Astrophile is our weekly column covering curious cosmic objects, from within the solar system to the furthest reaches of the multiverse
Object type: Supernova remnant
Distance: 26,000 light years
Ten millennia ago, when humanity was busy inventing agriculture, a bright new star in the constellation we know as Centaurus may have awed our ancestors. After exploding as a supernova, the star would have faded from view within a year or so ? and eventually from living memory, until, 25 years ago, a radio telescope near Canberra, Australia, found its curious remains.
And what remains they are. Remnants of supernovae tend to be seen as roundish clouds expanding symmetrically from the original explosion site, but the Centaurus remnant is shaped like a frying pan.
Fresh calculations confirm that this unique shape is not just a curiosity: it is a map of the supernova's entire history, which includes one of the fastest-moving stars in the galaxy.
Back in 1986, the original discovery team ? led by Michael Kesteven, then of the Herzberg Institute of Astrophysics in Victoria, British Columbia, Canada ? noted the odd shape of the remnant.
Cosmic lighthouse
In addition to the usual vaguely round shell of hot, expanding gas, this one had something long and narrow sticking out of it. Was this some sort of jet shot out from the dying star, the team wondered?
There was little further progress until 2009, when another team found an important new clue to the shape of this peculiar object, which they nicknamed the frying pan. Led by Fernando Camilo of Columbia University in New York, they had another look at the object with another Australian telescope: the Parkes Observatory radio telescope in New South Wales.
At the end of the frying pan's handle they discovered a neutron star ? the crushed core of the star that had died in the supernova. This neutron star is spinning fast and, like a cosmic lighthouse, gives off radio beams that sweep around as the star rotates, appearing to us as regular pulses. Such pulsing neutron stars are appropriately called pulsars.
The team concluded that the supernova explosion hurled this stellar corpse from the blast site, leaving behind a glowing trail, which is still seen today as the handle of the frying pan.
Entire history
Now new radio measurements and calculations by a team led by Stephen Ng of McGill University in Montreal, Canada, confirm this picture.
The pulsar is unlikely to be an interloper that just happened to pass through the supernova remnant ? the odds of that are about 800 to 1, given that the remnant is relatively small and pulsars are few and far between, the team says.
Other glowing pulsar trails have been found, but this is the first that is connected all the way back to its supernova remnant. That makes it a record of the supernova's entire history, from the explosion right up to the dead core's current position.
"Most pulsar tails are too old ? the supernova remnant has already dissipated," says Ng.
Asymmetrical mystery
The pulsar is thought to have left the glowing trail because of the wind of energetic particles that it spews into the surrounding space. This wind ploughs into galaxy's interstellar gas, energising it and making it glow.
Based on the width of the trail, Ng's team estimates the pulsar's speed at between 1000 and 2000 kilometres per second. That could make it the fastest star known: the current record-holder is another neutron star, racing at 1500 kilometres per second from the Puppis A supernova remnant where it was born.
Such speeding neutron stars are a puzzle, because supernova explosions should be pretty symmetrical, making it unlikely that they would provide a strong kick in any one direction. Solving the puzzle of the frying pan's origin may have deepened another one.
Reference: arxiv.org/abs/1109.2233
Read previous Astrophile columns: The most surreal sunset in the universe, Saturn-lookalike galaxy has a murky past, The impossibly modern star, The diamond as big as a planet
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