<p>In this article <a href="https://www.quora.com/What-is-the-shortest-distance-between-stars" rel="nofollow noreferrer">Shortest distance between stars</a> it is mentioned that </p>

<blockquote>
  <p>Some double stars can actually be in contact with each other.</p>
  
  <p>This occurs when a red giant star has a white dwarf star companion in
  a very close orbit.</p>
</blockquote>

<p>However, this isnt the case</p>

<p><a href="https://earthsky.org/space/hottest-heaviest-touching-double-star-vfts-352" rel="nofollow noreferrer">Hottest, heaviest touching double stars</a></p>

<blockquote>
  <p>In the case of VFTS 352, however, both stars in the system are of
  almost identical size. Material is, therefore, not sucked from one to
  another, but instead may be shared.</p>
</blockquote>

<p>My question then is, can any type of stars be contact binaries, or are there some limitations in the type of stars for contact binaries to appear?</p>

CC BY-SA 4.0
2019-02-07T16:51:41.763Z
It will depend a bit on your definition of "stable."  Should both stars remain in their current phase of life for  1e6 years, or 1e9 years, for example?  BTW, I'd be cautious about quoting quora.com as a solid source.  But here's a page that may be informative:  https://physics.stackexchange.com/questions/197110/what-is-the-smallest-distance-possible-between-two-stars
Carl Witthoft
CC BY-SA 4.0
2019-02-07T16:53:42.290Z
But, skimming various articles, I get the feeling that "We don't know for sure" is the correct answer, and as we find more unusual and interesting things out there, we may see all sorts of possible outcomes for close-orbit binaries.
Carl Witthoft
CC BY-SA 4.0
2019-02-07T21:44:25.337Z
I bet there aren't any contact neutron star pairs. ;) They'd just squish together, and if the combined mass is high enough, they'd collapse into a black hole
PM 2Ring
CC BY-SA 4.0
2019-02-08T00:01:47.723Z
@PM2Ring 2 very close neutron stars would spiral in towards each other creating gravity waves.   That might make a good question as to what happens when 2 neutron stars collide.   I'll research it a bit first, but I'm not sure a black hole would be the end result.
userLTK
CC BY-SA 4.0
2019-02-08T05:54:25.757Z
@userLTK I'm aware of Hulse & Taylor's binary pulsar PSR B1913+16. I'm also aware of the gravitational wave event [GW170817](https://en.wikipedia.org/wiki/GW170817) detected by LIGO & Virgo in August 2016, which was most likely a neutron star merger, that produced a cloud of neutron-rich elements. Wikipedia says the remnant was most likely a hypermassive neutron star which collapsed into a black hole in milliseconds. In my previous comment, I was simply noting that 2 neutron stars could not orbit in contact for more than a very brief time because they would rapidly merge.
PM 2Ring
<star-systems><contact-binaries>
Can any type of stars be contact binaries?
Pablo
# Can any type of stars be contact binaries?

(Asked by: username_0 on 2019-02-07)

In this article [Shortest distance between stars](https://www.quora.com/What-is-the-shortest-distance-between-stars) it is mentioned that

> Some double stars can actually be in contact with each other.
>
> This occurs when a red giant star has a white dwarf star companion in
> a very close orbit.

However, this isnt the case

[Hottest, heaviest touching double stars](https://earthsky.org/space/hottest-heaviest-touching-double-star-vfts-352)

> In the case of VFTS 352, however, both stars in the system are of
> almost identical size. Material is, therefore, not sucked from one to
> another, but instead may be shared.

My question then is, can any type of stars be contact binaries, or are there some limitations in the type of stars for contact binaries to appear?

**Tags:** star-systems, contact-binaries
> **Comments:**
> **username_1**: It will depend a bit on your definition of "stable."  Should both stars remain in their current phase of life for  1e6 years, or 1e9 years, for example?  BTW, I'd be cautious about quoting quora.com as a solid source.  But here's a page that may be informative:  https://physics.stackexchange.com/questions/197110/what-is-the-smallest-distance-possible-between-two-stars  
> **username_1**: But, skimming various articles, I get the feeling that "We don't know for sure" is the correct answer, and as we find more unusual and interesting things out there, we may see all sorts of possible outcomes for close-orbit binaries.  
> **username_2**: I bet there aren't any contact neutron star pairs. ;) They'd just squish together, and if the combined mass is high enough, they'd collapse into a black hole  
> **username_3**: @PM2Ring 2 very close neutron stars would spiral in towards each other creating gravity waves.   That might make a good question as to what happens when 2 neutron stars collide.   I'll research it a bit first, but I'm not sure a black hole would be the end result.  
> **username_2**: @userLTK I'm aware of Hulse & Taylor's binary pulsar PSR B1913+16. I'm also aware of the gravitational wave event [GW170817](https://en.wikipedia.org/wiki/GW170817) detected by LIGO & Virgo in August 2016, which was most likely a neutron star merger, that produced a cloud of neutron-rich elements. Wikipedia says the remnant was most likely a hypermassive neutron star which collapsed into a black hole in milliseconds. In my previous comment, I was simply noting that 2 neutron stars could not orbit in contact for more than a very brief time because they would rapidly merge.  

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## 0 answers

