Following on from https://tokyo3.org/forums/holiday/topics/15789/ Comet C/2014 UN271

I got to wondering about other objects in the solar system.

For starters, how many named rocks are there in the solar system? What is the smallest? What are the furthest? How many moons are there? etc.

Let’s start with named rocks. “Pluto” counts as a name, “(15788) 1993 SB” does not. The website https://minorplanetcenter.net/iau/lists/MPNames.html gives an alphabetical list of names of minor planets. Copying that to Excel, I count 23,172 different names of named minor planets. Last updated on 2022 Apr. 11.

So you’d expect that list to be complete. It isn’t. I immediately noticed that Xiangliu is missing from the list.

This website https://www.go-astronomy.com/planets/planet-moons.htm lists 219 moons of planets and dwarf planets. Including Xiangliu.

Number of Moons:
Earth – 1. (Note, Earth also has temporary moons, but they’re included among minor planets).
Mars – 2.
Jupiter – 79 moons, of whom 57 have names (others called S/2016 J1 and similar)
Saturn – 82 moons, of whom 53 have names
Uranus – 27 moons, all named
Neptune – 14 moons, all named
Pluto – 5 moons, all named
Haumea – 2 moons
dwarf planets Orcus, Makemake, Eris, Salacia, Quaoar, Varda, Gonggong – 1 moon each, all named

Xiangliu is the moon of Gonggong, Actaea is the moon of Salacia, Ilmarë is the moon of Varda, etc.

making 219 moons of planets and dwarf planets in all, of which 168 are named.

What of Dactyl, Linus and Petit-Prince? Still missing. Dactyl is famous as the moon of asteroid Ida. The other two are also asteroid moons. Any other named asteroid moons?

Yes. These range from near-Earth to main belt to Jupiter trojans to trans-Neptunian. There is no guarantee that this list is complete.
Dimorphos is the moon of Didymos.
Squannit is the moon of Moshup.
Peneius is the moon of Daphne.
Romulus & Remus are the two moons of Sylvia.
Aegis & Gorgoneion are two moons of Minerva.
Alexhelios & Cleoselene are two moons of Kleopatra.
Olympias is the moon of Roxane.
Menoetius is the moon of Patroclus.
Skamandrios is the moon of Hektor.
Queta is the moon of Eurybates.
Hiisi & Paha are the two moons of Lempo.
Gǃòʼé ǃHú is the moon of Gǃkúnǁʼhòmdímà.

Have they doubled up on the name “Romulus” by any chance? Used once for an asteroid and a second time for a moon?
If so, this may be the only slip-up in accidentally duplicating solar system body names.

Anyway, I get 19 names for moons of asteroids and small TNOs.

What about comets? Comets are included.

So to summarise, the number of named bodies in the solar system is:

23,172 – Asteroids and trans-Neptunians
168 – Moons of planets and dwarf planets
19 – Moons of asteroids and small trans-Neptunians
8 – planets
1 – star

Making a total of 23,368 named bodies in the solar system as at 11 April 2022.

Approximately.

So if you want a name for your child or grandchild or godchild then there are plenty from the Solar System to choose from.

> For starters, how many named rocks are there in the solar system? What is the smallest? What are the furthest? How many moons are there? etc.

> how many named rocks are there in the solar system?
> Making a total of 23,368 named bodies in the solar system as at 11 April 2022.

> What is the smallest?

See https://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_size
The smallest named one is Duende, just 47.5 metres in diameter.
There are smaller asteroids, 2008 TS26 is just 1 metre in diameter.

> What are the furthest?

See https://earthsky.org/space/farthest-known-object-solar-system-farfarout/
“Farfarout” is a nickname rather than a formal name. As of February 10, 2021, this object, with the formal designation 2018 AG37, is indeed the farthest object in the solar system yet discovered. Farfarout’s current distance of 132 astronomical units from the sun.

As delightful as the name Farfarout is, the object will get an official name in coming years after more observations provide more information. Astronomers estimate the dim solar system body to be about 400 km across, which puts it at the small end to be labelled a dwarf planet..

The named rock furthest away is Eris, not Sedna. And Gonggong is between the two. Eris is currently about as far out as it will get, it will be at about half this distance in about 200 years time. Gonggong is also somewhat near as far as iot will ever be. Sedna by way of contrast is about as near as it will get. At Aphelion it will be in the inner fringes of the Oort Cloud.

Eris, as you will know, is only a whisker smaller than Pluto. The initial belief that Eris was larger than Pluto led to the loss of Pluto as a planet. Eris has a mean diameter of 2326±12 km. Pluto has a mean diameter of 2376.6±1.6 km and is perfectly spherical within limits of measurement.

Eris has moon Dysnomia, with a diameter of 700 ± 115 km.

Gonggong has mean diameter 1230±50 km and moon Xiangliu with mean diameter <100 km.

> How many moons are there?

> 219 moons of planets and dwarf planets in all, of which 168 are named.
> 19 named of moons of asteroids and small TNOs.

At least 15 unnamed moons of asteroids and small TNOs. Can I find more?

Yes.

https://en.wikipedia.org/wiki/Minor-planet_moon#List_of_minor_planets_with_moons

As of January 2022, there are 457 minor planets (systems) with 477 known companions.

There’s some overlap here because dwarf planets were already included earlier.

> Pluto – 5 moons, all named
> Haumea – 2 moons
> dwarf planets Orcus, Makemake, Eris, Salacia, Quaoar, Varda, Gonggong – 1 moon each, all named

So the total number of Moons known in the Solar System as of January 2022 is
219 (moons of planets ad dwarf planets), plus
+477 (moons of asteroids, TNOs and dwarf planets), minus
-14 (moons of dwarf planets), counted twice.

making 682 known moons in the Solar System (not counting temporary moons).

https://earthsky.org/space/farthest-known-object-solar-system-farfarout/

Roolly farfknout maan :)

Ian said:

https://earthsky.org/space/farthest-known-object-solar-system-farfarout/

Roolly farfknout maan :)

:-)

mollwollfumble said:

What of Dactyl, Linus and Petit-Prince? Still missing. Dactyl is famous as the moon of asteroid Ida. The other two are also asteroid moons. Any other named asteroid moons?

Yes. These range from near-Earth to main belt to Jupiter trojans to trans-Neptunian. There is no guarantee that this list is complete.
Dimorphos is the moon of Didymos.
Squannit is the moon of Moshup.
Peneius is the moon of Daphne.
Romulus & Remus are the two moons of Sylvia.
Aegis & Gorgoneion are two moons of Minerva.
Alexhelios & Cleoselene are two moons of Kleopatra.
Olympias is the moon of Roxane.
Menoetius is the moon of Patroclus.
Skamandrios is the moon of Hektor.
Queta is the moon of Eurybates.
Hiisi & Paha are the two moons of Lempo.
Gǃòʼé ǃHú is the moon of Gǃkúnǁʼhòmdímà.

Have they doubled up on the name “Romulus” by any chance? Used once for an asteroid and a second time for a moon?
If so, this may be the only slip-up in accidentally duplicating solar system body names.

Anyway, I get 19 names for moons of asteroids and small TNOs.

So adding together:
What about comets? Comets are included.

So to summarise, the number of named bodies in the solar system is:

23,172 – Asteroids and trans-Neptunians
168 – Moons of planets and dwarf planets
19 – Moons of asteroids and small trans-Neptunians
8 – planets
1 – star

Making a total of 23,368 named bodies in the solar system as at 11 April 2022.

Approximately.

So if you want a name for your child or grandchild or godchild then there are plenty from the Solar System to choose from.

Let’s check that.

Moons of near-earth asteroids. 2 named:

Moons of Mars-crossing asteroids. None named, (31 moons known in all)

Moons of main belt asteroids. 12 named

Moons of Jupiter trojans. 3 named, (7 known in all)

Moons of TNOs including dwarf planets. 25 named

Subtracting off moons of dwarf planets, of Pluto, Orcus, Salacia, Haumea, Quaoar, Makemake, Varda, Gonggong, Eris.
That’s 14 named moons.

Putting it together.
2+12+3+25-14 = 28 named moons. Up from my previous count of 19.

23,172 – Asteroids and trans-Neptunians and comets
168 – Moons of planets and dwarf planets
28 – Moons of asteroids and small trans-Neptunians
8 – planets
1 – star

Making a total of 23,377 named bodies in the solar system as at 11 April 2022.