Astronomers detect more of Einstein's ripples in space
- Lorraine Burke
Weighty black holes are hard to explain, because the stars that collapsed to form them must have been even more massive.
"Our handful of detections so far is revealing an intriguing black hole population we did not know existed until now", said Northwestern's Vicky Kalogera, a senior astrophysicist with the LIGO Scientific Collaboration (LSC), which conducts research related to the twin LIGO detectors, located in the U.S.
The third detection is described in a new paper accepted for publication in the journal Physical Review Letters. Einstein's equations tell us that energy and mass are interchangeable.
Gravitational waves are caused by cosmic events like colliding black holes or neutron stars, explosive supernovas - even the birth of the universe.
Further, the LIGO-Virgo team was able, through the new observation, to put tighter constraints on the mass of the graviton, the hypothesized particle that supposedly mediates the gravitational force (analogous to the way that the photon, for example, mediates electromagnetic force).
By studying both the chirp and the ringdown, LIGO physicists worked out the masses of the two initial black holes, determining that the merged black hole weighed 49 solar masses - the difference being radiated away in the form of gravitational waves.
GW170104 was detected during the second run for the Advanced LIGO system, which is still in progress. When gravitational waves were detected in 2015, they were found from the formation of a black hole with 62 times the mass of our Sun and 21 times the mass.
The recent detection is the farthest yet, with the black holes located about 3 billion light-years from Earth.
Black holes are some of the most massive objects in the universe, and can be billions of times bigger than the Sun.
LIGO is an global collaboration with members around the globe.
This detection also hints at new information on how black holes spin.
Astronomers detect more of Einstein's ripples in space
After carefully analysing the signal, the LIGO team determined it was the fingerprint of a catastrophic collision between two black holes, one with a mass equal to roughly 30 suns, and the other with the mass of 19 suns.
This puts the merger right in the middle of the same weight class as the previous two black hole mergers - a class that scientists had not expected to encounter.
In this case, researchers were also able to tease out details that suggest at least one of the black holes was spinning in a direction opposite to the direction that the black holes were orbiting each other as they converged.
"Although our measurement can not precisely determine if the black holes were tilted, we have indication that at least one of the two black holes was misaligned, which favors the first theory", said Cadonati.
"That's either because heavy black hole spins are small, or because they're tilted, so their net effect cancels out", O'Shaughnessy said.
The other model proposes that the black holes are born together, forming when each star in a pair explodes and then, because the original stars were spinning in alignment, the black holes remain aligned.
They did not see evidence of dispersion, but if they had, it would have contradicted Einstein's theory. This happens when light waves in a physical medium travel at different speeds, depending on their wavelength. With no sign of dispersion, the LIGO team can say that if gravitons exist and have mass, it has to be less than 7.7 x 10 electronVolts.
"The upgrades will improve our reach into space, and allow for our third observation run ultimately to commence", said Caltech's Mike Landry, who directs LIGO's Hanford Observatory. "What's tremendous and exciting about it is that it's a completely new way of discovering things that we don't yet know".
Indian scientists have done foundational work over the last three decades in modelling the signal waveforms and developing mathematical techniques to search for gravitational wave signals in noisy data.
So it's possible that a binary neutron star merger could still be seen this year, or after the LIGO collaboration upgrades its instruments over the coming years. So, stay tuned: It's only been a bit more than a year since we first detected gravitational waves; no doubt they have much more to tell us about our universe.
"A squeezed light source will be installed to manipulate the quantum nature of light and make the detectors even more precise measurement devices", she said.
Gravitational waves produced by the birth of a massive black hole, a record-breaking billions of light-years from Earth, have been detected by the Laser Interferometer Gravitational-wave Observatory (LIGO).
Before gravitational wave astronomy, no scientist had observational proof that two black holes could orbit each other. LIGO partners with the Virgo Collaboration, a consortium including 280 additional scientists throughout Europe supported by the Centre National de la Recherche Scientifique (CNRS), the Istituto Nazionale di Fisica Nucleare (INFN), and Nikhef, as well as Virgo's host institution, the European Gravitational Observatory.
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Kushner is under scrutiny - not necessarily the subject of any investigation or suspected of any wrongdoing - in the FBI's probe. So it doesn't predispose you toward any sort of content of that conversation or anything.
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