# What is Binary system: Definition and 49 Discussions

A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter (also see animated examples). More restrictive definitions require that this common center of mass is not located within the interior of either object, in order to exclude the typical planet–satellite systems and planetary systems.
The most common binary systems are binary stars and binary asteroid, but brown dwarfs, planets, neutron stars, black holes and galaxies can also form binaries.
A multiple system is like a binary system but consists of three or more objects such as for trinary stars and trinary asteroids.

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1. ### I Why Do Stars in Binary Systems Assume a Teardrop Shape?

In binary star systems, it is said that one of the stars can assume a teardrop shape resulting from the gravitational pull of the companion star. This shape is typically portrayed as asymmetric (i.e., there is no teardrop shape on side of the star away from the companion star). Yet the...
2. ### I Star with quadrupole in a binary system violates Newton's 3rd Law?

Assume that, in a binary system, one (and only one) of the two stars has a non-zero quadrupole moment. Then the other star feels the usual gravity force $F_g$ plus an additional force $F_q$ coming from the quadrupole potential. On the other hand, the first star feels only the usual gravity force...
3. ### I Gravitational Waves Emitted by a Binary System

Let's assume a binary system with an inclination angle ##i## (angle between the orbital plane and line of sight). Then, according to this source - equations (128) and (129) - for the amplitudes of the tensor polarization modes ("plus": ##+## and "cross": ##\times## polarization) I could write...
4. ### B Measuring distance between two stars in a binary system

Hello I am trying to teach myself some basic maths for astronomy from a book, namely trying to calculate the distance between two stars in a binary system. One thing i am confused with is what angular separation means and how it can be translated to true physical distance between them using...
5. ### Help on how to find stellar radius with an eclipsing binary system

My best guess right now is use Newton's version of Kepler's 3rd Law to maybe find a combined mass, as I'm under the impression that the smaller star's mass would still be too large to ignore, but I'm not confident. And I wouldn't be sure as where t go from their, either. Any guidance would be...
6. ### Mass Transfer in a Binary Star System

Homework Statement: A binary star system consists of M1 and M2 separated by a distance D. M1 and M2 are revolving with an angular velocity w in circular orbits about their common center of mass. Mass is continuously being transferred from one star to the other. This transfer of mass causes...
7. ### A Understanding gravitational waves (GR)

I am reading the following paper on the basic physics of a binary black hole merger: https://arxiv.org/ftp/arxiv/papers/1608/1608.01940.pdf Imagine two black holes orbiting each other until a point they merge. As you can see in Figure 1, the wave period is decreasing and thus the frequency...
8. ### Binary System in circular orbit: Separation distance between stars

Distance is d=1/0.07 = 14.3 parsecs The Doppler shift of one star is, Δλ = 512 - 512.04 = -0.04 So the radical of the velocity of the star is = (-0.04/512) x (3.00 x 10^5 km/s) = 23.4km/s which is the same for both stars because they have the same mass. This is as far as I've got.
9. ### Writing: Input Wanted World destroying solar storm/binary orbit

Soooo, hi PF, it's been a long time since I needed your help, but here I am again. I've been doing some worldbulding lately and I came up with this idea of a world in which civilisation and life are much, much older than in ours. Yet it isn't as developed due to some kind of natural disaster...
10. ### Why am I encountering the binary system in this problem?

Hi, This is not homework. I need to understand why the binary number system works in the case of a particular problem. While trying to solve the puzzle below, I set out to finding the minimum number of denominations required to create a particular amount. To create any amount up to \$15, I just...
11. ### Binary Stellar System: 15M⊙ & 10M⊙ Revisited

Homework Statement A binary stellar system is made of one star with ##M_1=15{M}_\odot## and a second star with ##M_2=10{M}_\odot## revolving around circular orbits at a relative distance of ##d=0.001pc##. At some point ##M_1## explodes in a supernovae leaving a neutron star of mass...
12. ### Binary system of stars (##\alpha## - centauri)

Homework Statement ##\alpha##-Centuary is in a binary visual system with another star. Their separation, from their CM, is 8.0'' and 9.7''. The distance from the Earth is 1.31pc. Their revolution period around the CM is 80.1 years. I have to find masses and luminosities for each star. Homework...
13. ### Kepler's 3rd law and a binary system

Homework Statement I am having a issue with the question, when I check the solution to the problem, I can't seem to make sense of how they have derived there equation. Q: By analyzing the superposition of frequencies and amplitudes in the radial velocity data for a star 55 Cancri A, the first...
14. ### Centre of mass of binary system calculation

Homework Statement Given a graph (see below) containing the velocities of two stars with respect to the sun, I am asked to calculate the velocity of the centre of mass of a binary system. I am not given the mass of either star, nor the shape of the orbit nor the velocity of the centre of mass...
15. ### I Determining The Inclination Angle of A Stellar Binary System

I am a Physics undergraduate at the University of Texas at Arlington. I am currently taking an Astrophysics class in which my professor talked about the inclination angle of the orbital plane of the binary star system and how it is impossible to determine that angle. I was wondering why is it...
16. ### Two Black Holes orbiting as a binary system

Homework Statement In 2009, astronomers found convincing evidence of two such black holes orbiting as a binary system. From data collected, they estimated that the separation of the black holes was 3.2 × 1015 m and that their masses were 1.6 × 1039 kg and 4.0 × 1037 kg. The black holes orbit...
17. ### Lattice Models for Fluids - Regular Solution Model

1. Problem Statement: For the regular solution model, develop the equations for the compositions of the coexisting phases in a binary system and plot the phase boundary as a function of χ/RT.2. This question stems from Sandler's Introduction to Applied Statistical Thermodynamics. The Attempt...
18. ### I Simulating Binary Systems with RK4 in C

I'm writing a C program to simulate the orbits of a binary system with a 4th order Runge-Kutta method; basically I'm considering the 2 bodies rotating around a fictitious 3rd body(which would be their center of mass) and I turned down the reciprocal gravitational pulls between the bodies to...
19. ### I Planet at barycenter of a binary system.

Say you have a binary system (with similar mass) in the following orbit with a planet located at the barycenter, is this possible and is this a dynamically stable system (over billion of years) ?? If this system was an Earth like system would I assume correctly that it would not have a nigh...
20. ### B Binary/Ternary Systems: Could Stars Orbit a Non-Stellar Central Object?

Dear PF Forum, Sorry for asking two questions in a row. Because I think my next question belongs to a new thread. After all it's Sunday here. My friend told me about Kelt - 4A. Orbitting 3 stars. So, in this galaxy (and universe) if let alone to the law of gravity and chance. 1: Can there be a...
21. ### I Binary system of a neutron star with a black hole

I am reading about mergers of a neutron star with a black hole and the association with GRB. While talking about the accretion disk, the paper I am reading says about the last stable circular orbit. Firstly I thought it was where the Roche limit lies, where mass transfer or matter ejection from...
22. ### I Energy of a Rotating Binary system

- We have two identical point masses, they are moving in uniform circular motion and in the same plane. - Both masses are 180 degrees out of phase, they are always on opposite ends of their circular path. -The "orbit" radii for both masses are the same.We consider only SR effects, no GR.Now we...
23. ### Finding the mass of a planet is a binary system

Homework Statement Plaskett’s binary system consists of two stars that revolve in a circular orbit about a center of mass midway between them. This statement implies that the masses of the two stars are equal. Assume the orbital speed of each star is 220 km/s and the orbital period of each is...
24. ### So is this scary? (Black Hole in binary system)

http://www.cnn.com/videos/tech/2015/07/07/black-hole-awakens-erupts-nasa-orig.cnn 8K ly seems awfully close. the cnn version of the story... is a bit thin o_O
25. ### Discovering the First Binary Star System: The Fascinating Binary System Story

which is the first binary star system discovered ever?
26. ### Explore Binary System Inspiral w/ 1.5 Solar Masses

From Wiki. The pulsar and its neutron star companion both follow elliptical orbits around their common center of mass. The period of the orbital motion is 7.75 hours, and the two neutron stars are believed to be nearly equal in mass, about 1.4 solar masses. Radio emissions have been detected...
27. ### Radial Velocity of the centre of mass of spectroscopic binary system

My book says (Foundations of Astrophysics): " The radial velocity ... can be found from the Doppler shift of the star's absorption lines: \nu_{r}=\frac{\Delta\lambda}{\lambda}c If the star you are observing is part of a spectroscopic binary system, you can separate the radial velocity of...
28. ### How to Calculate Mass in a Binary System with Given Orbital Period and Radius?

Homework Statement See attachment. Homework Equations The Attempt at a Solution Ok, so for Qd) my attempt was: d = vt = 75x10^3 * (2*2.8*86400*365) = 1.32x10^13 m, (circumference of orbit) because the star periodically shifts from red to blue shifted frequencies every 2.8...
29. ### About accretion disk of a binary system

In an X-ray binary system, in which one of the two objects is black hole candidate, there are several ways to exchange mass. A paper states that" their host systems are mass-exchange binaries containing a nondegenerate star that supplies gas to the black hole via a stellar wind or via...
30. ### What is the trigonometric parallax of a binary system?

Hi It is stated that: "for a visual binary system, the measured trigonometric parallax is 0.3749+/-0.0057 arcsec." I don't know this angle is parallax of what? I can guess it like this: 0.3749+0.0057 arcsec is the parallax of the whole system when they are at most distance of each other...
31. ### Deriving Total Energy of a Binary System

Homework Statement Beginning with the kinetic and potential energies of two objects with masses m1 and m2, show that the total energy of a binary system is given by: E=\frac{1}{2}\muv2 - G\frac{M\mu}{r} Homework Equations The one given K =\frac{1}{2}mv2 U = G\frac{Mm}{r} The...
32. ### Is binary system the only choice for the computer?

Hi Using the binary system for computing is a natural choice because of its two states: 0 and 1. But is this possible to use base 10, which is used in everyday matters, instead of base 2? Please remember that I'm neither a student of comp. science nor of science/math, in general. Thanks...
33. ### What is the apparent magnitude of the binary system?

Homework Statement Two stars are in a circular visual binary system. The orbital period of the binary is 30 years. The distance to the binary is 20 parsecs. The angular radius of the orbit of each star is 1". What are the masses of the two stars? each star works out to be 4.4 solar...
34. ### How a binary system affects gravity on members?

Hi, I have a rather simple question, how does a binary system with a common center of gravity affect the gravity on both members of the system. If we have a case of a single planet and ignore the star it orbits, the center of gravity should be in the dead middle of that planet. If we...
35. ### Two separate barycenters of a binary system in a small closed universe?

EDITED: I decided to move the thought experiment that led me to this question to the bottom of this thread. I will first state what my question is. Suppose that we live in a closed universe of three spatial dimensions and this universe is in a state of rapid collapse. Now suppose that all of...
36. ### Prove Binary System Brighter by 3/4 Magnitude Than Single Star

I have to prove that a binary system of stars of equal mass, temp, etc. is brighter by a magnitude of 3/4 than a single star of equal mass, temp, etc. I've been trying to work it out with (m1-m2)=-2.5log(f1/f2) Might anyone be able to tell me if I am even on the right track?
37. ### Energy of a Binary System (Gravitation)

Homework Statement What is the kinetic energy and total mechanical energy of a binary system of identical spheres orbiting around their common center of mass? M = mass R = radius Homework Equations Force of gravity = GM^2/2R K = 1/2MV^2 The Attempt at a Solution I don't know whether...
38. ### Finding magnitude of part of binary system

3. A very cool, faint white dwarf is identified as such from its spectrum and is known to have an apparent visual magnitude, mv = 16.73. A series of observations over several years yields a parallax measurement of 171±2 mas (milli-arcseconds). (i) How far away is the white dwarf, and what...
39. ### Astrophysics: Finding the mass of a hidden star in a binary system

Homework Statement The spectral lines in a low mass main sequence star show sinusodal velocity variations with an amplitude of 500 km/s and a time period of 10 hours calculate a lower limit to the mass of the unseen binary companion Homework Equations M1 + M2 =...
40. ### Determining the masses of 2 stars in a binary system.

Homework Statement A binary star is resolved on the sky, the orbit is circular, it has a period of 30 years and the semi-minor and semi-major axes are observed to be 0.5 and 4 arcseconds respectively. If the distance to the system is 10pc, what are the masses of the stars? give an answer in...
41. ### Orbital period variation in binary system

Homework Statement Using the conservation of angular momentum and Kelper's third law, show that the relative change in orbital period produced by mass transfer is given by 1/P * dP/dt = 3 dM1/dt * (M1 - M2)/(M1M2) Homework Equations L = mu * sqrt(GMa) P^2 = (4*PI^2)/(G(M1+M2)) * a^3...
42. ### Semimajor axis of binary system help

Default semimajor axis of binary system help hi, I'm not sure if I am posting in the right place but I could really do with some help figuring out the semi major axis of a binary star system. I have been give the mean distance of each star from the center of mass (star A = 3.96 AU star B =...
43. ### Astrophysics - Apparent Magnitude of stars in a close binary system

Homework Statement 2 solar type stars are in a close binary system. Each indivual star has an apparent brightness of m = 10 mag. Determine the apparent magnitudes of the combined system of the 2 stars assuming they cannot be resolved as individual objects. Determine the minimum brightness...
44. ### Why Is 2r Used in Calculating the Masses in Plaskett's Binary System?

hey i've been having trouble understanding a part in this question. i'll just map out the basics to the question: 2 stars with a velocity of 220km/s are orbiting at equal distance. the masses of the stars are equal. period = 14.4 days it asks to find the mass of each star. i understand that...
45. ### Is Binary a Fit Numbering System?

Allright, now we know using the decimal system you can represent any number you want because you use a base 10 system. my question about the binary system is: you can very well represent numbers from 0 to 255 using 8 bits. Now, how can you show that you can represent EVERY number between these 2...
46. ### Masses of binary system (quick q)

I have this problem: Given is period of an eclipsing binary star system is 34 days, rest wavelength is 6563 angstroms while max doppler shift of 2.34 angstroms I used the doppler equation to figure out the orbital speed of the star; now the question says to use the simplistic model of...
47. ### Gas binary system vinyl chloride - water

hello, how I can calculate the composition of a gas binary mixture of vinyl chloride and water knowing that I have only the following informations: the water is saturated by the vinyl chloride the pressure of the mixture is 4bars or can you tell me what I have to look as information to...
48. ### Calculating Mass of Stars in a Binary System

Q: Suppose that a binary star system consists of two stars of equal mass. They are observed to be separated by 340 million kilometers and take 5.0 Earth years to orbit about a point midway between them. What is the mass of each? I figured out that: mass=4pi^2(radius)^2/Gravitational...
49. W

### Stability of Binary System with Anti-Particle Circulation in Quantum Physics

Hi, I have a question about anti-particle. In the modern physics, we "know" (I don't think we really know it) the reason, why the shell electron did not collapse into its ion core, because of quantum theory. But is it possible a electron "circulate" a positron without annihilation. Is there...