42 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 ...
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  • 90.9k
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 ...
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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 ...
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15 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 ...
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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 ...
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  • 478
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 ...
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8 votes

How do scientists know there are about 300 billion stars in a galaxy and there are about 100 billion galaxies?

The way it works is as follows. We do detailed studies of stars in the solar neighbourhood. This establishes the local density of stars and the mix of masses they possess (called the stellar mass ...
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  • 117k
7 votes
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Estimates of exoplanets distribution consistent with current data

As you've correctly mentioned observation biases play a huge role in current understanding of planetary populations. Let's have a look at a slightly outdated plot (age 2 months) that shows us the ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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5 votes
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Do all stars have the potential to have life supporting planets?

Great question. The goldilocks zone is usually defined in terms of a region where the equilibrium temperature of the planet lies between some temperature limits (these temperature limits are somewhat ...
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5 votes
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Pulsation Modes of Cepheids

Cepheid pulsations The basic description of the mechanism behind Cepheid pulsations is given here: The accepted explanation for the pulsation of Cepheids is called the Eddington valve,[38] or κ-...
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  • 2,692
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} ...
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  • 117k
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 ...
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  • 1,160
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 ...
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  • 774
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 ...
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  • 1,402
5 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 ...
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  • 4,336
5 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 ...
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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 ...
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  • 117k
5 votes

When calculating the mass of stars, is it considered that additional mass could be added because of pair-production?

The mass of a star is determined by its gravitational effects, not by summing up the components that give rise to that gravity. If we were to do the latter, then we would have to include all the mass ...
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4 votes
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The defintion of star/planetary/solar system

I think it's largely a matter of personal preference. Some people will want you to be technically correct and only use "solar system" to refer to the Sun and the objects that are under its ...
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  • 34.1k
4 votes

Potential Re-Capture of Rogue Planets

The processes by which planets can be removed from their parent stars are discussed in some detail by Davies et al. (2014). These include direct ejection through interactions with other stars in dense ...
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  • 117k
4 votes

How many nested stable (1 Mio years) orbits are theoretically possible?

Yes, it's possible to have many nested levels, all stable. Each nested orbit needs to be inside the Hill sphere of its central body in order to be stable. You can't nest any further when the Hill ...
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4 votes
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Why is the exoplanet HD 131399Ab so hot?

It's a giant planet and it's young. p.3 of the paper you reference gives a likely age of 16 million years. The heat arises from gravitational contraction and it would be a similar temperature even if ...
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