Finding hints of gravitational waves in the stars

September 22, 2014, American Museum of Natural History
Energetic events, such as this artist’s rendition of a binary-star merger, are thought to create gravitational waves that cause ripples in space and time.  Credit: NASA

Scientists have shown how gravitational waves—invisible ripples in the fabric of space and time that propagate through the universe—might be "seen" by looking at the stars. The new model proposes that a star that oscillates at the same frequency as a gravitational wave will absorb energy from that wave and brighten, an overlooked prediction of Einstein's 1916 theory of general relativity. The study, which was published today in the Monthly Notices of the Royal Astronomical Society: Letters, contradicts previous assumptions about the behavior of gravitational waves.

"It's pretty cool that a hundred years after Einstein proposed this theory, we're still finding hidden gems," said Barry McKernan, a research associate in the Museum's Department of Astrophysics, who is also a professor at CUNY's Borough of Manhattan Community College; a faculty member at CUNY's Graduate Center; and a Kavli Scholar at the Kavli Institute for Theoretical Physics.

Gravitational waves can be thought of like the emitted after an earthquake, but the source of the "tremors" in space are energetic events like supernovae (exploding ), binary neutron stars (pairs of burned-out cores left behind when stars explode), or the mergers of black holes and neutron stars. Although scientists have long known about the existence of gravitational waves, they've never made direct observations but are attempting to do so through experiments on the ground and in space. Part of the reason why detection is difficult is because the waves interact so weakly with matter. But McKernan and his colleagues from CUNY, the Harvard-Smithsonian Center for Astrophysics, the Institute for Advanced Study, and Columbia University, suggest that gravitational waves could have more of an effect on matter than previously thought.

The shows that stars with oscillations—vibrations—that match the of gravitational waves passing through them can resonate and absorb a large amount of energy from the ripples.

"It's like if you have a spring that's vibrating at a particular frequency and you hit it at the same frequency, you'll make the oscillation stronger," McKernan said. "The same thing applies with gravitational waves."

If these stars absorb a large pulse of energy, they can be "pumped up" temporarily and made brighter than normal while they discharge the energy over time. This could provide scientists with another way to detect gravitational waves indirectly.

"You can think of stars as bars on a xylophone—they all have a different natural oscillation frequency," said co-author Saavik Ford, who is a research associate in the Museum's Department of Astrophysics as well as a professor at the Borough of Manhattan Community College, CUNY; a faculty member at CUNY's Graduate Center; and a Kavli Scholar at the Kavli Institute for Theoretical Physics. "If you have two black holes merging with each other and emitting gravitational waves at a certain frequency, you're only going to hit one of the bars on the xylophone at a time. But because the black holes decay as they come closer together, the frequency of the gravitational waves changes and you'll hit a sequence of notes. So you'll likely see the big stars lighting up first followed by smaller and smaller ones."

The work also presents a different way to indirectly detect gravitational waves. From the perspective of a on Earth or in space, when a star at the right frequency passes in front of an energetic source such as merging , the detector will see a drop in the intensity of gravitational waves measured. In other words, stars—including our own Sun—can eclipse background sources of .

"You usually think of stars as being eclipsed by something, not the other way around," McKernan said.

The researchers will continue to study these predictions and try to determine how long it would take to observe these effects from a telescope or detector.

Explore further: Measuring gravitational waves with eLisa

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Uncle Ira
3.4 / 5 (5) Sep 22, 2014
I mean one would think that if 2 super massive point sources of infinite gravity combine/merge into a single point source, twice as massive, inside a field of invisible gravity generating matter, which is being driven apart by another invisible field of energy, all held together by a frequency of energy vibration, which is only detectable for a fraction of a femto second by accelerating protons at each other and colliding them at relativistic velocities.....SOMETHING should manifest in the structural lattice of the universe that tells us it happened.

But wait...why?

If mass produces gravity, what is the difference between 2 massive objects 1000KM apart and 2 massive objects combining in the same space? The center of gravity will never change whether the objects are seperate or if they combine and the gravity at that point won't increase due to the merger. Hmmmm.


no-Skippy, could you dumb that down a little for me so I can vote on him?
Uncle Ira
3.7 / 5 (3) Sep 22, 2014
@ no-Skippy. I'll sit this one out and not vote, I got no idea what all that means.
Goika
Sep 22, 2014
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Goika
Sep 22, 2014
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yyz
4.9 / 5 (8) Sep 22, 2014
Zeph,

The new high Galactic latitude Planck analysis referred to in your linked article is available here: http://arxiv.org/abs/1409.5738

If the BICEP2 results are mostly from foreground Galactic contamination, well, so be it. At least a useful upper limit for gravitational waves could be derived from these observations, the most sensitive of their kind ever made. Also, the latest Planck results point to other regions of the sky with far less Galactic foreground than the BICEP2 region, fertile areas for other teams (and BICEP2/Keck) to search for a signal.
Mimath224
3.3 / 5 (4) Sep 22, 2014
So basically the 'jury is still out' with regard to GW? I haven't got any problem with that but glad to hear about more experiments. What I don't like is when they use terms like '...invisible ripples in the fabric of space and time...'. If one is inclined toward AWT then the term 'fabric' would make more sense because the term 'fabric' implies that space-time is flowing on/in another medium. It's just as easy to use the definition 'GW are fluctuations in the curvature of space-time. Ah...perhaps I'm being too fussy?
Goika
Sep 23, 2014
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Goika
Sep 23, 2014
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Goika
Sep 23, 2014
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ChangBroot
1 / 5 (1) Sep 23, 2014
"But because the black holes decay as they come closer together, the frequency of the gravitational waves changes and you'll hit a sequence of notes. So you'll likely see the big stars lighting up first followed by smaller and smaller ones."

Before reading to this point, I was thinking of the same thing. However, I think we might be missing another aspect of these waves. What if they are not reasonable like light? Just as a fast moving rocket with a flash light cannot boost speed of light any further, something totally strange might be happening with the gravitation waves too.
ViperSRT3g
not rated yet Sep 23, 2014
Yes a collision involving two massive bodies can be violent and destructive but the gravity of those 2 objects can't be changed as a result of the collision. This is the physics behind why I don't believe in gravity waves.

If they could be generated, I think you would have to observe a large, sudden shift in "A" center of gravity's spacial co-ordinates. There is no way to have this as interacting objects, according to mainstream theory, do so because of a center of gravity regardless of whether it's a collision or an orbital path.

Try comparing the gravity within a certain spacial region around your two objects with two objects at the surface of a pool of water. Lets say they are spiraling towards each other to eventually combine in the center. While they do this, they are creating ripples in the surface of the water. The overall total amount of water is not changing, but the distribution of it is. You'll see crests and troughs, changes in the height of the water. I feel that comparing it in this method is the closest one can get to imagining not only how, but why gravity waves may form.

You seem to be operating under the condition that gravity is an instantaneous phenomenon that reaches everything it affects with no regard to any passage of time. If that is the case, I'm not sure we'll ever be able to measure it.

If gravity does follow the universal speed limit, it is then possible that we can detect the waves that would eventually come about.
Fleetfoot
5 / 5 (4) Sep 23, 2014
There is a center of gravity around which they orbit until combining (their mutual IRF), the force of gravity emanating from that IRF is calculated strictly upon the mass value inside it and doesn't change.


You can understand this with just Newton's inverse square law. For example, using the Pythagorean triple (9,40,41): consider two equal mass BH 18 light years apart orbiting a point 40 light years away from us. When Earth and the BHs are all aligned, the gravitational effect here is

1/(40-9)^2 + 1/(40+9)^2

When the line joining them is perpendicular to the line between us and their centre, it is:

2/(41^2)

The effect measured here therefore varies with two peaks per orbit. The details in GR are much more complex but the result is similar.
11791
Sep 28, 2014
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Returners
1 / 5 (3) Sep 28, 2014
Put in "Youtube" and watch.

OdnhKE95AqM

Now a few entries down is my argument a few months ago about why this theory is wrong.

I actually got a response from a guy justifying the existence of a "cartoon universe" by saying it both exists and doesn't exist at the same time...

lol.

Is this what "science" has come to?
TheGhostofOtto1923
5 / 5 (1) Sep 28, 2014
Lrrkrrr

Why dont you post a decent link? Is it against your religion?
ROBTHEGOB
1 / 5 (1) Sep 29, 2014
There is no such thing as "time". There is only space.
nswanberg
1 / 5 (1) Sep 29, 2014
Seems to me one would have to instantaneously create mass on a planetary scale to measure gravity waves. The mass in these examples is already in place it is just being suddenly moved about. Same for measuring the speed of gravity. One would have to instantly create a large mass and then measure how long it takes for other nearby bodies to feel the effects.
mscheue1
not rated yet Nov 07, 2014
RobTheGob, give me a minute to think about that. Okay, now give me a mile to think about it again. Nope, I still don't agree.

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