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38
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5answers
5k views

How do LIGO and Virgo know that a gravitational wave has its origin in a neutron star or a black hole?

It is being said that gravitational-wave detectors are now able to distinguish neutron star waves from those originating from black holes. Two Questions: How do LIGO and Virgo know that a ...
1
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1answer
39 views

What comes out of binary black holes at end of inspiral?

When 2 blackholes are orbiting each other so close that they lose more energy in form of gravitational wave, this process is inspiral and is unstoppable until it explodes. This is an extremely violent ...
1
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1answer
51 views

Why do external observers see LIGO results if an object falling into a black hole never reaches the event horizon? [duplicate]

If I throw a clock towards a black hole, its time slows down, it is redshifted, and according to many theories it never reaches the event horizon from my point of view. How is it then, that a star can ...
1
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1answer
47 views

black hole chirp physics

I have read that the chirp frequency in the first LIGO data is related to the period of the orbit of merging black holes. I have also read that that the frequency is related to time-dependent ...
5
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1answer
133 views

Why do numerical relativity papers show $\ddot{h}_\times$ instead of $h_\times$ for gravitational waves amplitude?

I am very confused about why numerical relativity papers, when talking about gravitational wave extraction, usually plot the real part of the fourth Weyl scalar, $\Psi_4$, instead of its double ...
1
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0answers
23 views

How are black hole masses calculated from gravitational waves? [duplicate]

I would like to know what data is used from gravitational wave detections to calculate black hole masses and how. Also, what else can you deduce from gravitational wave detections? What was the exact ...
0
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1answer
44 views

Variability of the orbital inclination of a black hole merger?

How variable should we expect the orbital inclination of a typical black hole merger to be, relative to the galactic plane? The LIGO simulation seems to give the impression that the orbital ...
0
votes
1answer
44 views

Difference in Gravitational Waveforms for different objects?

This is an extension of one of my older questions: How would the gravitational strain waveform look like for a planet in orbit with a star? Let's say at some distance D there are two objects which ...
1
vote
1answer
645 views

How to know the distance of the black hole merger? [duplicate]

I have a question about the detection of the gravitational waves by LIGO. When there is no electromagnetic wave coming from the black holes, then how do they know in which distance it is?
1
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1answer
106 views

Why does the magnitude of the Gravitational wave reach maximum peak upon merger?

We all know that objects which are accelerating in space-time produce Gravitational waves. My question is why is there a burst of GW upon two black holes merging. Also, does that mean that let's say ...
3
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4answers
1k views

How do Black Hole event horizons grow? [duplicate]

I was trying to understand how matter falls into black holes, and I got confused by this thought experiment. A small mass falls into a black hole (which negligibly effects the Schwarzschild radius) A ...
1
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1answer
46 views

Where does the rate of mergers per halo in the “Did LIGO detect dark matter?” paper come from?

It was recently proposed that dark matter (DM) could be made of primordial black holes (PBHs) of $\sim 30 M_{\odot}$, like the first ones detected by LIGO. This idea was written in "Did LIGO detect ...
4
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0answers
109 views

Black hole merger for a distant observer

Recently, the LIGO detections of the gravitational waves from black hole merger events have rightly caused a lot of media attention. There is something I do not quite understand, however. In the ...
10
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1answer
164 views

What LIGO should detect that it has not yet?

What would the lack of detection of such phenomena tell us about the Universe? What should be the most frequent signals detected, theoretically speaking? I'm a lay person in the area, so you might ...
5
votes
2answers
171 views

Colliding black holes

If objects approaching the event horizon of a black hole appear to slow down to outside observers, how was LIGO abel to "see" black holes collide? Wouldn't their collision appear to stop as their ...
2
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1answer
209 views

Why does the gravitational wave amplitude at merger of two black hole vary with mass of the blackhole?

I was running a PyCBC simulation of black hole mergers and I found a very peculiar question. When I was simulating two black holes colliding I observed that the peak positive amplitude of the merger ...
2
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2answers
420 views

LIGO Gravitational wave discovery - how did they know the cause of spike? [duplicate]

I understand how unbelievably lucky the discoverers were to catch the wave produced billions of years ago by an event that happens so rarely one hour into a test run of their equipment. But one thing ...
1
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0answers
87 views

Formula to calculate the ringdown frequency of two black holes given their mass?

Is there a simple formula to approximately calculate the ringdown frequency of two black holes given that we know their masses?
6
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1answer
458 views

Formula to calculate the frequency of gravitational waves emitted by two bodies inspiral?

Is there a small straightforward equation which can give the approximate frequency of the gravitational waves emitted by the inspiral of two bodies?
1
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1answer
52 views

How would the gravitational strain waveform look like for a planet in orbit with a star?

So far I've read and seen about various type of waveforms for different sources of Gravitational waves such as black holes, neutron stars etc. So the waveforms would be for Compact Binary Coalescence ...
3
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2answers
218 views

Black holes are obvious answer to dark matter, why is that wrong? [duplicate]

Primordial Black Holes as dark matter candidate. I think this is interesting and new, in that there is a window of PBH masses (link from Count Iblis) And the first GW event from Ligo is right in that ...
17
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2answers
3k views

What is black hole spin?

First of, congrats to the people at LIGO. In this article, the BBC notes that the latest LIGO results show that a new black hole was formed with a spin of $0.2$ (dimensionless number). What exactly ...
-5
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1answer
456 views

Why does Ligo's second detection of gravitational waves and a black hole merger look absolutely nothing like the first? [closed]

Why does Ligo's reported second detection of gravitational waves and a black hole merger look absolutely nothing like the first detection announced in Februaray? Here is the data from the first LIGO ...
4
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4answers
156 views

Can we “see” into a black hole using gravity?

I believe the "no hair" theorem means all black holes settle down into a state only determined by a few parameters, typically listed as mass, charge and angular momentum. But I don't think they can ...
2
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1answer
261 views

Is there high ring-down frequencies in LIGO's recent discovery?

This question is from Physics overflow: question in physicsoverflow. I am reading LIGO's new discovery of gravitational waves by black hole merger. During the merger, two phases are not hard to ...
1
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0answers
36 views

What would the effects of the GW150914 gravity wave burst be on observers much closer that 1.3B LY? [duplicate]

The effects of the GW150914 gravity wave burst were barely observable with state of the art instruments, i.e. LIGO. What would the effects of GW150914 gravity wave burst be on observers much closer ...
1
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1answer
82 views

LIGO detection: What do we know about the black hole system?

I would to know how much we can infer from the LIGO detection on the black hole system. I understand that at least the following can be verified: Spins Inclination Initial masses Final masses ...
3
votes
2answers
263 views

Can we make any implications about the internal structure of black holes from the 'chirp' that LIGO observed?

Are there any implications about a black hole's internal structure we can make based on the chirp issued? For example that a black hole does in fact contain or does not contain a singularity rather ...
-12
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1answer
1k views

Could the September 2015 LIGO gravitational wave “detection” from “merging black holes” be fake? [closed]

The following Physical Review D article gives reasonable bounds for gravitational wave detection for Supernova core collapse. These bounds cannot be overwhelmingly different from the bounds on GW ...
2
votes
1answer
238 views

How they can estimate when the black holes collided in the recent LIGO discovery? [duplicate]

How they can estimate when the black holes collided in the recent LIGO discovery? If LIGO can detect ripples in the gravitational waves, how they can figure out how old those waves are? Surely ...
7
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2answers
990 views

Does the mass lost by merging black holes depend on how they merged?

We've all heard the news about the detection by gravitational waves of two black holes, one 29 solar masses and the other 36 solar masses, spiraling into each other to create a single black hole of 62 ...
12
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5answers
2k views

Are the LIGO observations proof of a black hole merger, and what happened to the black holes?

Recent reports claim that the gravitational waves detected by LIGO match up with the signal expected from two black holes merging as predicted by general relativity. Additionally, the masses of both ...
5
votes
3answers
303 views

How would we estimate, ahead of time, “the chances” of LIGO spotting black holes colliding in the period that it has been operating? [duplicate]

Can anyone summarize calculations that have been done about the theoretical probability of a detectable black hole collision happening in the observable universe within the time that LIGO has been ...
1
vote
2answers
155 views

What actually is the event that we think we have detected with gravitational waves? [duplicate]

This answer shows the "event" that is creating excitement. It looks to the untrained eye like a single "blip" on a detector. It appears to last less than a second. It is, later in the answer, ...
13
votes
3answers
395 views

Do gravitational waves add mass to black hole?

Due to the recent discovery of gravitational waves by LIGO I was wondering suppose a black hole stood between a gravitational wave then due to the fact that black hole can attract every thing then ...
2
votes
1answer
357 views

How did the scientists know two black holes collided 1.3 billion years ago?

I saw a TEDx talk the previous day about the LIGO experiment and in that video he said they are waiting for the day Jan 1st 2017 for the Ripple in Gravity caused by two black holes colliding each ...
10
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3answers
2k views

How were the solar masses and distance of the GW150914 merger event calculated from the signal?

The GW150914 signal was observed, giving us the frequency and amplitude of the event. Because LIGO has two detectors a rough source location could be derived. But how do these three factors allow for ...
3
votes
2answers
89 views

Can we see the famous black hole pair or its effect on other stars in any other means but LIGO?

If the source of LIGO's detection is a pair of black holes, can we see them using a traditional electromagnetic/neutrino/some other kind of telescope? Or can we see their effect on other stars in ...
2
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1answer
277 views

How did LIGO detect the source location of the black holes mentioned to be the cause of today's announcement?

Today LIGO announced discovery of Gravitational waves. What method was used to determine the source location of the waves?