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38 votes
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How far apart are stars in a binary system?

Distances ($a$) between binary stars vary wildly, from the order of the radius of the stars, to more than a light-year! The plot below (from here) shows a compilation of several surveys, with the ...
pela's user avatar
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32 votes
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Why are there so many binary systems?

Collapsing gas clouds fragment into multiple cores because the Jeans mass, that determines the minimum mass that becomes gravitationally unstable to collapse, becomes smaller if the cloud is able to ...
ProfRob's user avatar
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31 votes

Why can't our Sun be a binary with Jupiter as a T or Y dwarf?

But why can't Jupiter be a Y Dwarf who is in the binary relationship with the Sun? There are two reasons: One is that Jupiter is too small to have ever undergone fusion of any sort. To qualify as a ...
David Hammen's user avatar
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28 votes

Are there any double stars that I can actually see orbit each other?

𝛾 Vir (12h 42m, –01° 27′) Probably Porrima, $\gamma$ Vir, is the best candidate for most observers in the Northern Hemisphere to see changes in a binary orbit, particularly using a small telescope. ...
amateurAstro's user avatar
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18 votes
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Metallicity in gravitational wave astronomy

As you say, metallicity in this context refers to the proportion of the interstellar medium a star forms from that consists of elements heavier than helium. It can be expressed as a (mass) fraction (...
ProfRob's user avatar
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18 votes
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How would a person know if a planet is orbiting a binary star?

The light from the two stars would be Doppler shifted in a sinusoidal pattern (for a circular orbit). The signals from the two stars would be in anti-phase and would oscillate at the orbital period of ...
ProfRob's user avatar
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17 votes
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Will Sirius B start accreting from A and become a supernova type Ia?

Will Sirius B start accreting? Yes, it is doing so now. Sirius A will have a wind and some of that wind will be captured by the white dwarf. The effectiveness of wind capture is a strong function of ...
ProfRob's user avatar
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16 votes

Are there any double stars that I can actually see orbit each other?

α Centauri (14h 40m, –60° 50′) The most obvious visual multiple system, where orbital changes can be observed is Alpha Cen A+B, (together with Proxima Centauri). The A/B system has an orbital period ...
ProfRob's user avatar
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15 votes
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Binaries consisting of a black hole and a non-black hole?

Black hole and main sequence star/giant star We can observe binary systems containing a black hole by looking for emissions from accretion disks which may form when matter is transferred from the ...
HDE 226868's user avatar
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13 votes

How are binary star systems created?

There are two main theories for the formation of binary stars - one accepted, and one mainly deprecated. The fission hypothesis. The fission hypothesis states that the binary system forms after the ...
HDE 226868's user avatar
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12 votes
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What do the words "p-type" and "s-type" mean?

"Satellite type" and "Planet type". The terms seem to have been coined by Rudolf Dvorak in 1982 paper "Planetenbahnen in Doppelsternsystemen" Due to the fact that ...
James K's user avatar
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12 votes
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Effects of a binary star system on a tidally locked planet

The "three-body" problem and its stability are still an unsolved problem in general. There are papers that do long term integrations of planet orbits in binary systems to study their ...
ProfRob's user avatar
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11 votes

Are multiple stars actually more common than singles?

Too long for a comment: There is one ambiguity you are going to have to deal with, because nobody agrees what “star” means. Suppose that you see three points of light in the sky, and then with a ...
Martin Kochanski's user avatar
10 votes
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Do main sequence stars in binaries transfer mass by Roche lobe overflow?

Yes. An example would be the Cataclysmic Variable stars (CVs), where the donor star (often in the main sequence), loses material via Roche Love overflow onto a compact white dwarf companion. The other ...
ProfRob's user avatar
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9 votes

What's the name for [the other kind of planet] in a binary star system?

I don't know about names for the planets, specifically, but the orbits are called S-type and P-type: S-type: The planet orbits around one star, and the host star has a binary companion (i.e., "the ...
J. O'Brien Antognini's user avatar
9 votes

How many actual stars are Polaris?

Polaris consists of multiple stars, α UMi Aa is the main star. It is a supergiant, and a cepheid variable. α UMi Ab and α UMi B are smaller (but still larger than the sun) and both are in orbit with ...
James K's user avatar
  • 123k
9 votes

Why are there so many binary systems?

Two massive bodies orbiting each other form stable orbits. This is called the "two-body problem." Add a 3rd body to the system and the results are unstable orbits. It's akin to the motion of a ...
Kyle's user avatar
  • 421
8 votes

Multiple Star-system percentages

Your best bet for finding relevant information on this is to look up actual published papers. I'll walk you through my research process to help in the future, as well as provide the results I found. ...
zephyr's user avatar
  • 15k
8 votes

How many actual stars are Polaris?

It's worth noting that in many cases, if not most, we simply don't know the exact answer to such excellent questions as the one you ask. Note that the book you mention (ISBN-13: 978-0471409762) was ...
Fattie's user avatar
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8 votes
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Could the word "multiple stars" include binary stars?

I'm not aware of any official (i.e., IAU) definition of a multiple star system. However, as someone who used to do research in that field, I would interpret multiple star system as encompassing ...
J. O'Brien Antognini's user avatar
8 votes

How far is the nearest (known) black hole from our solar system? Is there an official list?

According to table 2 of Corral Santana (2015) (The BlackCAT catalogue of stellar mass black holes in X-ray transients - which other than gravitational waves, is how they are found), the nearest known ...
ProfRob's user avatar
  • 153k
8 votes
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Why is a giant planet around a tiny star unusual when binary stars are common?

It's important to realize that binary stars form much differently than planets do. Assuming that both stars form in situ (i.e. excluding scenarios where one is captured from outside the system), there ...
HDE 226868's user avatar
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8 votes
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How many exoplanets have been found around binary stars?

Go to the exoplanets.org database. Top left hand dropdown menu - select "Stars" You get a table listing all the known stars with exoplanets. Click on the big plus sign in the top right hand of the ...
ProfRob's user avatar
  • 153k
8 votes

What exactly is the orbital period value of Sirius binary star system?

Bond et al. (2017) measure the orbital period of the Sirius system to be $50.1284 \pm 0.0043$ years. I believe this is the most precise and accurate value (I cannot find any more recent papers, with ...
ProfRob's user avatar
  • 153k
8 votes

Are multiple stars actually more common than singles?

That's a good question with a non-intuitive answer. The main point is: one has to distinguish stellar systems from stars themselves. Consider an essemble of 30 stellar systems. 33% or 10 of them are ...
planetmaker's user avatar
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7 votes

How many stars can stay close to each other without collapsing?

At least 7. We currently know of two star systems with 7 stars: Nu Scorpii and AR Cassiopeiae. The two have different structures, both of which are complicated but appear to be stable on stellar ...
HDE 226868's user avatar
  • 36.6k
7 votes

Multiple Star-system percentages

The answers are out there. The problem with your question is that the answer is highly mass-dependent. The mass dependence is also somewhat uncertain, with the best empirical knowledge for solar-type ...
ProfRob's user avatar
  • 153k
7 votes
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Can a binary star optically "orbit" a planet?

Planets don't orbit stars. Stars don't orbit planets. Whenever there are two bodies bound by gravity, they are both orbiting their common center of mass. For example, both the Earth and the Moon ...
Florin Andrei's user avatar
7 votes
Accepted

Binary Star Initial Speed

You will always get a "stable" orbit if the stars have less than escape velocity relative to each other. (unless you are modelling the stars as having non-zero radii so they can collide) ...
James K's user avatar
  • 123k

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