Questions tagged [galaxy]

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

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2answers
852 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, ...
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1answer
117 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-...
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1answer
727 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 ...
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1answer
66 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 ...
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1answer
583 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 ∼...
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1answer
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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 ...
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1answer
94 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 ...
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1answer
445 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?
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2answers
335 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 ...
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0answers
186 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? ...
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3answers
426 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 ...
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2answers
385 views

Can we see the stars 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 Milky Way that we actually see with different telescopes. I know the Milky Way disk is ...
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1answer
409 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 ...
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1answer
1k 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. ...
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1answer
791 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?
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11answers
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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 ...
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1answer
50 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?
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484 views

Has the Milky Way collided with another galaxy?

Has the Milky Way ever collided with another galaxy? Or will the collision with Andromeda be our first?
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71 views

Star formation rate question

Could someone please tell me if this ratio is important in determining star formation rates? The ratio is : $$\frac{L_B}{L_{H\alpha}}.$$ Additionally, could someone please explain the implication ...
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1answer
164 views

How was the galactic plane established?

As pointed out in this answer the axes of galactic coordinates are defined such that galactic longitude and latitude (0, 0) point toward the galactic center. But then the plane defined by galactic ...
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1answer
406 views

Can you translate a GPS coordinate to a Galactic coordinate?

I am a complete newbie to astronomy and all the related. So if i say something stupid i am sorry. But i was wondering if it is possible to translate GPS coordinates like the following: ...
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50 views

How the observed deuterium abundance constrains big bang nucleosynthesis?

I know deuterium can be used as a good tracer to constrain the big bang nucleosynthesis. But can anyone tell me the in details how this is actually done?
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0answers
119 views

How to to compute the expected number of collisions between stars when Milkyway and Andromeda merged? [duplicate]

Can some one tell me how you can roughly estimate the number of collisions when Milkyway and Andromeda merged with each other. I know it is somehow related to the mean free path of the star. But ...
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3answers
159 views

Will we be able to see our galaxy if we travel far enough?

Will we be able to see our galaxy if we travel far enough? When we leave earth far enough, we'll be able to see Earth from distant, is it same with the galaxy? if we travel far enough, will we see the ...
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1answer
109 views

Extragalactic Magnetic Fields - General Information That I'm Missing

I have started studying Extragalactic Magnetic Fields, and mainly focusing on Biermann Battery Theory. I have gathered much information on other Dynamo Theories, as well as about our current ...
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2answers
356 views

Do elliptical galaxies look similar to globular clusters?

If we got close enough to an elliptical galaxy would it look similar to a globular cluster?
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1answer
1k views

Is this photocomposition of Andromeda's galaxy and the Moon accurate?

I recently saw the below image circulating around twitter/facebook/reddit. It is titled "Andromeda's actual size if it was brighter" One of the comments provides a link to another comparison provided ...
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1answer
113 views

How is the redshift of starlight precisely measured?

When galaxies move away from us (caused by the expanding spacetime) their light seems to show a redshift. But what is really needed for this? What time lap is for example needed to see a difference ...
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1answer
104 views

Metals and dust locked into planets

I wonder what is the contribution of metals and dust locked into planets, with respect to the amount in the interstellar medium (ISM). In other words, when we measure the metallicity and the dust mass ...
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0answers
99 views

Which physical quantity is the real/definitive tracer of galaxy evolution? [closed]

Which physical quantity is the real / definitive tracer of galaxy evolution? Let me explain better: if you aimed at understanding as much as possible about the evolution of galaxies and you had to ...
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1answer
90 views

Do boxy bulges indicate barred spirals?

Some face-on spiral galaxies show barred structure in their central bulges, whereas some edge-on spiral galaxies have boxy bulges. I wonder if there is any relation between these two. In particular, ...
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1answer
404 views

What can the total stellar mass of galaxies tell us?

The total stellar mass of a galaxy cannot be measured directly. Astronomers can infer it from the galaxy spectrum by stellar population synthesis. However, since high-mass stars dominate the spectrum ...
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1answer
60 views

Galactic revolutions relative to the age of the universe [duplicate]

If the universe is only 40 to 50 galactic revolutions old, how has it acquired its present state so "quickly" relative to this time scale?
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1answer
109 views

Could a dwarf galaxy host a star at the center instead of a SMBH?

I don't think this would be possible, but I'm curious, and as what ever query I googled I only found posts about black holes indeed existing, what black holes are, that even the Milky Way has a black ...
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1answer
83 views

Find a planet with incomplete information of a star chart [closed]

I am wondering why it was so hard to locate Luke in Star Was Episode 7, if you already have the small part of the map. Suppose we have a sector of our galaxy that roughly equals the one missing in ...
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3answers
207 views

Knowing time any where and any when

My question is if I put you down somewhere in the Milky Way galaxy in any given period of time, is there a way for you to tell when and where you are based on stars or constellations? Or some known ...
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1answer
136 views

The photos of the outer space

How did the humans take photos for the galaxies, black holes, stars, nebulas etc in the outer space?! I guess they went out of the Earth planet and nearly out of the Milky Way galaxy by space-ships ...
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5answers
16k views

Does the Milky Way move through space?

Does our galaxy moves through space? Or does it stay in a single location? If it does move, what causes it to move?
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6answers
15k views

How do we have photos of galaxies so far away?

A possible answer for this is that, light emitted from the galaxies travelled a billion miles all the way to earth, where the hubble space telescope picked up this light through its sensors, and was ...
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1answer
2k views

What are the chances of a star colliding with another during a galactic collision?

My specific example for the question is the future collision of the galaxies Milky Way (our own galaxy) and Andromeda in a couple billion years. The star in question is obviously the sun in this case. ...
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1answer
675 views

How did the object CO-0.40-0.22 get its name, and how is it distinct from CO-0.40-0.22*?

There seems to be three things described in the recent Nature Astronomy paper Millimetre-wave emission from an intermediate-mass black hole candidate in the Milky Way: Molecular cloud CO–0.40–0.22 ...
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2answers
115 views

Is it possible for galaxy clusters to interact?

Galaxies commonly interact and collide with other galaxies. Is it possible that clusters of galaxies similarly interact and collide? Have people tried to study this phenomenon previously? I couldn't ...
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1answer
651 views

How is the bar formed in a Barred-Spiral galaxy?

How does the bar in a barred spiral galaxy form? What prevents it from being spirals all the way down like water spiralling down a plughole?
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1answer
110 views

What are evidences of stationarity of rotation of galaxies

Recently I have found the article Does There Really Exist the Problem of the Dark Matter in Spiral Galaxies? which states that dark matter does not exist because astronomers are wrong assuming ...
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2answers
208 views

Rule of Exception in All Nearest Objects

I once heard of a strange phenomenon, but now cannot find anything about it on the Internet. I might be looking for the wrong keywords or misremember some relevant aspect. So maybe someone here can ...
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1answer
247 views

Would our galaxy appear as a spiral when seen from the Andromeda galaxy?

I'm wondering how our galaxy is tilted with respect to the Andromeda galaxy. Seen from the Andromeda galaxy, what would our galaxy look like? Would it appear as a spiral, or would it be seen ...
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1answer
273 views

Do most astronomers think that Andromeda will collide with Milky Way?

Most astronomers say it is likely to happen. Is this true? Are there any scientists that reject this?
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2answers
217 views

What differentiates a “group of rogue stars” from a galaxy?

According to Wikipedia, a rogue star or intergalactic star is not gravitationally bound to a galaxy. But according to a citation on the same Wikipedia page, the first intergalactic stars were ...
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4answers
3k views

What are the criteria for the classification of galaxies?

There are lots of galaxies, for example, the Milky Way and so on. These galaxies consist of lots of stars. I want to know how galaxies are classified. Is it only by their shape that is caused by ...
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1answer
134 views

What have we learned from the observation of most distant galaxies [closed]

We have seen galaxies around 13 billion years old. Since these galaxies formed so early in the history of the known universe, are there observables about these galaxies that are apparently different ...

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