Astronomy Stack Exchange
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How can maser emission be unpolarized?

I was reading that: However, unlike Galactic sources such as W3(OH), the emission is unpolarized and the 1667 MHz line is stronger than the 1665 MHz line. but how is this possible? Does not the 1665 MHz line and 1667 MHz line correspond to a…
Mathews24
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Are black holes expected to contain the same ratio of dark matter to regular matter as the rest of the universe?

Are black holes expected to contain the same ratio of dark matter to regular matter as the rest of the universe? I've heard that dark matter is distributed in halos around galaxies. Does that make it less likely to be ingested into a black hole?
joseph.hainline
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Relatable comparison of VY Canis Majoris to the Sun?

I was trying to describe how vast the largest known star is to someone and felt I wasn't quite able to relate the scale difference. I know it's roughly 1500 times larger than the sun. Anyone know of a good analogy?
Jacxel
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Mass of black holes compared to parent star

What is the range of percentage mass of parent star left in a stellar black hole directly after its formation? What factors determine this number for a specific case?
Frank J
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Is the moon "perfectly" tidally locked and, if not, how long would it take us to observe it's rotation?

I have a general understanding of how and why a body in space can be tidally locked to it's planet or sun and I'm aware that our moon is in such a state. My question is, if our moon once had a rotation, has it slowed down to a point where across the…
RLH
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Do solstices and equinoxes shift over time?

Right now, I think the winter solstice is around December 21. Has it always been around this date constantly? Since the earth's axis's 23.45° tilt will be on the exact opposite side in 13000 years (or was 13000 years ago) due to precession, it'd…
Mickael Caruso
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Is the Apophis asteroid a concern for planet Earth?

I was watching the TED lecture How to defend Earth from asteroids , and the speaker Phil Plait spoke of the possibility of this asteroid hitting Earth. Is this really a concern?
Larian LeQuella
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Why is there a supermassive black hole at the center of every galaxy?

According to https://en.wikipedia.org/wiki/Sphere_of_influence_(black_hole) the gravitational sphere of influence of a supermassive black hole is really limited compared to the size of its hosting galaxy, why then is there one at the center of every…
betolink
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Why can't our Sun be a binary with Jupiter as a T or Y dwarf?

I just learned about Brown Dwarfs, they are "failed" stars, they narrowly missed the stellar mass mark. I learned that Y Dwarfs have temperature as low as 80 Fahrenheit (The first one found by WISE observatory), why aren't those not called a…
fahadash
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How can neutron stars have gaseous atmospheres?

Neutron stars can have small atmospheres. However, they also have extremely strong gravitationally pulls. Shouldn't the all the gas molecules be drawn to the star's surface, and become solids under the immense pressure? Maybe I'm thinking about this…
Sir Cumference
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Can dark matter be found in the shape of planets, galaxies etc.?

If dark matter has gravity just like normal matter, does that mean it can also form planets, solar systems and so on? Any answer will be appreciated.
Vase Dodevski
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Why are there so many seemingly blue-shifted galaxies in deep space

NASA released this image of deep space. The way light shifting vis-a-vis universe expansion is supposed to work is by making the furthest galaxies appear mostly red-shifted. But NASA's image shows somewhat of an even balance between blue and red…
Adl A
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Is it safe to watch solar eclipse's reflection in water?

There will be a solar eclipse soon at my area... naturally I want to watch this with my son. Is it safe for us to watch the solar eclipse's reflection in the water? There is a swimming pool near my house and I plan to watch it there.. is it safe to…
Rosdi Kasim
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Why are planets spherical?

I am a complete novice when it comes to astronomy, but someone asked me the above question casually. It seems as though planets are all roughly spherical, whereas other celestial bodies aren't necessarily. Is there are particular reason for this?
LanceLafontaine
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Is Earth unique in its fairly clear atmosphere?

So, we have surface pictures from two alien planets, Venus (captured by the Venera 13), and Mars (captured by the rover). Both of these pictures appear to be very dusty. For Venus we see strong storms; that makes sense. However, the Martian air also…
Sidney
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