Nothing ever escapes a black hole, right? Wrong. New research has revealed that Sagittarius A*, the supermassive black hole which lie the heart of the Milky Way, regularly issues forth balls of gas that can be as big as a planet.
Strictly speaking, these don’t actually come from the black hole itself, because their point of origin lies outside the event horizon. What happens is that, every few thousand years, a star will come to close the black hole and be ripped apart by its ultra-high gravity. But the black hole won’t necessarily consume all of the star’s gas – some of it can escape, whipping outwards in a long stream.
Previously, it was believed that these streamers would eventually disperse. Now, however, new research by undergraduates Eden Girma and James Guillocochon at the Harvard-Smithsonian Center for Astrophysics in the USA has shown that the gas can in fact cluster together again, forming hundreds of planet-sized globules that are then flung across the Milky Way at speeds of up to 10,000km/s, with most eventually exiting the Galaxy entirely.
As all galaxies are now believed to have a supermassive black hole at their centres, it’s likely that there are countless such ‘cosmic spitballs’ weaving their way across the Universe – although wandering or ‘rogue’ planets still outnumber them by around 999 to one.