<p>This is the inverse of <a href="https://astronomy.stackexchange.com/questions/16578/will-gaia-detect-inactive-neutron-stars">Will Gaia detect inactive neutron stars?</a> (to which the answer was &quot;probably not&quot;).</p>
<p>So if Gaia can't do it, what would it take? How could such a search work, and what technological advances would be needed to have a reasonable chance of it working?</p>

CC BY-SA 4.0
2020-11-26T18:53:49.153Z
Highly relevant to any answer: https://astronomy.stackexchange.com/questions/16678/how-far-away-is-the-nearest-compact-star-remnant-likely-to-be
ProfRob
CC BY-SA 4.0
2020-11-26T18:55:41.660Z
Steve, old neutron stars don't have to be cold. So are you specifically talking about the ones that are? e.g. There could be a chance of detecting soft X-rays emitted by an old neutron star accreting from the interstellar medium. But that wouldn't be cold (or some of it wouldn't be anyway).
ProfRob
CC BY-SA 4.0
2020-11-26T19:10:02.573Z
Supernova explosions can be rather asymmetrical, which can give the neutron star (or black hole) remnant quite a kick. One of the fastest known neutron stars is pulsar B1508+55, which has a speed around 1000 km/s relative to its neighbourhood. See https://arxiv.org/abs/astro-ph/0509031. An old cold neutron star won't lose much of its natal speed. So we just need to look for lensing events caused by dense objects with large proper motion...
PM 2Ring
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2020-11-26T20:11:46.377Z
@RobJeffries Not too worried about cold, although I guess it would be interesting to see one that was relatively quiescent compared to a pulsar.
Steve Linton
<neutron-star>
How could we search for old cold neutron stars?
Steve Linton
# How could we search for old cold neutron stars?

(Asked by: username_0 on 2020-11-26)

This is the inverse of [Will Gaia detect inactive neutron stars?](https://astronomy.stackexchange.com/questions/16578/will-gaia-detect-inactive-neutron-stars) (to which the answer was "probably not").

So if Gaia can't do it, what would it take? How could such a search work, and what technological advances would be needed to have a reasonable chance of it working?

**Tags:** neutron-star

> **Comments:**
> **username_1**: Highly relevant to any answer: https://astronomy.stackexchange.com/questions/16678/how-far-away-is-the-nearest-compact-star-remnant-likely-to-be  
> **username_1**: username_0, old neutron stars don't have to be cold. So are you specifically talking about the ones that are? e.g. There could be a chance of detecting soft X-rays emitted by an old neutron star accreting from the interstellar medium. But that wouldn't be cold (or some of it wouldn't be anyway).  
> **username_2**: Supernova explosions can be rather asymmetrical, which can give the neutron star (or black hole) remnant quite a kick. One of the fastest known neutron stars is pulsar B1508+55, which has a speed around 1000 km/s relative to its neighbourhood. See https://arxiv.org/abs/astro-ph/0509031. An old cold neutron star won't lose much of its natal speed. So we just need to look for lensing events caused by dense objects with large proper motion...  
> **username_0**: @RobJeffries Not too worried about cold, although I guess it would be interesting to see one that was relatively quiescent compared to a pulsar.  

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