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ESO Telescopes Observe First Light from Gravitational Wave Source

566 points by acqq 9y ago

seomint 9y ago
Non-scientist here, is this a Nobel Prize caliber discovery? Just trying to get some perspective here. It sounds exciting.
- scentoni 9y ago
  Basically they've made the first direct observations of what causes a https://en.wikipedia.org/wiki/Gamma-ray_burst https://en.wikipedia.org/wiki/Gamma-ray_burst I expect there will be a Nobel, not immediately but after years of accumulating statistics on many different GRBs.
- raverbashing 9y ago
  You mean like this? https://www.nobelprize.org/nobel_prizes/physics/laureates/2017/ https://www.nobelprize.org/nobel_prizes/physics/laureates/20...
- semaphoreP 9y ago
  Quite possibly I think. This is both confirmation that neutron star mergers do indeed exist and create kilonova, and the first detection of an astronomical event with both gravitational waves and light. Nobel prize is only limited to three people though, so it's unclear who they would give it to, given there are thousands of people that contributed to this.
- ISL 9y ago
  Yes.
- perlgeek 9y ago
  If this year's Nobel Prize hadn't been for a Gravitational Wave discovery, I'd said "yes" without hesitation. Now I'm not sure.
bd 9y ago
Here is LIGO live stream: https://www.youtube.com/user/VideosatNSF/live https://www.youtube.com/user/VideosatNSF/live This was LIGO (US) + Virgo (EU) + 70 ground- and space-based observatories collaboration: http://www.ligo.org/ http://www.ligo.org/ http://www.virgo-gw.eu/ http://www.virgo-gw.eu/
apetresc 9y ago
It appears this was the discovery, they're talking about it on stream now: http://www.eso.org/public/news/eso1733/ http://www.eso.org/public/news/eso1733/ (ESO Telescopes Observe First Light from Gravitational Wave Source) The stream is at: http://www.eso.org/public/ http://www.eso.org/public/ It's currently being explained right now.
- 1001101 9y ago
  Taking a while to load. The summary suggests that GRBs are caused by neutron star mergers: "ESO’s fleet of telescopes in Chile have detected the first visible counterpart to a gravitational wave source. These historic observations suggest that this unique object is the result of the merger of two neutron stars. The cataclysmic aftermaths of this kind of merger — long-predicted events called kilonovae — disperse heavy elements such as gold and platinum throughout the Universe. This discovery, published in several papers in the journal Nature and elsewhere, also provides the strongest evidence yet that short-duration gamma-ray bursts are caused by mergers of neutron stars."
netcraft 9y ago
awesome discovery. Can't wait to see the pictures. So much closer than the other detections of black holes - I assume the detection range of neutron starts is much smaller.
- guelo 9y ago
  Yes. It mentions that in note 4 here https://www.eso.org/public/news/eso1733/ https://www.eso.org/public/news/eso1733/
deleted 9y ago
[deleted]
czardoz 9y ago
This seems to be the press release: https://www.eso.org/public/news/eso1733/ https://www.eso.org/public/news/eso1733/ Edit: The main link points here as well now.
- acqq 9y ago
  This link here always pointed to the link you have given, you probably confused this post and another on the first page: https://news.ycombinator.com/item?id=15483186 https://news.ycombinator.com/item?id=15483186 That one is only an announcement of the press event, posted cca 7 minutes before the start of the event, not what was discovered, which was officially published exactly at the start of the hour, as the news conferences started. Anyway, at the moment there are still live streams, like https://www.youtube.com/watch?v=mtLPKYl4AHs https://www.youtube.com/watch?v=mtLPKYl4AHs 10:00 am EDT - Press Conference (Part 1) 11:00 am EDT - YouTube Q&A (ask us in the chat, we will answer on camera) 11:15 am EDT - Press Conference (Part 2) 12:30 am EDT - YouTube Q&A (Part 2) Also, in Europe (the European Southern Observatory), (edit: finished, now you can watch the recorded conference at the same link) https://www.youtube.com/watch?v=9ISr4juIkDg https://www.youtube.com/watch?v=9ISr4juIkDg ) There's a nice 1 minute animation: https://www.youtube.com/watch?v=nziW8fywwmg https://www.youtube.com/watch?v=nziW8fywwmg There's also Reddit "AskScience AMA Series: European Southern Observatory announcement concerning groundbreaking observations" unlocked now, starting at 18:30 CEST / 12:30 ET: https://www.reddit.com/r/askscience/comments/76ne3p/askscience_ama_series_european_southern/ https://www.reddit.com/r/askscience/comments/76ne3p/askscien...
SideburnsOfDoom 9y ago
And do the gravitational waves propagate at the speed of light?
- perlgeek 9y ago
  Yes
  - LeifCarrotson 9y ago
    Basically, yes: The speed of both gravity waves and light waves is limited by c, the speed of light in vacuum. But actually, no, because the light is not in a vacuum - it's ricocheting out from the center of a star, and bouncing through the interstellar medium (which is incredibly sparse; very nearly a vacuum: but there's an awful lot of it between these events and us). This is also the mechanism behind neutrino detectors. When a star's core goes supernova, it releases a cataclysm of neutrinos which pass through the upper layers of the star almost unaffected. The light and radio waves are still bouncing around trying to get to the surface of the star, and the blast wave is still physically propagating much slower than the speed of light, but the neutrinos are long gone. That gives scientists a short time period to point their telescopes in the right direction! Further reading: https://physics.stackexchange.com/questions/235450/do-gravitational-waves-travel-faster-than-light https://physics.stackexchange.com/questions/235450/do-gravit... https://news.ycombinator.com/item?id=6253263 https://news.ycombinator.com/item?id=6253263
    - jamiek88 9y ago
      Yes and this is different in as much as LIGO / gravitational waves gave us the 'tip off' that the light was incoming, we fortunately had a satellite that captured that. It's a whole other information stream we are just learning how to use, basically with using gravitational waves we are at the stage Galileo was at with light. Very early, very low res but enough to give us massive new discoveries. So exciting.
- fpoling 9y ago
  For 130 million light years the difference between gravitational wave signal and gamma burst is 2s. That constrains the speed difference to 1.6e-18 m/s. This is fascinating number especially given that speed of light is 3e8.
occultist_throw 9y ago
BTW, this is also the basis of a story by Greg Egan. Diaspora. (Aside: I highly recommend Greg Egan's work, especially Diaspora) The claim he makes in the fiction novel, is that a neutron star-neutron star collision event would be enough energy to sterilize 100 light year radius around the event. The one in the novel happens closer than 100ly. http://www.gregegan.net/DIASPORA/DIASPORA.html http://www.gregegan.net/DIASPORA/DIASPORA.html
Gravityloss 9y ago
Can some astronomer or physicist actually make an image where the source is marked? All I see is some stars and a galaxy which is basically and some textual explanation where I should look for it.
- chriskanan 9y ago
  This article has pictures: https://www.washingtonpost.com/news/speaking-of-science/wp/2017/10/16/scientists-detect-gravitational-waves-from-a-new-kind-of-nova-sparking-a-new-era-in-astronomy/ https://www.washingtonpost.com/news/speaking-of-science/wp/2...
- knice 9y ago
  There are before and after comparison photos here: http://reports.news.ucsc.edu/neutron-star-merger/media/ http://reports.news.ucsc.edu/neutron-star-merger/media/
- WD-42 9y ago
  Here is a nice image https://lco.global/files/blog/lco_skymap_logo.jpg https://lco.global/files/blog/lco_skymap_logo.jpg
- acqq 9y ago
  There's a time lapse video where the change can be seen, linked on the very page of the press release: https://www.eso.org/public/videos/eso1733c/ https://www.eso.org/public/videos/eso1733c/
knice 9y ago
A team from UC Santa Cruz used the data from the Swope telescope in Chile to locate the source of the gravitation waves and observe the light from the event. The data provides evidence of how gold and other heavy elements formed in the universe. http://reports.news.ucsc.edu/neutron-star-merger/ http://reports.news.ucsc.edu/neutron-star-merger/ https://www.youtube.com/watch?v=R5EkI5qbYYc https://www.youtube.com/watch?v=R5EkI5qbYYc Full disclosure: I work at UC Santa Cruz and built the site linked above. :-)
- espadrine 9y ago
  Congrats! How do you automate screening the sky? Do you have robots that map stars, diff the images, and send an email when the diff has a new spot of light? How frequently does the sky get fully screened? Could there be events fast enough that we don't detect them?
  - knice 9y ago
    Apologies, I'm not one of the researchers involved in the discovery. I'm just the web developer who built the announcement site for UCSC. Ryan Foley will participate in a Reddit AMA tomorrow (Tuesday, 10/17). I imagine your questions might get answered there.
  - semaphoreP 9y ago
    Not involved in this, I'm guessing this is how it goes: there are algorithms that automatically register the image that was just taken, diff it with a reference image of the sky from before, and if there's a significant difference that passes some false positive tests, then there's some notification for human intervention. Indeed there could be events we are missing right now. Astronomers are building instruments that have larger fields of view (e.g., LSST), so that they can scan the sky ever few days.
  - knice 9y ago
    This paper by one of the team members has more detail about the process used to narrow down the search field to a list of galaxies and identify possible locations of the event: [edit]: link to the exact paragraph that discusses the method http://science.sciencemag.org/content/early/2017/10/13/science.aap9811.full#p-9 http://science.sciencemag.org/content/early/2017/10/13/scien...
zitterbewegung 9y ago
This is awesome! We should be able to find more gravitational wave sources and it will give us a better picture of the cosmos. Also, that we have more sources with better correlation and more information.
- cryptonector 9y ago
  The best part is that gravitational waves stand out in a way that events in the visible spectrum do not, so these gravitational wave observatories will be helping find events and get them observed in every portion of the electromagnetic spectrum that we can observe. That means we'll be observing many more of these kilonovae now. This truly is a new era, as we'll now be able to use all these observatories at the same time to observe the same events, and this will yield the highest possible resolution imaging of these events, as far-flung telescopes are able to function as one really, really big, virtual one.
  - mark-r 9y ago
    How often are these kilonovae expected to occur?
sandworm101 9y ago
Cool, but i want more. All we have so far is confirmations of rather well-understood interactions. I want "we see these massive waves, but have no idea what is causing them." If they are being seen, such results aren't published.
- dspillett 9y ago
  > All we have so far is confirmations of rather well-understood interactions. Confirmations of commonly assumed interactions. This is vital, as numbers of other hypothesise/theories/other rely on that understanding. Without results like these all that work is on shaky ground, now it looks far more solid. Confirming current understanding isn't as sexy as discovering new physics, but just as important, possibly more so.
  - sandworm101 9y ago
    That depends. I'd bet money that LIGO was not pitched on the idea that it would only confirm the existence of waves. New instruments are pitched on the expectation of novel measurements. the "new physics". The parallels to the LHC and other massively-expensive instruments are striking. They confirm something that has already been widely accepted, generate the expected prize and raft of phds, but when it is all over the universe hasn't changed. I worry that those greenlighting these projects are being too conservative, only investing in projects that have clear pathways. This trend matters. Physics needs these giant instruments to generate something truly new otherwise the billions will drift towards other disciplines.
    - acqq 9y ago
      You are wrong. The LHC was absolutely prepared to observe new "unexpected" (for the "Standard model") particles. It just didn't happen. A lot of theorists who had developed the theoretical extensions of the "Standard model" are disappointed about that, but that's what is observed. Regarding the gravitational waves, you're also wrong, as the theory and the observations matched even without the gravitational waves being directly observed, the science is simply so good that completely unexpected results (in the sense you talk) are outside of the resulting limits of the previous measurements and calculations. The level of the science we have now is really stunning. The only sad part of the story is that all investments in the science are really minute compared to all the money spent on armies and weapons (e.g. just as the order of magnitude one year of the US military budget is at least 30 times bigger than the NASA's). There's immense amount of the new information that can be obtained by the repeated observations. But the expectation of anything to disprove too much of what we know up to now is simply not realistic.
azizsaya 9y ago
NPR article does a good job of simplifying this, I hope it is technically correct! http://thin.npr.org/s.php?sId=557557544 http://thin.npr.org/s.php?sId=557557544
zymhan 9y ago
The Gravitational wave was detected 2 seconds before the Gamma Ray Burst. I wonder why it is faster? > On 17 August 2017 the NSF's Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, working with the Virgo Interferometer in Italy, detected gravitational waves passing the Earth. This event, the fifth ever detected, was named GW170817. About two seconds later, two space observatories, NASA’s Fermi Gamma-ray Space Telescope and ESA’s INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL), detected a short gamma-ray burst from the same area of the sky.
- deleted 9y ago
  [deleted]
- oppositelock 9y ago
  Is it faster, or did the gravitational waves simply precede the GRB?
  - valarauca1 9y ago
    You are correct. Waves come from the final in spiral, before the black hole forms. The GRB is from the rapid in fall, and friction of neutron star matter falling into the black hole.
- delibes 9y ago
  That's the fun science bit where we say "Oh that's odd" :) Is there some matter along the path that interacts with the gamma ray burst and slows it by two seconds? Why is it two seconds? Does it tell us something about the source? All very exciting.
  - sdenton4 9y ago
    Yeah my first thought was that space isn't quite a vacuum, which maybe adds up over 130M light years to something measurable. Meanwhile, the gravitational wave is a fluctuation in space itself, so always moves at SoL? The sibling comment about one simply happening after another also seems very plausible though.
runeb 9y ago
After observers found the source of the collision the scientist at the Chile observatory claims to have spent 45 minutes to locate it in the sky. Do they not have some sort of coordinate system they could use to pinpoint it?
- scentoni 9y ago
  The resolution of our present gravitational wave observations is very low. Adding VIRGO to LIGO helps reduce the area of the sky to look in.
cromwellian 9y ago
Veritasium summary is one of the best easily digestable I've seen. https://www.youtube.com/watch?v=EAyk2OsKvtU https://www.youtube.com/watch?v=EAyk2OsKvtU
- acqq 9y ago
  I like much more this one by the Science Magazine: https://www.youtube.com/watch?v=e_uIOKfv710 https://www.youtube.com/watch?v=e_uIOKfv710 and this one by The Georgia Institute of Technology: https://www.youtube.com/watch?v=pLivjAoDrTg https://www.youtube.com/watch?v=pLivjAoDrTg
  - spuz 9y ago
    I disagree, the Veritasium video has way more information than the two videos you linked. It shows how the gamma ray telescopes and gravitational wave detectors worked together to narrow the source in the sky of event. What a gravitational wave signal looks like, what a gamma ray signal looks like. The fact that the optical signal was made 11 hours after that. Etc. There is a lot more info on top of that which makes the video worth watching.
    - cromwellian 9y ago
      Yes, the fact that the negative detection by Virgo was actually significant was interesting.
    - acqq 9y ago
      It probably reflects my personal tastes, I understand he's a kind a Youtube star or something, but I find the Veritasium presenter too attention-grabbing distracting, so much that I can't even concentrate to what he is talking about. There is no visible presenter in the Science Mag video, ad I like that, and there is another presenter appearing in the Georgia Tech video (Laura Cadonati, a professor), but there I definitely don't have that "WTH the presenter is demanding more attention than the topic" effect, even if she has an accent. I surely in this case react just like a "mom" from this comment: "Showed this video with amazing science discoveries about the universe to my mom and all she said was : "this guy likes orange decorations"." I also just see the guy, his appearance, his body movements and his room decorations etc and I just have this "look at me" impression. I can imagine that helps his personal popularity on that medium, and I guess he optimizes for that, but it obscures the actual content, at least to me. So I don't have energy to analyze it further, but I have had an impression that the videos I've suggested contain some information that doesn't exist in the Veritasium's video, and that the level of the information is better suited for those who need short summary. Maybe there is a target group which, like I, better responds to the videos I've suggested. For those who are really interested in the details, I think there's no substitute to reading the main scientific paper, written by 4600 people(!): http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 It is much more accessible than you'd imagine, it starts with: "Over 80 years ago Baade & Zwicky (1934) proposed the idea of neutron stars, and soon after, Oppenheimer & Volkoff (1939) carried out the first calculations of neutron star models..." (Yes, it's "the" Oppenheimer, who later go to be called "the father of the atomic bomb." Fritz Zwicky was apparently "the first astronomer to propose the existence of dark matter, supernovas, neutron stars, galactic cosmic rays, gravitational lensing by galaxies, and galaxy clusters.") Reading the original sources further, the first map of the potential area on the sky and the first trigger that set everything in motion is: "On 2017 August 17 12:41:06 UTC the Fermi Gamma-ray Burst Monitor (GBM; Meegan et al. 2009) onboard flight software triggered on, classified, and localized a GRB." My understanding is that it was therefore never technically necessary for Virgo to reject the second (lower) LIGO area on this image: http://www.virgo-gw.eu/images/GW170817.png http://www.virgo-gw.eu/images/GW170817.png but the Virgo's operation helped narrowing down the upper area a little.
gigatexal 9y ago
As a fan of the Astro-sciences I am so glad to be alive. I have all the confidence that within my lifetime hopefully (next 50 years hopefully) we will see great things maybe even a unification relativity and quantum mechanics.
Boothroid 9y ago
Am I the only one that's a bit men about this given the pre-conference hyperbole? I was expecting aliens :(
quickthrower2 9y ago
Was about to submit https://qz.com/1102917/observing-the-merger-of-neutron-stars-finally-explains-where-in-the-universe-heavy-elements-are-made/ https://qz.com/1102917/observing-the-merger-of-neutron-stars...
WD-42 9y ago
If any of you are interested in some of the software that made this discovery possible, check out two of the papers from Las Cumbres Observatory: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature24291.html?foxtrotcallback=true http://www.nature.com/nature/journal/vaop/ncurrent/full/natu... http://iopscience.iop.org/article/10.3847/2041-8213/aa910f/meta;jsessionid=24CB64879B5A141DC8F45A67DC33EAA0.c2.iopscience.cld.iop.org#apjlaa910fs2 http://iopscience.iop.org/article/10.3847/2041-8213/aa910f/m... We run a network of 20 telescopes that are triggered remotely (mostly via API). Because of our ability to schedule observations quickly, we were the only ones able to observe the peak luminosity of the kilonova. Disclosure: I am a software engineer at LCO.
- spuz 9y ago
  Given that GRBs have been detected for a long time and thought to have been a result of neutron star mergers, has a GRB detection ever led to an optical light detection of such a merger before? Is the news here that gravitational wave detection allowed us to see neutron star mergers optically or that they simply coincided with detections of the previously seen optical and gamma ray events?
  - scrumper 9y ago
    Yes, in around 1997 I believe. http://www.nature.com/nature/journal/v396/n6708/full/396233a0.html?foxtrotcallback=true http://www.nature.com/nature/journal/v396/n6708/full/396233a... My read is that the news here is that this is the first visual counterpart to a gravitational wave detection. (It's also very strong supporting evidence for the leading theory that neutron stars merging are sources of those gravitational waves.)
  - WD-42 9y ago
    Yes, there have been optical counterparts to GRBs before. What is news here is the first optical counterpart to a gravitational wave detection, along with a GRB, which gives us the strongest evidence yet that these are neutron star mergers.
    - 9y ago
hliyan 9y ago
To put this in perspective: Since the first hominids looked up at the stars, till literally yesterday, mankind had only one fundamental force to observe the universe with: electromagnetic waves, be it light, radio waves or infrared. From today, we have two. The other two remaining fundamental forces do not operate at astronomical scales. Of course, we had LIGO before yesterday, but for me, the confirmation through electromagnetic wave observations is key. This is an historic day!
- pvg 9y ago
  We've detected neutrinos from the rest of the universe for some time.
- semaphoreP 9y ago
  We've also been observing the universe using neutrinos (generated by the weak force). In fact, there have even been one neutrino event linked to a possible astrophysical source[1], but with less certainty than this gravitational wave/EM detection. [1]: https://www.nasa.gov/feature/goddard/2016/nasas-fermi-telescope-helps-link-cosmic-neutrino-to-blazar-blast/ https://www.nasa.gov/feature/goddard/2016/nasas-fermi-telesc...
  - pvg 9y ago
    Supernovae neutrinos have been detected for 30 years, it's not just one event.
epberry 9y ago
This is so cool because we used our ears (the LIGO detectors) to hear/feel the gravitational wave hit then used our eyes (electromagnetic radiation telescopes) to focus in on where we thought we felt the ripple. And what's more, machines all over the planet were involved. Just awe-inspiring.
- zyngaro 9y ago
  Wonderfully summed up. Thank you. By the way I thought gravitational waves have only been a theory. How can they be detected and is there such a thing as a gravitational quantum ?
  - epberry 9y ago
    I don't know about the quantums but to detect the waves you basically split a laser beam using mirrors and redirect each split to a detector. When the wave hits it stretches each split in the beam slightly which causes an interference pattern. That pattern, as it evolves over time as the wave hits, can be converted into sound which is that "chirp" that everyone talks about.
  - jasonwatkinspdx 9y ago
    Gravitational wave detectors like LIGO (https://www.ligo.caltech.edu/page/what-is-ligo https://www.ligo.caltech.edu/page/what-is-ligo) are very precise laser range finders used as rulers. They can measure extremely small expansions and contractions of space itself. Discovering a quantized theory of gravity is possibly _the_ major open question in physics atm. We presume there's a 'graviton' of some sort, but have not observed it yet.
    - peeters 9y ago
      If I'm remembering the analogy in the livestream correctly, if you applied the laser's precision to astronomical scales, it would be the equivalent of measuring the distance to the moon with a tolerance the width of a human hair. And in the scales they deal with, a tolerance one-tenth the diameter of a proton.
  - 9y ago
platz 9y ago
So, was there a telescope monitoring the light location already, or was the light only found after the Gr detection... I.e. Was it not truly concurrent?
- nerfhammer 9y ago
  they swung the telescopes around to look for it shortly after the detection event
acqq 9y ago
The main paper about the detections: http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 "Multi-messenger Observations of a Binary Neutron Star Merger" published in The Astrophysical Journal Letters. PDF: http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/pdf http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/p... ePub: http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/epub http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/e... "Some researchers say it has 4600 authors," I haven't counted myself.
smortaz 9y ago
Relevant: if you want run their actual code via your browser, check out their jupyter notebooks: https://notebooks.azure.com/roywilliams/libraries/LIGOOpenScienceCenter https://notebooks.azure.com/roywilliams/libraries/LIGOOpenSc... Click View to read or Clone to make your own copy and run.
johnvega 9y ago
This stuff makes Elon Musk's plan to colonize Mars relatively less exciting.
CaiGengYang 9y ago
Why is this post given so many points (521) ? Anyone can explain? Isn't it simply a post of something someone saw on the internet ?
martyvis 9y ago
Is it just me, or does anyone else think that its strange that an observatory press release on the specific subject of the "observed light" can only lead it with what I assume is an artists'impression? I'm sure that there is oodles of data to go through, but after 3 months, surely a representation of the actual data imaged could be presented?
- acqq 9y ago
  The actual images are also on the very same page where you only see an artist impression: PR Image eso1733b, PR Image eso1733c, PR Image eso1733d, PR Image eso1733e, PR Image eso1733h, PR Image eso1733k, PR Image eso1733m. There also are actual pictures in the scientific papers, for example: http://www.nature.com/nature/journal/vaop/ncurrent/fig_tab/nature24291_F2.html http://www.nature.com/nature/journal/vaop/ncurrent/fig_tab/n... Also see the actual main paper, written by 4600 scientists together: there were many more observations and images than these two, but unfortunately they aren't "sexy" for the general public: a dot which appears and then disappears later. But the astronomers know how to even detect the presence of gold in that dot! Note: the chemical element helium, which today is even used to fill the balloons for the children, was first discovered on the Sun(!), using that kind of observations and analysis, and only later at our Earth. There is also a video, directly linked from the page you criticize, and part of the press release, which was made from the real images taken at different times, where the changes in time are visible: https://www.eso.org/public/videos/eso1733c/ https://www.eso.org/public/videos/eso1733c/ Also, there are a lot of papers that are published, most observers will publish or have published their observations. The galaxy where the kilonova happened is some 130 million light years away, or 8 billion times more distant than the Sun is away from us, and what's observed (in different spectrums) is a source of a lot of light (or electromagnetic radiation) at the edge of that galaxy, and also the gravitational waves. To compare the sizes, there could be 1000 of our own galaxies placed one after another to fill the distance to that kilonova. There are around 400 billion stars just in our own galaxy.

566 points by acqq 9y ago

Non-scientist here, is this a Nobel Prize caliber discovery? Just trying to get some perspective here. It sounds exciting.

scentoni 9y ago
Basically they've made the first direct observations of what causes a https://en.wikipedia.org/wiki/Gamma-ray_burst https://en.wikipedia.org/wiki/Gamma-ray_burst I expect there will be a Nobel, not immediately but after years of accumulating statistics on many different GRBs.
raverbashing 9y ago
You mean like this? https://www.nobelprize.org/nobel_prizes/physics/laureates/2017/ https://www.nobelprize.org/nobel_prizes/physics/laureates/20...
semaphoreP 9y ago
Quite possibly I think. This is both confirmation that neutron star mergers do indeed exist and create kilonova, and the first detection of an astronomical event with both gravitational waves and light. Nobel prize is only limited to three people though, so it's unclear who they would give it to, given there are thousands of people that contributed to this.
ISL 9y ago
Yes.
perlgeek 9y ago
If this year's Nobel Prize hadn't been for a Gravitational Wave discovery, I'd said "yes" without hesitation. Now I'm not sure.

bd 9y ago

Here is LIGO live stream: https://www.youtube.com/user/VideosatNSF/live https://www.youtube.com/user/VideosatNSF/live This was LIGO (US) + Virgo (EU) + 70 ground- and space-based observatories collaboration: http://www.ligo.org/ http://www.ligo.org/ http://www.virgo-gw.eu/ http://www.virgo-gw.eu/

apetresc 9y ago

It appears this was the discovery, they're talking about it on stream now: http://www.eso.org/public/news/eso1733/ http://www.eso.org/public/news/eso1733/ (ESO Telescopes Observe First Light from Gravitational Wave Source) The stream is at: http://www.eso.org/public/ http://www.eso.org/public/ It's currently being explained right now.

1001101 9y ago
Taking a while to load. The summary suggests that GRBs are caused by neutron star mergers: "ESO’s fleet of telescopes in Chile have detected the first visible counterpart to a gravitational wave source. These historic observations suggest that this unique object is the result of the merger of two neutron stars. The cataclysmic aftermaths of this kind of merger — long-predicted events called kilonovae — disperse heavy elements such as gold and platinum throughout the Universe. This discovery, published in several papers in the journal Nature and elsewhere, also provides the strongest evidence yet that short-duration gamma-ray bursts are caused by mergers of neutron stars."

netcraft 9y ago

awesome discovery. Can't wait to see the pictures. So much closer than the other detections of black holes - I assume the detection range of neutron starts is much smaller.

guelo 9y ago
Yes. It mentions that in note 4 here https://www.eso.org/public/news/eso1733/ https://www.eso.org/public/news/eso1733/

deleted 9y ago

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czardoz 9y ago

This seems to be the press release: https://www.eso.org/public/news/eso1733/ https://www.eso.org/public/news/eso1733/ Edit: The main link points here as well now.

acqq 9y ago
This link here always pointed to the link you have given, you probably confused this post and another on the first page: https://news.ycombinator.com/item?id=15483186 https://news.ycombinator.com/item?id=15483186 That one is only an announcement of the press event, posted cca 7 minutes before the start of the event, not what was discovered, which was officially published exactly at the start of the hour, as the news conferences started. Anyway, at the moment there are still live streams, like https://www.youtube.com/watch?v=mtLPKYl4AHs https://www.youtube.com/watch?v=mtLPKYl4AHs 10:00 am EDT - Press Conference (Part 1) 11:00 am EDT - YouTube Q&A (ask us in the chat, we will answer on camera) 11:15 am EDT - Press Conference (Part 2) 12:30 am EDT - YouTube Q&A (Part 2) Also, in Europe (the European Southern Observatory), (edit: finished, now you can watch the recorded conference at the same link) https://www.youtube.com/watch?v=9ISr4juIkDg https://www.youtube.com/watch?v=9ISr4juIkDg ) There's a nice 1 minute animation: https://www.youtube.com/watch?v=nziW8fywwmg https://www.youtube.com/watch?v=nziW8fywwmg There's also Reddit "AskScience AMA Series: European Southern Observatory announcement concerning groundbreaking observations" unlocked now, starting at 18:30 CEST / 12:30 ET: https://www.reddit.com/r/askscience/comments/76ne3p/askscience_ama_series_european_southern/ https://www.reddit.com/r/askscience/comments/76ne3p/askscien...

SideburnsOfDoom 9y ago

And do the gravitational waves propagate at the speed of light?

perlgeek 9y ago
Yes
- LeifCarrotson 9y ago
  Basically, yes: The speed of both gravity waves and light waves is limited by c, the speed of light in vacuum. But actually, no, because the light is not in a vacuum - it's ricocheting out from the center of a star, and bouncing through the interstellar medium (which is incredibly sparse; very nearly a vacuum: but there's an awful lot of it between these events and us). This is also the mechanism behind neutrino detectors. When a star's core goes supernova, it releases a cataclysm of neutrinos which pass through the upper layers of the star almost unaffected. The light and radio waves are still bouncing around trying to get to the surface of the star, and the blast wave is still physically propagating much slower than the speed of light, but the neutrinos are long gone. That gives scientists a short time period to point their telescopes in the right direction! Further reading: https://physics.stackexchange.com/questions/235450/do-gravitational-waves-travel-faster-than-light https://physics.stackexchange.com/questions/235450/do-gravit... https://news.ycombinator.com/item?id=6253263 https://news.ycombinator.com/item?id=6253263
  - jamiek88 9y ago
    Yes and this is different in as much as LIGO / gravitational waves gave us the 'tip off' that the light was incoming, we fortunately had a satellite that captured that. It's a whole other information stream we are just learning how to use, basically with using gravitational waves we are at the stage Galileo was at with light. Very early, very low res but enough to give us massive new discoveries. So exciting.
fpoling 9y ago
For 130 million light years the difference between gravitational wave signal and gamma burst is 2s. That constrains the speed difference to 1.6e-18 m/s. This is fascinating number especially given that speed of light is 3e8.

occultist_throw 9y ago

BTW, this is also the basis of a story by Greg Egan. Diaspora. (Aside: I highly recommend Greg Egan's work, especially Diaspora) The claim he makes in the fiction novel, is that a neutron star-neutron star collision event would be enough energy to sterilize 100 light year radius around the event. The one in the novel happens closer than 100ly. http://www.gregegan.net/DIASPORA/DIASPORA.html http://www.gregegan.net/DIASPORA/DIASPORA.html

Gravityloss 9y ago

Can some astronomer or physicist actually make an image where the source is marked? All I see is some stars and a galaxy which is basically and some textual explanation where I should look for it.

chriskanan 9y ago
This article has pictures: https://www.washingtonpost.com/news/speaking-of-science/wp/2017/10/16/scientists-detect-gravitational-waves-from-a-new-kind-of-nova-sparking-a-new-era-in-astronomy/ https://www.washingtonpost.com/news/speaking-of-science/wp/2...
knice 9y ago
There are before and after comparison photos here: http://reports.news.ucsc.edu/neutron-star-merger/media/ http://reports.news.ucsc.edu/neutron-star-merger/media/
WD-42 9y ago
Here is a nice image https://lco.global/files/blog/lco_skymap_logo.jpg https://lco.global/files/blog/lco_skymap_logo.jpg
acqq 9y ago
There's a time lapse video where the change can be seen, linked on the very page of the press release: https://www.eso.org/public/videos/eso1733c/ https://www.eso.org/public/videos/eso1733c/

knice 9y ago

A team from UC Santa Cruz used the data from the Swope telescope in Chile to locate the source of the gravitation waves and observe the light from the event. The data provides evidence of how gold and other heavy elements formed in the universe. http://reports.news.ucsc.edu/neutron-star-merger/ http://reports.news.ucsc.edu/neutron-star-merger/ https://www.youtube.com/watch?v=R5EkI5qbYYc https://www.youtube.com/watch?v=R5EkI5qbYYc Full disclosure: I work at UC Santa Cruz and built the site linked above. :-)

espadrine 9y ago
Congrats! How do you automate screening the sky? Do you have robots that map stars, diff the images, and send an email when the diff has a new spot of light? How frequently does the sky get fully screened? Could there be events fast enough that we don't detect them?
- knice 9y ago
  Apologies, I'm not one of the researchers involved in the discovery. I'm just the web developer who built the announcement site for UCSC. Ryan Foley will participate in a Reddit AMA tomorrow (Tuesday, 10/17). I imagine your questions might get answered there.
- semaphoreP 9y ago
  Not involved in this, I'm guessing this is how it goes: there are algorithms that automatically register the image that was just taken, diff it with a reference image of the sky from before, and if there's a significant difference that passes some false positive tests, then there's some notification for human intervention. Indeed there could be events we are missing right now. Astronomers are building instruments that have larger fields of view (e.g., LSST), so that they can scan the sky ever few days.
- knice 9y ago
  This paper by one of the team members has more detail about the process used to narrow down the search field to a list of galaxies and identify possible locations of the event: [edit]: link to the exact paragraph that discusses the method http://science.sciencemag.org/content/early/2017/10/13/science.aap9811.full#p-9 http://science.sciencemag.org/content/early/2017/10/13/scien...

zitterbewegung 9y ago

This is awesome! We should be able to find more gravitational wave sources and it will give us a better picture of the cosmos. Also, that we have more sources with better correlation and more information.

cryptonector 9y ago
The best part is that gravitational waves stand out in a way that events in the visible spectrum do not, so these gravitational wave observatories will be helping find events and get them observed in every portion of the electromagnetic spectrum that we can observe. That means we'll be observing many more of these kilonovae now. This truly is a new era, as we'll now be able to use all these observatories at the same time to observe the same events, and this will yield the highest possible resolution imaging of these events, as far-flung telescopes are able to function as one really, really big, virtual one.
- mark-r 9y ago
  How often are these kilonovae expected to occur?

sandworm101 9y ago

Cool, but i want more. All we have so far is confirmations of rather well-understood interactions. I want "we see these massive waves, but have no idea what is causing them." If they are being seen, such results aren't published.

dspillett 9y ago
> All we have so far is confirmations of rather well-understood interactions. Confirmations of commonly assumed interactions. This is vital, as numbers of other hypothesise/theories/other rely on that understanding. Without results like these all that work is on shaky ground, now it looks far more solid. Confirming current understanding isn't as sexy as discovering new physics, but just as important, possibly more so.
- sandworm101 9y ago
  That depends. I'd bet money that LIGO was not pitched on the idea that it would only confirm the existence of waves. New instruments are pitched on the expectation of novel measurements. the "new physics". The parallels to the LHC and other massively-expensive instruments are striking. They confirm something that has already been widely accepted, generate the expected prize and raft of phds, but when it is all over the universe hasn't changed. I worry that those greenlighting these projects are being too conservative, only investing in projects that have clear pathways. This trend matters. Physics needs these giant instruments to generate something truly new otherwise the billions will drift towards other disciplines.
  - acqq 9y ago
    You are wrong. The LHC was absolutely prepared to observe new "unexpected" (for the "Standard model") particles. It just didn't happen. A lot of theorists who had developed the theoretical extensions of the "Standard model" are disappointed about that, but that's what is observed. Regarding the gravitational waves, you're also wrong, as the theory and the observations matched even without the gravitational waves being directly observed, the science is simply so good that completely unexpected results (in the sense you talk) are outside of the resulting limits of the previous measurements and calculations. The level of the science we have now is really stunning. The only sad part of the story is that all investments in the science are really minute compared to all the money spent on armies and weapons (e.g. just as the order of magnitude one year of the US military budget is at least 30 times bigger than the NASA's). There's immense amount of the new information that can be obtained by the repeated observations. But the expectation of anything to disprove too much of what we know up to now is simply not realistic.

azizsaya 9y ago

NPR article does a good job of simplifying this, I hope it is technically correct! http://thin.npr.org/s.php?sId=557557544 http://thin.npr.org/s.php?sId=557557544

zymhan 9y ago

The Gravitational wave was detected 2 seconds before the Gamma Ray Burst. I wonder why it is faster? > On 17 August 2017 the NSF's Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, working with the Virgo Interferometer in Italy, detected gravitational waves passing the Earth. This event, the fifth ever detected, was named GW170817. About two seconds later, two space observatories, NASA’s Fermi Gamma-ray Space Telescope and ESA’s INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL), detected a short gamma-ray burst from the same area of the sky.

deleted 9y ago
[deleted]
oppositelock 9y ago
Is it faster, or did the gravitational waves simply precede the GRB?
- valarauca1 9y ago
  You are correct. Waves come from the final in spiral, before the black hole forms. The GRB is from the rapid in fall, and friction of neutron star matter falling into the black hole.
delibes 9y ago
That's the fun science bit where we say "Oh that's odd" :) Is there some matter along the path that interacts with the gamma ray burst and slows it by two seconds? Why is it two seconds? Does it tell us something about the source? All very exciting.
- sdenton4 9y ago
  Yeah my first thought was that space isn't quite a vacuum, which maybe adds up over 130M light years to something measurable. Meanwhile, the gravitational wave is a fluctuation in space itself, so always moves at SoL? The sibling comment about one simply happening after another also seems very plausible though.

runeb 9y ago

After observers found the source of the collision the scientist at the Chile observatory claims to have spent 45 minutes to locate it in the sky. Do they not have some sort of coordinate system they could use to pinpoint it?

scentoni 9y ago
The resolution of our present gravitational wave observations is very low. Adding VIRGO to LIGO helps reduce the area of the sky to look in.

cromwellian 9y ago

Veritasium summary is one of the best easily digestable I've seen. https://www.youtube.com/watch?v=EAyk2OsKvtU https://www.youtube.com/watch?v=EAyk2OsKvtU

acqq 9y ago
I like much more this one by the Science Magazine: https://www.youtube.com/watch?v=e_uIOKfv710 https://www.youtube.com/watch?v=e_uIOKfv710 and this one by The Georgia Institute of Technology: https://www.youtube.com/watch?v=pLivjAoDrTg https://www.youtube.com/watch?v=pLivjAoDrTg
- spuz 9y ago
  I disagree, the Veritasium video has way more information than the two videos you linked. It shows how the gamma ray telescopes and gravitational wave detectors worked together to narrow the source in the sky of event. What a gravitational wave signal looks like, what a gamma ray signal looks like. The fact that the optical signal was made 11 hours after that. Etc. There is a lot more info on top of that which makes the video worth watching.
  - cromwellian 9y ago
    Yes, the fact that the negative detection by Virgo was actually significant was interesting.
  - acqq 9y ago
    It probably reflects my personal tastes, I understand he's a kind a Youtube star or something, but I find the Veritasium presenter too attention-grabbing distracting, so much that I can't even concentrate to what he is talking about. There is no visible presenter in the Science Mag video, ad I like that, and there is another presenter appearing in the Georgia Tech video (Laura Cadonati, a professor), but there I definitely don't have that "WTH the presenter is demanding more attention than the topic" effect, even if she has an accent. I surely in this case react just like a "mom" from this comment: "Showed this video with amazing science discoveries about the universe to my mom and all she said was : "this guy likes orange decorations"." I also just see the guy, his appearance, his body movements and his room decorations etc and I just have this "look at me" impression. I can imagine that helps his personal popularity on that medium, and I guess he optimizes for that, but it obscures the actual content, at least to me. So I don't have energy to analyze it further, but I have had an impression that the videos I've suggested contain some information that doesn't exist in the Veritasium's video, and that the level of the information is better suited for those who need short summary. Maybe there is a target group which, like I, better responds to the videos I've suggested. For those who are really interested in the details, I think there's no substitute to reading the main scientific paper, written by 4600 people(!): http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 It is much more accessible than you'd imagine, it starts with: "Over 80 years ago Baade & Zwicky (1934) proposed the idea of neutron stars, and soon after, Oppenheimer & Volkoff (1939) carried out the first calculations of neutron star models..." (Yes, it's "the" Oppenheimer, who later go to be called "the father of the atomic bomb." Fritz Zwicky was apparently "the first astronomer to propose the existence of dark matter, supernovas, neutron stars, galactic cosmic rays, gravitational lensing by galaxies, and galaxy clusters.") Reading the original sources further, the first map of the potential area on the sky and the first trigger that set everything in motion is: "On 2017 August 17 12:41:06 UTC the Fermi Gamma-ray Burst Monitor (GBM; Meegan et al. 2009) onboard flight software triggered on, classified, and localized a GRB." My understanding is that it was therefore never technically necessary for Virgo to reject the second (lower) LIGO area on this image: http://www.virgo-gw.eu/images/GW170817.png http://www.virgo-gw.eu/images/GW170817.png but the Virgo's operation helped narrowing down the upper area a little.

gigatexal 9y ago

As a fan of the Astro-sciences I am so glad to be alive. I have all the confidence that within my lifetime hopefully (next 50 years hopefully) we will see great things maybe even a unification relativity and quantum mechanics.

Boothroid 9y ago

Am I the only one that's a bit men about this given the pre-conference hyperbole? I was expecting aliens :(

quickthrower2 9y ago

Was about to submit https://qz.com/1102917/observing-the-merger-of-neutron-stars-finally-explains-where-in-the-universe-heavy-elements-are-made/ https://qz.com/1102917/observing-the-merger-of-neutron-stars...

WD-42 9y ago

If any of you are interested in some of the software that made this discovery possible, check out two of the papers from Las Cumbres Observatory: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature24291.html?foxtrotcallback=true http://www.nature.com/nature/journal/vaop/ncurrent/full/natu... http://iopscience.iop.org/article/10.3847/2041-8213/aa910f/meta;jsessionid=24CB64879B5A141DC8F45A67DC33EAA0.c2.iopscience.cld.iop.org#apjlaa910fs2 http://iopscience.iop.org/article/10.3847/2041-8213/aa910f/m... We run a network of 20 telescopes that are triggered remotely (mostly via API). Because of our ability to schedule observations quickly, we were the only ones able to observe the peak luminosity of the kilonova. Disclosure: I am a software engineer at LCO.

spuz 9y ago
Given that GRBs have been detected for a long time and thought to have been a result of neutron star mergers, has a GRB detection ever led to an optical light detection of such a merger before? Is the news here that gravitational wave detection allowed us to see neutron star mergers optically or that they simply coincided with detections of the previously seen optical and gamma ray events?
- scrumper 9y ago
  Yes, in around 1997 I believe. http://www.nature.com/nature/journal/v396/n6708/full/396233a0.html?foxtrotcallback=true http://www.nature.com/nature/journal/v396/n6708/full/396233a... My read is that the news here is that this is the first visual counterpart to a gravitational wave detection. (It's also very strong supporting evidence for the leading theory that neutron stars merging are sources of those gravitational waves.)
- WD-42 9y ago
  Yes, there have been optical counterparts to GRBs before. What is news here is the first optical counterpart to a gravitational wave detection, along with a GRB, which gives us the strongest evidence yet that these are neutron star mergers.
  - 9y ago

hliyan 9y ago

To put this in perspective: Since the first hominids looked up at the stars, till literally yesterday, mankind had only one fundamental force to observe the universe with: electromagnetic waves, be it light, radio waves or infrared. From today, we have two. The other two remaining fundamental forces do not operate at astronomical scales. Of course, we had LIGO before yesterday, but for me, the confirmation through electromagnetic wave observations is key. This is an historic day!

pvg 9y ago
We've detected neutrinos from the rest of the universe for some time.
semaphoreP 9y ago
We've also been observing the universe using neutrinos (generated by the weak force). In fact, there have even been one neutrino event linked to a possible astrophysical source[1], but with less certainty than this gravitational wave/EM detection. [1]: https://www.nasa.gov/feature/goddard/2016/nasas-fermi-telescope-helps-link-cosmic-neutrino-to-blazar-blast/ https://www.nasa.gov/feature/goddard/2016/nasas-fermi-telesc...
- pvg 9y ago
  Supernovae neutrinos have been detected for 30 years, it's not just one event.

epberry 9y ago

This is so cool because we used our ears (the LIGO detectors) to hear/feel the gravitational wave hit then used our eyes (electromagnetic radiation telescopes) to focus in on where we thought we felt the ripple. And what's more, machines all over the planet were involved. Just awe-inspiring.

zyngaro 9y ago
Wonderfully summed up. Thank you. By the way I thought gravitational waves have only been a theory. How can they be detected and is there such a thing as a gravitational quantum ?
- epberry 9y ago
  I don't know about the quantums but to detect the waves you basically split a laser beam using mirrors and redirect each split to a detector. When the wave hits it stretches each split in the beam slightly which causes an interference pattern. That pattern, as it evolves over time as the wave hits, can be converted into sound which is that "chirp" that everyone talks about.
- jasonwatkinspdx 9y ago
  Gravitational wave detectors like LIGO (https://www.ligo.caltech.edu/page/what-is-ligo https://www.ligo.caltech.edu/page/what-is-ligo) are very precise laser range finders used as rulers. They can measure extremely small expansions and contractions of space itself. Discovering a quantized theory of gravity is possibly _the_ major open question in physics atm. We presume there's a 'graviton' of some sort, but have not observed it yet.
  - peeters 9y ago
    If I'm remembering the analogy in the livestream correctly, if you applied the laser's precision to astronomical scales, it would be the equivalent of measuring the distance to the moon with a tolerance the width of a human hair. And in the scales they deal with, a tolerance one-tenth the diameter of a proton.
- 9y ago

platz 9y ago

So, was there a telescope monitoring the light location already, or was the light only found after the Gr detection... I.e. Was it not truly concurrent?

nerfhammer 9y ago
they swung the telescopes around to look for it shortly after the detection event

acqq 9y ago

The main paper about the detections: http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 "Multi-messenger Observations of a Binary Neutron Star Merger" published in The Astrophysical Journal Letters. PDF: http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/pdf http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/p... ePub: http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/epub http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9/e... "Some researchers say it has 4600 authors," I haven't counted myself.

smortaz 9y ago

Relevant: if you want run their actual code via your browser, check out their jupyter notebooks: https://notebooks.azure.com/roywilliams/libraries/LIGOOpenScienceCenter https://notebooks.azure.com/roywilliams/libraries/LIGOOpenSc... Click View to read or Clone to make your own copy and run.

johnvega 9y ago

This stuff makes Elon Musk's plan to colonize Mars relatively less exciting.

CaiGengYang 9y ago

Why is this post given so many points (521) ? Anyone can explain? Isn't it simply a post of something someone saw on the internet ?

martyvis 9y ago

Is it just me, or does anyone else think that its strange that an observatory press release on the specific subject of the "observed light" can only lead it with what I assume is an artists'impression? I'm sure that there is oodles of data to go through, but after 3 months, surely a representation of the actual data imaged could be presented?

acqq 9y ago
The actual images are also on the very same page where you only see an artist impression: PR Image eso1733b, PR Image eso1733c, PR Image eso1733d, PR Image eso1733e, PR Image eso1733h, PR Image eso1733k, PR Image eso1733m. There also are actual pictures in the scientific papers, for example: http://www.nature.com/nature/journal/vaop/ncurrent/fig_tab/nature24291_F2.html http://www.nature.com/nature/journal/vaop/ncurrent/fig_tab/n... Also see the actual main paper, written by 4600 scientists together: there were many more observations and images than these two, but unfortunately they aren't "sexy" for the general public: a dot which appears and then disappears later. But the astronomers know how to even detect the presence of gold in that dot! Note: the chemical element helium, which today is even used to fill the balloons for the children, was first discovered on the Sun(!), using that kind of observations and analysis, and only later at our Earth. There is also a video, directly linked from the page you criticize, and part of the press release, which was made from the real images taken at different times, where the changes in time are visible: https://www.eso.org/public/videos/eso1733c/ https://www.eso.org/public/videos/eso1733c/ Also, there are a lot of papers that are published, most observers will publish or have published their observations. The galaxy where the kilonova happened is some 130 million light years away, or 8 billion times more distant than the Sun is away from us, and what's observed (in different spectrums) is a source of a lot of light (or electromagnetic radiation) at the edge of that galaxy, and also the gravitational waves. To compare the sizes, there could be 1000 of our own galaxies placed one after another to fill the distance to that kilonova. There are around 400 billion stars just in our own galaxy.