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

3
votes
1answer
62 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
36 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
139 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
55 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
23 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
70 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 ...
3
votes
0answers
82 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
27 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
29 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
184 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
160 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
97 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
71 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
51 views

Escape velocity of Milky Way galaxy [duplicate]

I'm wondering that what would be the escape velocity of our Galaxy?
4
votes
3answers
194 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
70 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
26 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
57 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
80 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
33 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
81 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
138 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
80 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
68 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
25 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
29 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
94 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
46 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
36 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 ...
3
votes
2answers
63 views

A rough analytical expression for the Milky Way's radial mass distribution?

I found the image below in Space.com's article This 3D Color Map of 1.7 Billion Stars in the Milky Way Is the Best Ever Made, although it is not the map mentioned in the title. The caption for this ...
5
votes
2answers
79 views

Names of specific galaxies in Hubble's XDF

I'm working on a little side project that traces and identifies galaxies in Hubble's XDF using OpenCV. This is my current progress with tracing the more prominent galaxies: I was wondering if there ...
1
vote
2answers
241 views

Is this an actual nebula or CGI?

I'm thinking of putting a large wall paper with an astronomical motive on a wall. I found quite a number of wall papers by various vendors, but most of them are obviously computer generated images, ...
0
votes
0answers
116 views

What's the stellar density at points of the Milky Way?

I'm trying to work this out and getting conflicting numbers... (All based on numbers from Wikipedia) On the one hand, the galaxy is between 100k and 180k light years across, and has between 100 and ...
1
vote
1answer
71 views

What are six different methods to measure distances in Astronomy?

What are six different methods to measure distances in Astronomy in regards of their respective range in terms of astronomical objects? So far I can name 4: Parallax method, radar ranging, main-...
0
votes
1answer
234 views

How to convert from Cartesian J2000 coordinates to Cartesian Galactic coordinates?

I'm using a star database (the HYG database) which has xyz positions and velocities for the stars. This has +X towards the vernal equinox, +Z towards north celestial pole, +Y towards Right Ascension 6 ...
0
votes
1answer
48 views

What's that limit, where we start to see infrared galaxies?

All the nearby galaxies we see come in visible range, many are visible from ground based telescopes. And the farthest galaxy that hubble discovered recently, 13.4 billion light years away is in infra ...
9
votes
0answers
271 views

Is it “weird” that all disc galaxies rotate once every billion years?

In a recent paper (Cosmic clocks: A Tight Radius - Velocity Relationship for HI-Selected Galaxies by Meurer, et al.), it was noted in the conclusion that: [This] implies a constant orbital time of ∼...
1
vote
1answer
174 views

Coordinates of known black holes in our Galaxy (Milky Way)

There are some articles in wikipedia with the list of known (or candidates) black holes here and list of nearest black holes. Also there is a map of Milky Way. My question is where can I get ...
3
votes
1answer
75 views

Information speed and our view of the cosmos

It is common knowledge that when we look at the stars we look back in time. And most stars are thousands of lightyears away from each other. The information that photons cary about the position of a ...
-2
votes
1answer
125 views

How does space time differ between galaxies? [duplicate]

Does the gravity wells differ enough between galaxies to have different speeds in space time? How much slower in space time would the biggest galaxy have compared to the Milky Way?
1
vote
2answers
199 views

How does space time differ within a galaxy?

Not the same question but is similar to other marked duplicate. How much time dilation does the center of a galaxy can exist and sustain human life from our point of view? What would a day equal to ...
5
votes
0answers
101 views

Gravitational eddies across the galaxy?

I read about natural gravitational eddies that travel in a wave that black holes have. They also have a strong magnetic field. Does those eddies follow magnetic field lines of the rotating black hole? ...
1
vote
3answers
225 views

Is the Milky Way seen as how it looked millions of years ago?

The distant an interstellar object is, the more time is required for light to travel, which is known, measured as light years. So are the farthest stars and gas clusters in the Milky Way seen as how ...
5
votes
1answer
146 views

Can we see the stars the at the edge of the Milkyway?

This question proved much more difficult to formulate than I initially imagined. It concerns how far out in the Milkyway that we actually see with different telescopes. I know the Milkyway disk is ...
4
votes
1answer
115 views

In galaxy optical spectra, why are Hbeta and Hdelta sometimes absorption lines?

I've heard that $\mathrm{H\beta}$ and $\mathrm{H\delta}$ lines in galaxy spectra might be either emission lines or absorption lines, is that correct? From Wikipedia, Balmer lines are usually emission ...
3
votes
1answer
239 views

How to determine age of an old galaxy

Recently a galaxy A1689B11 was discovered, having an age of 11 billion years. How that age was determined ? News sources reported that some cutting edge technology with gravitational lensing was used. ...
6
votes
1answer
261 views

How many stars are between Milky way and Andromeda?

Are there some stars between those two galaxies? In photos is only black. And if so, how many we could find there?
41
votes
11answers
15k views

Why do Black Holes in the middle of galaxies not suck up the whole galaxy?

As stated in several sources, it's supposed that in every galaxy there is a black hole in the middle. My question is, why do these black holes in the middle of galaxies not suck up all the ...
0
votes
1answer
43 views

Would there be any difference for our solarsystem to be not in the Milky Way? [duplicate]

Guessing, the solar system would be taken out of our galaxy of any reason, would there be any difference to the live on earth or even to the mechanics in within our solar system?