Almost all the remnants ever formed are still out there, sliding like ghosts through interstellar space." "Finally, unlike a snooker table, there is no friction - so they never slow down. Plus, the table's not flat, so the stellar remnants go on complex orbits threading through the galaxy. But in space, the objects and speeds are just vastly bigger. "If you know which direction the ball is hit, and how hard, then you can work out where it will end up. "It's a little like in snooker," said Sweeney. Supernova explosions are asymmetric, and the remnants are ejected at high speed - up to millions of kilometres per hour - and, even worse, this happens in an unknown and random direction for every object."īut nothing in the universe sits still for long, so even knowing the likely magnitudes of the explosive kicks was not enough: the researchers had to delve into the depths of cosmic time and reconstruct how they behaved over billions of years. "The bones of these rare massive stars had to be out there, but they seemed to shroud themselves in mystery."Īdded Sweeney: "The hardest problem I had to solve in hunting down their true distribution was to account for the 'kicks' they receive in the violent moments of their creation. "It was like trying to find the mythical elephant's graveyard," said Professor Tuthill, referring to a place where, according to legend, old elephants go to die alone, far from their group. But the oldest neutron stars and black holes are like ghosts still haunting a house demolished long ago, so they are harder to find. Newly-formed neutron stars and black holes conform to today's galaxy, so astronomers know where to look. It has been a major task to model all of this to find them." "The oldest neutron stars and black holes were created when the galaxy was younger and shaped differently, and then subjected to complex changes spanning billions of years. "One of the problems for finding these ancient objects is that, until now, we had no idea where to look," said Sydney Institute for Astronomy's Professor Peter Tuthill, co-author on the paper. Both types of stellar corpses warp space, time, and matter around them.Īlthough billions must have been formed since the galaxy was young, these exotic carcasses were flung out into the darkness of interstellar space by the supernova that created them, and hence slipped beyond sight and knowledge of astronomers - until now.īy carefully recreating the full lifecycle of the ancient dead stars, the researchers have constructed the first detailed map showing where their corpses lie. If the mass of the original star is greater than 25 times our Sun's, that gravity-driven collapse continues, until the core is so dense that not even light can escape. In neutron stars, the core is so dense that electrons and protons are forced to combine at the subatomic level into neutrons, squeezing its total mass into a sphere smaller than a city. This triggers a runaway reaction that blows the outer portions of the star apart in a titanic supernova explosion, while the core keeps compressing in on itself until - depending on its starting mass - it becomes either a neutron star or a black hole. Neutron stars and black holes are formed when massive stars - more than eight times larger than our Sun - exhaust their fuel and suddenly collapse.
0 Comments
Leave a Reply. |