<p>Per the <a href="https://carnegiescience.edu/news/dozen-new-moons-jupiter-discovered-including-one-%E2%80%9Coddball%E2%80%9D" rel="noreferrer">Carnegie Science article</a> that Magic Octopus Urn linked from NASA in the comments, a Carnegie Science team led by Scott S. Sheppard noticed something new in spring of 2017 (though some observations occurred as early as 2016). It took a year to confirm the discovery of the new moons.</p>

<p>Ten of the moons orbit in the outer swarm of moons, which is one of the ways to divide the groups of moons. Nine of these follow the pattern of the other moons which orbit Jupiter in retrograde (the opposite direction of the planet's rotation). One they call "oddball" because it orbits prograde (the same direction as the planet's rotation) and has a more inclined orbit than the inner prograde moons.</p>

<p>Two of the moons orbit in the inner group, which is what brings the total number of discoveries up to twelve, as referenced in the first set of articles in your post. Like the other inner moons, these orbit prograde.</p>

<p>One of the retrograde moons and the "oddball" were first noticed in 2016. One of the inner group and the rest of the retrograde moons were discovered in 2017. The second inner group moon was discovered in 2018, then most were announced together on July 17, 2018. (Dates collected from <a href="https://en.wikipedia.org/wiki/Moons_of_Jupiter#List" rel="noreferrer">Wikipedia</a>.)</p>

<p>The retrograde moon discovered in 2016 and one of the retrograde moons discovered in 2017 were announced in 2017, this means only ten moons were announced on July 17, 2018, which is why the Nature article refers to ten new moons. The EarthSky article talks some about the ten and the twelve, and it does clarify both groups (divided by inner/outer and year of announcement).</p>

CC BY-SA 4.0
2018-07-19T14:38:59.100Z
I wonder if the people at JPL are starting to regret their numbering scheme. The barycenter of the Jovian system has ID# 500, the Jovian moons are numbered 501 to 598 (not all taken, yet), and Jupiter itself is 599. Twenty new discoveries will blow that numbering system away. A collision between this oddball and one of the retrograde moons will completely blow it away.
David Hammen
CC BY-SA 4.0
2018-07-19T15:43:24.090Z
@DavidHammen When it breaks, I could see them hacking the system: $59\alpha$ or something like that. At least in the short term.
called2voyage
CC BY-SA 4.0
2018-07-19T16:43:57.230Z
@called2voyage they could switch to base16 and then base36. And when _that_ breaks, maybe even a four-digit system.
John Dvorak
CC BY-SA 4.0
2018-07-19T16:56:14.673Z
@JohnDvorak Somehow I doubt we'll be tracking >~1300 objects at Jupiter under the current system, but you never know!
called2voyage
CC BY-SA 4.0
2018-07-19T13:13:45.057Z
2018-07-19T14:30:21.577Z
2018-07-19T14:30:21.577Z
called2voyage
<p>I saw multiple news sites reporting that a team discovered 12 new Jupiter's moons:</p>

<ul>
<li><a href="https://www.cnet.com/videos/twelve-new-jupiter-moons-found-including-one-reckless-one/" rel="nofollow noreferrer">c|net - Twelve new Jupiter moons found, including one reckless one</a></li>
<li><a href="http://blogs.discovermagazine.com/d-brief/2018/07/17/new-jupiter-moons/" rel="nofollow noreferrer">Discover - Jupiter’s Got Twelve New Moons — One is a Bit of a Problem Child</a></li>
</ul>

<p>While some other news sites claim that they found only 10 new moons:</p>

<ul>
<li><a href="https://www.nature.com/articles/d41586-018-05725-6" rel="nofollow noreferrer">nature - Jupiter has 10 more moons we didn't know about — and they're weird</a></li>
<li><a href="http://earthsky.org/space/10-new-moons-discovered-jupiter-1-oddball" rel="nofollow noreferrer">EarthSky - Astronomers discover 10 new moons for Jupiter</a></li>
</ul>

<p>Why does the number of moons differ in the different articles? Did the team now found 10 or 12 moons?</p>

CC BY-SA 4.0
2018-07-19T13:21:43.927Z
@called2voyage I was thinking it was something like that, but I only saw the prograde-oddball and that'd make 11/12 so I held my tongue after listing sources. Good catch.
Magic Octopus Urn
CC BY-SA 4.0
2018-07-19T13:57:06.310Z
@MagicOctopusUrn - You wouldn't take news from nature.com? Nature ranks amongst the best of scientific journals.
David Hammen
CC BY-SA 4.0
2018-07-19T14:07:33.133Z
@DavidHammen personally, no, I wouldn't without verification; but that's because, personally, I've never used them. Which, in turn, means my opinion about them is also without warrant.
Magic Octopus Urn
CC BY-SA 4.0
2018-07-19T14:09:49.410Z
@DavidHammen To be fair, a Nature news article is different than a scientific paper published by Nature, but I did find the skepticism unusual as well. It makes sense though given that Magic Octopus Urn hadn't heard of Nature (which is amazing, but there's a first time for everything, I guess).
called2voyage
CC BY-SA 4.0
2018-07-19T14:13:50.987Z
In this case, the Nature article is in a sense more correct than the news release from Carnegie Science. Two of the twelve most recently discovered Jovian moons were reported a bit over a year. The remaining ten were reported yesterday.
David Hammen
CC BY-SA 4.0
2018-07-19T22:32:17.407Z
I don't find it that surprising that we found more rocks around Jupiter though. What I find surprising is how many has Galileo found with his equipment.
Tomáš Zato
<jupiter><natural-satellites>
Did we discover 10 or 12 new moons of Jupiter?
Yannick Huber
# Did we discover 10 or 12 new moons of Jupiter?

(Asked by: username_0 on 2018-07-19)

I saw multiple news sites reporting that a team discovered 12 new Jupiter's moons:

* [c|net - Twelve new Jupiter moons found, including one reckless one](https://www.cnet.com/videos/twelve-new-jupiter-moons-found-including-one-reckless-one/)
* [Discover - Jupiter’s Got Twelve New Moons — One is a Bit of a Problem Child](http://blogs.discovermagazine.com/d-brief/2018/07/17/new-jupiter-moons/)

While some other news sites claim that they found only 10 new moons:

* [nature - Jupiter has 10 more moons we didn't know about — and they're weird](https://www.nature.com/articles/d41586-018-05725-6)
* [EarthSky - Astronomers discover 10 new moons for Jupiter](http://earthsky.org/space/10-new-moons-discovered-jupiter-1-oddball)

Why does the number of moons differ in the different articles? Did the team now found 10 or 12 moons?

**Tags:** jupiter, natural-satellites
> **Comments:**
> **username_1**: @called2voyage I was thinking it was something like that, but I only saw the prograde-oddball and that'd make 11/12 so I held my tongue after listing sources. Good catch.  
> **username_2**: @MagicOctopusUrn - You wouldn't take news from nature.com? Nature ranks amongst the best of scientific journals.  
> **username_1**: @DavidHammen personally, no, I wouldn't without verification; but that's because, personally, I've never used them. Which, in turn, means my opinion about them is also without warrant.  
> **username_3**: @DavidHammen To be fair, a Nature news article is different than a scientific paper published by Nature, but I did find the skepticism unusual as well. It makes sense though given that Magic Octopus Urn hadn't heard of Nature (which is amazing, but there's a first time for everything, I guess).  
> **username_2**: In this case, the Nature article is in a sense more correct than the news release from Carnegie Science. Two of the twelve most recently discovered Jovian moons were reported a bit over a year. The remaining ten were reported yesterday.  
> **username_4**: I don't find it that surprising that we found more rocks around Jupiter though. What I find surprising is how many has Galileo found with his equipment.  

---

## 1 answers

### Answer by username_3 on 2018-07-19. Score: 20 | Accepted answer

Per the [Carnegie Science article](https://carnegiescience.edu/news/dozen-new-moons-jupiter-discovered-including-one-%E2%80%9Coddball%E2%80%9D) that Magic Octopus Urn linked from NASA in the comments, a Carnegie Science team led by Scott S. Sheppard noticed something new in spring of 2017 (though some observations occurred as early as 2016). It took a year to confirm the discovery of the new moons.

Ten of the moons orbit in the outer swarm of moons, which is one of the ways to divide the groups of moons. Nine of these follow the pattern of the other moons which orbit Jupiter in retrograde (the opposite direction of the planet's rotation). One they call "oddball" because it orbits prograde (the same direction as the planet's rotation) and has a more inclined orbit than the inner prograde moons.

Two of the moons orbit in the inner group, which is what brings the total number of discoveries up to twelve, as referenced in the first set of articles in your post. Like the other inner moons, these orbit prograde.

One of the retrograde moons and the "oddball" were first noticed in 2016. One of the inner group and the rest of the retrograde moons were discovered in 2017. The second inner group moon was discovered in 2018, then most were announced together on July 17, 2018. (Dates collected from [Wikipedia](https://en.wikipedia.org/wiki/Moons_of_Jupiter#List).)

The retrograde moon discovered in 2016 and one of the retrograde moons discovered in 2017 were announced in 2017, this means only ten moons were announced on July 17, 2018, which is why the Nature article refers to ten new moons. The EarthSky article talks some about the ten and the twelve, and it does clarify both groups (divided by inner/outer and year of announcement).

> **Comments:**
> **username_2**: I wonder if the people at JPL are starting to regret their numbering scheme. The barycenter of the Jovian system has ID# 500, the Jovian moons are numbered 501 to 598 (not all taken, yet), and Jupiter itself is 599. Twenty new discoveries will blow that numbering system away. A collision between this oddball and one of the retrograde moons will completely blow it away.  
> **username_3**: @DavidHammen When it breaks, I could see them hacking the system: $59\alpha$ or something like that. At least in the short term.  
> **username_5**: @called2voyage they could switch to base16 and then base36. And when _that_ breaks, maybe even a four-digit system.  
> **username_3**: @JohnDvorak Somehow I doubt we'll be tracking >~1300 objects at Jupiter under the current system, but you never know!  

---

