This simulation helps explain an odd light signal thought to be coming from a close-knit pair of merging black holes, PG 1302-102, located 3.5 billion light-years away. Credit: Columbia University
Entangled by gravity and destined to merge, 2 candidate black holes in a distant galaxy appear to be locked in an intricate dance. Researchers using data from NASA’s Galaxy Evolution Explorer (GALEX) and NASA’s Hubble Space Telescope have come up with the most compelling confirmation yet for the existence of these merging black holes and have found new details about their odd, cyclical light signal.
The candidate black hole duo, called PG 1302-102, was first identified earlier this year using ground-based telescopes. The black holes are the tightest orbiting pair detected so far, with a separation not much bigger than the diameter of our solar system. They are expected to collide and merge in less than a million years, triggering a titanic blast with the power of 100 million supernovae. Researchers are studying this pair to better understand how galaxies and the monstrous black holes at their cores merge – a common occurrence in the early universe. But as common as these events were, they are hard to spot and confirm.
PG 1302-102 is one of a few good binary black hole candidates. The researchers with telescopes in the Catalina Real-Time Transient Survey, demonstrated the varying signal is likely generated by the motion of 2 black holes, which swing around each other every 5 years. While the black holes themselves don’t give off light, the material surrounding them does.
In the new study they found more evidence to support and confirm the close-knit dance of these black holes. Using UV data from GALEX and Hubble, they were able to track the system’s changing light patterns over the past 20 years. The UV light was important to test a prediction of how the black holes generate a cyclical light pattern.One of the black holes in the pair is giving off more light – it is gobbling up more matter than the other one, and this process heats up matter that emits energetic light. As this black hole orbits around its partner every five years, its light changes and appears to brighten as it heads toward us.
What’s causing the changes in light? One set of changes has to do with the “blue shifting” effect, in which light is squeezed to shorter wavelengths as it travels toward us in the same way that a police car’s siren squeals at higher frequencies as it heads toward you. Another reason has to do with the enormous speed of the black hole.
The brighter black hole is, in fact, traveling at nearly 7% the speed of light ie really fast. At speeds as high as this, aka relativistic, the light becomes boosted and brighter. The results will also help researchers understand how to find even closer-knit merging black holes in the future, what some consider the holy grail of physics and the search for gravitational waves. In the final moments before the ultimate union of two black holes, when they are tightly spinning around each other like ice skaters in a “death spiral,” they are predicted to send out ripples in space and time. These so-called gravitational waves, whose existence follows from Albert Einstein’s gravity theory published 100 years ago, hold clues about the fabric of our universe.
http://www.jpl.nasa.gov/news/news.php?feature=4719
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