<p>It's currently very hard to impossible to observe asteroids around other stars.</p>
<p>Asteroids are bodies with a size of at least several metres to a few hundred kilometres in diameter. There's three main ways to detect bodies:</p>
<ol>
<li>by their characteristic thermal emission</li>
<li>by obstructing the light of their central star</li>
<li>by reflecting light of their central start to us</li>
</ol>
<p>Either of those three methods is extremely challenging for bodies of that size: they are not very numerous and their thermal emissions is in the mid-IR (depending on proximity of their host star) and is easily drowned in the emissions of their host star.</p>
<p>Obstruction of the direct light of their host star (transit method). This relies on their geometric cross-section which is very small. We can detect reasonably transits of fraction of 0.001 or possibly with quiet stars and good conditions down to even 0.0001. An asteroid will cause a smaller signal.</p>
<p>They are so small that any reflected light is also very hard to detect even with interferometric imaging methods. This has only been proven possible for <a href="http://www.mpia.de/news/science/2020-15-beta-pictoris" rel="nofollow noreferrer">some</a> objects at quite a separation to their host star and which are much larger. The reflected light is also much smaller at those separations, and given their size so that we cannot make direct observations.</p>
<p>So in summary: we are currently at the edge of detecting planets of Earth size and are <a href="http://exoplanet.eu/diagrams/" rel="nofollow noreferrer">approaching</a> Mars and Mercury with the transit method - both are considerably larger than asteroids.</p>
<p>Thermal emissions are mostly used for <a href="https://arxiv.org/abs/1603.03123" rel="nofollow noreferrer">dust</a>. Single asteroids have a much smaller total surface and thus are not big enough to cause a significant IR excess at their typical emission wavelength (even to indicate the presence of an asteroid belt with more than single object).</p>
<p>Detection of asteroids via astrometry is unlikely even in the near and mid-term future. We currently only have technology to detect (rather distant and larger) gas-giants around nearby planets. The best we have for astrometric detection currently is the Gaia satellite which has detected a 10 Jupiter-mass <a href="https://arxiv.org/abs/1808.06257" rel="nofollow noreferrer">gas giant in a 22 year orbit as a companion to Beta Pictoris</a>.</p>

CC BY-SA 4.0
2021-03-01T22:26:44.907Z
Not the original poster, but as a follow-on: while I assume it'd be too diffuse to detect individual asteroids, could the existence and some of the general aggregate characteristics (total mass, density, maybe some ballpark orbital characteristics) be determined by gravitational influences?
Kurt Weber
CC BY-SA 4.0
2021-03-02T11:07:53.537Z
I added a paragraph on astromety @KurtWeber
planetmaker
CC BY-SA 4.0
2022-02-01T09:56:01.050Z
A follow-up question from my side: How would a telescope need to look like, to be able to detect individual asteroids? What dimensions would theoretically be necessary?
NullAndVoid
CC BY-SA 4.0
2021-03-01T11:40:05.960Z
2021-03-02T11:07:21.863Z
2021-03-02T11:07:21.863Z
planetmaker
<p>With existing or planned technology (e.g. the ELT or the JWST), would it be possible to infer the presence of a ring of asteroids similar to our own asteroid belt? Or would any signal be drowned out in the noise?</p>

<observational-astronomy><asteroids><planetary-systems>
Would it be possible to discover an asteroid belt around another star?
usernumber
# Would it be possible to discover an asteroid belt around another star?

(Asked by: username_0 on 2021-03-01)

With existing or planned technology (e.g. the ELT or the JWST), would it be possible to infer the presence of a ring of asteroids similar to our own asteroid belt? Or would any signal be drowned out in the noise?

**Tags:** observational-astronomy, asteroids, planetary-systems


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## 1 answers

### Answer by username_1 on 2021-03-01. Score: 6 | Accepted answer

It's currently very hard to impossible to observe asteroids around other stars.

Asteroids are bodies with a size of at least several metres to a few hundred kilometres in diameter. There's three main ways to detect bodies:

1. by their characteristic thermal emission
2. by obstructing the light of their central star
3. by reflecting light of their central start to us

Either of those three methods is extremely challenging for bodies of that size: they are not very numerous and their thermal emissions is in the mid-IR (depending on proximity of their host star) and is easily drowned in the emissions of their host star.

Obstruction of the direct light of their host star (transit method). This relies on their geometric cross-section which is very small. We can detect reasonably transits of fraction of 0.001 or possibly with quiet stars and good conditions down to even 0.0001. An asteroid will cause a smaller signal.

They are so small that any reflected light is also very hard to detect even with interferometric imaging methods. This has only been proven possible for [some](http://www.mpia.de/news/science/2020-15-beta-pictoris) objects at quite a separation to their host star and which are much larger. The reflected light is also much smaller at those separations, and given their size so that we cannot make direct observations.

So in summary: we are currently at the edge of detecting planets of Earth size and are [approaching](http://exoplanet.eu/diagrams/) Mars and Mercury with the transit method - both are considerably larger than asteroids.

Thermal emissions are mostly used for [dust](https://arxiv.org/abs/1603.03123). Single asteroids have a much smaller total surface and thus are not big enough to cause a significant IR excess at their typical emission wavelength (even to indicate the presence of an asteroid belt with more than single object).

Detection of asteroids via astrometry is unlikely even in the near and mid-term future. We currently only have technology to detect (rather distant and larger) gas-giants around nearby planets. The best we have for astrometric detection currently is the Gaia satellite which has detected a 10 Jupiter-mass [gas giant in a 22 year orbit as a companion to Beta Pictoris](https://arxiv.org/abs/1808.06257).

> **Comments:**
> **username_2**: Not the original poster, but as a follow-on: while I assume it'd be too diffuse to detect individual asteroids, could the existence and some of the general aggregate characteristics (total mass, density, maybe some ballpark orbital characteristics) be determined by gravitational influences?  
> **username_1**: I added a paragraph on astromety @username_2  
> **username_3**: A follow-up question from my side: How would a telescope need to look like, to be able to detect individual asteroids? What dimensions would theoretically be necessary?  

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