Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [galaxy]

Questions regarding systems of large numbers of stars held together by gravity.

1
vote
0answers
28 views

What's the easiest way to get 3D-positional data of galaxies

Is there a database with cartesian coordinates (x, y, z) of galaxies? I only need positional data and calculating that using degrees and redshift for all galaxies could take a while and would be ...
2
votes
1answer
66 views

What would the night sky look like from a planet at the centre of a ring galaxy?

If there were an observer on a planet in the centre of a ring galaxy (omitting the galactic core) what could they expect to see in their night sky? I am currently under the impression that their night ...
1
vote
1answer
57 views

Can we learn anything from observing galaxies edge-on, like the Spindle Galaxy?

I was reading about NGC 5866, sometimes referred to as the Spindle Galaxy. It's notable because of its inclination relative to Earth; we see the disk from the side, rather than face-on. The difference ...
3
votes
2answers
64 views

Why is the metallicity of elliptical galaxies low?

As far as I understand, metallicities of old stars are usually low and those of new stars are usually high. If elliptical galaxies form after merger of galaxies, then surely that means the elliptical ...
2
votes
3answers
55 views

Catalog of Galaxies in the Visible Universe

I have seen the Gaia project from here which is about mapping the stars in the Milky Way galaxy. But I'm wondering if there is any open data on the positions (or something like "positions" since it ...
3
votes
0answers
44 views

How active was the Milky Way in its first 5 billion years?

When I look into the history of the Milky Way, it seems like the Milky Way has been the pinnacle of stability. It seems highly likely that our galaxy has eaten several smaller galaxies/dwarf galaxies ...
1
vote
0answers
19 views

How the Galactic objects are moving? [duplicate]

We know that the Galaxies are moving very fast, not only the Galaxies other known and unknown objects in the universe, are moving. But when it was started where is the starting point, and how it move ...
12
votes
3answers
120 views

Does the rotation of galaxies precess?

Does the axis of a galaxy as a whole "wobble" the same way that the Earth does? If so do we have any idea how much or how fast the Milky Way is doing so?
7
votes
0answers
56 views

How much greater is the star density in our galactic bar?

As much as we know about the bar of our galaxy, How much denser is it in the galactic bar than the "normal" density at the same radius? Is it just a tiny overdensity (a few percent?) or is it, say, "...
2
votes
0answers
43 views

Galactic rotation speeds - questions from a non-astronomer

Are there any observations that more distant galaxies appear to rotate more slowly than closer galaxies? What methods are used to measure the rotational speed of galaxies? (both orbital speed ...
7
votes
2answers
3k views

Do all galaxies have a black hole in the center?

Would I be correct if I stated that all galaxies have a black hole in the center? Since other galaxies orbit around a center point in a galaxy - the barycenter, right? - I would assume at this point ...
2
votes
0answers
34 views

What are the odds for any two bodies to collide during the milky way-Andromeda collision? [duplicate]

When the two main galaxies of the local group will collide, it is very unlikely for stars to collide with another, but how unlikely is it in the initial collision? And over the whole merging process?
1
vote
2answers
81 views

Are there any stars that one day we could collide with?

I'm not talking about tomorrow but in the far far future could we say our Sun could collide with another star or otherwise within our current detectable range?
1
vote
1answer
18 views

DSO carthesian coordinate estimations

I'm more in the CS based stack exchange, but this question prompted me to come in here. I've been compiling a large set of ephemerides for solar system, stars with mag > 6.8, exo planets etc, and I ...
1
vote
2answers
62 views

Movement of the Sun in space

Does the Sun undergo any cycles or revolutions approximately every 24,000 years or 8.6 million years? In Hinduism it is believed that the Sun revolves in an elliptical orbit around a large mass at ...
4
votes
1answer
35 views

How can I estimate the M/L ratio from a fitted SED on a galaxy?

This answer (here in the forum) provides background to my question: https://astronomy.stackexchange.com/a/5953 I am trying to understand the process in which a stellar population synthesis (SPS) is ...
5
votes
2answers
76 views

Number Density of Dark Matter Halos

Is there a way to calculate the expected number density of Dark Matter Halos above a given mass, in a certain redshift range, and in a certain area?
4
votes
1answer
129 views

What would stargazing be like at the edge of our galaxy?

Let's say, for the sake of speculation, we acquire the technology necessary to travel to the outer edge of one of the spiral arms of our galaxy. We go to a star in this "outer rim" and land on a ...
9
votes
1answer
115 views

Why is M87's relativistic jet bent?

The end of the relativistic jet that emerges from M87 looks curved like a hook. See here: Data from the VLA array show more of the jet: at the far end, the jet makes a complete 180 degree turn ...
3
votes
1answer
111 views

What is the escape velocity of our Galaxy relative to?

I've been thinking that everything has a relative escape velocity, if it has Mass, seemingly. You can escape orbit around the earth by accelerating enough. You can escape the orbit of the sun by ...
3
votes
1answer
65 views

Studies of isotropy from different ends of the visible universe?

Have there been studies to compare structures that are 26 billion light years distant (i.e. from one side of the observable universe to the other) to search for faint differences?
2
votes
1answer
62 views

How bright is Andromeda's center, in magnitudes per square arcminute or something similar?

I'd like to know how bright the Andromeda galaxy's core is as an extended object, not the total integrated brightness. Ideally a contour map or scan across the center might show brightness in ...
5
votes
2answers
154 views

Is it possible to view the Andromeda galaxy with the naked eye in Greece?

I am living in the northern hemisphere in Greece and in class 4 area (light pollution scale). Is it possible to see the Andromeda galaxy with a naked eye?
5
votes
1answer
69 views

What distance is considered 'close' for the 9th nearest neighbor of a galaxy?

I am currently working on determining the nth nearest neighbors of a large survey of galaxies. I am not an astronomer by trade, so I am unsure of interpreting some of my results. I have discovered for ...
3
votes
0answers
29 views

Why Tidal Tails in Disk Galaxies, but not in Ellipticals?

Why do tidal tails result from only disk galaxies but not ellipticals. I understand that tidal tails are results of gravitational interactions not strong enough to completely plunge out the material ...
5
votes
2answers
82 views

What does the ']' in the spectral line “CIII] 1909 Å” mean?

The above emission line, as I understand, is a useful probe of early star-forming galaxies. However, I do not understand what the ']' to the right of the 'CIII' means. I could not find any online ...
4
votes
0answers
311 views

Which galaxy is closest to the center of the KBC void?

I was reading up on Bootes void and came across this list of the largest voids in the visible universe, and apparently the one we're in, the KBC void, is not only the biggest, but damned-near ...
0
votes
0answers
29 views

Moving galaxies that exceed the speed of light [duplicate]

I read in a article that there are galaxies moving faster then the speed of light. My understanding of this that is not the galaxy that is moving away from us at the speed of light or faster, but the ...
1
vote
1answer
39 views

What factors determines the size of a galaxy?

Recently i saw a post comparing sizes of different galaxies with the Milky Way. The largest one being the Ic 1011.What makes this galaxy so large? What factors decide the size of a galaxy?
8
votes
3answers
201 views

Can “rogue” supermassive black holes be made this way?

Could two galaxies (one big and one small)intersect at a velocity to allow the smaller black hole to escape but not the galaxy around it?
0
votes
2answers
182 views

What is the fastest a galaxy or other body has been measured to (or can) travel?

Our solar system travels at an average speed of 515,000 mph and our galaxy at 1.3 million mph through space. What is the fastest moving body in space recorded and the fastest can a black hole or ...
2
votes
2answers
102 views

Are galaxies expanding away from us at more than the speed of light? [duplicate]

If you go to the following video, at this certain time: https://youtu.be/Iy7NzjCmUf0?t=435 you will see that the narrator says: "We simply don't know what else is out there because the light from ...
7
votes
1answer
78 views

How far would EGSY8p7 be away now?

Apparently EGSY8p7 is the object with the longest light travel distance, 13.2 gly or a redshift of z = 8.68 (Wikipedia). So the light took 13.2 billion years to travel to us from that object, but we ...
2
votes
1answer
63 views

Escape velocity of Milky Way galaxy [duplicate]

I'm wondering that what would be the escape velocity of our Galaxy?
5
votes
3answers
272 views

Why do photos of Earth always have a black background?

if we are in the milky way, and people are able to take photographs from Earth that look like this: Then how come almost all of Earth's photos look like this? In the first photo, we are seeing what ...
3
votes
2answers
77 views

Are magnetic field lines Spiral for Spiral Galaxies? If no, then how it look like topologically?

I am an undergraduate doing summer project at USO. I am working on Sun's Magnetic field model. I got spiral graph for that, which looks like any spiral Galaxy. Do you think that there is some ...
1
vote
0answers
30 views

Efficiently calculating power spectra from galaxy catalogs

I am dealing with a problem which requires calculating either the correlation function or the power spectrum. At times, the 2-point-correlator seems the better route, at others, the PS. Right now I am ...
1
vote
0answers
69 views

Correctly scaling Power Spectrum and Correlation Function of Galaxies from Mock Catalogues

I'm currently writing a code to compute the two-point correlation function of a set of galaxies. As I work with a loooot of galaxies, it was suggested to me not to do it in real space, but to compute ...
5
votes
1answer
120 views

Generating random galaxy catalogs for correlation functions

The galaxy correlation function, when computed directly from a galaxy catalog, relies on computing a randomly generated counterpart catalog. When dealing with a simulated galaxy mock-catalog, where ...
2
votes
0answers
39 views

What's the profound reason(s) why the star formation rate drives the scatter of the mass-metallicity relation in galaxies?

Since decades it's well known that a correlation between stellar mass and metallicity (Z; both stellar and gas-phase Z, but here I focus on the gas-phase Z) exists (e.g., Tremonti+04; analysis of >...
0
votes
2answers
142 views

What other galaxies can be seen with the naked eye in the night sky?

What other galaxies can be seen with the naked eye in the night sky? Can we see any other galaxy besides Andromeda and Magellanic Clouds?
2
votes
1answer
302 views

Do we see stars from other galaxies (not Milky way) in the night sky with the naked eye?

I saw reports that only Andromeda Galaxy and Big/Small Magellanic Cloud galaxy stars could be visible with the naked eye (how many stars would be from them out of a few thousand visible?) This ...
4
votes
1answer
94 views

How many galaxies can be seen in a given patch of sky

Similar to the question asked here, but my question is not about what can be seen with the naked eye but rather what might be seen if pointing my Newtonian reflector (full specs outlined below) at an ...
3
votes
1answer
88 views

Question from Introduction to Modern Cosmolgy by Andrew Liddle

The exact question goes like this: In the real Universe the expansion is not completely uniform. Rather, galaxies exhibit some random motion relative to the overall Hubble expansion, known as their ...
1
vote
0answers
27 views

Looking for a Dwarf Galaxy < 500 L.y. in Diameter, which is not a Satellite / Companion, or is at least 500 000 L.y. away from another Galaxy

My goal is to learn about an example of a Dwarf Spheroidal or a Dwarf Irregular Galaxy which is not a Satellite / Companion Galaxy (or is at least 500 000 L.y. away from another Galaxy), and doesn't ...
2
votes
1answer
32 views

Relationship between galactic rotation and stellar lifetime

I have read that the lifetime of stars is much less than the period of rotation for a spiral galaxy. For example https://www.coursera.org/learn/evolvinguniverse/lecture/wlYhz/the-origin-of-spiral-arms ...
11
votes
6answers
6k views

What will happen to the shape of a galaxy when a super massive black hole lying in its center dies(evaporates out)?

What's at the Center of the Milky Way? In this article it is said that a supermassive black hole lies in the center of milky way galaxy. At its center, surrounded by 200-400 billion stars and ...
4
votes
1answer
179 views

Tests for code that computes two-point correlation function of galaxies

I'm currently writing a code to compute the two-point correlation function of a set of galaxies. As I work with a loooot of galaxies, it was suggested to me not to do it in real space, but to compute ...
0
votes
1answer
71 views

Redshifting restframe SED

I have a template spectral energy distribution (SED) at z=0. I want to shift the template SED to an arbitrary redshift (z>0), how to do this in python?
3
votes
1answer
37 views

Photometric redshift

I have decided to do undergraduate thesis on "estimating photometric redshift" or something related to this using machine learning. Reading previous papers, I have come to know that work has been done ...