For a cosmic adrenaline rush, it’s hard to beat a supernova. It happens when a star detonates at the end of its life, blasting gases and other debris outward with unimaginable violence. The explosion is so powerful that for a few days at least, a single supernova can outshine an entire galaxy of 100 billion stars or more. And when the dust finally settles, so to speak, what’s left behind (depending on the original star) might be a neutron star—an object so dense that a teaspoon’s worth would weigh 10 million tons—or even a black hole.
Given all this, it’s not as if supernovas need something to make them even more exciting. But they’ve got it anyway: astronomers have long known that some neutron stars aren’t simply left in place when a supernova goes off; they’re shot into space at millions of miles per hour. The presumed cause is some asymmetry in the explosion, possibly caused by turbulence, which gives the stellar remnant a powerful kick.
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Now, observers using the Chandra X-ray Observatory have spotted a speeding, wobbling neutron star trailing a twisted, comet-like tail behind it—a tail that stretches across more than 200 trillion miles. It is, said Lucia Pavan, of the University of Geneva, in a press release, “almost ten times longer than the distance between the Sun and our nearest star.”
The neutron star, which bears the catchy name IGR J11014-6103, is a pulsar, a body whose magnetic field sends out a blip of radio noise once per revolution. The blips are so incredibly regular that when they were first detected, they were briefly known as “LGMs,” since there was at least a chance that they were signals from little green men—that is, aliens.
These radio blips normally come from a pulsar’s north and south poles, generated by particles accelerated to high speed by the pulsars’ intense magnetic fields, but for some reason the astronomers can’t explain, the jet of particles that creates the tail in this case is coming off at right angles to the poles. “This gives us clues,” said co-author Gerd Puehlhofer, of the University of Tubigen, also in a release, “that exotic physics can occur when some stars collapse.” Exactly what form that exotic physics takes is still unknown.
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The pulsar’s estimated speed, say the scientists is somewhere between 2.5 and 5 million m.p.h. (4 to 8 million k/h), and the blast that created it happened about 15,000 years ago. Astronomers can still see the expanding cloud of gas from the original explosion, in the southern-hemisphere constellation Carina.
Millions of years from now, the speeding pulsar will leave the Milky Way entirely, and since the phenomenon that produced it isn’t all that uncommon, there are presumably plenty of fast-moving pulsars already zipping through the empty spaces between the galaxies. There could even be black holes doing the same thing, since the forces that blast a neutron star into space would presumably affect a black hole the same way. The only difference is that a speeding black hole would be vastly harder for us to spot. This also means there are undoubtedly fast-moving black holes that haven’t yet left the Milky Way. Fortunately, the odds that a black hole is headed straight at us at millions of m.p.h. are vanishingly small.
They aren’t literally zero, though. So when astronomers tell us that our Sun won’t end its life as a supernova and become a black hole (it’s far too small), it’s not necessarily as reassuring as it sounds.