Gravitational waves will let us see inside stars as supernovae happen

Gravitational waves will let us see inside stars as supernovae happen
Artistic representation of the material around the supernova 1987A. Credit: ESO/L. Calçada

On February 11th, 2016, scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO) announced the first detection of gravitational waves. This development, which confirmed a prediction made by Einstein's Theory of General Relativity a century ago, has opened up new avenues of research for cosmologists and astrophysicists. Since that time, more detections have been made, all of which were said to be the result of black holes merging.

However, according to a team of astronomers from Glasgow and Arizona, astronomers need not limit themselves to detecting waves caused by massive gravitational mergers. According to a study they recently produced, the Advanced LIGO, GEO 600, and Virgo gravitational-wave detector network could also detect the gravitational waves created by supernova. In so doing, astronomers will able to see inside the hearts of collapsing for the first time.

The study, titled "Inferring the Core-Collapse Supernova Explosion Mechanism with Three-Dimensional Gravitational-Wave Simulations," recently appeared online. Led by Jade Powell, who recently finished her Ph.D. at the Institute for Gravitational Research at the University of Glasgow, the team argue that current gravitational wave experiments should be able to detect the waves created by core collapse supernovae (CSNe).

Otherwise known as Type II supernovae, CCSNe are what happens when a massive star reaches the end of its lifespan and experiences rapid collapse. This triggers a massive explosion that blows off the outer layers of the star, leaving behind a remnant neutron star that may eventually become a black hole. In order for a star to undergo such collapse, it must be at least 8 times (but no more than 40 to 50 times) the mass of the Sun.

When these types of supernovae take place, it is believed that neutrinos produced in the core transfer gravitational energy released by core collapse to the cooler outer regions of the star. Dr. Powell and her colleagues believe that this gravitational energy could be detected using current and future instruments. As they explain in their study:

"Although no CCSNe have currently been detected by gravitational-wave detectors, previous studies indicate that an advanced detector network may be sensitive to these sources out to the Large Magellanic Cloud (LMC). A CCSN would be an ideal multi-messenger source for aLIGO and AdV, as neutrino and electromagnetic counterparts to the signal would be expected. The gravitational waves are emitted from deep inside the core of CCSNe, which may allow astrophysical parameters, such as the equation of state (EOS), to be measured from the reconstruction of the gravitational-wave signal."

Dr. Powell and her also outline a procedure in their study that could be implemented using the Supernova model Evidence Extractor (SMEE). The team then conducted simulations using the latest three-dimensional models of gravitational-wave core collapse supernovae to determine if background noise could be eliminated and proper detection of CCSNe signals made.

As Dr. Powell explained to Universe Today via email:

"The Supernova Model Evidence Extractor (SMEE) is an algorithm that we use to determine how supernovae get the huge amount of energy they need to explode. It uses Bayesian statistics to distinguish between different possible explosion models. The first model we consider in the paper is that the explosion energy comes from the neutrinos emitted by the star. In the second model the explosion energy comes from rapid rotation and extremely strong magnetic fields."

From this, the team concluded that in a three-detector network researchers could correctly determine the explosion mechanics for rapidly-rotating supernovae, depending on their distance. At a distance of 10 kiloparsecs (32,615 light-years) they would be able to detect signals of CCSNe with 100% accuracy, and signals at 2 kiloparsecs (6,523 light-years) with 95% accuracy.

In other words, if and when a supernova takes place in the local galaxy, the global network formed by the Advanced LIGO, Virgo and GEO 600 gravitational wave detectors would have an excellent chance of picking up on it. The detection of these signals would also allow for some groundbreaking science, enabling scientists to "see" inside of exploding stars for the first time. As Dr. Powell explained:

"The are emitted from deep inside the core of the star where no electromagnetic radiation can escape. This allows a gravitational wave detection to tell us information about the explosion mechanism that can not be determined with other methods. We may also be able to determine other parameters such as how rapidly the star is rotating."

Gravitational waves will let us see inside stars as supernovae happen
Illustration showing the merger of two black holes and the gravitational waves that ripple outward as the black holes spiral toward each other. Credit: LIGO/T. Pyle

Dr. Powell, having recently completed work on her PhD will also be taking up a postdoc position with the RC Centre of Excellence for Gravitational Wave Discovery (OzGrav), the gravitational wave program hosted by the University of Swinburne in Australia. In the meantime, she and her colleagues will be conducting targeted searchers for supernovae that occurred during the first and seconds advanced detector observing runs.

While there are no guarantees at this point that they will find the sought-after signals that would demonstrate that supernovae are detectable, the team has high hopes. And given the possibilities that this research holds for astrophysics and astronomy, they are hardly alone!

Explore further

Collapsing star gives birth to a black hole

More information: Inferring the core-collapse supernova explosion mechanism with three-dimensional gravitational-wave simulations.
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Sep 12, 2017
How come such an old story is dug out to look as a fresh story? Let me tell you, LIGO actually never detected any black hole mergers in the past too. The least I can say is that the reported mergers were a result of the intense imagination of the LIGO folks, to say the least. And now to slip in the final secret -- Speed of gravity is infinite while LIGO shows it to be equal to the speed of light in its so-called observations. That is why all the gravitational wave observations by LIGO are false. Let me add, 6 years earlier, minuscule gravitational waves of a wide frequency range (nearly zero to around 3 KHz) were first produced and detected in my lab late in 2010 and were reported in a US patent application which now is a US patent 8521029. You can find the patent detail on the USPTO site as well as on https://www.googl...S8521029 . You can check out gravitational waves and my work on Wikipedia.

Sep 12, 2017
What? What the hell do you think is causing the gravity waves we've detected?

Sep 12, 2017
more detections have been made, all of which were said to be the result of black holes merging.

So, two physically impossible objects merged multiple times and each merger was detected by LIGO....I will write formal letters of apology to all whom I have offended with my skepticism, insults about their intelligence and trash talk about the science... just one image that proves they exist.

Of course should reality demonstrate that a Black hole is complete bullshit, I will expect the same in return....blahahahahaha....not.

No one cares about you or your incorrect opinions enough to ever want an apology. We already know you are wrong and do not have the time or energy to explain it in words simple enough for even you to understand it. Astrophysics is a mature and ever developing field and is perfectly happy to not count you among its peerage.

Sep 12, 2017
Why are you commenting on science if you don't care about it?

Sep 13, 2017
@PTTG LIGO observations are false because there is no proof that gravitational waves travel at c or at any other speed. It was always a conjecture that the speed of gravitational waves should not exceed speed of light. The fact that LIGO showed the speed of GW as c was a trap they themselves set and fell into. The reality is GW travels at infinite speed, unlike c. I have worked extensively to find the details why. My patent sums up the initial view as of in 2010. The nature of GW and EM radiation is totally different, and it is erroneous to assume c to be the cosmic traffic law, unless you understand why c is a constant. Only after that understanding you can try to understand whether GW is of the same nature as EM radiation. LIGO prematurely jumped the gun and showed GW = c; eventually, long enough man-made GW links will establish the speed of GW as infinity and LIGO finding will be an embarrassment to all. High intensity GW production by gravity modulation can demonstrate it.

Sep 13, 2017
@bschott Thanks. When I started out, it was simply to investigate photon pumping effect on invariant mass/gravity of a glass target by possible Compton scattering. It was a simple energy to mass conversion route. It did work and the invariant mass of the glass target could be increased by static photon beams and modulated by a photon pulse train. I proposed a possible theory for it in my patent. That GW was not the effect of mechanical vibration of atoms, but the invariant mass fluctuations of the atoms. The GW sensor was so close to the glass target that it was impossible to measure the speed of the generated GW. Later analysis pointed out the fact that I noted in me first comment -- GW is completely different from EM, although, It is generated by EM means, their wave natures are different. Ours is an EM-GW-mix universe, where gravitation, indeed, plays a key role. I await the reporting of my next stage of investigations. GW is FTL and is impossible to detect it by interferometry.

Sep 13, 2017
@bschott Further, LIGO is producing GW in its own mirrors, that creates vibrations which are impossible to prevent and might be picked up as "GW signals": http://www.scienc...them-too
Modulating EM radiation is present everywhere, falling on every object; hence, there is so much of GW noise that even a correct (non-interferometer based) GW sensor cannot receive waves from BH mergers. If you want updates on my work you can mail. [However, LIGO is so much scared that before the Feb '16 announcement, they sent a business intelligence agent all over from Zurich who probed me to the extent of my work. My emails are blocked constantly, still, we may try to keep in touch over email.]

Sep 13, 2017
@bschott LIGO-Virgo have retracted their neutron star merger rumor: https://physics.a...6.062002

Sep 14, 2017
@bschott In the above-linked paper, it appears they just denied finding any NS mergers in their O1 run. It just seems a way to show that they also cannot do a few things and makes them look a bit human. However, to keep the pot boiling, they have kept their options open for the O2 run (which they can cook any time). This make Reitze look like a hard working leader to the Nobel committee. If they miss the prize this time, there would have a paper announcing NS mergers during this year O2 run before October 2018. Interestingly, during O1 run, Virgo never reported any BH mergers!

Sep 14, 2017
O.18mm to 0.03mm in the experiment to check invariant mass static increase by a multiple photon beam (total power 0.4 watt),; the feeling mass was a graphite slug ~7mg resting on the thin mylar membrane of an electret microphone. Later to check GW transmission, a frequency of 1 to ~4 kHz was used till a distance of 200mm, target was a rectangular glass slab, with a large weight at 200mm as a sensor.

Sep 15, 2017
The graphite got lighter during the experiment. Showing that it was pulled upwards by the glass piece when exposed to photon beam. In the 200mm experiment, once the receiver mass was resonant to the test tone, there was a signal in the piezo sensors on which the receiver mass rested. The receiver mass was composed of silica filled glass aluminum.iron shell. In the first experiment there always was a tone in the sensor; however, to clarify whether the graphite piece was getting pulled or was getting repulsed, the static mass change readings were taken.

Sep 15, 2017
Text from pat grant, brackets [] added now, "Further, in an earlier experiment the graphite slug height was 0.72 mm and the sensitivity was never more than 1 dB; an increase of 0.15 mm, resulted in a clear increase in sensitivity, while the gap between the bottom mirrored layer and the upper surface of the graphite slug reduced from 0.18 mm to 0.03 mm; as the height of the glass cylinder was 4.2 mm and the laser beams were centered 1.4 mm below the vertical center of the glass cylinder with approximate spot diameter being 2 mm, following the inverse square law of photometry, if the source of [gravitational] radiation were the bottom mirrored layer, the increase in the photonic push would have been nearly (0.18 mm/0.03 mm)^2 or nearly 15 dB; however, if a gravitational radiation from the center of the laser beam spots is considered, the increase in that radiation would have been nearly (0.88 mm/0.73 mm)^2 or nearly 1.6 dB which is in agreement with the experimental result of 2 dB. "

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