Now It's Much More Exclusive to be In Club Planet!

OK! Not only did the ludicrous idea of allowing all the asteroid riff-raff in end, they even went the step in the right direction and decreed Pluto to be an asteroid itself. Pluto and Charon seem to have a friendly relationship and that works well for them, but let's face it, what planet has a moon its size and that also happens to be a rough asteroid? So we went, in a brief span of time, from nine planets to 12 planets to 53 (!) planets and now we are holding at eight. I'm sure Percival Lowell is spinning in his grave to know that Pluto (not named for the Disney dog, for the love of little apples) is no longer a planet and has been dissed, so to speak!

Well, really.

You have the Solar System. See the above image. If you click on it, you'll get the blown up version, which will make the terrestrial planets visible. This image is meant to show scale and I think we all know that when it comes to scale, Jupiter is the big cheese. No mystery there! This is an older image, so there is a Pluto in there.

Mercury is your first terrestrial planet and looks a lot like the moon - our moon, not someone else's. It is pocked with old craters, but let's face it - it is close enough to the sun to be bombarded by all the junk that something the size of the yellow G-type star would suck into it. It has a very short sidereal year - 59 days (not 88 as previously thought) and zing! It's time to ring in the new year again! The confusing part is that its sidereal day is 176 days long... that is one LONG day for a planet so close to the sun. Just one of those freaky things, I guess. Mercury is not easily visible without a telescope and some kind of guide to give you optimal viewing times and coordinates. And don't be stupid - you absolutely need a solar filter to try to view Mercury!

Our next stop in the pantheon of solar system live-ins is Venus. While Venus looks pretty enough from space, don't let that lethal atmosphere fool you. It is as harsh as any terrestrial planet could be and looks more like the jovian planets than it does the terrestrial ones. (A siderial year is one measured by the placement of a specific star in the sky.) While it has a siderial year of a 224.7 days, it's rotational period (siderial day) is much slower than that of Mercury, one day being -243 of our days! Wondering about the negative? It's not a typo - Venus rotates retrograde, so it has a western sunrise and an eastern sunset. How strange is that? On 8 June 2004, Venus passed directly between the Earth and the Sun, appearing as a large black dot travelling across the Sun's disk. This event is known as a "transit of Venus" and is very rare: the last one was in 1882, the next one is in June of 2012 but after than you'll have to wait until 2117.

You've been to earth - or Terra - and while you may not have seen much of it, you know the basics - it is in the right place to have water, enough of a breathable atmosphere to support life and while temperatures can be drastic, we still manage to live on most of the planet. We have a generously sized moon, too, just known as the Moon - no Greek or Roman names for this one. Interstingly, the moon has a siderial rotation length of 27.321661 days - one Terran month, for the most part. Its sidereal year? The same.

Mars we all know. It is comparible to Terra in size, shape, axial tilt, length of day 24.6 hours instead of 23.934 hous for us. Its siderial year is 686.93, nearly twice the length of our year. It has a ruddy look to it from the amount of iron in its soil. There seems to be no doubt of the existence of water on Mars, but it has too weak a gravitational pull to really hold onto a good viable atmosphere. Mars does have two moons, Phobos and Deimos, but having seen images of them, they clearly appear to be asteroids that are amenable to following Mars around rather than staying put in the huge asteroid belt separating Mars and Jupiter or our terrestrial planets from our jovian planets.

Speaking of that asteroid belt, it is known as the Main Belt and has over 90,000 numbered asteroids in it. So the next time you are scratching your head over those two not-so-moon-like moons that Mars has, this is undoubtedly their origin! The Main Belt does not need a lot of attention, other than to point out its placement and number of known bits and pieces.

Onto the fun stuff, the four jovian planets, separated from us Terretrial planets in so many, many ways!

Jupiter is no small creature. And all that bulk definitely attracts some of the smaller moons to crowd around it. At this time, Jupiter is very busy with its brood of 63 moons! I know of about 12 - 15 but not 63. I suspect when you are that size, with that kind of gravitational pull, you are getting everyone! Jupiter has a siderial day of 9.925 Earth hours - wow, that is one fast-moving day! However, its siderial year is 11.8865 of our years. It probably could have been faster, but may be held up by its mass... Where we have an orbital inclination of 23.5 degrees and Mars is our sister planet with an inclination of 25.2 degrees, Jupiter has hardly any axial tilt - just 3 degrees! Pretty short. Then again, I can't quite see spring, summer, autumn and winter there, can you?

And here is a list of Jupiter's many, many satellites... (just the named ones...)

1. Metis
2. Adrastea
3. Amalthea
4. Thebe
5. Io
6. Europa
7. Ganymede
8. Callisto
9. Themisto
10. Leda
11. Himalia
12. Lysithea
13. Elara
14. Iocaste
15. Praxidike
17. Harpalyke
18. Ananke
19. Isonoe
20. Erinome
21. Taygete
22. Chaldene
23. Carme
24. Pasiphae
26. Kalyke
27. Megaclite
28. Sinope
29. Callirrhoe
30. Euporie
31. Kale
32. Orthosie
33. Thyone
34. Euanthe
35. Hermippe
36. Pasithee
37. Eurydome
38. Aitne
39. Sponde
40. Autonoe

Yikes. Again, those are just the named ones...!

There is Saturn, huge in its orbit but the first to be noticed by astronomer Galilieo as having "ears". Its sidereal day is about 10.656 hours; but its sidereal year is 29.4 years. Wow, that is a long time. The bigget attraction, of course, are the rings, of which we have the A through F belts. The largst gap between them is the Cassini Division. Pretty cool, eh? The fun part is postulating how the rings got there... was it a freak accident? A moon that somehow bit the dust and ended too pulverized to be a satellite but not so much that it didn't leave a really obvious trail around its home planet. Saturn is not lacking for moons. It has a total of 56 moons, of which 35 are named:

1. Albiorix
2. Atlas
3. Calypso
4. Daphnis
5. Dione
6. Enceladus
7. Epimetheus
8. Erriapo
9. Helene
10. Hyperion
11. Iapetus
12. Ijiraq
13. Janus
14. Kiviuq
15. Mimas
16. Methone
17. Mundilfari
18. Paaliaq
19. Narvi
20. Pan
21. Pallene
22. Pandora
23. Phoebe
24. Polydeuces
25. Prometheus
26. Rhea
27. Siarnaq
28. Skathi
29. Suttungr
30. Tarvos
31. Telesto
32. Tethys
33. Thrymr
34. Titan

35. Ymir

That is an insane amount of moons to have orbiting one planet, no matter how generously sized that planet may be! I suspect that as more moons (or small trapped objects encircling Saturn) come to the fore, more got names outside of the usual Roman/Greek pantheon. Prometheus, Rhea, Titan, those all look quite familiar and known but when I look at names like Sianaq, Suttungr and Paaliaq, I find myself thinking that those names have more Middle Eastern flavour...

Well, the best is yet to come!

The best will always be Uranus, (pronounced YOOR un us), a gorgeous blue ball with very faint rings of its own. Once considered one of the blander-looking planets, Uranus has been revealed as a dynamic world with some of the brightest clouds in the outer solar system and 11 rings. The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet from the Sun is so distant that it takes 84 years to complete one orbit. Fortunately its siderial day is considerably shorter at -17.54 hours. Yes, Uranus' rotation is retrograde.

Uranus is even more unusual in that its axial tilt or equatorial inclination is 97.86 degrees - which basically means that it has east and west polar regions and the sun rises in the north and sets in the south - I think. That seems very odd. Not one of the other celestail bodies that comprise our solar system have such a different approach to things like Uranus does!

Uranus also keeps a fair amount of moons, as seen below.


1. Cordelia
2. Ophelia
3. Bianca
4. Cressida
5. Desdemona
6. Juliet
7. Portia
8. Rosalind
9. Mab
10. Belinda
11. Perdita
12. Puck
13. Cupid
14. Miranda
15. Francisco
16. Ariel
17. Umbriel
18. Titania
19. Oberon
20. Caliban
21. Stephano
22. Trinculo
23. Sycorax
24. Margaret
25. Prospero
26. Setebos
27. Ferdinand

Not as out of hand as the other two gas giants, Uranus still has its shares of moons. Those names are all fairly obvious although how Juliet snuck in without Remeo or any of the others from Romeo & Juliet is a mystery to me... Maybe there is a Juliet in A Midsummer's Night Dream...

And then there is, finally, the last planet in our very exclusive group: Neptune. The eighth planet from the Sun, Neptune was the first planet located through mathematical predictions rather than through regular observations of the sky. (Galileo had recorded it as a fixed star during observations with his small telescope in 1612 and 1613.) When Uranus didn't travel exactly as astronomers expected it to, a French mathematician proposed the position and mass of another as yet unknown planet that could cause the observed changes to Uranus' orbit. After being ignored by French astronomers, Le Verrier sent his predictions to Johann Gottfried Galle at the Berlin Observatory, who found Neptune on his first night of searching in 1846. Seventeen days later, its largest moon, Triton, was also discovered. Nearly 4.5 billion kilometers (2.8 billion miles) from the Sun, Neptune orbits the Sun once every 165 years. It is invisible to the naked eye because of its extreme distance from Earth. Interestingly, due to Pluto's unusual elliptical orbit, Neptune is actually the farthest planet from the Sun for a 20-year period out of every 248 Earth years.

Neptune, like its brethren, is a fast bugger on the sidereal day level, taking a zippy 16.11 hours to complete one rotation! But the length of its year is a bit on the long side - longer than our life spans! Its equatorial inclination sounds a lot more like us: 29.58 degrees, although I still can't imagine its seasonal changes being anything like ours.

There are visitors that come on a regular basis to visit, such as a plethora of comets (the most well-known being Halley's Comet who pops in about once every 76 years. (I saw Halley's Comet through the telescope on Garrett Mountain... good thing, otherwise there'd have been nothing to see! I had a much better time viewing Hale-Bopp, which wizzed through over the course of many days in the spring and the winter as it made its slingshot arouns the sun. It was delightfully visible to the naked eye, and more amazing through the lowest setting on my telescope!

We also have the Oort cloud and the Kuiper Belt as part of our solar system, but I am happy to say that Pluto, while a part of our solar system and certainly welcome to stay, is now what it always was: an asteroid!