<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
CC BY-SA 4.0
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**: 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).  
> **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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