Apr 9 2013
New detections of X-rays from a white-dwarf star that exploded as a supernova in 1604 will help astronomers to better understand the important class of stars known as "Ia supernovae," which are used to probe the distant universe.
This composite of images from NASA's Chandra X-ray Observatory shows the remnant of Kepler's supernova in low-energy (red), intermediate-energy (green) and high-energy (blue) X-rays. The background is an optical star field taken from the Digitized Sky Survey. The distance to the object is uncertain, with estimates ranging from 13,000 to 23,000 light-years, but recent studies favor the maximum range. This image spans 12 arcminutes or about 80 light-years at the greatest distance. Image: NASA/CXC/NCSU/M.Burkey et al.; optical: DSS
"It is fascinating that we are still learning new things from one of the first supernova explosions of the modern astronomical era," said David Burrows, professor of astronomy and astrophysics at Penn State. Burrows is a member of the research team that made the discovery by detecting X-rays from the glowing remains of the exploded star using the Japan-led Suzaku satellite. The team discovered that the star had a greater fraction of heavy elements than the sun. "These results were made possible by the high sensitivity and excellent energy resolution of Suzaku's X-ray Imaging Spectrometer (XIS)," Burrows said.
"Modern imaging X-ray spectrometers, similar to ones developed here at Penn State, have made it possible in recent years to make detailed measurements of the amounts of different elements produced in supernova explosions," Burrows said. These highly detailed measurements help astronomers to refine their our models of the explosion mechanisms in this important class of stars. "These new observations demonstrate the power of this experimental technique," Burrows said.
The scientists discuss their findings in a paper scheduled for publication in the April 10 issue of The Astrophysical Journal Letters, now available online.
The best way to explore the star's makeup is to perform a kind of post-mortem examination on the shell of hot, rapidly expanding gas produced by the explosion. By identifying specific chemical signatures in the supernova remnant, astronomers can obtain a clearer picture of the composition of the star before it blew up.
"The composition of the star, its environment, and the mechanism of the explosion may vary considerably among type Ia supernovae," said Sangwook Park, an assistant professor of physics at the University of Texas at Arlington and one of the leaders of the multi-institution research team. "By better understanding them, we can fine-tune our knowledge of the universe beyond our galaxy and improve cosmological models that depend on those measurements."
In 2011, astrophysicists from the United States and Australia won the Nobel Prize in physics for the discovery that the expansion of the universe is picking up speed, a conclusion based on measurements of type Ia supernovae. An enigmatic force called dark energy appears to be responsible for this acceleration, and understanding its nature is now a top science goal. Recent findings by the European Space Agency's Planck satellite reveal that dark energy makes up 68 percent of the universe.
In addition to Penn State and the University of Texas, other institutions have scientists who were involved in this research, including the University of Pittsburgh, the University of Miyazaki in Japan, the University Politécnica de Catalunya in Spain, Los Alamos National Laboratory, Rutgers University, the Harvard-Smithsonian Center for Astrophysics, and the Korea Astronomy and Space Science Institute.
Launched on July 10, 2005, Suzaku was developed at the Japanese Institute of Space and Astronautical Science (ISAS), which is part of the Japan Aerospace Exploration Agency (JAXA), in collaboration with NASA and other Japanese and U.S. institutions.