Japanese researchers were studying a supernova remnant when they discovered that a black hole likely messed around with its gas.
The team, led by graduate student Masaya Yamada of Keio University, was studying W44 – a supernova remnant located 10,000 light-years away that was created by an exploding star. They were trying to work out how much energy the explosion gave to the molecular gas, but instead they discovered signs of a black hole.
The observation, reported in the Astrophysical Journal Letters, showed a curious cloud formation within the nebula. Due to its motion and shape, the researchers called it the "Bullet", and it’s moving at more than 100 times the speed of sound in interstellar space. However, it can’t be explained with just a supernova.
“Most of the Bullet has an expanding motion with a speed of 50 km/s, but the tip of the Bullet has a speed of 120 km/s,” said Yamada in a statement. “Its kinetic energy is a few tens of times larger than that injected by the W44 supernova. It seems impossible to generate such an energetic cloud under ordinary environments.”
The scientists proposed two possible scenarios, both of which involve black holes. The first requires the clouds to move near a static black hole. Most of the cloud front would move unaffected, but the massive compact object would attract some of the gas very quickly, creating an explosion. This explosion would propel some of the gas forward like a slingshot and create the bullet formation we see.
The other scenario instead requires a fast-moving black hole. In this scenario, the black hole comes through like a wrecking ball, pulling gas along. The team estimate that in the latter case, the black hole should have a mass of at least 36 times the mass of the Sun. In the static case, it was a more modest 3.5 times solar masses.
While the explanations are compelling, the team was not able to distinguish between the two scenarios with their current data set. The team plans to use the Atacama Large Millimeter/submillimeter Array to produce a more detailed view of the system and work out which of the two scenarios is more likely.
Theoretical models suggest between 100 million and 1 billion black holes in the Milky way, but so far we have only found about 60 of them. This could be a new way to find more black holes.