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

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Stars in star clusters in SMC and LMC

Is there any catalog or any paper published in any journal that enlists the stars discovered under which ever star-cluster of Small Magellanic Cloud (SMC) they belong to? There is one for Large ...
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2answers
359 views

How many stars are visible to naked eyes around Equator area?

In the best sky conditions, we can see about 44,000 stars in the sky. But what if I am located around Equator area? How many stars I can see? From what I know, the number of stars I can see should ...
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1answer
70 views

Distance of extra-galactic Classical Cepheids

There have been many questions and answers about finding the distance of a star from the earth. But as I did some research on the net, I found that we have specific approaches for finding the ...
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2answers
76 views

What is the difference between LMC and SMC?

Apart from the obvious difference as suggested by their names that the Large Magellanic Cloud is 'larger' than the Small Magellanic Cloud, what are the other differences between them? Do give all the ...
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2answers
95 views

What is meant by “Radial Direction” of a galaxy?

There is a scientific journal article having a line: "In order to study the star formation scenario in the radial direction of the LMC...." What is meant by 'radial direction' of a galaxy ?
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0answers
31 views

Torus of the AGN

How much do we know about the structure of the torus surrounding the galactic nuclei? Is the shape defined or still under speculations? And are there different structures for this torus possible i.e., ...
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1answer
145 views

Dark Flow: statistical limits on existence

Dark Flow has been thrown around as a term a lot lately, especially with the latest Planck results. New Scientist reported last year that it was now statistically improbable, but the paper by Atrio ...
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2answers
100 views

Metallicity of Celestial Objects: Why “Metal = Non-metal”?

Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium. Note: The other elements may or may not be actual ...
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1answer
37 views

Active Galactic Nuclei - categorisation on the basis of observer?

As we know AGNs are considered to be one of the most luminous objects to be found in the cosmos.Based on the observer, for instance on Earth, we categorize them on the basis of the angle between the ...
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3answers
112 views

Pulsation Modes of Cepheids

There are various modes of Cepheids like single modes: fundamental (F), first overtone (1O), and likewise. And then we have double modes: F/1O, 1O/2O etc. triple modes: 1O/2O/3O etc. ...
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2answers
96 views

What does “Normalized to Si 10 to the power 6” mean?

I'm writing a space game that I want to give a more "realistic" feel. When looking for a reference as to distribute elements in planets (for mining, etc) Instead of finding the more usual percentage ...
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1answer
88 views

Active Galaxies

I've read that there are 4 distinct although related forms of AGs : Seyferts, Quasars, Radio and Blazars. Are there any other forms possible? Also do these forms ever intermix to give something new?
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3answers
94 views

Quasars and SMBH

Quasars are known to contain supermassive Black Holes at their cores. So does that mean that the number of quasars is equal to that of the SMBHs out there?
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1answer
116 views

why are galaxies different in color?

whether its in movies,television,real-life or some planetarium different galaxies are shown in different color. For ex:- Milky way is always seen in Blue where as Andromeda gives out a bit reddish ...
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2answers
155 views

How can we predict a Big Crunch when all galaxies are moving further apart?

I've read that the further away a Galaxy is from us the faster it moves away. By this logic how can scientists predict that there will eventually be a big crunch when every piece of matter is ...
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1answer
146 views

What is the probability that there is life on other planets?

I would like to know, from a mathematical point of view what is the probability that 1) There is organic life on other planets 2) There are advanced species like us or even greater than us on other ...
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3answers
172 views

Is there a fundamental difference between a small galaxy, and a large star cluster?

For instance, If a large globular cluster were somehow ejected from its galaxy, and was observed by astronomers, would they call it a galaxy, or would there be characteristics of the star cluster that ...
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1answer
106 views

Is there another explanation, apart from the doppler effect, for the redshift observed in distant galaxies?

On episode 10 of the original Cosmos TV series, Carl Sagan mentions that some scientist don't agree that the redshift observed in distant galaxies is evidence of the big bang, stating that probably ...
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5answers
10k views

What will happen to life on Earth when Andromeda and Milky Way galaxies collide?

It is said that, Andromeda and Milky way galaxies are coming close to each other with the speed of approx $400000 \ km/hours$. They will be together in the next $4 \ billion years$. What will ...
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2answers
112 views

Apogalacticon and Perigalacticon

What is the length of the apogalacticon and perigalacticon of the Sun and Milky Way? The general terms seem to be apoapsis and periapsis. My greatest efforts at Googling have failed miserably. If ...
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4answers
169 views

What is the speed of light relative to (in space)?

From what I understand the universe is expanding faster than the speed of light and accelerating so that it's possible that a given galaxy: $A$ will no longer be visible to another given galaxy: $B$. ...
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3answers
135 views

How fast is the universe expanding?

I've hear several theories stating that the universe is expanding faster than the speed of light, others claim that the universe expands faster the further away you measure it. Which of this is ...
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2answers
143 views

Age of the universe

A Galactic year is estimated to be around 250 million "terrestrial" years. That means there will be about 4 rotations per billion years. And age of the universe is estimated to be near 13.8 billion ...
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4answers
377 views

Do solar systems have to evolve in a galaxy?

Is it possible for a solar system like ours to exist and evolve apart from all other star systems and galaxies. Sort of like a stand alone solar system or rogue solar system for lack of a better name. ...
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2answers
266 views

Galaxies are moving away from each other then how Milkyway and Andromeda galaxy coming towards each other?

The Andromeda Galaxy is approaching the Milky Way at about 684000 mi/hours, making it one of the few blueshifted galaxies. The Andromeda Galaxy and the Milky Way are thus expected to collide in about ...
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2answers
117 views

Can we know whether any distant galaxy is moving away in same direction or in opposite direction w.r.t. our galaxy?

The Hubble law states that the recessional velocity of a galaxy is proportional to its distance from us. It takes redshift and angular sizes (for distance) of the galaxy to determine velocity, and ...
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2answers
1k views

Was the Milky Way ever a quasar?

Is there any evidence that the Milky Way could have been a quasar in it's early history? Is it thought that most galaxies come from quasars?
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1answer
188 views

Do stars of a galaxy change their positions relatively to each other?

Complete astronomy noob over here who would be happy if he get a simple answer (and who is also aware that this may be not possible)... I've learned from a tv documentary that the stars at the edge ...
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1answer
339 views

Explaining Dark Matter and Dark Energy to layman

With my little knowledge, I know this: Dark Matter The center of a galaxy controls/attracts its objects (stars, planets, comets etc.) towards itself because of gravity. But the mass of the center of ...
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1answer
187 views

Computing the Sérsic profile of a galaxy from jpg images

I am trying to calculate the Sérsic profile of various galaxies from the SDSS based on the images provided by the galaxy zoo site. I am doing this as part of a kaggle competition on using machine ...
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1answer
222 views

Is it possible that we see our solar system as a star?

A few days ago I just read here that our galaxies (one of which we are part of) move or expand faster than light, And read here that light we see from stars is extremely old, maybe more than several ...
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2answers
81 views

Are Gamma Ray Bursts of galactic or extragalactic origin?

I read about the 1995 Lamb-Paczynski debate on whether GRBs are galactic or extragalactic in origin. With our current experimental evidence, have we found whether GRBs are galactic or extragalactic?
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2answers
41 views

what is the highest throughput astronomy project in pixels?

I was having a discussing about big scientific projects with colleagues, and I postulated that astronomy is still one of the scientific fields with biggest projects per amount of data dealt with, ...
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1answer
88 views

Do galaxies have a preferred orientation?

This article: http://physicsworld.com/cws/article/news/2011/jul/25/was-the-universe-born-spinning asserts that the universe was "born spinning" and that there is a preferred rotation direction for ...
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1answer
178 views

Where is Voyager 1 (or 2) going? In which direction?

Knowing it has exited the solar system, is it traveling in the direction of the center of the galaxy, away from it, orbiting it, or maybe even going perpendicular from the disk-shaped galaxy?
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1answer
209 views

Our galaxy, the Milky Way, forms part of a galaxy group called The Local Group. What are the parameters that dictate what a galaxy group is?

Are there different classifications or just the one? How does our galaxy group compare with others?
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1answer
177 views

How do we know Milky Way is a 'barred' spiral galaxy?

In reference to the question, "How can we tell that the milky way is a spiral galaxy?" The answers there clearly sum up the question asked. But Milky Way is not just a spiral galaxy. It is further ...
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1answer
104 views

How do we calculate the escape velocity of galaxies?

How do we calculate the escape velocity of galaxies? Do we have to know the total mass? What is the escape velocity for Milky Way?
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2answers
318 views

Why are galaxies disk shaped?

I always see galaxies in "disk" shape in pictures. It is like, there is a rotational movement on a plane and the system is balanced by the pulling-in gravitational force which prevents the stars to ...
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1answer
151 views

How do scientists know there are about 300 billion stars in a galaxy and there are about 100 billion galaxies?

Just to think about this is mind boggling. But how do scientist get these numbers? What technology/system/theory do they they use?
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2answers
260 views

How are Galaxy Super Clusters Generated

I have seen pictures of clusters of galaxies, usually used in regards to theories of dark matter and galaxy formations. One of the most famous ones has the perceived shape of a stick-figure. If I am ...
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1answer
2k views

How many stars and galaxies can be seen naked eye?

How many of the luminous dots that we see naked are galaxies and not stars from our galaxy? I immagine that the majority of the luminous points that we see naked eye during the night, are actually ...
5
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1answer
185 views

What do we know about the lifecycle of the Milky Way (or any other spiral galaxy)?

I know that the Milky Way will collide with Andromeda in the distant future but based on what we know so far there is a supermassive black hole in the center of each galaxy and thus the Milky Way will ...
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2answers
1k views

How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it?

How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it? We know the Sun is orbiting the galactic center every 225 million years. But how far are we from the ...
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3answers
725 views

How long until we cannot see any stars from other galaxies?

Since all the galaxies are moving further away from each other at a faster and faster rate, eventually we won't be able to see stars from other galaxies. How long until we can't see stars from other ...
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1answer
102 views

Have we observed any rogue/wandering stars?

Do we know (have we observed and cataloged) any rogue star, being not part of galaxy, but drifting somewhere in inter-galactic space? I know that determining if a star is a part of galaxy or not is a ...
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2answers
1k views

Why is our solar system “tipped” about 63° with respect to the plane of our galaxy?

Our own solar system is "tipped" by about 63 degrees with respect to the plane of the galaxy. Has it ever been researched or is there any scientific theory which could explain the reason why our solar ...
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2answers
2k views

How many planetary systems exist in our galaxy?

For many years scientists have studied our own solar system and modern technology allows them to look deeper and deeper into space. Knowing the Sun is only one of a few billion stars in the Milky Way ...
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2answers
150 views

How often does Earth cross the galaxy regions with higher supernovae activity?

According to Summa Technologiae, a book by a Polish author Stanisław Lem that based his science fiction novels on scientific research of the era, the Earth crossed in the moment of forming of life the ...
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2answers
159 views

Which galaxy is receding from the Milky Way the fastest? What is known of the mechanism behind its recession?

Galaxies are always in motion relative to the Milky Way. My question is, which galaxy is receding the fastest from our viewpoint? What is the theorised mechanism that causes this?