Origin of key cosmic explosions revealedFebruary 18th, 2010 - 3:40 pm ICT by ANI
Washington, Feb 18 (ANI): New findings from NASA’s Chandra X-ray Observatory have shown that mergers of two dense stellar remnants are the likely cause of many of the supernovae that have been used to measure the accelerated expansion of the universe.
These supernovae, called Type 1a, serve as cosmic mile markers to measure expansion of the universe because they can be seen at large distances, and they follow a reliable pattern of brightness.
However, until now, scientists have been unsure what actually causes the explosions.
“These are such critical objects in understanding the universe,” said Marat Gilfanov of the Max Planck Institute for Astrophysics in Germany.
“It was a major embarrassment that we did not know how they worked. Now we are beginning to understand what lights the fuse of these explosions,” he said.
Most scientists agree a Type 1a supernova occurs when a white dwarf star - a collapsed remnant of an elderly star - exceeds its weight limit, becomes unstable and explodes.
Scientists have identified two main possibilities for pushing the white dwarf over the edge: two white dwarfs merging or accretion, a process in which the white dwarf pulls material from a sun-like companion star until it exceeds its weight limit.
“Our results suggest the supernovae in the galaxies we studied almost all come from two white dwarfs merging,” said co-author Akos Bogdan, also of Max Planck. “This is probably not what many astronomers would expect,” he added.
The difference between these two scenarios may have implications for how these supernovae can be used as “standard candles” - objects of a known brightness - to track vast cosmic distances.
Because white dwarfs can come in a range of masses, the merger of two could result in explosions that vary somewhat in brightness.
Because these two scenarios would generate different amounts of X-ray emission, Gilfanov and Bogdan used Chandra to observe five nearby elliptical galaxies and the central region of the Andromeda galaxy.
A Type 1a supernova caused by accreting material produces significant X-ray emission prior to the explosion.
A supernova from a merger of two white dwarfs, on the other hand, would create significantly less X-ray emission than the accretion scenario.
The scientists found the observed X-ray emission was a factor of 30 to 50 times smaller than expected from the accretion scenario, effectively ruling it out.
This implies that white dwarf mergers dominate in these galaxies. (ANI)
- 'Cosmic candles' result of colliding dead stars - Feb 22, 2010
- Origin of key cosmic explosions still shrouded in mystery - Jul 13, 2010
- New evidence on what triggered ancient Supernovas - Apr 27, 2011
- How white-dwarf stars merge and become a supernova - Jan 08, 2010
- What makes black holes at galaxy centre become active - Jun 16, 2010
- 'Satnav' could pave man's way beyond solar system - Mar 29, 2012
- Symmetry of supernova's remnants can reveal how the star exploded - Dec 18, 2009
- Astronomers find supermassive black holes - Sep 01, 2011
- Scientists clear away "cosmic dust" to get better look at youngest supernova remnant - Apr 23, 2009
- Milky Way's fastest stars circle each other at 500 kms a second - Mar 13, 2010
- New Hubble observations reveal composition of 'star guts' pouring out - Sep 04, 2010
- NASA finds 30-yr-old 'youngest' nearby black hole - Nov 16, 2010
- NASA's Swift satellite finds unseen black-hole-powered galaxies - Jan 21, 2011
- Mysterious supernova remnant puzzles astronomers - Jun 10, 2009
- Scientists discover active black hole in the 'Eye of Sauron' - Mar 11, 2011
Tags: akos, chandra x ray, companion star, cosmic distances, cosmic explosions, expansion of the universe, max planck, max planck institute, mile markers, nearby elliptical galaxies, ray emission, ray observatory, s chandra, standard candles, stellar remnants, supernovae, type 1a supernova, understanding the universe, white dwarf star, white dwarfs