Astronomers were able to observe the expanding thermonuclear fireball from a nova explosion in an unprecedented clarity never been achieved before, a milestone that could help shed more light on the nature of these cosmic blasts.
A nova, which should not be confused with supernova, is a stellar explosion that occurs when a very dense planet-sized star called a white dwarf s gets in very close orbit with its companion star and then draws in sufficient amount of hydrogen from this star to its own surface.
Novae go off quite frequently but the observation, which was reported in the study "The expanding fireball of Nova Delphini 2013," which was published in the journal Nature on Oct. 26, marks the first time that astronomers were able to observe the explosion in detail.
The nova described was detected in the constellation Delphinus by the Center for High Angular Resolution Astronomy (CHARA) Array which is operated by the Georgia State University, last year.
The constellation Delphinus is located about 14,800 light years away, which means that although scientists have only spotted the star going nova last August, the phenomenon actually occurred about 15,000 years ago.
Study co-author Peter Tuthill, from The University of Sydney's Institute for Astronomy described how the white dwarf managed to suck matter from its bigger companion star. He said that the white dwarf continued to draw hydrogen from its companion star resulting in the formation of an ocean on the surface.
"After drawing about as much mass as the entire planet Saturn, the pressure reaches a critical point," Tuthill said. "The stellar surface turns into one titanic hydrogen bomb hurling a fireball out into space and propelling a formerly dim, obscure star system into prominence as a nova in our night skies."
The researchers who have made the observations found that a day after the explosion, the size of the thermonuclear fireball was comparable to the radius of the Earth's orbit. After the second it was the size of the orbit of planet Mars and 43 days later, grew to size equal to that of the solar system.
"It was amazing to see the material expanding outward each day after the explosion," said study author and Georgia State University Astronomer Gail Schaefer.
Based on the researchers' calculation, the expansion rate was 1.3 million miles per hour. The CHARA observations also revealed that as the fireball expanded, its outer layer become more transparent and diffuse.
