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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
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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5 votes

Are there naked eye binary stars with periods less than 100,000 years?

I queried the 4th Catalog of Orbits of Visual Binary Stars for systems with both components having $V<6$ and period $<10^5$ years. There were 77 examples, but the widest separation is 17.5 ...
ProfRob's user avatar
  • 155k
5 votes
Accepted

How long would we survive an approaching neutron star?

The following was too long for a comment, but I don't claim it is an answer. The first part is easy. At a relative velocity of 500 km/s, the neutron star will race, probably almost unperturbed, ...
ProfRob's user avatar
  • 155k
4 votes
Accepted

Extend CDF to physical range

The data do not demonstrate that the eccentricity can practically cover the whole range from 0 to 1. You have no binaries with $0.0 < e < 0.2$ and no binaries with $0.64<e<1$, so it seems ...
ProfRob's user avatar
  • 155k
4 votes

For binary stars, what is the average semi-major axis?

Take a look at Tokovinin (2014) From binaries to multiples II: hierarchical multiplicity of F and G dwarfs for a discussion of the statistics of binary pairs and the issues in estimating things like ...
James K's user avatar
  • 124k
3 votes

Is Proxima Centauri a Planet?

Per the IAU definition: A "planet" is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ...
James K's user avatar
  • 124k
3 votes

Keplers laws and this question

The correct version of Kepler's third law is $$(M + m)P^2 = a^3$$ where $Ma' = ma''$ and $a = a' +a''$, where $a''$ is the distance of mass $m$ from the centre of mass. The result follows from ...
ProfRob's user avatar
  • 155k
2 votes

Resource suggestions?

You should read the AAVSO tutorials, especially the tutorial on light curve data processing, but you should also read the observing tutorials, so you get a better idea of where the data comes from (...
James K's user avatar
  • 124k
2 votes

Are multiple stars actually more common than singles?

You might also like to consider the probability that a number of the singleton stars that are visible might have once been part of a binary system and have devoured their companion. There may also be ...
Michael Mcgarry's user avatar
2 votes

Keplers laws and this question

Kepler's third law is too much like the equation in the exercise to be useful in proving it. Instead, assume a circular orbit (a' > 0) and let the centripetal force on the planet equal the ...
Mike G's user avatar
  • 18.7k
1 vote

Keplers laws and this question

Kepler's third law is in general given by $$G (M+m)\cdot P^2 = 4 \pi^2 a^3$$ where $G$ is the gravitational constant, $M$ and $m$ the masses of the two bodies, $P$ their orbital period and $a$ the ...
Thomas's user avatar
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