Nasa’s Chandra X-ray observatory has been in orbit since 1999 and it’s still producing results. Like this stunning image of the remnant of the Type Ia supernova first observed by Danish astronomer Tycho Brahe in 1572. The data for the images was collected in 283 hours of observation from 2 pointings between April 29, 2003 and May 3, 2009. (Credit: NASA/CXC/Chinese Academy of Sciences/F. Lu et al)
From the text accompanying Chandra’s Tycho photo album
This new image of Tycho’s supernova remnant, dubbed Tycho for short, contains striking new evidence for what triggered the original supernova explosion, as seen from Earth in 1572. Tycho was formed by a Type Ia supernova, a category of stellar explosion used in measuring astronomical distances because of their reliable brightness.
Low and medium energy X-rays in red and green show expanding debris from the supernova explosion. High energy X-rays in blue reveal the blast wave, a shell of extremely energetic electrons. Also shown in the lower left region of Tycho is a blue arc of X-ray emission. Several lines of evidence support the conclusion that this arc is due to a shock wave created when a white dwarf exploded and blew material off the surface of a nearby companion star (see accompanying illustration below). Previously, studies with optical telescopes have revealed a star within the remnant that is moving much more quickly than its neighbors, hinting that it could be the companion to the supernova that was given a kick by the explosion.
And from the Chandra press release
One popular scenario for Type Ia supernovas involves the merger of two white dwarfs. In this case, no companion star or evidence for material blasted off a companion should exist. In the other main competing theory, a white dwarf pulls material from a “normal,” or sun-like, companion star until a thermonuclear explosion occurs. Both scenarios may actually occur under different conditions, but the latest Chandra result from Tycho supports the latter one.
In addition, the Tycho study seems to show the remarkable resiliency of stars, as the supernova explosion appears to have blasted very little material off the companion star. Previously, studies with optical telescopes have revealed a star within the remnant that is moving much more quickly than its neighbors, hinting that it could be the missing companion.
“It looks like this companion star was right next to an extremely powerful explosion and it survived relatively unscathed,” said Q. Daniel Wang of the University of Massachusetts in Amherst. “Presumably it was also given a kick when the explosion occurred. Together with the orbital velocity, this kick makes the companion now travel rapidly across space.”
Using the properties of the X-ray arc and the candidate stellar companion, the team determined the orbital period and separation between the two stars in the binary system before the explosion. The period was estimated to be about 5 days, and the separation was only about a millionth of a light year, or less than a tenth the distance between the Sun and the Earth. In comparison, the remnant itself is about 20 light years across.
The arc of material stripped away from the companion star and the resulting debris ‘shadow’ is labelled in this image showing iron debris in Tycho’s supernova remnant. (Credit: NASA/CXC/Chinese Academy of Sciences/F. Lu et al)
And there’s an illustration showing an explanation for the origin of the x-ray arc. (Credit: NASA/CXC/M.Weiss)
Nasa have a separate, equally stunning, image with a background provided by the Digitized Sky Survey. (Credits: X-ray: NASA/CXC/Rutgers/K.Eriksen et al.; Optical: DSS).
From the Nasa press release
“We’ve seen lots of intriguing structures in supernova remnants, but we’ve never seen stripes before,” said Kristoffer Eriksen of Rutgers University, who led the study. “This made us think very hard about what’s happening in the blast wave of this powerful explosion.” This latest study from Chandra provides support for a theory about how magnetic fields can be dramatically amplified in such blast waves.
In this theory, the magnetic fields become highly tangled and the motions of the particles very turbulent near the expanding supernova shock wave at the front edge of the supernova remnant. High-energy charged particles can bounce back and forth across the shock wave repeatedly, gaining energy with each crossing. Theoretical models of the motion of the most energetic particles — which are mostly protons — are predicted to leave a messy network of holes and dense walls corresponding to weak and strong regions of magnetic fields, respectively.
The X-ray stripes discovered by the Chandra researchers are thought to be regions where the turbulence is greater and the magnetic fields more tangled than surrounding areas, and may be the walls predicted by the theory. Electrons become trapped in these regions and emit X-rays as they spiral around the magnetic field lines.
However, the regular and almost periodic pattern of the X-ray stripes was not predicted by the theory.
“It was a big surprise to find such a neatly arranged set of stripes,” said co-author Jack Hughes, also of Rutgers. “We were not expecting so much order to appear in so much chaos. It could mean that the theory is incomplete, or that there’s something else we don’t understand.”
Assuming that the spacing between the X-ray stripes corresponds to the radius of the spiraling motion of the highest energy protons in the supernova remnant, the spacing corresponds to energies about 100 times higher than reached in the Large Hadron Collider. These energies equal the highest energies of cosmic rays thought to be produced in our Galaxy.
Finally, here’s a short video from the cxc channel looking closely at Tycho’s supernova remnant.