87
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Why do Black Holes in the middle of galaxies not suck up the whole galaxy?
You shouldn't think of black holes as "sucking things in". Black holes interact with matter through gravity, just the same as any other object. Think of our Solar System. All the planets orbit around ...
- 3,166
85
votes
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Does the Milky Way move through space?
Does the Milky Way move through space?
Yes it does.
I'm very fascinated with space, although I don't have a degree or any formal education, I'm still very in love with everything about it and ...
- 2,547
67
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Does the Milky Way orbit around anything?
The object which has less mass and gravitational pull orbits around the nearest object with more mass and gravitational pull.
Actually, both the heavier and the lighter object orbit around their ...
- 18.4k
66
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How did Hubble know the red shift difference between "moving away" and "old"?
The "redshift" measurements that Hubble used to determine his law are based on looking at the spectrum of distant galaxies. That is, splitting the light coming from the object in its ...
- 2,800
54
votes
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How do we have photos of galaxies so far away?
There are two reasons that often — but not always — light from galaxies millions and even billions of lightyears away make it through the Universe and down to us:
Particle number and particle size
...
- 39.6k
51
votes
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How are constellations intact if the stars are rotating around galactic nuclei?
Yes, the shape of the constellation does and will change over time. All the stars have their own peculiar velocities and have some random motion which over time will ruin all the constellations. ...
- 1,095
46
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What keeps galaxies together?
The galaxy is kept together by the combined mass of the matter in the galaxy, of which the supermassive black hole is a negligible part. There are galaxies that don't have a central black hole (such ...
- 129k
44
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Are there any stars that orbit perpendicular to the Milky Way's galactic plane?
The Sun and most of the other stars are in the bulging disk of the Milky Way galaxy, but about 1% of the galaxy's stellar mass is in the galactic halo. The halo also includes 50 globular clusters and ...
- 16.7k
41
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Does the Milky Way move through space?
Galaxies move through space with velocities of the order of a several 100 km per second; small velocities for small groups (~100 km/s; e.g Carlberg et al. 2000) and large velocities for rich clusters (...
- 39.6k
32
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Why does the 70-solar-mass black hole in the LB-1 system challenge current astrophysics?
There're several pieces of information one needs to understand this.
Although stars more massive than 70 solar masses exist, when they become black holes, they usually lose mass in the process. The ...
- 4,851
32
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What keeps galaxies together?
This was studied many years ago.
Not only do galaxies have to hold together, but there also has to be enough matter to hold it tightly enough to spin at the speed it turns. (Imagine swinging an object ...
- 1,030
32
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How hard is it to find the Sun's "sisters?"
Here are the problems/issues:
Most stars are born in clusters/associations but a cursory investigation of cluster demographics with age reveals that the vast majority of clusters do not survive to old ...
- 162k
31
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What will happen to the shape of a galaxy when a super massive black hole lying in its center dies(evaporates out)?
Presumbably we rotate beacuse of the BH.
No. The galaxy is being held in one piece due to its own total gravity. The black hole is only a small fraction of that. Basically, the BH doesn't matter.
...
- 18.4k
31
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Can a photon orbit around a galaxy?
No.
The milky way has a lot of mass — about 1.5 trillion times the mass of the sun.
For light to orbit it would have to follow a null geodesic, ie the photon sphere at 1.5 times the Schwarzschild ...
- 129k
30
votes
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Do the axes of rotation of most stars in the Milky Way align reasonably closely with the axis of galactic rotation?
There is very likely to be a random scatter.
Unlike planets orbiting the Sun in the Solar System, most of the stars in the Galaxy did not form at the same time as the Galaxy itself. There is therefore ...
- 162k
29
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Why are there so few supernovae in M31 (Andromeda)?
The low supernova rate in M31 can be directly attributed to the fact that the galaxy's star formation rate is much lower than the Milky Way's.
Andromeda is currently in a relatively quiet phase in ...
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29
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Is it possible for the Milky Way and Andromeda to get ejected upon colliding instead of merging?
A full merger may not occur on that timescale. The encounter in 4.5 billion years will take place but the galactic centers may be far enough apart that it is a "glancing blow". Regardless, ...
- 162k
29
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How are we observing the newly discovered "dark galaxy" J0613+52, if it has no stars and is so far away from other galaxies?
The low surface brightness survey at the GBT is looking for H(I) emission, i.e. emission from neutral hydrogen atoms (for example see O'Neil 2023).
The most obvious signature they use is the 21 cm ...
- 162k
27
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What is the probability of a photon from one of these galaxies hitting the James Webb detector?
Probability without lensing
The probability of any one photon of an ensemble of isotropically emitted photons is indeed proportional to ratio between the area of the detector, and the area of the &...
- 39.6k
27
votes
Could a galaxy be the sun of a planet?
We are IN a Galaxy. It doesn't feel very warm to me when I go outside at night, compared with direct sunlight!
Your basic problem here is the enormous distance between stars compared with the distance ...
- 162k
26
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How do we have photos of galaxies so far away?
As Rob Jeffries says, the universe is mostly empty space. A photon can easily travel thousands of light years without interacting with anything. Most of the interaction would occur when photons ...
- 4,504
25
votes
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Is it possible that a star is the center of a galaxy?
It won't stay in the center for long.
Galaxy nuclei are full of stars. Any star passing by will exchange momentum with the central star and will perturb its position. Stars of similar mass will be ...
- 2,879
25
votes
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Was the total glaciation of the world, a.k.a. snowball earth, due to Bok space clouds?
Bok globules are unlikely as explanations for Snowball Earth episodes, mainly because of their duration. The Huronian lasted 300 my, the Sturtian 57 my, and the Marinoan 22.2 my. This is much longer ...
- 15.7k
24
votes
What will happen to the shape of a galaxy when a super massive black hole lying in its center dies(evaporates out)?
Answer: Not much
The Milky Way's central black hole (BH) masses about 5 million suns, while the galaxy masses 100 billion to a trillion suns. Consequently, the central BH is pretty much irrelevant ...
- 7,690
23
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How do we have photos of galaxies so far away?
There's a misconception in your question I don't think the other answers have addressed.
If light emitted from the galaxy travels in all directions, then how
is it that we can still map out the ...
- 330
23
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Milky Way vs Milky Way Galaxy
I think that distinction is wrong, or at least not commonly accepted.
We live in a disk-shaped galaxy, which is interchangeably called "the Milky Way", "the Milky Way Galaxy", or &...
- 39.6k
23
votes
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Milky Way vs Milky Way Galaxy
Milky Way vs Milky Way Galaxy
I recommend recognizing and honoring the distinction!
The two words being interchangeable is a narrow view that only one well versed in Astronomy can have, and doesn't ...
- 30.7k
23
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Is it possible that a star is the center of a galaxy?
The short answer is, not really. Galaxies are unlikely to have a star at the "center".
When you say a star is at the center, what you're really trying to say is that that star is the ...
- 15.1k
Only top scored, non community-wiki answers of a minimum length are eligible