Gravitational Wave Astronomy - Has LIGO Launched A New Science?
Gravitational waves have been seen for the second time by astronomers utilizing the LIGO observatory. The phenomenon was recorded emanating from a region in space where a pair of black holes are seen colliding.
An ancient globular cluster housing a massive quantity of stars is home to the two black holes seen in the new study. Northwestern University physicists examining the event made a bold prediction in 2015 about the underlying causes of the interstellar merger. This new finding seems to back up the hypothesis concerning the dynamic interactions in the region, which some astronomers are referring to as a "mosh pit." Measurements of gravitational waves from the system suggests the black holes may have once left the globular cluster, only to come together again before merging.
"Thanks to LIGO, we're not just theorists speculating anymore — now we have data. A relatively simple and well understood process seems to work. Simple freshman physics — Newton's first law of motion — explains the gravitational dynamics of the first black holes detected by LIGO," said Frederic A. Rasio, an astrophysicist at Northwestern University.
The collision of a pair of black holes is a highly-energetic event, but the process does not release any visible light. However, gravitational waves are produced en masse, according to theories. However, these waves are exceptionally difficult to detect, and none were seen prior to 2015.
Globular clusters are mostly-spherical gatherings of around one million stars. By contrast, our own Milky Way galaxy contains between 200 and 400 billion stellar bodies. The team led by Rasio predicted these families of stars could naturally produce binary pairs of black holes that could collide, merging into one larger body.
The black holes seen in the latest observations had masses roughly eight and 14 times as large as our sun. After merging, the resultant black hole was approximately 21 times as massive as our parent star. The event, which took place roughly 1.4 billion years ago, converted an amount of mass equal to our sun into gravitational waves. By measuring the difference in time at which the event was recorded by a pair of detectors, astronomers were able to calculate the approximate position of the collision in space.
"It is very significant that these black holes were much less massive than those observed in the first detection. Because of their lighter masses compared to the first detection, they spent more time — about one second — in the sensitive band of the detectors. It is a promising start to mapping the populations of black holes in our universe," Gabriela González, LIGO spokesperson from Louisiana State University, said.
Computer models suggest that similar collisions of black holes could result in an average of 100 such events each year in such a system.
Gravitational waves were first predicted by Albert Einstein in his General Theory of Relativity, published a century ago. Detection of gravitational waves was announced by the LIGO team on Feb. 11, 2016.
As additional observations of gravitational waves are recorded, investigators believe we may witness the birth of a new branch of science — gravitational wave astronomy.