<p>There is a problem with very high velocity dust particles orbiting the Sun at distances much closer than Mercury with masses of micrograms and below. These particles can do damage to spacecraft that move close to the Sun in order to study it. With the Sun's <a href="https://en.wikipedia.org/wiki/Standard_gravitational_parameter" rel="noreferrer">standard gravitational parameter</a> of 1.327E+20 m^3/s^2 and the <a href="https://en.wikipedia.org/wiki/Vis-viva_equation" rel="noreferrer">vis-viva equation</a> we see that at 0.1 AU for example the speed of a circular orbit is 100,000 m/s, <span class="math-container">$\sqrt{10}$</span> larger than Earth's orbital velocity at 1 AU.</p>
<p>Below is from <a href="https://astronomy.stackexchange.com/q/16707/7982">What is the origin of the dust near the sun?</a> and the answer(s) about how this dust got there are quite informative <em>and</em> <em><strong>the answer</strong></em> <em>is worth a read and an up vote!</em></p>
<p><strong>note:</strong> Solar Probe+ is now officially <a href="https://en.wikipedia.org/wiki/Parker_Solar_Probe" rel="noreferrer">Parker Solar Probe</a></p>
<blockquote>
<p>...Reading a <a href="http://solarprobe.jhuapl.edu/mission/docs/SolarProbePlus2008.pdf" rel="noreferrer">2008 report</a> I saw that there is an elevated exposure to high velocity dust near the sun...</p>
<blockquote>
<p>4.3.5 Micrometeoroid and Dust. Solar Probe+ will encounter dust particles ranging in diameter from submicron up to several hundred microns and consisting of highly refractory carbon and silicate species with a typical bulk density of ~2.5 g/cm2. The particles will be traveling at relative speeds as high as 350 km/s. To define the shielding requirements for Solar Probe+, a dust model was developed based primarily on the work of Mann et al. (2004). The model employs the following assumptions...</p>
</blockquote>
<p><a href="https://i.sstatic.net/BtQ13.png" rel="noreferrer"><img src="https://i.sstatic.net/BtQ13.png" alt="Figure 4-6. Predicted dust environment at 0.1 AU (20 Rs) (from Mann et al. 2004 and Ishimoto, 2000)" /></a></p>
<p><strong>above:</strong> screen shot from <a href="http://solarprobe.jhuapl.edu/mission/docs/SolarProbePlus2008.pdf" rel="noreferrer">SolarProbePlus2008</a></p>
</blockquote>

CC BY-SA 4.0
2020-12-17T02:46:14.233Z
The OP ask specifically about bigger than planetesimals, not micrometeoroids
planetmaker
CC BY-SA 4.0
2020-12-17T02:49:04.410Z
@planetmaker ya, I saw the title "**Is there anything orbiting the Sun** with a shorter orbital period than Mercury?" and answered it without reading the fine print. *[Rats!](https://scifi.stackexchange.com/q/240183/51174)*
uhoh
CC BY-SA 4.0
2020-12-17T05:26:55.833Z
I think your answer is on point with respect to the OP's original question.  +1 and thanks for the information!
Connor Garcia
CC BY-SA 4.0
2020-12-16T22:31:12.530Z
2020-12-16T23:00:57.613Z
2020-12-16T23:00:57.613Z
uhoh
<p>2022 update.</p>
<p>The asteroid <a href="https://en.wikipedia.org/wiki/2021_PH27" rel="noreferrer">2021 PH27</a> has an orbital period of 114.6 days, setting a new record for any non-Mercury solar system object.</p>

CC BY-SA 4.0
2022-10-03T14:59:06.853Z
You can view its orbit at https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2021%20PH27
PM 2Ring
CC BY-SA 4.0
2022-10-03T22:28:40.410Z
Latest SBDB query shows [2021 VR3](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=2021%20VR3) in second place at 142.5 d.
Mike G
CC BY-SA 4.0
2022-10-03T13:54:58.450Z
2022-10-03T13:54:58.450Z
SE - stop firing the good guys
<p>A hypothetical asteroid that orbited the sun inside the orbit of Mercury would be called a <a href="https://en.wikipedia.org/wiki/Vulcanoid" rel="noreferrer">vulcanoid</a>. No vulcanoids have so far been discovered, although there is a population of asteroids that <a href="https://en.wikipedia.org/wiki/List_of_Mercury-crossing_minor_planets" rel="noreferrer">cross Mercury’s orbit</a>, and some pass very close to the sun indeed.</p>

CC BY-SA 4.0
2020-12-16T20:02:05.367Z
2020-12-16T20:02:05.367Z
gandalf61
<p>The recently discovered asteroids <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K19L06F" rel="noreferrer">2019 LF6</a> and <a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K20A02V" rel="noreferrer">2020 AV2</a>, each taking 151 days to orbit the Sun, have the shortest periods currently listed in the <a href="https://ssd.jpl.nasa.gov/sbdb_query.cgi" rel="noreferrer">JPL Small Body Database</a>.</p>
<p><a href="https://en.wikipedia.org/wiki/Vulcanoid" rel="noreferrer">Vulcanoids</a> are difficult to detect from Earth; none are known yet.
To remain in such an orbit, <a href="https://ui.adsabs.harvard.edu/abs/1999Natur.399...41E/abstract" rel="noreferrer">Evans and Tabachnik 1999</a> estimate a minimum diameter of 100 m and a semimajor axis between 0.09 and 0.21 au.</p>
<p>There are various competing definitions for a planet's neighborhood.
<a href="https://ui.adsabs.harvard.edu/abs/2006AJ....132.2513S/abstract" rel="noreferrer">Soter 2006</a> says:</p>
<blockquote>
<p>Two bodies share an &quot;orbital zone&quot; if their orbits cross a common radial distance from the primary and their periods are nonresonant and differ by less than an order of magnitude.</p>
</blockquote>
<p>A Sun-grazing asteroid with perihelion 0.01 au and aphelion 0.31 au (Mercury's perihelion) would orbit in 23 days, well above the 9 day minimum for that definition.</p>

CC BY-SA 4.0
2020-12-19T01:25:43.077Z
@BenCrowell Maybe it would take 100M years, but they think [Poynting-Robertson](https://en.wikipedia.org/wiki/Poynting%E2%80%93Robertson_effect) drag at 0.2 au would decay the orbit of a 30 m asteroid.
Mike G
CC BY-SA 4.0
2020-12-16T20:33:20.737Z
2020-12-17T15:30:54.163Z
2020-12-17T15:30:54.163Z
Mike G
<p><a href="https://en.wikipedia.org/wiki/Mercury_(planet)" rel="noreferrer">Mercury</a>'s orbital period around the Sun is about 88 days.  Comets and other things have gotten closer to the Sun than Mercury does.  But has there ever been an asteroid or some other body discovered that has a shorter orbital period?  Are there theoretical constraints on if such a body can exist?</p>
<p>The IAU defines a planet as one that has <a href="https://astronomy.stackexchange.com/questions/39851/did-mercury-clear-its-neighborhood">swept out its orbit</a>.  Does the neighborhood of Mercury extend to the Sun?</p>

CC BY-SA 4.0
2020-12-18T04:59:48.227Z
Related: https://physics.stackexchange.com/questions/144406/what-is-the-speed-of-the-fastest-moving-body-in-our-solar-system
Nilay Ghosh
CC BY-SA 4.0
2022-10-04T03:40:04.267Z
Mercury's moons are the same. I guess there must be, although rocks sublimate with UV snd light intensity that high. The radiation and solar wind knock the atoms off.
bandybabboon
<the-sun><orbit><asteroids><orbital-mechanics><mercury>
Does anything orbit the Sun faster than Mercury?
Connor Garcia
# Does anything orbit the Sun faster than Mercury?

(Asked by: username_0 on 2020-12-16)

[Mercury](https://en.wikipedia.org/wiki/Mercury_(planet))'s orbital period around the Sun is about 88 days. Comets and other things have gotten closer to the Sun than Mercury does. But has there ever been an asteroid or some other body discovered that has a shorter orbital period? Are there theoretical constraints on if such a body can exist?

The IAU defines a planet as one that has [swept out its orbit](https://astronomy.stackexchange.com/questions/39851/did-mercury-clear-its-neighborhood). Does the neighborhood of Mercury extend to the Sun?

**Tags:** the-sun, orbit, asteroids, orbital-mechanics, mercury

> **Comments:**
> **username_1**: Related: https://physics.stackexchange.com/questions/144406/what-is-the-speed-of-the-fastest-moving-body-in-our-solar-system  
> **username_2**: Mercury's moons are the same. I guess there must be, although rocks sublimate with UV snd light intensity that high. The radiation and solar wind knock the atoms off.  

---

## 4 answers

### Answer by username_7 on 2020-12-16. Score: 22 | Accepted answer

The recently discovered asteroids [2019 LF6](https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K19L06F) and [2020 AV2](https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=K20A02V), each taking 151 days to orbit the Sun, have the shortest periods currently listed in the [JPL Small Body Database](https://ssd.jpl.nasa.gov/sbdb_query.cgi).

[Vulcanoids](https://en.wikipedia.org/wiki/Vulcanoid) are difficult to detect from Earth; none are known yet.
To remain in such an orbit, [Evans and Tabachnik 1999](https://ui.adsabs.harvard.edu/abs/1999Natur.399...41E/abstract) estimate a minimum diameter of 100 m and a semimajor axis between 0.09 and 0.21 au.

There are various competing definitions for a planet's neighborhood.
[Soter 2006](https://ui.adsabs.harvard.edu/abs/2006AJ....132.2513S/abstract) says:

> Two bodies share an "orbital zone" if their orbits cross a common radial distance from the primary and their periods are nonresonant and differ by less than an order of magnitude.

A Sun-grazing asteroid with perihelion 0.01 au and aphelion 0.31 au (Mercury's perihelion) would orbit in 23 days, well above the 9 day minimum for that definition.

> **Comments:**
> **username_7**: @BenCrowell Maybe it would take 100M years, but they think [Poynting-Robertson](https://en.wikipedia.org/wiki/Poynting%E2%80%93Robertson_effect) drag at 0.2 au would decay the orbit of a 30 m asteroid.  

---

### Answer by username_3 on 2020-12-16. Score: 16

There is a problem with very high velocity dust particles orbiting the Sun at distances much closer than Mercury with masses of micrograms and below. These particles can do damage to spacecraft that move close to the Sun in order to study it. With the Sun's [standard gravitational parameter](https://en.wikipedia.org/wiki/Standard_gravitational_parameter) of 1.327E+20 m^3/s^2 and the [vis-viva equation](https://en.wikipedia.org/wiki/Vis-viva_equation) we see that at 0.1 AU for example the speed of a circular orbit is 100,000 m/s, $\sqrt{10}$ larger than Earth's orbital velocity at 1 AU.

Below is from [What is the origin of the dust near the sun?](https://astronomy.stackexchange.com/q/16707/7982) and the answer(s) about how this dust got there are quite informative *and* ***the answer*** *is worth a read and an up vote!*

**note:** Solar Probe+ is now officially [Parker Solar Probe](https://en.wikipedia.org/wiki/Parker_Solar_Probe)

> ...Reading a [2008 report](http://solarprobe.jhuapl.edu/mission/docs/SolarProbePlus2008.pdf) I saw that there is an elevated exposure to high velocity dust near the sun...
>
> > 4.3.5 Micrometeoroid and Dust. Solar Probe+ will encounter dust particles ranging in diameter from submicron up to several hundred microns and consisting of highly refractory carbon and silicate species with a typical bulk density of ~2.5 g/cm2. The particles will be traveling at relative speeds as high as 350 km/s. To define the shielding requirements for Solar Probe+, a dust model was developed based primarily on the work of Mann et al. (2004). The model employs the following assumptions...
>
> [![Figure 4-6. Predicted dust environment at 0.1 AU (20 Rs) (from Mann et al. 2004 and Ishimoto, 2000)](https://i.sstatic.net/BtQ13.png)](https://i.sstatic.net/BtQ13.png)
>
> **above:** screen shot from [SolarProbePlus2008](http://solarprobe.jhuapl.edu/mission/docs/SolarProbePlus2008.pdf)

> **Comments:**
> **username_4**: The OP ask specifically about bigger than planetesimals, not micrometeoroids  
> **username_3**: @username_4 ya, I saw the title "**Is there anything orbiting the Sun** with a shorter orbital period than Mercury?" and answered it without reading the fine print. *[Rats!](https://scifi.stackexchange.com/q/240183/51174)*  
> **username_0**: I think your answer is on point with respect to the OP's original question.  +1 and thanks for the information!  

---

### Answer by username_8 on 2020-12-16. Score: 8

A hypothetical asteroid that orbited the sun inside the orbit of Mercury would be called a [vulcanoid](https://en.wikipedia.org/wiki/Vulcanoid). No vulcanoids have so far been discovered, although there is a population of asteroids that [cross Mercury’s orbit](https://en.wikipedia.org/wiki/List_of_Mercury-crossing_minor_planets), and some pass very close to the sun indeed.


---

### Answer by username_5 on 2022-10-03. Score: 7

2022 update.

The asteroid [2021 PH27](https://en.wikipedia.org/wiki/2021_PH27) has an orbital period of 114.6 days, setting a new record for any non-Mercury solar system object.

> **Comments:**
> **username_6**: You can view its orbit at https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2021%20PH27  
> **username_7**: Latest SBDB query shows [2021 VR3](https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=2021%20VR3) in second place at 142.5 d.  

---

