The Fermi space telescope has recorded gamma rays in certain type of nova for the first time, upending a long-held idea in astronomy.
The Large Area Telescope (LAT), an instrument that makes up part of the Fermi Space Telescope, was used to record gamma rays being produced in the interactions of a pair of stars.
Gamma rays are the most powerful form of electromagnetic energy, billions of times more powerful than visible light, which we use to see objects. The Fermi Space Telescope surveys the entire sky in these wavelengths every three days.
Novas are created in binary stars systems containing a white dwarf, a small, hot stellar body. As the two stars orbit each other, material can migrate from the larger stellar body to its smaller companion. This gas and dust can build up, until temperatures and pressures become great enough to ignite a sudden fusion reaction, similar to a thermonuclear bomb. This instantaneous outburst can produce as much energy as the white dwarf would normally emit in 100,000 years. This process can happen time and again, as long as the larger companion supplies enough stellar material for the cycle to continue.
Astronomers previously believed that novas did not produce enough energy to create gamma rays. These high-energy waves can be produced when particles are accelerated to velocities near the speed of light, something novas were not thought capable of accomplishing. That long-held belief may now be turned on its head.
"No one suspected novae were violent enough to be emitting at these very high energies. However, it now seems possible that a signification fraction - near 100 percent - of novae are gamma ray sources," Sumner Starrfield of Arizona State University, said.
One nova, V407 Cygni, was studied by Starrfield using the LAT instrument aboard Fermi in March 2010. This stellar couple lie around 9,000 light years away from Earth. Contrary to popular belief, the astronomer witnessed the production of gamma rays in gas emitted in the blasts. Two years later, a pair of additional events were also seen during the study, labeled Nova Sco 2012 and Nova Mon 2012. Novas are usually detected as sudden increases in the brightness of visible light from a binary pair.
Recurrent symbiotic nova are a special type of nova, in which the red giant member of the pair pulsates, expelling large quantities of gas to space. The stellar companion of V407 Cyg is one of these types of star, and the nova occurs within this pocket of gas. Starrfield believes the gamma rays are produced when the blast wave from the explosion crashes into the gas from the giant star, although the exact mechanism remains a mystery.
