# Questions tagged [gravitational-waves]

Waves in spacetime formed by the acceleration of massive bodies. A passing wave causes spacetime to be stretched and squashed by a very small amount. Typically we can only detect the most energic gravitational events such as black hole mergers.

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### Is it possible to overcome the problem of blind spot(s) of current gravitational wave detectors?

If gravitational wave pass through specific points (which are know as blind spots) current GW detectors aren't able to detect the passed waves so over the time will we be able to completely overcome ...
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### Why does the sensitivity to GWs drops off inversely proportional to the distance?

This answer makes me wonder why the sensitivity to gravitational waves decreases proportionally to the distance. Since gravitational waves extend in all directions, my (uneducated) guess would be ...
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### Is there a limit to the distance of detectable gravitational wave events?

This is somewhat a follow up question to this one. This article indicates that the binaries detected have a distance between 320 and 2840 Mpc. With the current technology, is there a limit to the ...
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### How far away are the events that caused the gravitational waves that have been detected?

A certain number of gravitational wave events have been detected. Is it possible to know how far away the mergers that caused those gravitational wave events are?
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### What is a thermal distribution of eccentricities?

The abstract of the new (open access) paper in Nature A statistical solution to the chaotic, non-hierarchical three-body problem says: The three-body problem is arguably the oldest open question in ...
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### Do gravitational waves really travel in “nothing”?

How does a Gravitational wave create ripple in the fabric of space, if space itself is an empty and it is made-up of nothing. Through out my academic life in school, I was told that space is made-up ...
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### Have more recent LIGO/VIRGO gravitational wave measurements narrowed down the speed of gravity further?

This answer to How precise are the observational measurements for the speed of gravity? says: ...in 2013 a Chinese group built a model using Earth's tides that helped them narrow it down. ...
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### Two body orbit dynamics for orbital periods approaching light cone limit

How do you model a system of two large celestial bodies, where they achieve a rotation very close to the limit at which information can escape the system (heat, light, etc.), do they begin to appear ...
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### Expected nature of LISA's data; will it be more like a forest of static peaks, or a series of individual events?

@RobJeffries' clear answer to Which things “LIGO can see things that LISA can't”, and vice-versa? explains that the Laser Interferometer Space Antenna or LISA will only be sensitive to gravitational ...
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### Which things can LIGO see that LISA can't, and vice-versa?

CNET's Astronomers discover two ferociously fast stars locked in a death spiral quotes Kevin Burdge, lead author on the new paper in Nature General relativistic orbital decay in a seven-minute-...
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### Is there a standardized “Astronomical Alert” system?

“Who saw” the binary neutron star merger first? What was the sequence of events? (GRB/GW170817) highlights a particularly notable astronomical alert, but I am sure that there are alerts triggered by ...
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### Why can't supermassive black holes merge? (or can they?)

The CNet article Astronomers discover two supermassive black holes in a death spiral links to Discovery of a Close-separation Binary Quasar at the Heart of a z ~ 0.2 Merging Galaxy and Its ...
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### Gravitational waves: how can scientists derrive the sizes and spin and distance of two merging black holes?

After recording the ripples of passing gravity waves I would imagine that some high-power math would be required to derive information about the sizes, spin, and distance of the merging black holes. ...
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### What's the actual speed of electromagnetic radiation in space?

The speed of EM radiation is very slightly less than $c$, because space is not quite a vacuum. Say EM travels at $(1-\varepsilon)c$. For example, this results in a slight delay between receiving a ...
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### What actually determines the angular uncertainty of the source of a detected gravitational wave?

This answer and comments got me thinking. Astrometry 101 tells us that while we can use $\lambda/D$ as an estimator of resolution, if we can assume a point source we can determine the centroid or ...
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### Gravitational wave distortion

Gravitational waves detected are from merging of black holes few millions of light years away. While waves have reached us after travelling so far, they must have encountered many black-holes and have ...
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### Can gravitational waves pass through a black hole?

As the title says, what happens when a gravitational wave approaches a black hole? I would presume that something interesting happens because of the way spacetime works near black holes but I have no ...
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### What produces gravitational waves with “periods between about 100 - 8000 seconds”?

The Ulysses mission has a compelling story. I was sent to Jupiter to perform a gravitational assist shooting it out of the plane of the ecliptic in order to fly over the Sun's north and south poles to ...
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### Can't pulsars and stars be used for gravitational wave measurement?

Suppose that we collected photons from a distant star, and they arrive regularly at 15 photons every microsecond onto a CCD, when a gravity wave bends space time, wouldn't the regular 15 photons graph ...
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### Are gravitational waves part of dark energy?

Do the current models of the universe consider the energy release of gravitational waves? E.g. iirc, the last black hole merger detected had a gravitational wave energy equal to ~3 solar masses (hope ...
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### How far away was the binary black hole that produced GW170729?

GW170729 was gravitational wave signal's detected by the Virgo and LIGO detectors. I read the following in a news report: Known as GW170729, in accordance with the date of its discovery (in US ...
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### Expansion and Gravity

If space is undergoing accelerated expansion then regions of space are becoming inaccessible to us even at light speed. If gravity is bounded by light speed then inaccessible regions of space no ...
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### What can be learned from, or noted in this LIGO Orrery video?

The Ars Technica article Physicists detected gravitational waves from four new black-hole mergers notes that This brings the total number of events detected by LIGO and Virgo to 11. It also has a ...
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### Does a gravitational wave loses energy over distance?

How does a gravitational wave travel over vast distances without losing its energy? Could they go on forever as long as the Space? Thank you
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### What does “GPU-accelerated butterfly matched filtering over dense bank of time-symmetric chirp-like templates” mean? (GW170817)

A new analysis of gravitational wave (and other data) from GW170817 on 2017-Aug-17 has been published, strongly suggesting that the merger of two neutron stars resulted in a large, rapidly rotating ...
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### What changes are being made to VIRGO and LIGO (if any)?

Gravitational wave detectors VIRGO and LIGO are currently down for some updates, slated to be completed sometime early next year (they hope). What exactly are they doing? I hadn't heard it was down ...
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### Do gravitational waves have distinct bands or parameters from which a source redshift can be inferred? [duplicate]

In optical astronomy, much (most?) electromagnetic radiation is emitted at well defined frequencies, and this can be used to infer a redshift for the source, and hence its recessional velocity, age, ...
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### What does gravity-wave noise resemble locally?

Now that we know that gravity waves exist, we can consider to design a new unit of measurement, i.e. deciGravs (from dB) and we can predict what the backround noise of dG's is locally and in space. ...
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### Would LIGO Detect Head-On Collision?

Assume two black holes collide head-on. In other words, they were not orbiting one another before the collision. I know this is unlikely. Further assume that their sizes and distance from Earth are ...
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### GW from merging of neutron stars and black holes

If it had been detected gravitational waves from merging of black holes (BH), and neutron stars (NS), why there are no detection of black holes merging with neutron stars? Why a BH-NS merging should ...
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### Could gravitational waves near merging black holes collapse to a black hole themselves?

I have understood that merging black holes emit considerable amount of their mass as gravitational waves (up to 5-10%). Based on what I have understood from gravitational waves, the closer black holes ...
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### Why is frequency different for gravitational waves coming from SMBHs vs small compact binaries?

Why do gravitational waves emitted by supermassive black holes binaries have low-frequency range (~10$^{-9}$ - 10$^{-2}$ Hz) than those emitted by stellar mass compact binaries (~10$^{-4}$ - 10$^2$ ...
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### What does the word “compact” mean in astronomy/astrophysics?

I have seen countless times the adjective "compact" in astronomy, e.g. compact stars, compact binaries, etc. I would like to know, what exactly is this supposed to mean? From this source, I am led to ...
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### What do the acronyms in “AT 2017 gfo” mean?

About 11 hours after the detection of GW170817 by Ligo/Virgo and the quickly succeeding detected GRB170817, a transient afterglow in the optical-nIR frequency appeared which showed many signs of r-...
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### Items at the Event Horizon vs. colliding Black Holes

Items reaching a Black Hole's Event Horizon seem to be frozen in time from the point of view of an outside observer. On the other hand, Black Holes collide and merge, in finite steps, producing ...
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### The size of the radius of the event horizon of a black hole created by the merger of a black hole binary system

Let's assume that you had a black hole binary system and everything said here is possible. Their large masses would lead to a large emission of gravitational waves. The loss of orbital energy and ...
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### Maximum disturbance to space time of gravitational waves, and will this affect humans? [duplicate]

Do we have a theory that can tell us how much change gravitational waves can make to space time. If it is infinite then I think any time we can see biggest change in space time and how much could it ...
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### Can two detectors for gravitational waves be combined into a very long baseline interferometer?

While detectors for gravitational waves are interferometers themselves, the question here is about an increase in resolution resulting from two or more detectors far away from each other.
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### Do mixed type remnant collisions produce anything interesting?

The recent detection of a binary neutron star inspiraling and colliding raises an interesting question in my mind. Type Ia supernovae are believed to be caused by white dwarf/regular star pairs and/or ...
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### “Who saw” the binary neutron star merger first? What was the sequence of events? (GRB/GW170817)

I'm trying to read Multi-messenger Observations of a Binary Neutron Star Merger the "cast of thousands" OPEN Access ApJ letter 848:L12 (59pp), 2017 October 20 https://doi.org/10.3847/2041-8213/aa91c9 ...
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### What is the detection threshold of gravitational waves for LIGO?

Since now two neutron stars have been detected merging via gravitational waves, I was wondering what is the current detection threshold that the LIGO detectors can achieve. Considering that the first ...
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### Are binary neutron star mergers needed to explain the abundance of gold?

The NPR News item Astronomers Strike Gravitational Gold In Colliding Neutron Stars mentions and quotes "Daniel Kasen, a theoretical astrophysicist at the University of California, Berkeley:" He ...
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### Why is the discovery of merging neutron stars important?

I'm fairly certain people here will have heard about it, already, but apparently, two supernova leftovers clashed some 130 million years ago and some billion billion kilometres away ... What I haven'...
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### What would it feel like to be orbiting near a merging black hole?

The recent 4th discovery of gravitational waves where the black hole masses were 31 and 25 times the mass of the sun, and they released 3 solar masses of energy as gravitational waves, made me wonder ...
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### How did Earth get here before gravitational waves?

If GWs propagate at near the speed of light, how did Earth (and its constituent elements) arrive at its current location billions of years before the GW arrived here (or light from distant stars for ...
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### Will the detection of colliding neutron stars by LIGO help answer the question of where heavy elements came form?

I have read about and heard about the theory that most of the heavy elements we have here on Earth came from colliding neutron stars rather than by way of supernovae. I'm not sure how strong this ...
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### Is there an official list of objects in the sky?

I would like to know how many known quasars there are in the Universe as well as x-ray binary black holes (not Neutron stars) but I don't seem to be able to. I also want to know how many black holes ...
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### From where does the energy for gravitational waves come from?

As far as I understand, in the events detected by LIGO, about 4% of the total mass of merging binary black holes was converted to gravitational waves. Where does this energy come from, i.e. what ...