<p>One kilometer, no way! That would've been known since long ago. Most asteroids of that size have already been found, all the way out to the asteroid belt beyond Mars. Earth has <a href="https://en.wikipedia.org/wiki/Other_moons_of_Earth">no second Moon</a>. But there are always some tiny asteroids around, which are temporarily captured by Earth's gravity. Here's a <a href="http://www.space.com/25321-minimoons-asteroids-human-spaceflight.html">funny illustration</a> of such an orbit, it is not what we would like to call a moon. I think that only one of them have been found, the 5 meter diameter <a href="https://en.wikipedia.org/wiki/2006_RH120">2006RH120</a>. Smaller objects would not be detectable today, but there are at any moment likely many meter and submeter sized asteroids visiting the Sun-Earth Lagrange points. <a href="http://arxiv.org/pdf/1112.3781v1.pdf">A paper about it</a>.</p>

<p>Space is not yet being scanned, but telescopes are now being built to do that. It will be a new kind of astronomy, looking for the unexpected, and who knows what will be found out there in the blackness. Still today amateur astronomers can discover asteroids with the telescope in their backyard. I'm afraid that space telescopes like <a href="http://sci.esa.int/gaia/">Gaia</a> will kill their hobby and that this classic astronomical mapping of the sky will finally be finished.</p>

CC BY-SA 3.0
2014-12-19T11:33:23.800Z
2014-12-19T11:33:23.800Z
LocalFluff
<p>The chances of what you are suggesting are almost nil. Though we might be constantly scanning our surrounding atmosphere to detect fragments of, or actual meteorites, other than the debris and artificial satellites that we ourselves have put in orbit around the earth, there is no second moon currently in orbit around us to the best of our knowledge.</p>

<p>There is, however, a theory that proposes the presence of another moon in the past. As per this theory, there was a planet "Theia" immediately close to earth that underwent a close collision with Earth to form two moons, which ultimately coalesced to form the single moon we see today.</p>

<p>Read here:</p>

<p><a href="http://www.space.com/12529-earth-2-moons-collision-moon-formation.html" rel="nofollow">http://www.space.com/12529-earth-2-moons-collision-moon-formation.html</a></p>

<p><a href="http://news.discovery.com/space/two-moons-earth-110804.htm" rel="nofollow">http://news.discovery.com/space/two-moons-earth-110804.htm</a></p>

<p><a href="http://www.telegraph.co.uk/news/science/space/10165036/Earth-had-two-moons-scientists-claim.html" rel="nofollow">http://www.telegraph.co.uk/news/science/space/10165036/Earth-had-two-moons-scientists-claim.html</a></p>

CC BY-SA 3.0
2015-06-29T07:35:07.490Z
2015-06-29T07:35:07.490Z
Riptide
<p>Not strictly satellites/moons, but certainly companions are <a href="https://en.wikipedia.org/wiki/2010_TK7">2010 TK<sub>7</sub></a> with a diameter of ~300&nbsp;m, an <a href="https://en.wikipedia.org/wiki/Earth_trojan">Earth trojan</a> at the <a href="https://en.wikipedia.org/wiki/List_of_objects_at_Lagrangian_points#L4">L4</a> point, and the ~5&nbsp;km <a href="https://en.wikipedia.org/wiki/3753_Cruithne">3753 Cruithne</a> in a peculiar orbit locked to the Earth's.</p>

CC BY-SA 3.0
2014-12-19T12:52:39.343Z
2014-12-20T02:44:47.110Z
2014-12-20T02:44:47.110Z
Conrad Turner
<p>I was just wondering what are the chances that there is a small object (say less than 1&nbsp;km but more than few meters) that orbits the Earth but has remained undetected by us? Are we actually scanning the space around the Earth continuously for orbiting bodies?</p>

CC BY-SA 3.0
2014-12-19T21:40:13.953Z
You mean _besides_ the $10,000$ or so artificial bodies of about that size already there?
geometrian
<the-moon><earth><near-earth-object>
Does the Earth have another moon?
Sathish
# Does the Earth have another moon?

(Asked by: username_0 on 2014-12-19)

I was just wondering what are the chances that there is a small object (say less than 1 km but more than few meters) that orbits the Earth but has remained undetected by us? Are we actually scanning the space around the Earth continuously for orbiting bodies?

**Tags:** the-moon, earth, near-earth-object
> **Comments:**
> **username_1**: You mean _besides_ the $10,000$ or so artificial bodies of about that size already there?  

---

## 3 answers

### Answer by username_4 on 2014-12-19. Score: 26 | Accepted answer

Not strictly satellites/moons, but certainly companions are [2010 TK7](https://en.wikipedia.org/wiki/2010_TK7) with a diameter of ~300 m, an [Earth trojan](https://en.wikipedia.org/wiki/Earth_trojan) at the [L4](https://en.wikipedia.org/wiki/List_of_objects_at_Lagrangian_points#L4) point, and the ~5 km [3753 Cruithne](https://en.wikipedia.org/wiki/3753_Cruithne) in a peculiar orbit locked to the Earth's.


---

### Answer by username_2 on 2014-12-19. Score: 14

One kilometer, no way! That would've been known since long ago. Most asteroids of that size have already been found, all the way out to the asteroid belt beyond Mars. Earth has [no second Moon](https://en.wikipedia.org/wiki/Other_moons_of_Earth). But there are always some tiny asteroids around, which are temporarily captured by Earth's gravity. Here's a [funny illustration](http://www.space.com/25321-minimoons-asteroids-human-spaceflight.html) of such an orbit, it is not what we would like to call a moon. I think that only one of them have been found, the 5 meter diameter [2006RH120](https://en.wikipedia.org/wiki/2006_RH120). Smaller objects would not be detectable today, but there are at any moment likely many meter and submeter sized asteroids visiting the Sun-Earth Lagrange points. [A paper about it](http://arxiv.org/pdf/1112.3781v1.pdf).

Space is not yet being scanned, but telescopes are now being built to do that. It will be a new kind of astronomy, looking for the unexpected, and who knows what will be found out there in the blackness. Still today amateur astronomers can discover asteroids with the telescope in their backyard. I'm afraid that space telescopes like [Gaia](http://sci.esa.int/gaia/) will kill their hobby and that this classic astronomical mapping of the sky will finally be finished.


---

### Answer by username_3 on 2015-06-29. Score: 0

The chances of what you are suggesting are almost nil. Though we might be constantly scanning our surrounding atmosphere to detect fragments of, or actual meteorites, other than the debris and artificial satellites that we ourselves have put in orbit around the earth, there is no second moon currently in orbit around us to the best of our knowledge.

There is, however, a theory that proposes the presence of another moon in the past. As per this theory, there was a planet "Theia" immediately close to earth that underwent a close collision with Earth to form two moons, which ultimately coalesced to form the single moon we see today.

Read here:

<http://www.space.com/12529-earth-2-moons-collision-moon-formation.html>

<http://news.discovery.com/space/two-moons-earth-110804.htm>

<http://www.telegraph.co.uk/news/science/space/10165036/Earth-had-two-moons-scientists-claim.html>


---

