If you’re weary, feelin’ small, remember that somewhere out there, two supermassive black holes are heading for a cosmic mega-collision. Earlier this year, astronomers at Caltech identified a cosmic event that is occurring 3.5 billion light years from Earth: two supermassive black holes spiraling helplessly towards each other. Recent work by researchers at Columbia University adds further evidence that indeed the black holes are on a collision course. The consequences are not yet completely clear, but this meeting will certainly be cataclysmic for nearby stars and planets.
The Caltech astronomers estimate the collision of two supermassive black holes could release destructive gravitational waves through space-time, with the energy equivalent of 100 million supernova explosions. The researchers suspected the presence of a black hole collision when they observed a faint but consistent flickering originating in the center of the galaxy, also known as quasar. The Columbia researchers elaborated on this theory by proposing that the flickering quasar originates from a massive disk of gas that is orbiting the smaller of the two black holes.
Black holes are extremely dense objects whose gravitational pulls are so great that not even light can escape. Most galaxies seem to have a supermassive black hole, which can be problematic when galaxies merge. Two supermassive black holes usually enter into orbit with each other, until they interact with other celestial objects, like interstellar gas. As the discs of gas whirl around each other, the light they emanate is affected by the Doppler effect, which periodically increases the strength of the emitted light every five years. The Doppler effect is most concretely observed in the sound of an emergency siren, which becomes higher-pitched and louder as it approaches the listener.
Understanding this effect, the researchers proposed the variation between Doppler years and normal years would be two to three times larger in ultraviolet light than in visible light. They were correct. “What’s big is that the Doppler boost is inevitable,” says Dr. Zoltan Haiman, researcher at Columbia. “This is rare in ‘messy’ astronomy,” he said, “to have an indisputable clean effect, which explains the data.” Further testing will be required before the astronomers can explain exactly what is happening, but each step in the process is like the slightest opening of the treasure chest that holds the secrets of the universe.
Via New York Times