Astronomers now have a better understanding of how stars progress, thanks to NASA's Fermi Space Telescope that has detected numerous pulsars by the gamma rays they emit.

When a massive star explodes, it leaves behind a compact core called a pulsar. Like a spinning firecracker spitting out sparks, these magnetized cores emit high-energy light particles called gamma rays as they rapidly rotate.

Before Fermi, scientists detected pulsars by their radio wave emissions but understood little about their gamma-ray pulsations. Now that the telescope has identified 16 pulsars over five months, astronomers and physicists have more to work with.

"We have a population of pulsars to study and we can draw a lot of important conclusions about how they work," said Peter Michelson, Principal Investigator for the Large Area Telescope at Stanford Linear Accelerator Laboratory.

Fermi's new findings are solving stellar mysteries that once stumped scientists. Astronomers have moved beyond identifying the formerly unknown source of high-energy radiation and are now detecting a new class of pulsars seen only in gamma rays.

"These findings help to fill in part of the puzzle about the evolution of stars in our galaxy and what happens to them at the end of their lives," Michelson said.

Fermi also revealed that gamma rays pulsate in similar fashion from millisecond pulsars, which are hundreds of millions of years older than normal pulsars, Michelson explained. A spinning pulsar will eventually slow down and stop pulsing because of its magnetism and rotation.

If the pulsar is in a binary system, in orbit around another star, it will pull a mass of gas off the normal star and onto itself.

"In pulling the gas off, it has a lot of angular momentum. It's like water going down the pipe in a washing machine. The mass transfer from the normal star can spin up the neutron star so that it begins spinning rapidly," Michelson said.

These re-born pulsars are called millisecond pulsars because they rotate at periods between 100 and 1,000 times a second.

An international team of scientists working on the Fermi partnership will publish two papers of their Fermi findings in the July 2nd edition of Science Express.