Fire in the Sky
Astronomers at Georgia State’s Center for High Angular Resolution Astronomy (CHARA) at Mt. Wilson, Calif., have produced the first images of a nova as it exploded and measured the expansion of the fireball into space.
Georgia State astronomer and research scientist Gail Schaefer led the observations. “It’s not every day that you get to see a star going nova,” Schafer said. “When a nova happens, it happens really quickly.”
Schafer and her team were tipped off in 2013 when an amateur astronomer discovered a new star, named Nova Delphinus 2013. Within 15 hours of discovery, Schafer and the Mt. Wilson astronomers pointed the CHARA array of six, one-meter telescopes to image the fireball and measure it.
“We obtained size measurements of the nova on a total of 27 nights over the course of two months,” Schafer said.
Novae occur when a small, white dwarf star rips matter from a nearby red giant. Once the white dwarf has absorbed so much matter it can no longer support itself, it explodes as a nova. The observations produced the first images of a nova during that explosion and revealed how he structure of the ejected material evolves as the gas expands and cools.
The results of the observations were published in the November 2014 issue of Nature.
Measuring the expansion of the nova allowed the researchers to determine that Nova Delphinus 2013 is 14,800 light years from the sun, Schafer said. This means that, while the explosion was witnessed here on Earth last August, it actually took place nearly 15,000 years ago.