Data recently collected from the first exploded star close enough to Earth to be seen with the naked eye in four centuries has helped astronomers confirm their theories about how stars cease to shine, Harvard scientists said yesterday.
Known as a supernova, the exploded star was first sighted at the end of February by a University of Toronto astronomer working in Chile.
A supernova occurs after a star runs out of fuel to power its burning core and immediately implodes. The energy released during this event rapidly expels the star's outer gases.
In most cases, according to current astronomical theory, the supernova lessens in brightness leaving behind only remnants of the original star.
"This supernova is interesting because it is the nearest one that has gone off since the invention of the telescope," said Professor of Astronomy John P. Huchra, an observational cosmologist.
"It's the first bright supernova since Harvard was founded," said Professor Of Astronomy Robert P. Kirshner '70, who studying ultraviolet (UV) light emitted form the bright supernova. The most recent supernova observable from Earth with the naked eye was in 1604.
Kirshner, who has already travelled to NASA's Goddard Space Flight Center several times to collect data from a UV-detecting satellite, said he hopes to discover evidence which would support current theories on supernova evolution.
Supernova can also be used to measure the size and age of the universe, Kirshner said.
This supernova, called 1987A, is so close to our galaxy that "we've detected things other than light being given off" for the first time, Huchra said.
One of the theories 1987A confirmed was that neutrinos, subatomic elementary particles which pass through ordinary matter, are emitted during the explosion.
"When a massive star's core collapses in a supernova, the energy is partially emitted in neutrinos [according totheory]," Kirshner said. Although this idea hasbeen written about in astronomy texts for years,"now, we have actually observed [the particles],"he said.
Large detectors in Ohio and Japan picked uptraces of the neutrinos passing through the Earthat millions of miles per hour after travellingthousands of light-years through space.
Using data from the detector in Japan, HigginsProfessor of Physics Sheldon L. Glashow and JohnBahcall of the Institute for Advanced Study atPrinceton reported that the mass of neutrinoscould not be more than 10 electron-volts, a smallfraction of an atom's mass.
"This is important because we don't know themass of the neutrino, one of the essentialelementary particles. If there were no neutrinos,there would be no sun and no Earth," Glashow said.
"The real important question is whether theneutrino has mass at all," said Francis M. Pipkin,chairman of the physics department. He added thatneutrinos may account for some of the "missingmass" in the universe which astronomers theorizeshould exist but which they have yet to find.
Glashow's finding contradicts that of a Russianresearch team which set the mass at double hiscomputed value, Pipkin said