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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 color indicating the method by which they've been detected. Separations are roughly normally distributed in $\log a$, peaking at a typical separation of tens of AU....


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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 contract without heating up too much. i.e. $$M_J \propto T^{3/2} \rho^{-1/2},$$ where $\rho$ is the cloud density. Thus if the cloud density can increase but ...


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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 brown dwarf, an object needs to be large enough to have undergone deuterium fusion in its core. This requires a mass of at least 13 Jupiter masses. The other is ...


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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. It is a pair of stars with similar size and visual magnitude, of about 3.6. Their orbital period is about 169 years, but the orbit is eccentric, e = 0.88. They ...


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There is no observational evidence that the sun is a member of a binary (trinary, or more) star system, where "star" means an object that is at least ~80 times the mass of jupiter and emits energy/light via standard hydrogen fusion. Some evidence that people point to is that the majority of stars in the Galaxy (perhaps 60% or so) are binary. However, that ...


17

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 relative wind speed. An analytic approximation to the accretion rate, known as Bondi-Hoyle accretion, goes as the inverse cube of the relative speed. In its ...


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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 of 80 years, but because it is so close (1.34 parsec), the semi-major axis is a whopping 17.5 arcsecond. The two stars are currently separated by 5 arcseconds ...


14

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 companion star. X-ray binaries and microquasars are particularly notable types. The compact object doesn't have to be a black hole - neutron stars also sometimes ...


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Few important points about WISE: it was able to detect anything with a temperature above 70-100 K, whereas the coolest brown dwarfs are in the 500-600 K range (the coolest was discovered by WISE itself, see Mainzner et al., 2011); it was able to detect objects larger than 1km up to 3 AU from the Sun, or objects of 2-3 Jupiter masses in a distance up to 7-10 ...


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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 collapse of the original gas cloud into a protostar. Angular momentum is conserved, so as the extremely large cloud slowly contracts, it spins faster. After ...


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Well, if they have an angular momentum with respect to their center of mass, or in other words , if they are in orbit, gravitational collapse is not the issue. This is what happens when three bodies are in orbit around each other. Don't get disappointed so soon. There is indeed a way to avoid this. If the three bodies are of comparable mass, and one of the ...


9

This is a difficult question, It's been changing through the years and it's difficult to calculate accurately. Now it's know that this percentage changes depending on the star type and ranges from 50% for Sun like stars up to a 80% for type O stars. Fonts: http://www.space.com/1995-astronomers-wrong-stars-single.html (2006) http://www.space.com/22509-...


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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 α UMi Aa, (the former is close in, the latter is further out). There are two further stars: α UMi C and D. These stars are thought to have formed before α UMi ...


9

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 singe pendulum. A single pendulum swinging back and forth is a linear system with motion that is repeating and predictable. Similarly two bodies orbiting each ...


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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 systems with two or more stars. So a binary system, a triple system, and a quadruple system are all multiple star systems.


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Okay! Here are some of the popular targets, search for the season of visibility yourself please. The above list describes the angular seperation between the stars and also the magnification required to resolve it, both explicitly. So, this list is not only for amateurs, but there are some intermediate ones which you can try if you have a good enough ...


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I just found the answer to my question at this place: http://astronomynow.com/2015/02/18/suns-close-encounter-with-scholzsstar/ Here is the answer: Currently, Scholz’s Star is a small, dim red dwarf in the constellation of Monoceros, about 20 light-years away. However, at the closest point in its flyby of the solar system, Scholz’s Star would have ...


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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 other kind" in the XKCD comic) P-type: The planet orbits around both stars of the binary


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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 written around 2000 and appeared in 2002: that's a really long time ago in terms of all the amazing new instruments which have become available. For example, ...


6

Following the convention $\mathbf{r} = \mathbf{r}_2-\mathbf{r}_1$, $M = m_1+m_2$, in the center-of-mass frame we have, by definition, $$\begin{eqnarray*}\mathbf{r}_1 = -\frac{m_2}{M}\mathbf{r}\text{,}\quad&\mathbf{r}_2 = \frac{m_1}{M}\mathbf{r}\text{.}\end{eqnarray*}$$ Hence, $\ddot{\mathbf{r}} = -GM\hat{\mathbf{r}}/r^2$ implies that the individual ...


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I don't have enough reputation to comment... I think this might help you understand the formation or binary and more stars systems. This of course is not the only possible method but it might explain the systems with big mass differences. As the initial rotation speed increases (marked in the videos as beta) you will see how the protoplanetary disk breaks ...


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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. Step 1: Google Scholar is your friend I start out using Google Scholar. This is much like Google, but rather than returning any old website, it specifically ...


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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 stars, with rather more uncertain values and smaller statistical numbers for more and less massive stars. The best contemporary review of binarity for main ...


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The distance between Sirius A and B is between 8 and 31.5 AU and even when Sirius A becomes a red giant it will be still above 6 AU. Such distance is too large and does not allow Sirius B to accrete significant mass, almost all mass lost by Sirius A as a red giant and later AGB will escape into space. Sirius B may become a recurrent nova due to some ...


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In general those binaries will be hard to detect, but there is no reason why they wouldn't form. A whole class of objects, X-Ray binaries are in fact thought to be hosting a pair of BH and non-BH objects. The idea here is that the X-ray luminosity originates from mass accreted from the companion through Roche-Lobe-overflow. The mass from the companion or '...


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Prior to the discovery of gravitational wave sources, the only confirmed stellar-sized black holes, were those detected in binary systems with more "normal" stars. These were most detected via X-rays emitted by hot material that is accreted from the "normal" companion. The two main categories are high-mass and low-mass X-ray binaries: in the former, the ...


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From its RV graph alone, with no other information, you cannot calculate inclination. This is why RV velocity measurements are typically reported as "$v \sin{i}$", because what you're actually measuring is the orbital velocity projected along the line of sight. Without other information, you cannot disentangle the orbital velocity from the viewing angle. ...


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Sirius (α Canis Majoris, 06h 45m, −16° 43′) You could try Sirius B, which is a white dwarf orbiting Sirius A around their common centre of mass. Sirius is one of the closest stars to Earth, and Sirius B has a 50 year orbital period. At maximum separation the white dwarf is about 30 AU from Sirius A, which should allow you to separate them with a good ...


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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 are several main ways for a binary star system to form from a molecular cloud. The most widely-accepted model at the moment is the fragmentation hypothesis, ...


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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 table and select "Binary Flag" This will now show a boolean flag that indicates if the star is known to be part of a binary (or multiple) system. In the ...


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