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 ...
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32
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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 ...
- 146k
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 ...
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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. ...
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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 (...
- 146k
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 ...
- 146k
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 ...
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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 ...
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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 ...
- 35.9k
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 ...
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12
votes
Accepted
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 ...
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12
votes
Accepted
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 ...
- 146k
10
votes
Accepted
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 ...
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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 ...
- 1,078
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 ...
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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 ...
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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 ...
- 1,078
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 ...
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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.
...
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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 ...
- 146k
8
votes
Accepted
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 ...
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8
votes
Accepted
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 ...
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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 ...
- 146k
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 ...
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7
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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 ...
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7
votes
Accepted
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 ...
- 18k
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) ...
- 115k
7
votes
Could there be a planet at the barycenter between two or more stars revolving around each other?
No. Such an arrangement is at best "metastable". That is, although there are periodic solutions to the three body problem (stable orbits) an infintesimal perturbation (eg the proverbial ...
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