<p>In 2002–2003, an object called <a href="https://en.wikipedia.org/wiki/J002E3" rel="nofollow noreferrer">J002E3</a> passed close to the earth in a chaotic orbit.</p>
<p>According to NASA CNEOS (Center for Near Earth Object Studies) the orbit looked like this:
<img src="https://i.sstatic.net/PolL8.png" alt="Screenshot of path of object as of 2003 Jun 14 with surprising point circled in orange" /></p>
<p>(This is a screenshot of <a href="https://cneos.jpl.nasa.gov/images/j002e3/j002e3c.gif" rel="nofollow noreferrer">CNEOS's animation</a>, which holds the Earth fixed; <a href="https://cneos.jpl.nasa.gov/doc/j002e3/" rel="nofollow noreferrer">full CNEOS J002E3 page</a>.)</p>
<p>My question is about the point I've circled in orange.  It appears that J002E3 passed four times through almost the same point, relative to the Earth-Moon system.  It's a bit inside the orbit of the Moon.</p>
<p>There is a similar point on the other side of the Earth-Moon system that was crossed three times.</p>
<p>My question is: <strong>Is this at all surprising?  Is this sort of repeat crossing typical of chaotic orbits?</strong></p>
<p>Supposing that the apparent coincidence is real, I can think of some possible explanations for it:</p>
<ol>
<li>It's a lucky fluke.</li>
<li>J002E3 crossed the Moon's orbit 14 times, and if you distribute 14 points at random onto a circle there will naturally be some clumping and 4 points close together is not too surprising.</li>
<li>There is something in the physics of orbital mechanics that makes this sort of repeat crossing likely.</li>
</ol>
<p>or some combination of these.  (Perhaps three of the crossings can be explained by orbital mechanics, but the first crossing, which was in the opposite direction, is a coincidence.)  Or is it something else?</p>
<p>Also, what question should I have asked about this that I didn't think of?</p>

CC BY-SA 4.0
2023-06-13T11:32:55.957Z
Can you rule out that it is an optical artifact as a result of projecting a very 3D trajectory down to 2D? For example the 2nd image in [Have there been any documented mini-moons since 2006 RH120?](https://space.stackexchange.com/q/16738/12102) seems to show a triple and almost quadruple crossing, but the first image and my plot in [How would a small TCO (temporarily captured orbiter) or other natural Earth satellite most likely be detected?](https://astronomy.stackexchange.com/q/18387/7982) show that in 3D are aren't really any 3D "triple crossings".
uhoh
CC BY-SA 4.0
2023-06-13T11:40:11.347Z
I cannot rule that out, thanks for the suggestion. Still  I wouldn't expect a view from any particular direction to display this behavior, so the question remains.
MJD
CC BY-SA 4.0
2023-06-13T21:22:24.517Z
Well for example, looking down on to the ecliptic from above (or below) like this does maximizes the projected overlap of trajectories that happen to be primarily in the plane of the ecliptic.
uhoh
CC BY-SA 4.0
2023-06-13T21:24:05.320Z
@uhoh Unfortunately, the Horizons data for [J002E3](https://ssd.jpl.nasa.gov/api/horizons.api?format=text&MAKE_EPHEM=NO&COMMAND=J002E3) only spans March 1, 2003 to Jan 1, 2004. But over that span, its trajectory looks fairly flat. I used my 3D plotter in https://astronomy.stackexchange.com/a/49823/16685 I also plotted L1 (ID 31) & the Moon (ID 301), using the Earth as the center. The interesting stuff happens before 1-Jun-2003.
PM 2Ring
CC BY-SA 4.0
2023-06-13T22:17:15.343Z
In my plot, the plane of J002E3's trajectory is very close to the Moon's orbital plane.
PM 2Ring
<orbital-mechanics><near-earth-object>
Why did the path of J002E3 pass through almost the same point four times?
MJD
# Why did the path of J002E3 pass through almost the same point four times?

(Asked by: username_0 on 2023-06-13)

In 2002–2003, an object called [J002E3](https://en.wikipedia.org/wiki/J002E3) passed close to the earth in a chaotic orbit.

According to NASA CNEOS (Center for Near Earth Object Studies) the orbit looked like this:
![Screenshot of path of object as of 2003 Jun 14 with surprising point circled in orange](https://i.sstatic.net/PolL8.png)

(This is a screenshot of [CNEOS's animation](https://cneos.jpl.nasa.gov/images/j002e3/j002e3c.gif), which holds the Earth fixed; [full CNEOS J002E3 page](https://cneos.jpl.nasa.gov/doc/j002e3/).)

My question is about the point I've circled in orange. It appears that J002E3 passed four times through almost the same point, relative to the Earth-Moon system. It's a bit inside the orbit of the Moon.

There is a similar point on the other side of the Earth-Moon system that was crossed three times.

My question is: **Is this at all surprising? Is this sort of repeat crossing typical of chaotic orbits?**

Supposing that the apparent coincidence is real, I can think of some possible explanations for it:

1. It's a lucky fluke.
2. J002E3 crossed the Moon's orbit 14 times, and if you distribute 14 points at random onto a circle there will naturally be some clumping and 4 points close together is not too surprising.
3. There is something in the physics of orbital mechanics that makes this sort of repeat crossing likely.

or some combination of these. (Perhaps three of the crossings can be explained by orbital mechanics, but the first crossing, which was in the opposite direction, is a coincidence.) Or is it something else?

Also, what question should I have asked about this that I didn't think of?

**Tags:** orbital-mechanics, near-earth-object
> **Comments:**
> **username_1**: Can you rule out that it is an optical artifact as a result of projecting a very 3D trajectory down to 2D? For example the 2nd image in [Have there been any documented mini-moons since 2006 RH120?](https://space.stackexchange.com/q/16738/12102) seems to show a triple and almost quadruple crossing, but the first image and my plot in [How would a small TCO (temporarily captured orbiter) or other natural Earth satellite most likely be detected?](https://astronomy.stackexchange.com/q/18387/7982) show that in 3D are aren't really any 3D "triple crossings".  
> **username_0**: I cannot rule that out, thanks for the suggestion. Still  I wouldn't expect a view from any particular direction to display this behavior, so the question remains.  
> **username_1**: Well for example, looking down on to the ecliptic from above (or below) like this does maximizes the projected overlap of trajectories that happen to be primarily in the plane of the ecliptic.  
> **username_2**: @uhoh Unfortunately, the Horizons data for [J002E3](https://ssd.jpl.nasa.gov/api/horizons.api?format=text&MAKE_EPHEM=NO&COMMAND=J002E3) only spans March 1, 2003 to Jan 1, 2004. But over that span, its trajectory looks fairly flat. I used my 3D plotter in https://astronomy.stackexchange.com/a/49823/16685 I also plotted L1 (ID 31) & the Moon (ID 301), using the Earth as the center. The interesting stuff happens before 1-Jun-2003.  
> **username_2**: In my plot, the plane of J002E3's trajectory is very close to the Moon's orbital plane.  

---

## 0 answers

