After the discovery: Researchers study implications of gravitational waves

February 22, 2016 by Susan Gawlowicz

Rochester Institute of Technology researchers continue exploring gravitational waves in a series of upcoming papers. Their reports follow the first direct detection of these waves, predicted by Albert Einstein's general theory of relativity.

The international collaboration of scientists associated with the Laser Interferometer Gravitational Wave Observatory published its findings on Feb. 11 in Physical Review Letters. Six scientists from RIT's Center for Computational Gravitation and Relativity were co-authors on the discovery publication. They are John Whelan, associate professor in RIT's School of Mathematical Sciences and principal investigator of RIT's group in the LIGO Scientific Collaboration; Richard O'Shaughnessy, assistant professor in the School of Mathematical Sciences; Carlos Lousto, professor in the School of Mathematical Sciences and an American Physical Society Fellow; James Healy, post-doctoral research fellow; and graduate students in RIT's astrophysical sciences and technology program Jacob Lange and Yuanhao Zhang.

Several of the RIT researchers are listed on the 12 companion papers, including "Astrophysical Implication of the Binary Black-hole Merger GW150914," published in Astrophysical Journal Letters. Upcoming publications listing the RIT authors investigate properties of the binary black hole merger and infer the rate of such mergers based on their implications for the .

LIGO's discovery is consistent with the specific method O'Shaughnessy and his collaborators use to predict how massive stars evolve into and form merging pairs.

"LIGO has just proved that binary black holes merge frequently throughout the universe, much more than many people expected," O'Shaughnessy said. "But the discovery of a black hole merger is only the tip of the iceberg."

The scope of gravitational wave astronomy will widen as the international network of detectors becomes fully operational. Scientific runs at increasing levels of sensitivity are planned for the U.S.-based LIGO detectors and the Italian counterpart, Advanced Virgo, Whelan noted.

"We're looking not just for binary mergers, but for a range of signals from unexplained bursts to a background 'hum' from many weak signals from the distant universe or even the big bang," said Whelan, graduate program coordinator of RIT's astrophysical sciences and technology program. "Closer by, our own galaxy is also full of potential strong sources such as rapidly spinning neutron stars."

Neutron stars are stellar remnants that have collapsed under their own weight but are not massive enough to form into black holes. Merging pairs of neutron stars produce a fainter signal than binary black holes, but are expected to be more common in nearby galaxies. Whelan predicts that these mergers will be detected as the network's sensitivity improves.

An individual rapidly spinning neutron star can produce weaker generated by irregularities in its structure. A single neutron star can continuously emit periodic signals in contrast to the short-lived "chirps" that merging pairs of black holes or emit.

Whelan develops and implements methods to search for gravitational waves. He and Ph.D. student Zhang lead an effort targeting Scorpius X-1, a neutron star that emits X-rays as it "steals" matter from a companion star. Their method, reported in 2015 in Physical Review D, has the potential to detect gravitational waves from this neutron star once Advanced LIGO and Advanced Virgo have reached design sensitivity, Whelan said.

"At RIT, we have developed the current-best strategy to find gravitational waves from Scorpius X-1, one of the most promising sources of long-lived gravitational waves from our galaxy," Whelan said. "One of the strengths of the center is that we now play a major role in both the simulation of gravitational waves and the scientific analysis of the LIGO data itself."

Gravitational wave science in RIT's Center for Computational Relativity and Gravitation is a complementary effort of mathematically modeling astronomical systems, analyzing and interpreting gravitational waveforms in the LIGO data and creating scientific visualizations to illustrate their research.

"LIGO has just provided the first glimpse into the gravitational wave sky, but not the last," said Manuela Campanelli, director of the RIT center and an American Physical Society Fellow. "At RIT, we're working on a wide range of gravitational wave astrophysics. We're one of a handful of groups worldwide developing the tools and performing the simulations needed to interpret phenomena dominated by strong-field physics in Einstein's theory of gravity."

The LIGO Scientific Collaboration cites Campanelli's team as one of three groups that advanced modeling of black hole mergers on supercomputers and accurately predicted gravitational waveforms. Campanelli's 2005 method, the moving puncture approach, played an important role in enabling and interpreting the LIGO discovery. Lousto, a member of the original team, and Healy used the method to independently calculate the gravitational waves observed by the Advanced LIGO detectors on Sept. 14, 2015.

Lousto is confident in RIT's role in the new field of gravitational wave astronomy.

"Only by solving Einstein's theory on supercomputers can we fully capture the complexity that his theory allows," he said. "Simulations like those we perform at RIT are critical to extract all the information from these fantastic new observations, and put Einstein's theory to the test."

Explore further: Announcement Thursday on Einstein's gravitational waves

More information: B. P. Abbott et al. ASTROPHYSICAL IMPLICATIONS OF THE BINARY BLACK HOLE MERGER GW150914, The Astrophysical Journal (2016). DOI: 10.3847/2041-8205/818/2/L22

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baudrunner
2 / 5 (4) Feb 22, 2016
Einstein's prediction of gravity waves concerned the "motion of objects in space", not cataclysmic events, like colliding bodies in space. The LIGO researchers are currently waiting for another occurrence of the same type of event detected recently. That is to say, another shock wave, not a gravity wave, and which would represent further evidence of another cataclysmic event, like a super nova, or something similarly profound. They will continue to call them gravity waves, but that's not what Einstein was referring to. He presumed that someday we would be able to detect the gravity waves resulting from the motion of bodies in space, like the moon as it interacts with Earth, and the sun. The mislabeling of the experimental results is deliberate, in calling them "gravity waves", which was for no other reason than to vindicate Einstein. He had been wrong before, you know.

Gravity doesn't involve wave behavior. It is "spooky action at a distance".
EnsignFlandry
4.3 / 5 (6) Feb 22, 2016
Wow. Virtually the entire physics and astronomy community has it all wrong then.
We know that according to GR moving mass generates gravity waves, but for ordinary planetary or even most stellar masses these are very weak. The interaction of two massive black holes also distorts spacetime, resulting in gravity waves.
matt_s
3.7 / 5 (3) Feb 22, 2016
@Baud. Wouldn't the detection of "shockwaves" as you put it... lead directly to the detection of the other phenomenon?

Let me clarify.

They can only detect supernovas, BH mergers, etc. right now because they are what affect spacetime the most. In principle, if LIGO's sensitivity could be increased (several orders of magnitude), they could detect say, "the moon as it interacts with Earth, the sun, etc." I

How is that "mislabeling"? It's the same phenomenon, just at a different scale.

Gravity doesn't involve wave behavior. It is "spooky action at a distance".


We have direct evidence this claim is false.
baudrunner
1 / 5 (2) Feb 23, 2016
Wow. Virtually the entire physics and astronomy community has it all wrong then.
That is correct.
We know that according to GR moving mass generates gravity waves, but for ordinary planetary or even most stellar masses these are very weak.
That is a false presumption based on the idea that gravity involves wave behavior. That is incorrect.
They can only detect supernovas, BH mergers, etc. right now because they are what affect spacetime the most
That is a facile statement.
baudrunner
2.3 / 5 (3) Feb 23, 2016
We have direct evidence this claim is false.
I presume that you are talking about the LIGO results. In fact, you can't make this claim. Those ripples in space-time were caused by a shock wave. Shock waves aren't your gravity waves. If those were gravity waves causing those ripples in space-time, then where is the evidence of the shock waves that resulted from that collision? They are much more powerful than the "weak force" that gravity has been described as being - which is also false because gravity isn't even a force.
Zzzzzzzz
5 / 5 (2) Feb 23, 2016
baudrunner......the entire community is eagerly awaiting your published treatise and/or experimental results to validate your claims. Mere assertions are WORTHLESS.
geokstr
1 / 5 (1) Feb 28, 2016
Pardon my ignorance, but aren't gravity waves supposed to move outwards from mass? So how do two bodies, say Earth and the moon, both producing outward gravity waves produce an attracting force instead of one that repels?

I've seen the analogy with a body warping space-time and creating a gravity well, like a bowling ball on a sheet of rubber. If a smaller body gets too close, it's not an attractive force at all that pulls it in, but merely the smaller one falling into the gravity well of the other.

That would make sense if all gravity wells are infinite in size but weaken as the distance squared. The outward pressure of gravity waves would keep other objects revolving then when it was in equilibrium with the outward pressure of the smaller body, which would remain circling on the upper part of its gravity well.

Is it the outward pressure of the gravity wave itself that creates the gravity well by pushing against the gravity wells of other matter?

Whew. My head hurts. ???
Noumenon
not rated yet Feb 28, 2016
... aren't gravity waves supposed to move outwards from mass?


No. Only if there is some dynamical change in the mass. The gravitational field of the earth is static, so no waves. In order to produce significant gravitational waves the dynamical change in the source of gravitation, the mass-energy, has to be fast and and the source large.

Gravitational waves don't produce 'pressure outwards' [a pressure in what?]. They produce a change in the metric [invariant measure of space-time].

A object "hit by" a gravitational wave, would not be pushed away or repelled. It would distort instead. One of the first detectors proposed was simply a large metal bar with detectors glued onto it to detect strain and stress.

Phys1
5 / 5 (2) Feb 28, 2016
Einstein's prediction of gravity waves concerned the "motion of objects in space", not cataclysmic events, like colliding bodies in space.

Same thing.
The LIGO researchers are currently waiting for another occurrence of the same type of event detected recently. That is to say, another shock wave, not a gravity wave,

EM and gravity waves are never shock waves.
A shock wave is caused by an object moving faster that the wave velocity.
Since EM and gravity waves move at c, that is not possible.
Phys1
not rated yet Feb 28, 2016
@br
That is a false presumption based on the idea that gravity involves wave behavior. ...

Within the context of Special Relativity it is true.
They can only detect supernovas, BH mergers, etc. right now because they are what affect spacetime the most
That is a facile statement.

Nevertheless entirely correct.
br, you are not qualified to make any sense on this subject.

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