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The Solar System

The 29 largest bodies (by radius) in the Solar System. I stopped there because some of the others don't have names.

		Local stats			System stats
body	type¹	radius	rotational period⁴	axial tilt⁵	distance from primary⁶		orbital period		orbital incline⁹	mass	mass¹¹
		Earths³	days	degrees	AU⁷	1000 km	years	days	degrees	Earths¹⁰	%
Sun	Star	109.25	25.38	7.25	–		–⁸			332981	99.850
Jupiter	Planet	10.97	0.41	3.12	5.20		11.86		1.31	317.83	63.538
Saturn	Planet	9.14	0.44	26.73	9.54		29.45		2.48	95.162	52.175
Uranus	Planet	3.98	-0.72	97.86	19.19		84.02		0.76	14.536	16.664
Neptune	Planet	3.87	0.67	29.58	30.07		164.79		1.77	17.147	23.588
Earth	Planet	1.00	1.00	23.44	1.00		1.00		0.00	1.000	1.800
Venus	Planet	0.95	-243.02	177.30	0.72		0.62		3.39	0.815	1.494
Mars	Planet	0.53	1.03	25.19	1.52		1.88		1.85	0.107	0.200
Ganymede	(Jupiter)	0.41	synch	0.17		1070.40		7.15	1.85	0.025	0.046
Titan	(Saturn)	0.40	synch	0.00		1221.87		15.95	0.33	0.023	0.042
Mercury	Planet	0.38	58.65	0.00	0.39		0.24		7.00	0.055	0.103
Callisto	(Jupiter)	0.38	synch	0.00		1882.70		16.69	0.20	0.018	0.034
Io	(Jupiter)	0.29	synch	0.00		421.60		1.77	0.04	0.015	0.028
Moon	(Earth)	0.27	synch	6.68		384.40		27.32	23.43	0.012	0.023
Europa	(Jupiter)	0.25	synch	0.00		670.90		3.55	0.47	0.008	0.015
Triton	(Neptune)	0.21	synch	0.00		354.76		-5.88	157.00	0.004	0.007
Eris	sKuiper	0.18	?	?	67.67		557.00		44.19	0.003	0.005
Pluto	Kuiper	0.18	-6.39	119.61	39.48		247.92		17.14	0.002	0.004
Titania	(Uranus)	0.12	synch	0.00		436.30		8.71	0.36	0.001	0.001
Rhea	(Saturn)	0.12	synch	0.00		527.11		4.52	0.35	0.000	0.001
Oberon	(Uranus)	0.12	synch	0.00		583.52		13.46	0.34	0.001	0.001
Sedna	sKuiper²	0.12	0.42	?	525.86		12059.06		11.93	0.001	0.001
Iapetus	(Saturn)	0.11	synch	0.00		3560.82		79.32	0.35	0.000	0.001
Makemake	Kuiper	0.11	?	?	45.79		309.90		28.96	0.001	0.001
Charon	(Pluto)	0.10	synch	?		17.54		6.39	?	0.000	0.000
"Snow White"	sKuiper	0.09	?	?	67.33		552.52		30.70	0.000	0.001
Umbriel	(Uranus)	0.09	synch	0.00		266.00		4.14	0.26	0.000	0.000
Ariel	(Uranus)	0.09	synch	0.00		190.90		2.52	4.20	0.000	0.000
Haumea	Kuiper	0.09	0.17	?	43.34		285.40		28.19	0.001	0.001

All measurements are mean (average)

¹ (name in bracket) signifies a moon of the named larger object. Kuiper = Kuiper belt object. sKuiper = scattered Kuiper belt object. What's the difference? Astronomers can't even agree on the distinction.

² this is contested, as Sedna is too far out

³ as a fraction of Earth radius (6378.1 km)

⁴ synch = rotational period is the same as orbital period, so the same side always faces the planet

⁵ The inclination of the body's equator from its orbit

⁶ either the Sun or the planet which the body is orbiting

⁷ 1 AU = 149,597,870.7 km

⁸ the Sun orbits the galactic centre every 250 millions years approx

⁹ to Earth's orbital plane or orbited planet's equator

¹⁰ as a fraction of Earth mass (5.97×10²⁴ kg)

¹¹ as a percentage of the mass of all Solar System objects not larger than itself.

E.g. the figure given for the Sun is the Sun's mass as a percentage of the Solar system's mass. The figure given for Jupiter is the percentage of the Solar system's mass minus the Sun. For Saturn, minus the Sun and Jupiter. For Uranus, minus the Sun, Jupiter and Saturn etc.

A new planet

In 2005 a new "planet" was found, larger, but further away, than Pluto. If this was the tenth planet of the Solar System, what should it be called?

The other planets (except our own) were all named after major gods (usually Roman). Working out from the Sun, these were the gods of Travel, Love, War, the King, Agriculture, the Heavens (Greek), the Sea and the Underworld.

I favoured the new planet should be named after the Wind. So a little research turned up the following Roman gods of the Wind, who names had yet to be used for astronomical bodies.

Africus:	south west wind
Aquilo:	north wind
Auster:	south wind
Corus:	north west wind
Favonius:	west wind
Vulturnus:	south east wind

My favourite was Auster, as this was associated with the bringing of heavy cloud cover and fog.

Of course the discovery of this new "planet" caused a rethink of the definition of planet. And instead of the solar system gaining a tenth, it instead lost its ninth, with Pluto being demoted.

So now this discovery was classified as a plutoid, or dwarf planet.

New names were put forward including Persephone (already used), Xena (as in the Warrior princess, and not a valid name) and Lila (a Hindu god). Eventually the name Eris, the Greek goddess of chaos, was decided.