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43 votes
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Closest star system to Alpha Centauri?

The sun is the nearest star to Alpha Centauri (unless you count Proxima Centauri, which is really part of the same system). There is a very small and dim pair of brown dwarfs, called Luhman 16 that ...
James K's user avatar
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37 votes

Why are there no stars visible in cislunar space?

It is a matter of exposure and dynamic range. A sensor like a camera can only handle inputs in a certain range of intensities, and much of photographic skill (or smart presets) is about mapping the ...
Anders Sandberg's user avatar
33 votes

Are stars attracted to one another by their magnetic fields?

They behave just as other magnetic fields do - whether the force is attractive or repulsive would depend on the relative orientation of the fields. But magnetic forces are negligible compared with ...
ProfRob's user avatar
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20 votes

Why are nearby stars like Proxima Centauri and Barnard's star not visible to the naked eye?

John's answer is correct. For a few more details: Stars brightness works out to roughly the 4th power of their relative mass. This falls off a bit for very large stars, but for smaller stars it's ...
userLTK's user avatar
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16 votes

Why is detecting brown dwarfs difficult?

Brown dwarfs have historically been difficult to detect (directly) simply because of how faint they are. Typical luminosities may range from $10^{-3}L_{\odot}$ to $10^{-5}L_{\odot}$ depending on ...
HDE 226868's user avatar
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14 votes
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Why are there no stars visible in cislunar space?

Anders's answer is entirely fine, but I'd like to add some extra information. As evidenced by the transcripts, reflected Earth light is quite strong even at this distance: The earthshine coming ...
Luaan's user avatar
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13 votes
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Why can't a half-illuminated planet support life at all?

The phenomenon you are referring to is called "tidal locking", it occurs when the orbital period or one revolution of the planet is roughly equal to the time it takes to rotate in on its ...
Arjun's user avatar
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12 votes
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What is the upper bound of number of stable interacting stars in a star system?

There is no true upper bound. You could argue that a galaxy is a vast multiple star system, with hundreds of billions of stars. Natural galaxies are not perfectly stable (random encounters eject stars ...
Anders Sandberg's user avatar
12 votes

Why can't a half-illuminated planet support life at all?

Pierrehumbert (2010) modelled the possible climates of Gliese 581g. Although that planet has since been shown to probably not exist, the model of a planet with similar characteristics should still ...
gerrit's user avatar
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10 votes
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Can a Nova occur outside of a binary star system?

To form a classic nova you need a white dwarf to be accreting matter, specfically hydrogen, onto its surface. The "obvious" source of this matter is another star that is very close to the ...
James K's user avatar
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9 votes
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It's 12 June 2023, almost 11 PM... location: Chitral, KPK, Pakistan. What constellations, celestial objects can you identify in this picture. Help

The photo shows Lyra, Cygnus, and other nearby constellations. The diffuse glow to the right of center is the Cygnus Star Cloud, part of the Milky Way. Here is a Stellarium rendering edited to match: ...
Mike G's user avatar
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9 votes

What determines the edge/boundary of a star system?

I don't think there is a formal definition, but a working one would be that the system is gravitationally bound. This does impose an outer edge because of the tidal field of the Galaxy and other ...
ProfRob's user avatar
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8 votes

Did the Grus star get expelled from the Milky way because it was accelerated by the Sagittarius A black hole?

The linked reference 59 in the wikipedia article you quote (Koposov et al (2019)) closes with the question The fact that S5-HVS1 was ejected with a velocity almost twice that of all other known HVS ...
planetmaker's user avatar
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8 votes

What determines the edge/boundary of a star system?

Additional, or rather complementary, to the important 'gravitationally bound' criterion which applies to solid bodies like comets, asteroids and other outer solar system small bodies, one can go a ...
planetmaker's user avatar
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7 votes
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Nomenclature of Interstellar Objects and Stars

Names are common enough for solar system bodies, but generally stars don't have names, they have identifiers from various catalogues. In the case of Pulsars. they are named by their location in the ...
James K's user avatar
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7 votes
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Does the Final-Parsec problem apply to stellar collisions?

The "final parsec problem" describes the difficulty in getting two supermassive black holes close enough together that their merger timescale due to gravitational wave emission becomes ...
ProfRob's user avatar
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6 votes
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Has Science observed and recorded a stars birth?

The star formation process from giant molecular cloud to unobscured protostar is thought to take about a million years. So the answer is no. Similarly, there are very few large scale physical ...
ProfRob's user avatar
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6 votes
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What differentiates a "group of rogue stars" from a galaxy?

It is just a poor choice of words. The comment refers to a discovery paper by Ferguson et al. (1998), where they used a very deep image in the Virgo cluster to establish that there were an excess of ...
ProfRob's user avatar
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6 votes
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Fractional contribution of secondary star

It just means that in a star that is an unresolved binary system (i.e. the light you receive comes from both stars), the secondary contributes a fraction of that light. This fraction could be ...
ProfRob's user avatar
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6 votes
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Why are stars still distant from one another?

The initial star formation regions were regions that have a high enough mass density to form a star. The density of the early universe was not constant at different locations. Some regions had high ...
Natsfan's user avatar
  • 4,494
6 votes

Why are stars still distant from one another?

As jmh has answered, stars naturally form at large distances from each other. To add to the answer, what is the reason for this particular distance scale? If we imagine a very large, homogeneous cloud ...
Anders Sandberg's user avatar
6 votes

Nomenclature of Interstellar Objects and Stars

The rules from the the IAU for official designations are posted neatly here. More casual names, like the Black Widow Nebula, are not standardized, as far as I know. For astronomical objects outside of ...
Daddy Kropotkin's user avatar
5 votes
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Trisolar syzygy and it's effects on the planet

Is it just for the spoiler? My guess is that the 3 suns aligned create a sufficient gravity field for the outermost parts - less well attached - of the planet (atmosphere, people, buildings) to be ...
J. Chomel's user avatar
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5 votes
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Color changing celestial body near the moon

Judging by the time of your post, I would probably say the star you saw was Aldebaran as it was very close to the moon on that night. It's the brightest star in the constellation Taurus so is easily ...
MCG's user avatar
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5 votes
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What is the tidal radius of the Sirius system?

The tidal radius for a star or collection of stars near the Sun and on a circular orbit (matches Sirius reasonably well) is given by (e.g. Pinfield et al. 1998) $$R_T \simeq \left( \frac{GM}{2(A-B)^2} ...
ProfRob's user avatar
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5 votes
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How are solar systems found again after being discovered?

I think you're overestimating how quickly stars appear to move as viewed from Earth. Once a telescope like Kepler identifies a solar system around a star, we know where that star is. Stars have ...
Cody's user avatar
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5 votes
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Sun like star in our milkyway?

There's a whole Wikipedia page about it. https://en.wikipedia.org/wiki/Solar_analog If you don't want Alpha Cen A, then 18 Sco might be the one.
ProfRob's user avatar
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5 votes
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How do the orbits of Nu Scorpii and AR Cassiopeiae work?

I checked the Multiple Star Catalog for data on these systems. It has hierarchical information on Nu Scorpii and AR Cassiopeiae, which I also used for this answer. I'll try to explain the orbital ...
HDE 226868's user avatar
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5 votes
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Virial ratio behaviour

The ratio $T/\Omega$ tells you about the acceleration of the system - or more specifically, the second derivative of its moment of inertia - it does not tell you about the velocity. If the system ...
ProfRob's user avatar
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