Questions regarding systems of large numbers of stars held together by gravity.
Questions tagged [galaxy]
791 questions
22
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2 answers
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?
Stu
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22
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4 answers
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 leap out of the galaxy. What is the physical reason…
hkBattousai
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17
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How many galaxies have been discovered?
I know Andromeda is our nearest galaxy. But how many known galaxies have been discovered and what are they?
Unicorn
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13
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1 answer
How do Spiral Galaxies become flat?
Our galaxy has been described as roughly the shape of a pizza and the Andromeda galaxy, though I've never heard it described that way, appears similarly disk shaped. Spiral galaxies make up (roughly) about 60% of the observed galaxies in the…
userLTK
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Why do we see galaxies with their actual spiral shapes?
Since the actual position of stars is relative, and we see the light they emitted long time ago, and one galaxy has thousands of millions of stars, and those stars can be separated by hundred of thousands of light years, why don't we see galaxies as…
Mbbc
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10
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3 answers
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 galaxies?
Rich
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10
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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 backwards toward the galaxy it emerges from.
What…
h22
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10
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2 answers
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 learning to predict galaxy morphology. I have no…
James King
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10
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1 answer
What percentage of galaxies rotate with trailing arms?
I am looking for the percentage of galaxies that rotate with trailing arms. I know that only a small percentage of galaxies rotate with leading arms and would like to know whether there are any results that determine the percentage of spiral…
Sjoerd222888
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9
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Do galaxies change shape and size over time?
Galaxies come in different shapes and sizes. What factors determine the shape and size of a galaxy, and how can these change over time?
SwiftPushkar
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8
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Why aren't new stars in Earth's relative proximity constantly discovered?
Okay, bear with me. In layman's terms:
Еstimates vary, but on a clear night, away from big cities and their "light pollution," you'll see about 5000 stars up in the sky, give or take. Even though all of them are in the Milky Way, they're not…
Ricky
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Are new galaxies being formed and if so where?
When asked this question the answers tend to be evasive, dwelling on the development of existing galaxies by absorption. Are there nearby proto-galaxies or gas clouds expected to form a galaxy sometime?
Moggsy8
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6
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1 answer
How to determine the 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. Can anyone explain the exact procedure?
Gauti
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6
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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 gravity? Or are there some other criteria?
user123
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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 in the past. Also, our galaxy seems to be one of…
Curious Layman
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