# Questions tagged [binary-stars]

Binary stars are a system of two stars rotating around their center of mass, as opposed to single stellar systems such as our solar system.

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### How do astronomers calculate the mass of celestial bodies light year from Earth?

I have read in many scientific stuff that mass of this planet or that stars is about '$n$' times the mass of Sun. I have gone through many websites and videos on YouTube but didn't find the right ...
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### Time dilation effects at the center of a binary black hole system

Imagine two identical black holes in a circular orbit, and Alice is smack-dab in the middle of the system (at the barycenter). Bob is at infinity. Let's assume that Alice and Bob are stationary ...
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### How would I see if there is a transit in this light curve?

I am trying to detect if some binary star systems have exoplanets orbiting them. I've been completing this project for many weeks now, and have managed to write some code that will plot light curves ...
1 vote
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### How likely is it that a typical pair of black holes will eventually merge?

Gravitational wave observatories have found many pairs of black holes merging. I understand that before they were working there were estimates of the rate at which they ought to be found. To me it ...
484 views

### Can two relativistic black holes' event horizons overlap and separate again?

I have read this question: What I have not seen is a purely classical argument for the non-separation of a black hole merger. One can obviously take the time reversed spacetime manifold of a merger ...
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### Gauge independence of the gravitational-wave frequency and gauge dependence of the binary separation?

In the seminal paper by Cutler & Flanagan (1994), which uses multi-timescale analysis to derive waveforms in the post-Newtonian approximation without spin effects, they state that, "In Eq. (...
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### Black holes: Is merger inevitable when horizons touch?

I watched a simulation of the binary black hole merger of 2019 April 12 https://www.ligo.caltech.edu/video/ligo20200420v1 When the "apparent horizons" (their terminology; are those ...
1 vote
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### Dissipation caused by Gravitational Wave Emission

Two massive bodies orbiting each other can lose energy through gravitational wave emission until colliding. Can a single massive body, moving with constant velocity with respect to an observer, lose ...
367 views

### Is there an approximate expression for the force between two black holes?

Just curious: is there an approximate expression for the gravitational attraction between two Schwarzschild black holes of masses $M$ and $m$, held without relative speed at some center to center ... 127 views

### As of 2021 in how many binary systems has the period decrease due to gravitational waves been measured?

I am searching for data for the period decrease of binary systems due to gravitational waves. I am aware of three systems in which it was possible to measure this period decrease: The Hulse-Taylor ...
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### Gravitational waves in the post-Newtonian expansion

I have spent some time trying to understand gravitational waves in the context of the post-Newtonian expansion. As far as I understand it, the general relativistic equation of motion can be ...
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### Should the stars of a relativistic binary system have tangential acceleration?

Should the stars of a relativistic binary system have tangential acceleration?
1 vote
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### Why in binary star system the 2 bodies revolve around their center of mass?

Can you prove it mathematically? Is it just an observation? I know the force between them is $\frac{Gm_1m_2}{r^2}$. Centripetal force on any one of them is $\frac{mv^2}{r_1}$, where $r_1$ is radius of ...
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### An apparent paradox in General relativity using a binary black hole

Note: Quantum gravity effects are ignored in this question. Imagine 2 black holes each with mass $m$ approaching each other and after some time the Event Horizons (EHs) of both black holes touch each ...
1 vote
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### Relationships between G magnitude, Johnson V magnitude, and spectral type of stars?

I'm simulating a population of binary stars for a summer research project. I'm adding uncertainties to my simulated observables such as angular position and radial (line of sight) velocity. I'm using ...
1 vote
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### Why are wide binary systems assumed to contain negligible dark matter?

I'm doing a project that simulates wide binaries to do gravity tests, specifically a dark matter vs MOND test. I've come across similar papers, and their justification for using wide binaries for this ...
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### Would the 2 orbiting black holes emit gravitational waves?

Would the 2 orbiting black holes emit gravitational waves even if they are moving at a constant speed in orbits? Here, can we consider the changing direction of black holes in their orbits as ...
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### Find semi-minor axis of elliptical binary orbit given semi-major axis and mass ratio

I'm working on a simulation of binary stars. I'm using Kepler's Laws to solve for the angular velocity given the semi-major axis $a$ and the masses $m_1$ and $m_2$ of the two objects in an elliptical ...
1 vote
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### Could two planets trapped between two stars orbit each other?

Say there are two stars, each exerting and equal force on a point in the midde of them. For simplicity, we'll say the two stars have the same mass and are equidistant from the point. Now suppose that ...
The gravitational wave signal from a binary system approaching merger consists of a mixture of the two $h_+$ and $h_\times$ orthogonal polarisation states. If the binary is "face-on" (with ...