The famed Crab Nebula is all that’s left of a massive stellar giant that met an explosive end.
The star died a mere 6,500 light-years from Earth, creating a supernova that was witnessed by Chinese astronomers in 1054.
Ejected gas and dust now billow out from the star’s deathbed, forming the spindly nebula, which glows in multiple wavelengths.
Composite picture of the Crab Nebula—X-ray: NASA/CXC/ASU/J.Hester et al.; Optical: NASA/ESA/ASU/J.Hester & A.Loll; Infrared: NASA/JPL-Caltech/Univ. Minn./R.Gehrz
And deep in the heart of the Crab sits a tiny, ultradense neutron star—the collapsed core of the dead star.
This stellar corpse spins on its axis about 30 times a second, emitting regular pulses of radiation that earn the object its designation as a pulsar.
Now, a new time-lapse movie from NASA’s Chandra X-ray Observatory shows how this pulsar is churning up the innards of the Crab.
As seen in the video above, energy from the pulsar is driving high-speed particle “winds,” which are sending a shock wave rippling through the nebula.
This wave forms a ring around the pulsar that spews x-rays, created as the particles in the wave start to lose energy.
“The peeling off of the x-ray emission from the shock (and similar effects also seen in visible light) is a consequence of the details of the shock, the velocity of the particles, etc.,” Chandra project scientist Martin Weisskopf, based at NASA’s Marshall Space Flight Center, said in an email.
Stitching together images taken between September 2010 and April 2011, the Chandra team is now able to watch as the x-ray ring expands and changes shape.
However, the video is actually a bonus bit of cool, as Chandra was collecting these images for a completely different purpose.
In September 2010 scientists using a “sister” telescope—the Fermi Gamma Ray Observatory—saw an intense gamma-ray flare coming from the Crab Nebula, but Fermi couldn’t pinpoint its source.
The gamma-ray folk figured that more flares would be on the horizon, and they hoped Chandra’s high-resolution images would be able to help investigate. The Chandra team therefore made several x-ray observations six days after the flare, to establish a baseline.
Then, in April 2011, the Fermi group saw more flare activity spiking in the nebula, so Chandra was called back into action.
As luck (and carefully planned science) would have it, the x-ray ‘scope was watching the Crab when a series of even more impressive “superflares” erupted throughout the month.
But—as is often the case in science—looking for an answer offers no guarantee of finding one: Chandra saw no correlating x-ray activity with Fermi’s gamma-ray flares.
That’s not to say the effort was wasted. A null result is still a result, and the information will help scientists put boundaries on the possible mechanisms that produce the flares.
“Had the x-ray emission been directly correlated to the gamma-rays, we would have expected to see a similar brightening from a very small region. We did not,” Weisskopf said.
“This says that whatever model is correct for the production of the gamma-ray flare, it must also not produce a similar brightening in x-rays.”
It’s also possible the flares do generate both gamma rays and x-rays but are coming from regions *very* close to the pulsar, where it’s too bright for even Chandra to see, Weisskopf noted.
In the meantime, we get a very groovy movie of a pulsar in action.