Apr
10
2013

Suzaku ‘Post-mortem’ Yields Insight into Kepler’s Supernova

Kepler's supernova

This composite of images from NASA’s Chandra X-ray Observatory shows the remnant of Kepler’s supernova in low (red), intermediate (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.

Credit: X-ray: NASA/CXC/NCSU/M.Burkey et al.; optical: DSS

An exploding star observed in 1604 by the German astronomer Johannes Kepler held a greater fraction of heavy elements than the sun, according to an analysis of X-ray observations from the Japan-led Suzaku satellite. The findings will help astronomers better understand the diversity of type Ia supernovae, an important class of stellar explosion used in probing the distant universe.

“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. “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.”

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.

Read the rest of this entry »

Aug
02
2012

‘Cry’ of a Shredded Star Heralds a New Era for Testing Relativity

Last year, astronomers discovered a quiescent black hole in a distant galaxy that erupted after shredding and consuming a passing star. Now researchers have identified a distinctive X-ray signal observed in the days following the outburst that comes from matter on the verge of falling into the black hole.

This tell-tale signal, called a quasi-periodic oscillation or QPO, is a characteristic feature of the accretion disks that often surround the most compact objects in the universe — white dwarf stars, neutron stars and black holes. QPOs have been seen in many stellar-mass black holes, and there is tantalizing evidence for them in a few black holes that may have middleweight masses between 100 and 100,000 times the sun’s.

Illustration of the features of Swift J1644+57

This illustration highlights the principal features of Swift J1644+57 and summarizes what astronomers have discovered about it.

Credit: NASA’s Goddard Space Flight Center

Until the new finding, QPOs had been detected around only one supermassive black hole — the type containing millions of solar masses and located at the centers of galaxies. That object is the Seyfert-type galaxy REJ 1034+396, which at a distance of 576 million light-years lies relatively nearby.

Read the rest of this entry »

Jul
03
2012

In McNeil’s Nebula, a Young Star Flaunts its X-ray Spots

Using combined data from a trio of orbiting X-ray telescopes, including NASA’s Chandra X-ray Observatory and the Japan-led Suzaku satellite, astronomers have obtained a rare glimpse of the powerful phenomena that accompany a still-forming star. A new study based on these observations indicates that intense magnetic fields drive torrents of gas into the stellar surface, where they heat large areas to millions of degrees. X-rays emitted by these hot spots betray the newborn star’s rapid rotation.

During outbursts, the infant star in McNeil’s Nebula may brighten by 100 times at X-ray energies. In this animation, based on findings by NASA’s Chandra Observatory, the Japan/U.S. Suzaku spacecraft, and Europe’s XMM-Newton satellite, magnetic fields drive powerful flows onto the star, creating two hot spots that produce the high-energy emission.

Credit: NASA’s Goddard Space Flight Center

Astronomers first took notice of the young star, known as V1647 Orionis, in January 2004, near the peak of an outburst. The eruption had brightened the star so much that it illuminated a conical patch of dust now known as McNeil’s Nebula. Both the star and the nebula are located about 1,300 light-years away in the constellation Orion.

Astronomers quickly determined that V1647 Ori was a protostar, a stellar infant still partly swaddled in its birth cloud. “Based on infrared studies, we suspect that this protostar is no more than a million years old, and probably much younger,” said Kenji Hamaguchi, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and lead author of the study.

Read the rest of this entry »

Older posts «