January 8, 2010—One of the first two "fossil" fireballs ever detected glows deep in the supernova remnant W49B, according to a new study based on data from the Japan-U.S. Suzaku x-ray observatory. In the composite picture above, red and green represent infrared images of the remnant taken by ground-based telescopes, while blue shows x-ray data from NASA's Chandra X-ray Observatory.
W49B, which sits 35,000 light-years from Earth, is the glowing cloud of gas and dust left behind by the death of a massive star. As such stars age, they shed their outer layers, forming cocoons of gas and dust around dense cores. When the core explodes, it's believed that the initial blast wave can heat the cocoon to temperatures as high as 100 million degrees Fahrenheit (55 million degrees Celsius)—10,000 times hotter than the surface of the sun.
The debris then quickly thins and cools as it expands, creating a supernova remnant. Suzaku's highly sensitive x-ray vision allowed astronomers to spot the embers of the high-temperature inferno within that remnant, which immediately followed the blast that created W49B.
Suzaku's data revealed a region in the heart of the remnant in which iron atoms have been almost completely stripped of their electrons. For this to have happened, temperatures in the region must have been more than 55 million degrees Fahrenheit (30.5 million degrees Celsius)—about twice as hot as the remnant appears today.
Image courtesy JAXA/NASA/Suzaku, Tom Bash, and John Fox/Adam Block, NOAO/AURA/NSF
Suzaku's x-ray pictures revealed a similar fossil fireball (above in blue, yellow, and orange overlaid on an optical image) in the supernova remnant IC 443. Commonly called the Jellyfish nebula, the remnant lies about 5,000 light-years away.
Like a prism scattering white light into its colorful components, Suzaku can split apart x-rays based on their energy levels. This tells astronomers what types of processes are happening in a given nebula.
A patch of odd x-rays in the nebula's northern region can only be coming from fully ionized silicon and sulfur atoms, the study authors say. Stripped of all their electrons, these "naked" atoms are recapturing electrons in the Jellyfish remnant, emitting specific types of x-rays in the process.
Image courtesy JAXA/NASA/Suzaku
Jellyfish Nebula Closeup
A closeup of the "fossil" fireball in the Jellyfish nebula shows the glow of x-rays as fully ionized silicon and sulfur recapture electrons.
Completely removing electrons from silicon and sulfur requires temperatures upward of 30 million degrees Fahrenheit (17 million degrees Celsius)—much hotter than the modern supernova remnant, according to a study in published in the November issue of Astrophysical Journal.
"Suzaku sees the Jellyfish's hot heart," study co-author Midori Ozawa, a graduate student at Kyoto University, said in a statement.