<p>Compact stars are stars of great density; stellar remnants in which the fermion constituents have become degenerate. i.e. white dwarfs and neutron stars (though sometimes black holes would be included).</p>

<p>A compact binary is a binary star system containing at least one compact object.</p>

CC BY-SA 3.0
2018-02-27T00:09:27.980Z
2018-02-27T00:09:27.980Z
ProfRob
<p>Compact means closely and neatly packed together or dense. Since we are talking about space it normally either means a celestial body is dense or that a group of celestial bodies are occupying a small(relatively) space.</p>

CC BY-SA 4.0
2020-01-29T03:55:49.420Z
2020-01-29T03:55:49.420Z
Daosof
<p>I have seen countless times the adjective "compact" in astronomy, e.g. compact stars, compact binaries, etc. I would like to know, what exactly is this supposed to mean? From <a href="http://physics.open.ac.uk/~uckolb/research/" rel="nofollow noreferrer">this source</a>, I am led to believe that "compact" is meant to denote objects of the greatest matter densities in the universe, i.e. white dwarfs, neutron stars, and black holes. Is this correct?</p>

CC BY-SA 3.0
2018-02-26T16:55:21.823Z
Each of those cases use the word compact differently but they all have some relationship to higher density. The word means the same as in normal English, but in specific cases can have more specific meaning when talking about a specific objects.
A. C. A. C.
CC BY-SA 3.0
2018-02-26T19:21:32.057Z
This is like asking what "fast" and "rich" mean - they are context dependent and in these cases so is "compact".
StephenG - Help Ukraine
CC BY-SA 3.0
2018-02-26T20:31:42.530Z
Arturo, it simply has *different* meanings in each of the phrases it is used in.  (There's not one "general" meaning or definition.)
Fattie
<astrophysics><gravitational-waves><naming><gamma-ray-bursts>
What does the word "compact" mean in astronomy/astrophysics?
Arturo don Juan
# What does the word "compact" mean in astronomy/astrophysics?

(Asked by: username_0 on 2018-02-26)

I have seen countless times the adjective "compact" in astronomy, e.g. compact stars, compact binaries, etc. I would like to know, what exactly is this supposed to mean? From [this source](http://physics.open.ac.uk/~uckolb/research/), I am led to believe that "compact" is meant to denote objects of the greatest matter densities in the universe, i.e. white dwarfs, neutron stars, and black holes. Is this correct?

**Tags:** astrophysics, gravitational-waves, naming, gamma-ray-bursts

> **Comments:**
> **username_1**: Each of those cases use the word compact differently but they all have some relationship to higher density. The word means the same as in normal English, but in specific cases can have more specific meaning when talking about a specific objects.  
> **username_2**: This is like asking what "fast" and "rich" mean - they are context dependent and in these cases so is "compact".  
> **username_3**: Arturo, it simply has *different* meanings in each of the phrases it is used in.  (There's not one "general" meaning or definition.)  

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## 2 answers

### Answer by username_4 on 2018-02-27. Score: 2 | Accepted answer

Compact stars are stars of great density; stellar remnants in which the fermion constituents have become degenerate. i.e. white dwarfs and neutron stars (though sometimes black holes would be included).

A compact binary is a binary star system containing at least one compact object.


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### Answer by username_5 on 2020-01-29. Score: 0

Compact means closely and neatly packed together or dense. Since we are talking about space it normally either means a celestial body is dense or that a group of celestial bodies are occupying a small(relatively) space.


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