help guide the telescope. It appears, Middleditch adds, that the camera was used on Jan. 18, 1989, but not for subsequent looks at supernova 1987A until this month. "We're not absolutely sure if it is the TV camera alone or the camera and the electronics that guide the telecope," he says.

The search for the telltale pulses continues. Says Mark M. Phillips of the Cerro Tololo staff: "We still think a neutron star is in there."