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1500 questions
21
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2 answers
Does seeing a gravitationally lensed/magnified galaxy imply that they could also see us as well?
Does an observer in that galaxy see our galaxy magnified as well?
2080
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What would happen if a small black hole fell into a star?
Let's say you created a cannon that can shoot small black holes and you shoot it at some star.
Would the star just turn into a black hole silently? Or rather first destabilize and produce a last dying blast like supernovas do?
For high enough…
Filip Sondej
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21
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3 answers
How can telescopes see anything at all?
I'm impressed that we have any telescope imagery at all. Take the images we have from the "Pillars of Creation".
The Pillars of Creation is in the Eagle Nebula, some 7,000 light-years away from Earth. It's estimated its size is about 4 light…
Victor Debone
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21
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4 answers
Why doesn't the Moon, like the Sun, turn bright red when it's close to the horizon?
Why does the Moon, being close to the horizon, turn red only slightly, or not at all?
Aren't the causes that lead to the coloring of the Sun (atmospheric refraction) are also true for the Moon?
In addition, the spectrum of moonlight is more…
Vladimir Orlov
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21
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2 answers
Why is Venus's atmospheric pressure 75 times that of earth when carbon dioxide is only 1.5 times heavier than air?
Obviously I have forgotten by basic college chemistry. I am getting carbon dioxide at 1.87kg per cubic meter and compared it to nitrogen and oxygen but source says carbon dioxide is 1.5 times heavier than air. Let's go with that and since the earth…
Sedumjoy
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21
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2 answers
What equation tells you how far in space you can go from a point and return?
We know that hubble expansion increases the distance between points in space, and that the cosmological event horizon represents the distance from the observer at which objects are receding faster than the speed of light. We also know that objects…
user52978
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21
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6 answers
Why doesn't the IAU definition of "Planet" disqualify Mercury and Venus as planets?
Here's the IAU definition of a planet (source):
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 hydrostatic equilibrium (nearly round) shape,…
Schroeder
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21
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2 answers
How do we know that a comet passed by earth 50,000 years ago?
This article (https://gothamist.com/news/a-green-comet-is-sailing-over-new-york-and-earth-for-the-first-time-in-50000-years) claims that a comet will pass by earth soon for the first time in 50,000 years. How do we know that this exact comet passed…
coco
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21
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2 answers
Are heavy elements equally distributed throughout the Solar System?
I want to know if heavy elements are distributed roughly evenly throughout the Solar System or if they are (excluding the Sun) concentrated mostly in a particular area, such as the inner part. Would heavy elements be rarer in the Kuiper Belt and…
Wenver
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21
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5 answers
Why does electron degeneracy pressure not stop massive star collapse?
I was thinking a little bit, and never asked myself the following. If white dwarfs do not collapse, because electron degeneracy pressure stops the star from collapsing by its own gravity, and this is due to the Pauli exclusion principle, then why…
martín canullán
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21
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1 answer
Why doesn't dark matter clump strongly in the center of galaxies, since it doesn't feel either radiation pressure or the Pauli exclusion effect?
Dark matter is described as being spread not only throughout a galaxy, but also around it in a halo of some sort that extends far beyond the visible parts of the galaxy...
In fact, dark matter haloes are often described as being twice or more the…
Kurt Hikes
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21
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1 answer
What is the probability of a photon from one of these galaxies hitting the James Webb detector?
In the image of the SMACS 0723 galaxy from the James Webb space telescope can be seen distorted galaxies whose light has taken about 13 billion years to reach the telescope.
On the face of it, the probability of a particular photon launched from one…
DrMcCleod
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21
votes
7 answers
Could light be dark matter?
Is it possible that light itself is dark matter? I am speaking of photons (e.g. visible light, infrared, ultraviolet, etc...). I realize light is understood to be massless, but it is obvious it at least contains energy because we can see with it…
Jonathan
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21
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2 answers
Where in space would the Earth and Moon appear to be the same size?
If I'm directly in between the Earth and Moon, what distance from the Earth would I have to be so that the Earth and Moon have the same apparent size?
How big would the moon appear compared to it's normal size?
cowlinator
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21
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4 answers
Where is it possible to observe the Moon for 24 hours?
I wrote an astronomy olympiad yesterday and there was one task I couldn't figure out an answer to:
Estimate at what latitudes it is possible to observe the Moon for at least 24 hours. Under what conditions is it possible to observe the phenomenon…
ALiCe P.
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