Scientists detect biggest known black-hole collision

December 3, 2018, Australian National University
Artist's impression of two black holes merging. Credit: SXS

An international team of scientists have detected ripples in space and time, known as gravitational waves, from the biggest known black-hole collision that formed a new black hole about 80 times larger than the Sun – and from another three black-hole mergers.

The Australian National University (ANU) is playing a lead role in Australia's involvement with the gravitational wave discovery through a partnership in the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO), which is based in the United States.

Professor Susan Scott, who is Leader of the General Relativity Theory and Data Analysis Group at ANU, said the team discovered the four collisions by re-analysing data from Advanced LIGO's first two observing runs.

Scientists detected the event that formed the biggest known black hole from a of a binary system of two black holes on 29 July 2017. The event occurred about nine billion away.

"This event also had black holes spinning the fastest of all mergers observed so far. It is also by far the most distant merger observed," Professor Scott said.

The three other black-hole collisions were detected between 9 and 23 August 2017, were between three and six billion light years away and ranged in size for the resulting black holes from 56 to 66 times larger than our Sun.

"These were from four different binary black hole systems smashing together and radiating strong out into space," said Professor Scott, who is from the ANU Research School of Physics and Engineering and is a Chief Investigator with the Centre of Excellence for Gravitational Wave Discovery (OzGrav), which is funded by the Australian Research Council (ARC).

"These detections of black-hole collisions greatly improve our understanding of how many binary black hole systems there are in the Universe, as well as the range of their masses and how fast the black holes spin during a merger."

The researchers plan to continually improve the gravitational wave detectors so they can detect cataclysmic events much further out in space, one day hoping to reach back to the beginning of time just after the Big Bang which cannot be done with light.

After the initial observing runs were concluded, scientists recalibrated and cleaned the collected data.

"This increased the sensitivity of the detector network allowing our searches to detect more sources," Professor Scott said.

Graphic showing the masses of recently announced gravitational-wave detections and black holes and neutron stars. Credit: LIGO-Virgo / Frank Elavsky / Northwestern
"We have also incorporated improved models of the expected signals in our searches."

Since the second observing run finished in August 2017, scientists have been upgrading the LIGO and Virgo gravitational-wave detectors to make them more sensitive.

"This means during the upcoming third observing run, starting early next year, we will be able to detect events further out in space, meaning more detections and potentially gravitational waves from new and yet unknown sources in the Universe," Professor Scott said.

The international research team has detected gravitational waves from 10 different black-hole mergers and one neutron star collision during the past three years. Neutron stars are the densest in the Universe, with a diameter of up to about 20 kilometres.

Professor Scott's research group is also designing a new project to enable them to detect gravitational waves coming from a short-lived neutron star resulting from a neutron star merger.

Artists impression of merging neutron stars. Credit: Carl Knox, OzGrav

Dr. Karl Wette, a postdoctoral fellow in the group at ANU and a member of OzGrav, said scientists were not sure what was formed from the neutron-star merger that was detected in August last year.

"It could have been a neutron star that collapsed to a black hole after some time or turned immediately into a black hole," he said.

"Our new project will help to provide critical information about what we get from the merger of two ."

Professor Scott will present the new results at the Australian Institute of Physics Congress in Perth later this month.

The results of the discoveries will be published in Physical Review X.

Explore further: Gravitational waves from a merged hyper-massive neutron star

More information: "GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs," LIGO Scientific Collaboration & Virgo Collaboration, 2018. arxiv.org/abs/1811.12907

"Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo," LIGO Scientific Collaboration & Virgo Collaboration, 2018. arxiv.org/abs/1811.12940

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23 comments

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sparcboy
4.6 / 5 (8) Dec 03, 2018
What do they mean when they say 80 times bigger than the sun? 80 times the mass or 80 times the diameter? 80 times the mass of the Sun would of course be big, but a black hole 80 times the diameter of the sun would contain an incomprehensible amount of mass.
Nik_2213
5 / 5 (6) Dec 03, 2018
They will mean mass but, sadly, like oft-munged 'powers of 10', such niceties are often lost during too-hasty editing by PhysOrg...
:-(
Captain Stumpy
3.7 / 5 (3) Dec 03, 2018
@Nik
They will mean mass but, sadly, like oft-munged 'powers of 10', such niceties are often lost during too-hasty editing by PhysOrg...
:-(
Sorry, bro, but this one isn't on PO
Provided by: Australian National University
more than likely this is auto-posted because ANU has an account with various news aggregates, including PO

from their own press release
http://www.anu.ed...ollision
Whydening Gyre
3 / 5 (4) Dec 03, 2018
Regardless, I would like to see a detection of merging between two (already) black holes.... THAT would be a gravity wave,,,,
Da Schneib
3.4 / 5 (5) Dec 03, 2018
@Whyde, we've detected that many times now. But if you're talking about a merger of SMBHs LIGO doesn't have the right spectrum to detect it. The ones it can see are in the (approximately) 10-100 solar mass range. To detect when SMBHs merge, we'll have to wait for ELISA.
Da Schneib
3 / 5 (5) Dec 03, 2018
Unfortunately, @sparc and @Nik, this was written by the Australian National University, not physorg.
valeriy_polulyakh
1 / 5 (1) Dec 03, 2018
In search of black holes and dark matter astrophysicists are relying on indirect observations. It would seem that the measurement of the event horizon of a black hole directly would be a direct evidence. However, by the nature of a horizon, any real measurement of the event horizon will be indirect. The Event Horizon Telescope will get picture of the silhouette of the Sgr A* which is due to optical effects of spacetime outside of the event horizon. The result will be determined by the simple quality of the resulting image that does not depend on the properties of the spacetime within the image. So, it will be also indirect and an existence of BH is a hypothesis.
https://www.acade...ilky_Way
Whydening Gyre
5 / 5 (1) Dec 04, 2018
In search of black holes and dark matter astrophysicists are relying on indirect observations. It would seem that the measurement of the event horizon of a black hole directly would be a direct evidence. However, by the nature of a horizon, any real measurement of the event horizon will be indirect. The Event Horizon Telescope will get picture of the silhouette of the Sgr A* which is due to optical effects of spacetime outside of the event horizon. The result will be determined by the simple quality of the resulting image that does not depend on the properties of the spacetime within the image. So, it will be also indirect and an existence of BH is a hypothesis.
https://www.acade...ilky_Way

A silhouette would be direct. Would be like painting yourself black and standing in front of a moire pattern poster.
Da Schneib
3.5 / 5 (2) Dec 04, 2018
Remember though that it's a silhouette of the photon sphere, not the event horizon.
Ophelia
5 / 5 (4) Dec 04, 2018
For anyone who didn't bother to read the article or look at the illustrations, the chart clearly indicates the alleged mergers detected so far -- and one is of a slight less 40 mass and slightly bigger 40 mass solar black hole -- totalling about 80 solar masses.
richk
not rated yet Dec 04, 2018
please explain the chart's reference to "EM Black holes and Neutron stars" in the context of the indicated mergers, please.
dfjohnsonphd
5 / 5 (1) Dec 04, 2018
This merger occurring at an estimated 9 billion lights years (lys) distance is quite surprising. Now we have some ten confirmed mergers from about 1 billion to about 9 billion lys out.

It suggests some serious explaining needs to be done. At 9 lys out, shouldn't we be seeing a lot more mergers than what has been seen so far? It is hard to imagine that the signal strength alone was all that allowed us to see this largest merger, creating a black hole of some 80 SMs.

@Da Schneib, considering the increase in volume of space from 1 billion lys distance to 9 billion lys, shouldn't we be seeing a lot more distant mergers, than closer ones, and/or a lot more anyway? The universe was much denser that long ago. Should have had many more jumbo core-collapse black holes floating around. Could anything, anywhere at all, be interfering with the detectors?

I understand they picked these up going over old data. Maybe there ARE a lot more mergers! Makes you wonder who is minding the store...
Da Schneib
5 / 5 (1) Dec 04, 2018
@df, I don't think that black hole mergers of the indicated size would be more or less common over that short a time; if it were 12 or 13 billion light years I might think it significant. Also, since gravity is inverse-square, there will be a competing fall-off in signal strength with distance. This science is very young, and I'd be wary of drawing conclusions too quickly. Ask me in 20 years if I'm still around.
dfjohnsonphd
5 / 5 (1) Dec 05, 2018
Considering that binary black holes (BBHs) most likely arose from binary giant stars (BGs) going type II and eventually merging, one wonders at what frequency binary giant stars exist in general, and what number of these would then give rise to BBHs. Most but not all?! If BBHs are rare because binary giants are rare, than that is understandable.

It would seem at least that this might be a good starting point for estimating the rate of black hole mergers. One images that for any given gas rich galaxy at a similar evolutionary state, a considerable number of binaries (which are most "stars") must contain two giants. I understand the rationale for expecting many more mergers 9-13+ billion years ago, but to confirm only 10 in the last few years from many trillions of galaxies seems a tad on the short side. Only 10 mergers?! Just doesn't seem reasonable. I would expect at least some orders of magnitude more. They simply cannot be that rare with all those galaxies.
Da Schneib
5 / 5 (1) Dec 05, 2018
It would seem at least that this might be a good starting point for estimating the rate of black hole mergers.
Heh, theories will rise and fall in the next twenty years based on what we see. But it's going to take a really long time. Keep in mind that black holes are an end state; there are plenty of globulars around that contain Population III stars indicating they were formed very early in the history of the universe.
dfjohnsonphd
5 / 5 (1) Dec 05, 2018
No question about theories rising and falling. They have been doing that for a long time.

I suspect more advanced instruments will begin to detect more and more mergers as time goes by. As I recall, they did not detect any mergers until they realized that the sensitivity they were initially working with was too low. They goosed the system and shortly afterwards found the first merger.

From this alone I am going to estimate that they will have instruments sensitive enough to detect such mergers coming in one a day, or more.

Moreover, we should see an increase in the number of mergers the further out you "look". Signal strength could have a lot to do with my missing mergers. Perhaps there are a lot of smaller ones that are not yet detected, but still amount to that larger merger number that I am expecting.
Da Schneib
5 / 5 (1) Dec 05, 2018
Hmmm, I won't take your bet, but I'd say more like once a week, just off the top of my head.
dfjohnsonphd
5 / 5 (1) Dec 05, 2018
Changed my posting to eliminate the bet since you have no way of paying. :o)

One a day, or one a week. It will all depend on the instrument sensitivity and merger masses.

The signal strength rules in the end.
granville583762
not rated yet Dec 05, 2018
Scientists detect biggest known black-hole collision

This is delicious
BHs in twinly orbit
BHs in triply orbit
even more intriguing
these twinly BHs are not even BHs
even as x-pulsars proposed as neutron stars
it is uncertain these two are in all reality neutron stars
which at present as they are definitely pulsar stars
it is probably safer as long as they are still pulsing
calling them orbital pulsar stars

As to gravitational waves
it is not a wave as such
but the original lead ball on a string experiment
rotate the weight on its radius
and the gravitational force varies
so in all reality
as these two pulsar stars orbit
we are measuring a varying gravitational force
a varying gravitational force is not a wave
because a wave is something different
it is the equivalent of the photon whose frequency and wave is proportional to 299792458m/s
Whereas we are simply measuring a varying gravitational force
Steelwolf
not rated yet Dec 05, 2018
@Richk, I believe what they are talking about is Electromagnetically detected BH's and Neutron Stars. So they are showing the comparison in size and what size BH's and Neutron stars impacted detected by LIGO and the corresponding sized of ones detected by X-ray, IR and other high energy sources as black holes and neutron stars, especially pulsar/magnetars which we can study. Watching a known magnetar join with another neutron star or BH would be Interesting, to say the least.

But notice how there are some close similarities in masses, as well as the proportions of masses, even visually, looks very similar to elemental fusion in the heart of stars or in supernova/kilonova events with large releases of 'energy' in dense mass, as well as a heavier end product.

Not saying that it IS the same, too much difference in structure from what we know presently, but pointing out what looks almost like a fractal iteration of same proportional effects writ VERY Large upon the Cosmos.
Anonym540694
not rated yet Dec 05, 2018
Something that puzzles me: the references to the spin rates of the black holes before/after collision. I thought conventional wisdom has it that all the matter and energy that is inside the holes event horizon falls to the center - to a singularity. By definition a singularity has no radius, it is a point - how can it have a spin? If a point - it lacks a radius, a center, and any mass outside of the point location that could rotate around the center - it is the center.
jimmybobber
5 / 5 (2) Dec 05, 2018
@Anonym We don't have math to describe what really happens in a black hole. The current math is inadequate. It's an approximation.
savvys84
not rated yet Dec 14, 2018
This susan scott incharge of GR and ANU is a complete moron to rely on GR

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