‘New’ supernova discovered

Most supernovas seen by astronomers are at least 10,000 years old.

McClatchy Newspapers

RALEIGH, N.C. — The youngest supernova found in our galaxy to date has been discovered by a team of scientists led by an N.C. State University astrophysicist, the university announced Wednesday.

The exploding star is only 140 years old, making it 200 years younger than what had previously been the youngest supernova in the Milky Way galaxy — giving scientists a fresher specimen to study.

In this case, “you’re actually getting to see the rock that made the splash, not the wave that’s going out into the pond,” said Robert Kirshner, a Harvard University astronomer who is not affiliated with the study.

Stephen Reynolds, the NCSU astrophysicist, led a team of researchers who compared images of a celestial object in the Milky Way — scientists call it G1.9+0.3 — taken last year on an X-ray telescope and in 1985 on a radio telescope. That confirmed Reynolds’ theory that the object was the remnant of a young supernova.

The comparison also showed that it had increased in size by 16 percent during that 22-year span, enabling scientists to calculate that the initial explosion occurred, at most, 140 years ago. If the rate of expansion slowed down over the years, it’s even younger.

“My best estimate is that it’s 100 years old,” said Reynolds. “140 is the upper limit.”

Supernovas occur when a massive star suddenly collapses at the end of its life, bursting into a vividly bright mass and then shining awhile more as its core material condenses. The explosion propels matter into space, leaving a neutron star or black hole.

The discovery is significant because the younger the supernova, the easier it is to study how the star exploded and what it was made of, Reynolds said.

“It’s a little like one of those shows on TV where they investigate a death. This is a stellar death, all right, and the corpse is still warm,” Kirshner said during a teleconference with reporters that was covered by the Associated Press.

Astronomers typically observe supernova remnants that are 10,000 or so years old, not relative infants like this one. Getting the total picture, from the start, is important in figuring out how often supernovae explode in the Milky Way.

“This is exciting,” said Michael Castelaz, Director of Astronomical Studies and Education at the Pisgah Astronomical Research Institute in Transylvania County. “This gives us a better idea of the galaxy we live in — we can better understand how stars are formed and how they go through their lives.”

The elements that spew from a supernova form the basic material of new stars and planets. Many of the substances listed on the periodic table of elements, including the iron in our blood and the calcium in our bones, were forged in supernova explosions, Reynolds said.

Some supernovae, including G1.9+o.3, aren’t visible with optical telescopes because interstellar “murk” — gas and dust — obscure them, said Reynolds. But X-ray and radio telescopes can overcome that by detecting the radio waves and X-rays they emit.

The discovery will be published in the June 10 edition of Astrophysical Journal Letters.