What is Binary star: Definition and 68 Discussions

A binary star is a star system consisting of two stars orbiting around their common barycenter. Systems of two or more stars are called multiple star systems. These systems, especially when more distant, often appear to the unaided eye as a single point of light, and are then revealed as multiple by other means.
The term double star is often used synonymously with binary star; however, double star can also mean optical double star. Optical doubles are so called because the two stars appear close together in the sky as seen from the Earth; they are almost on the same line of sight. Nevertheless, their "doubleness" depends only on this optical effect; the stars themselves are distant from one another and share no physical connection. A double star can be revealed as optical by means of differences in their parallax measurements, proper motions, or radial velocities. Most known double stars have not been studied adequately to determine whether they are optical doubles or doubles physically bound through gravitation into a multiple star system.
Binary star systems are very important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined, which in turn allows other stellar parameters, such as radius and density, to be indirectly estimated. This also determines an empirical mass-luminosity relationship (MLR) from which the masses of single stars can be estimated.
Binary stars are often resolved as separate stars, in which case they are called visual binaries. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (spectroscopic binaries) or astrometry (astrometric binaries). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called eclipsing binaries, or, together with other binaries that change brightness as they orbit, photometric binaries.
If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, these close binary systems can exchange mass, which may bring their evolution to stages that single stars cannot attain. Examples of binaries are Sirius, and Cygnus X-1 (Cygnus X-1 being a well-known black hole). Binary stars are also common as the nuclei of many planetary nebulae, and are the progenitors of both novae and type Ia supernovae.

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  1. Sciencemaster

    I Database of binary star data info within 10 PC of Earth

    I'm looking for a database of binary stars within 10 PC of Earth, including information such as eccentricity of orbits, their distance from one another, etc. I'm hoping to find a list with this information, or just a collection of pages with this information. I've tried Simbad but I can't find...
  2. Kate_C

    B Question re binary star systems & possible orbits

    From what I gather, there are S-type, P-type & T-type systems, but I'm having a hard time wrapping my mind around the orbital possibilities. Would it be theoretically possible to have a planet in a binary star system where there is a daily "pre-sunrise" and a "pre (or post) sunset" due to the...
  3. K

    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...
  4. B

    Astrophysics question about a binary star system (AQA exam)

    https://pmt.physicsandmathstutor.com/download/Physics/A-level/Past-Papers/AQA-Old/Unit-5/June%202015%20MS%20-%20Unit%205-2A%20AQA%20Physics%20A-level.pdf mark scheme question 2 very simple question why is the change in wavlength not 656.05 - 656.52? instead. The difference being in the mark...
  5. A

    Binary Star initial positions and velocities

    Hi all, I've been tasked with computing binary star orbits based on their initial parameters, positions and velocities. In this problem everything must be expressed in terms of the masses, but I am struggling to define positions and velocities in terms of mass. It is assumed that the stars are...
  6. quasarLie

    How to Calculate Mass of Binary Star Systems Using Kepler's Law and Iteration?

    Homework Statement I have to calculate the mass of an astrometric binaries with P=10 years, and a1=15mas, parallax w=64mas the luminosity is neglected Homework EquationsThe Attempt at a Solution i used this equation: M_1 + M_2 = \frac{(a/w)^3}{p^2} but the problem is taht i don't have M1
  7. P

    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...
  8. F

    I Is Tabby's Star a Binary System or an Alien Megastructure?

    KIC 8462852, aka ‘Tabby’s Star’ is in the news again, with more BS ideas about "alien megastructures'. Isn't the simplest and most likely explanation for the intensity variability that it is a binary or multiple star system and that the Earth is in the same plane as the mutual orbit ?
  9. Unteroffizier

    Find Absolute Magnitude, distance and "T" of binary star system

    This is the problem given at my basic astronomy course. If I turn it in within a month correctly, I get 10 extra points in the finals. Problem: We have binary star system consisting of Star A and Star B. Astronomers have observed it for 11 years, during which it has moved from point A to point...
  10. L

    B Planets in binary star systems

    How can planets exist in star systems with two or three stars? Shouldn't the planets' orbits get severely disturbed by the other stars?
  11. R

    What is the distance and mass of a binary star system with given parameters?

    Homework Statement In an visual binary star system,the apparent magnitude of the primary star is m=9.8 and its spectrral type is G2V.The angular semi-major axis is φ=0''.1 and the period of the system is 24y.Find the distance of the system r and the two masses.The Sun's absolute magnitude is...
  12. CassiopeiaA

    A Take FFT to find time period for eclipsing binaries

    I am trying to use Kepler Data for Eclipsing Binaries to estimate time period, and then other parameters such as mass, eccentricity, semi-major axis, distance, etc. of the binary systems. I want to write code in MATLAB which will use FFT to find the time period. The available data has the...
  13. John Fluharty

    Planet at the center of mass of a binary star system

    I can't think of an instance of this in science fiction, but then I do not have the broadest knowledge of the field, so I could have missed something obvious to everyone else. I wonder, though, could a planet form at the center of mass of a binary star system or be captured there, and could...
  14. P

    Gravitation problem -- Binary star system

    Homework Statement Homework EquationsThe Attempt at a Solution the solution says to equate the moments about C or equate the centripetal forces but the moments, they used M1R1 = M2R2 how does the above represent the moment, and why is the moment even equal?similarly, why is the centripetal...
  15. E

    Metric matrix for binary star system?

    What does the metric matrix look like for a binary star system? Does each follow its usual geodesic about the other? It seems like the solution would have to be different somehow than that for a tiny planet circling a big sun.
  16. 2

    Confused about binary star systems?

    I was thinking about the motion of two stars in a binary star system, but there is something I cannot quite figure out. Suppose you have a binary star system with two stars masses m1 and m2 with m2>m1 so that m2 is closer to the centre of mass of the system. Then when the two stars are as far...
  17. W

    What happens in the center of mass of binary star system ?

    Good night! Please, what happens to an object (eg a spaceship) placed exactly in the center of mass of a binary star system (composed by two similar stars)? Would it be compressed by a huge gravitational mass (something like the mass of both stars)? Would it be stretched and torn? Or would it...
  18. M

    Binary Star Inclination Angle probability distribution

    Can someone explain why the probability of the inclination angle of a binary system being less than i_0 is 1-cos(i_0) i.e. why the fractional distribution of binary stars is df = sini * di, where i is the inclination angle? Where does the sin i come from? Why is not not uniformly distributed...
  19. L

    Binary Stars and Apparent Magnitudes

    Homework Statement A binary star system at a distance of 85pc consists of two stars of equal luminosity that are so close together that they are observed in a telescope as a single image. If the apparent magnitude of the two stars combined is 10.7 what would be the apparent magnitude of just...
  20. TheSodesa

    Problem related to the center of mass of a binary star.

    So here's my problem: The distance between two stars is constant(d = 4,3 * 1010m), and they have a common center of mass. Ms = mass of our star, ma = 0,82 * Ms and mb = 2,2 * Ms. What I'm supposed to do is calculate the period of orbit of both stars, which is the same for them both, since the...
  21. U

    M_p^3 = \frac{V_s^3}{2\pi G} PM_s^2Solve Binary Star Mass Homework Equation

    Homework Statement How do I show that for a binary star system, if one star has mass ##M_s##, speed ##V_s##, period ##P##, the mass of the other star is given by: ##M_P^3 \approx \frac{V_s^3}{2\pi G} PM_s^2##? Homework Equations The Attempt at a Solution \frac{GM_pM_s}{(a_p+a_s)^2} =...
  22. K

    Binary star period calculation

    The problem is attached, and the official answer is given. The step in the answer does not make a lot of sense to me. How does the luminosity L converted directly into distance d, and why is the solar distance is used? And where does the dm=0.75 come from. It's just not making sense to me...
  23. P

    Calculating Binary Star Masses

    Hello, I wasn't sure whether I should post this is the homework section since it's technically a textbook problem, but I figured I'd get better responses here. The problem is as follows: Sirius is a visual binary with a period of 49.94 years. Its measured parallax is .37931"## \pm...
  24. D

    Habitable zone for binary star systems

    Does anyone know which type of orbit is most likely to result in habitable worlds in a binary star system -- a planet orbiting one of the two stars, or orbiting both of the stars, or are they both very likely/unlikely? Wikipedia quotes a paper that simulated binary stars and found that 50-60%...
  25. P

    Binary star revolving arround center of mass

    why the binary star revolving around center of mass ? could type 2 supernova ever had a stellar wind after explosion ?
  26. S

    Binary Star Systems: Radial Velocities, Observations & Unresolved Eclipses

    Homework Statement Angular separation of stars 1.5 arcsecs Parallax 0.0050 arcsecs Apparent vis magnitude 2.5 (star a) and 7.5 (star b) The two stars may be in orbit about each other in a binary system, or may be separate stars viewed by chance in almost the same direction in the sky. (i)...
  27. B

    Modeling a binary star system

    I am tasked with modeling a binary star system using VPython. The language itself is relatively irrelevant, as I can deal with the syntax. My problem is with the logic of it and how I should go about structuring the necessary calculations. Homework Statement A binary star system consists of...
  28. M

    Colliding Binary Star (GPE Problem)

    I was looking over my old physics course problems, and I can't figure out how I'm doing this one wrong. Homework Statement Two identical stars, each having mass and radius M=2*10^29 kg and R = 7 *10^8 m are initially at rest in outer space. Their initial separation (between centers) is the...
  29. D

    Binary Star System Period of Revolution

    Homework Statement (a) Consider a binary star system in which the two stars have masses M1 and M2 and the stars move on circular orbits separated by a distance R. Derive the formula for the period of revolution. (b) Suppose M1= 1.22M and M2= 0.64M (where M = mass of the sun) and R= 0.63...
  30. B

    Special Relativity and Binary Star Systems

    Homework Statement Suppose that you decide to look at a known binary star system. The system is too far away to resolve the individual stars, so it appears to be just one point of light. By looking at the spectrum of the system, though, you should be able to use the Doppler shift to determine...
  31. Z

    Apparent magnitude of a binary star system

    Homework Statement A binary star system consists of a hot main sequence star (m=0.5m) and a red giant (m=1.2m), the parallax of the system is p=0.0012". Calculate the apparent magnitude of the system. Homework Equations I have b1/b2 = 2.512^(m2-m1) and p=1/r The Attempt at a...
  32. C

    Observed planets in binary star L4 or L5?

    It seems to me, from my understanding of the Lagrange points, that a binary system with the appropriate mass ratio between stars could support planets in the L4 and L5 Lagrange points (I've encountered this, actually, in science fiction; Larry Niven put such a planet in the Procyon system for...
  33. L

    Binary Star System: Kinetic Energy of an approaching Comet

    A binary star system has two stars, each with the same mass as our sun, separated by 1.6x10^12 m. A comet is very far away and essentially at rest. Slowly but surely, gravity pulls the comet toward the stars. Suppose the comet travels along a straight line that passes through the midpoint...
  34. L

    Photometry: Determining a binary star system.

    Homework Statement By performing CCD photometry on a pair of nearby stars A and B we obtain their relative magnitudes in the V filter and their colors: Star A: mV = 8.70 , (B − V )= 1.30 Star B: mV = 11.90 , (B − V )= 1.81 Star A is known to be a of a main sequence K0V type, while no other...
  35. R

    Binary Star System: Calculating Occultation Angle & Eclipse Duration

    Homework Statement Two stars, S1 and S2, with effective temperature of Te,1=25000 K and Te,2= 2000 K and photospheric radius of R1=Rsun/100 and R2=50 Rsun make a binary system. If the Star S2 is in circular orbit around the S1 with revolution period of P=180 days (1 day=24 hours), and S1 has a...
  36. S

    Solving Binary Star Systems: Doppler & Kepler's 3rd Law

    Application of the Doppler effect and Kepler's 3rd law Homework Statement (*This isn't the exact wording from a textbook, just as I had copied it down) An eclipsing binary star system containing stars A and B in concentric orbits (about their common centre of mass) has it's maximum red- and...
  37. T

    How emission theory was disproved by de sitter binary star experiment?

    Actually I was studying on 2nd postulate of special relativity. There I saw Ritz's emission hypotheses says for an object moving directly towards (or away from) the observer at v metres per second, this light would then be expected to still be traveling at (c + v) or (c − v) metres. Now...
  38. C

    Find the position of the center of mass of the binary star system

    Homework Statement A binary star system consists of a star P and a star Q, of mass 4.0 x 10^10 kg and 2.0 x 10^10 kg respectively, separated 6.3 x 10^9 m apart. Star P and Star Q move in circular orbits with their centers at the center of mass which remains at rest. Find the position of...
  39. K

    How Do You Calculate the Distance Between Two Stars in a Binary System?

    Homework Statement 2 stars are separated by a distancce r, one star has mass 2/3M the other has mass 2M (M is a solar mass). The period of revolution is 5 years, calculate r. Homework Equations Fg=(GM1M2)/r^2 The Attempt at a Solution Ok so I know that the binary star...
  40. M

    Astrophysics- unresolved binary star system

    Homework Statement Consider an unresolved binary star at a distance of 500pc consisting of an A1V dwarf and a K0III giant star. compute mb and mv and B-V for this object we know the mass, luminosty, radius, Mbol , Mv, Te , and B-V for each individual star. Homework Equations...
  41. C

    Calculating the Mass of a Binary Star System

    mass of a star... given is a binary star system, with mass m1=6*1.99*10^30kg, radius =r1, v=270km/s, orbital period, T=1.7days... the other star of the binary system(compact and dense)with mass m2, and radius r2 orbits around a same common point... (r1>r2, G=6.67*10^-11Nm^2kg^-2)...
  42. P

    Finding the Masses of a binary star using the distance, angle and orbital period

    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? Homework Equations I am assuming that...
  43. J

    Binary Star System Homework: M1=1.24, M2=3.04, Epsilon=0.691

    Homework Statement Consider a binary star system in which the two stars have masses M1 = 1.24 solar masses and M2 = 3.04 solar masses. The period of star 1 is 142 yr. The eccentricity of star 1 is \epsilon = 0.691. Use G = 6.67259 × 10−11 Nm2/kg2, take the astronomical unit to be...
  44. J

    Solving Binary Star System Homework Problem

    Homework Statement I have to write a computer program to simulate a binary star system and I can not assume that the larger mass is stationary. I am given their respective masses, and the period of the system. I am just wondering how to find the write combination of initial velocity and...
  45. J

    Binary star orbital inclination

    This question has been bugging me... I've rephrased the question a bit so it shouldn't require much astrophysics knowledge to understand, just a bit of regular physics. Consider a binary star system. By doing some geometry based on visual observations of the positions of the two stars over...
  46. O

    Setting up binary star (light density based on distance) problem

    For my vector calc class we were given an assingment to do some stuff with a binary star system. You might note the lack of vectors and the lack of calc; this is because I am just having an issue with the setup. I am sure I can get the rest without assistance. We are given the two stars of...
  47. B

    Binary Star Explosion: Calculating Total Energy and Period

    Homework Statement Two individual stars in a binary system (m1=mo, m2=2mo) are in circular orbit about their common centre of mass and are separated by a distance ro. At some stage, the more massive star explodes - resulting in the two stars having equal mass after the explosion...
  48. T

    Planetary orbits in a Binary Star system.

    http://spaceflightnow.com/news/n0210/11planet/ This is the only discovered planetary orbit around a close binary star that I know about. I have some general questions about planetary orbits around or within close binary systems or even the further apart binary star formations or triples...
  49. Astronuc

    What Caused the Ejection of Mu Columbae and AE Aurigae from Orion?

    I was listening to the regional NPR station yesterday and hear a brief discussion of two binary systems. http://stardate.org/radio/program.php?f=detail&id=2009-12-26 Is this common? Is it plausible? I presume that some how the velocity of Mu Columbae and the other star traveling 'north'...
  50. S

    Binary Star system common period

    Homework Statement The questions are about binary star system. Homework Equations Why the two stars in a binary star system are always diametrically opposite positions? Why the two stars have common period? Why the inner star is more massive? The Attempt at a Solution For the...