An illustration of Markarian 231, a binary black hole 1.3 billion light years from Earth. Their collision generated the first gravitational waves we've ever detected. Image: NASA

Gravitational Waves Discovered: A New Window on the Universe

11 Feb , 2016 by

“Ladies and Gentlemen, we have detected gravitational waves. We did it.”

With those words, Dave Reitze, executive director of the U.S.-based Laser Interferometry Gravitational-Wave Observatory (LIGO), has opened a new window into the universe, and ushered in a new era in space science.

Predicted over 100 years ago by Albert Einstein, gravitational waves are ripples in space-time. They travel in waves, like light does, but they aren’t radiation. They are actual perturbations in the fabric of space-time itself. The ones detected by LIGO, after over ten years of “listening”, came from a binary system of black holes over 1.3 billion light years away, called Markarian 231.

The two black holes, each 30 times as massive as the Sun, orbited each other, then spiralled together, ultimately colliding and merging together. The collision sent gravitational waves rippling through space time.

LIGO, which is actually two separate facilities separated by over 3,000 km, is a finely tuned system of lasers and sensors that can detect these tiny ripples in space-time. LIGO is so sensitive that it can detect ripples 10,000 times smaller than a proton, in laser beams 4 kilometres long.

The Laser Interferometer Gravitational-Wave Observatory (LIGO)facility in Livingston, Louisiana. The other facility is located in Hanford, Washington. Image: LIGO

The Laser Interferometer Gravitational-Wave Observatory (LIGO)facility in Livingston, Louisiana. The other facility is located in Hanford, Washington. Image: LIGO

Light is—or has been up until now—the only way to study objects in the universe. This includes everything from the Moon, all the way out to the most distant objects ever observed.  Astronomers and astrophysicists use observatories that can see in not only visible light, but in all other parts of the electromagnetic spectrum, to study objects in the universe. And we’ve learned an awful lot. But things will change with this announcement.

“I think we’re opening a window on the universe,” Dave Reitze said.

Another member of the team that made this discovery, astrophysicist Szabolcs Marka from Columbia University, said, “Until this moment we had our eyes on the sky and we couldn’t hear the music.”

Gravitational waves are a new way to study notoriously difficult things to observe like black holes and neutron stars. Black holes emit no light at all, and their characteristics and properties are inferred from cause and effect relationships with objects near them. But the detection of gravitational waves holds the promise of answering questions about black holes, neutron stars, and even the early days of our universe, including the Big Bang.

It’s almost impossible to overstate the magnitude of this discovery. Once we understand how to better detect and observe gravitational waves, we may come to a whole new understanding of the universe, and we may look back on this day as truly ground-breaking and revolutionary.

And it all started 100 years ago with Albert Einstein’s prediction.

For a better understanding of Gravitational Waves, their sources, and their detection, check out Markus Possel’s excellent series of articles:

Gravitational Waves and How They Distort Space

Gravitational Wave Detectors and How They Work

Sources of Gravitational Waves: The Most Violent Events in the Universe

 

 

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Steven
Member
Steven
February 11, 2016 3:37 PM

“Light is—or has been up until now—the only way to study objects in the universe. ”

Ummm – neutrinos?

Still I take your point.

But how about all that missing mass – transformed into energy and shot out at the speed of light in all directions. If gravity waves essentially take some measure of mass and send it out in waves…. is normal matter (and dark matter for example) evaporating?

N70SAK
Member
N70SAK
February 11, 2016 5:03 PM

robots with drills! smile

mewo
Member
mewo
February 12, 2016 3:48 AM

Before this discovery there were four sources of information:
*Light
*Probes directly detecting magnetic fields of Sun, Earth, planets, etc.
*Sampling of physical material. Meteorites, sample returns of Solar wind, asteroid dust, and Moon rocks
*Neutrinos

Gravitational waves makes five.

Steven
Member
Steven
February 12, 2016 8:51 PM

the IBEX probe watches for neutral atoms from the interstellar medium. Six.

Cosmic rays. Seven.

Manu
Member
Manu
February 11, 2016 5:20 PM

That header image caption can’t be right :S
The binary BH that merged is not Markarian 231.
https://en.wikipedia.org/wiki/Markarian_231

Steven
Member
Steven
February 11, 2016 9:28 PM

Other non-EM ways we learn of the cosmos… IBEX watch of neutral atoms… and the cosmic ray observances

Jeffrey Boerst
Member
February 12, 2016 2:37 AM

Cosmic rays are energetic atomic nuclei. Is that not counting as EM?

mewo
Member
mewo
February 12, 2016 7:15 AM

Sure, but what we observe of them is the cascades they cause in the atmosphere, and those are detected as EM waves.

Steven
Member
Steven
February 12, 2016 8:50 PM

No – EM is not cosmic rays. Gamma rays yes but not cosmic rays. We detect them by EM phenomena but they are themselves matter.

Brian Sheen
Member
Brian Sheen
February 12, 2016 3:49 AM

Does the discovery include a figure for the speed at which these wavs propagate ie is it the speed of light or slower?

mewo
Member
mewo
February 12, 2016 7:13 AM

Gravitational waves propagate at the speed of light, yes.

B-Ark
Member
B-Ark
February 12, 2016 7:24 AM

How do we know that these gravitational waves are from Markarian 231, as opposed to an event from some other corner of the universe? How ‘directional’ is LIGO?

Manu
Member
Manu
February 12, 2016 3:13 PM

Definitely not M231, that caption is bonkers (fix it UT!). For one thing, M231 is a binary supermassive BH, way bigger than the 30 solar masses BH that LIGO detected. Also M231 won’t merge for billions of years yet, if at all.

LIGO is poorly directional atm, 600 square degrees were mentioned and there is an image somewhere that shows the possible area over the sky. Things will get much better when more detectors get online: European VIRGO later this year, then a Japanese machine. It should be possible to locate sources within a few square degrees then, maybe enough for scopes to search for optical counterparts.

space_cookie
Member
space_cookie
February 12, 2016 6:16 PM

As Manu has pointed out, it is definitely not Markarian 231 – wrong masses (by many orders of magnitude), wrong distance (by a factor of ~ 2.2) and wrong celestial hemisphere. I can’t think what Evan Gough was thinking of when he posted this nonsensical bit of information.

You can download the LIGO paper from here:

https://dcc.ligo.org/public/0122/P1500218/012/GW150914_parameter_estimation_v13.pdf

It includes the ‘sky map’ indicating the likely direction of the source of the signal, see page 8.

space_cookie
Member
space_cookie
February 12, 2016 6:19 PM

@B-Ark

As Manu has pointed out, it is definitely not Markarian 231 – wrong masses (by many orders of magnitude), wrong distance (by a factor of ~ 2.2) and wrong celestial hemisphere. I can’t think what Evan Gough was thinking of when he posted this nonsensical bit of information.

You can download the LIGO paper from here:

https://dcc.ligo.org/public/0122/P1500218/012/GW150914_parameter_estimation_v13.pdf

It includes the ‘sky map’ indicating the likely direction of the source of the signal, see page 8.

Mich48
Member
Mich48
February 13, 2016 1:04 AM

I’ve heard this could be a totally new field of science. I propose it should be called “Gravitygraphy”.

B-Ark
Member
B-Ark
February 13, 2016 7:02 AM

My take:
So, bottom line, we don’t have a clue as to what caused this particular detected event.
And, even with multiple detectors, we will need optical/radio telescopes to find the ‘likely suspect’.

@MICH48 – Too many syllables – I’d go with gravigraphy.

space_cookie
Member
space_cookie
February 13, 2016 7:11 PM

@ B-ARK

If you read the LIGO paper at https://dcc.ligo.org/public/0122/P1500218/012/GW150914_parameter_estimation_v13.pdf you’ll find that the authors have a very good grasp of what caused this particular event.

As for pinning it down to an optical object, that sort of detail won’t be available until there are more LIGO class instruments in operation, and of course optical telescopes will be part of the process of finding the ‘likely suspect’ – same as in the early days of radio astronomy.

Pete
Member
Pete
February 14, 2016 6:04 PM

I’ve read now that the gravitational signal was received shortly after turning LIGO on. Is that just serendipitous? How often are signals like this expected to be seen? Will we see both stronger and weaker signals? How close to the lower limit of detectability was the signal that was received?
That’s just a few of the questions burning in my brain. Can someone in or close to the discovery team please answer them?

Jeffrey Boerst
Member
February 16, 2016 1:51 AM

They actually think there was another, smaller sighting they are still working on teasing out of the data.

wpDiscuz