Interesting - Earth Has a Second Moon?

[eclark1894]

And really, who gives a tinker's cuss what the 'official' definition of a 'planet' is - probably not the majority of the 9,600 members who weren't there for the vote, who were maybe too busy doing real science !

Well, there is a need for the definition other than "orbits the sun". Technically, Halley's Comet orbits the sun, albeit, in a 75 year elliptical orbit. Thing about that is, Halley's supposedly uses the sun to sling shot around the sun and back the other direction. My question is this: What sends it back this way? So, either Halley's is in a true orbit around the sun, or there's something big just beyond our known solar system.

 

[3dcheapskate]

Well, there is a need for the definition other than "orbits the sun". Technically, Halley's Comet orbits the sun, albeit, in a 75 year elliptical orbit...

I'd guess that the distinction between planets, comets, moons, and the other stuff has been fairly clear for several centuries at least (maybe less for the 'other stuff'), with occasional (and ongoing) refinements - and I'm thinking here of 'distinction' as having rather fuzzier boundaries than 'definition', with Pluto in the fuzzy area between planet and 'other stuff'.

...Thing about that is, Halley's supposedly uses the sun to sling shot around the sun and back the other direction. My question is this: What sends it back this way? So, either Halley's is in a true orbit around the sun, or there's something big just beyond our known solar system.

I always thought that the path of Halley's Comet was explained by Kepler's law (I think) and the sun and known planets? Isn't that the reason we know exactly when and where we'll see it next?

 

[Gadget Girl]

So I could be wrong, but this is my understanding of what happens with things like comets (actually I believe this is how all orbit's work, but it simply seems dramatic when it comes to something like Halley's comet because the orbit is so long and thing, rather than a more circular ellipse like the planets.

So let's assume that the sun is sitting at 0,0,0 of our axes. If we orient our axes so that when Halley's comet is traveling towards the sun it's traveling in the -Y direction, and when it's traveling away it's traveling up, or in the positive Y direction, this is what happens:

The sun's gravity pulls Haley's comet down (-Y). As Halley's comet get's closer to the sun, the pull of gravity gets stronger because the force of gravity in simple terms is mass/distance, so the closer you are, the stronger gravity is. But Halley's comet isn't traveling only along the Y direction it also has movement in the other axes as well and isn't headed on a crash corse towards the sun. So as it gets closer and closer to the sun, it builds up more and more speed and so more and more momentum. When it passes the sun it's moving pretty fast, so it doesn't just get pulled into the sun. But once it has passed the sun, the sun's gravity is still pulling on it, only now it starts to pull it along the X axis instead the Y. So it get's pulled around the sun and swings around. But it in doing so it's still got a lot of the original momentum from being pulled 'down' towards the sun in the first place. The swing around the sun is the 'slingshot' effect and so once it starts heading back up the Y axis, it has a lot of speed and starts heading away from the sun at a really fast pace, until it hits the zenith of it's orbit, at which point for a moment it has not movement in the Y direction, and then it starts falling back towards the sun again.

Like I said, I think that's right. At least here I don't have to explain what an axis is

 

[McGyver]

"That's no moon... It's a space station!..." Star Wars... In the Millennium Falcon... After finding the Alderan particles and discovering the Death Star... No?...
I'm fine with having a second moon... As long as it doesn't get bored and decide to visit earth.

 

[Miss B]

 

[eclark1894]

"That's no moon... It's a space station!..." Star Wars... In the Millennium Falcon... After finding the Alderan particles and discovering the Death Star... No?...
I'm fine with having a second moon... As long as it doesn't get bored and decide to visit earth.

Actually, you might have something there, McGyver. This "moon", Mimas, is in orbit around Saturn.

 

[Lorraine]

Hey, Mac!, long time no see

 

[eclark1894]

Also, a bit of trivia.... anyone know the "official" names of the moon, and the sun? I just found out today, and I actually thought I already knew this answer. I was wrong!

Bonus points if you know the 'official' names of the galaxy and universe we live in as well.

 

[Satira Capriccio]

Moon, Sun, Galaxy (aka Milky Way Galaxy, just not in technical writing), Solar System, and Universe.

At least ... according to the IAU.

 

[eclark1894]

Moon, Sun, Galaxy (aka Milky Way Galaxy, just not in technical writing), Solar System, and Universe.

At least ... according to the IAU.

Cheater.

 

[quietrob]

Our actual address according to Michio Kaku is Planet Earth, Solar System, Milky Way Galaxy, Local Group, Virgo Supercluster, Laniakea Galactic Supercluster and I will add the center of the Universe just to start trouble!

So There!

 

[Gadget Girl]

Hmm, interesting. I would be tempted to go with Luna and Sol for the moon and sun, but it does all bring up an interesting point. Those names are a bit Euro-centric. I kind of like the idea that the moon is just 'moon' in whatever language you happen to speak natively, and the same for the sun. On the other hand that would be a bit confusing at an international autonomy conference.

 

[Miss B]

Yeah, I like Luna and Sol as well, and Gaia for Earth.

 

[3dcheapskate]

Since the names that we use for the planets are Mercury, Venus, (then there's that 'Earth' one we live on that doesn't fit in name-wise), Mars, Jupiter, Saturn, Uranus*, Neptune, Pluto are all* names of Roman deities, then Sol and Luna would seem to fit in nicely. Gaia on the other hand is Greek, which doesn't seem to fit the pattern*?

But I did a bit of searching and found this interesting article - What is the sun’s proper name? | EarthSky.org

I like the conclusion that "people don’t agree on whether the sun has its own name, or what that name might be", although the IAU seems to implicitly approve of Sun, Moon and Earth (with an initial capital) - International Astronomical Union | IAU (that link was from the EarthSky article).

*Roman (or Greek)? Mercury (Hermes), Venus (Aphrodite), Mars (Ares), Jupiter (Zeus), Saturn (Kronos), Uranus (?), Neptune (Poseidon), Pluto (Hades).

 

[3dcheapskate]

- Timeout on editing the previous post: another interesting article from the USGS (the earthquake people) - Planetary Names: Categories for Naming Features on Planets and Satellites
(and there's hours-worth of interesting reading from the navigation links top-left of that page, e.g. Planetary Names: The Moon
- Regarding Uranus, the standard online answer appears to be Uranus=Caelus=Sky god. I eventually found this Uranus: Museum Victoria "Its name comes from the Greek Uranus, meaning 'sky', and was therefore the first planet with a Greek, rather than Roman, name. He was never actually worshipped by the Greeks and has no Roman equivalent. From his union with his mother Gaia bore the Titans." How I miss my books!

... I actually thought I already knew this answer. I was wrong!...

It seems to me that curiously, the older and wiser we get the more this seems to happen?
(I personally believe that it's because they're secretly changing the answers behind our backs! )

Also, a bit of trivia.... anyone know the "official" names of the moon, and the sun? Bonus points if you know the 'official' names of the galaxy and universe we live in as well.

I'd've put my money (but not very much!) on some form of catalog designations, as for me 'official' brings to mind bean-counters and umpteen-plicate copies of everything. And Vogons.
Second bet would've been Luna, Sol, Via Lactea (to keep that Latin* thing going), and Universum
Third would've been my first answer before the question was actually asked, i.e. the Sun, the Moon, the Milky Way, and the Universe.

*English, Latin, or Greek? Milky Way, Via Lactea, or Γαλαξίας (Galaxias)... mmmmm... chocolate ! Oh, and that's probably where the word 'galaxy' actually comes from in the first place - I probably knew that. A long, long time ago.

 

[3dcheapskate]

Earth I (Moon) ! - Planetary Names: Planet and Satellite Names and Discoverers

 

[Zaarin]

Earth I (Moon) ! - Planetary Names: Planet and Satellite Names and Discoverers

Actually, based on current naming conventions it would be Earth b.

 

[quietrob]

Of Course they keep changing the answers. When this whole shindig started, all of the heavenly bodies were orbiting the Earth. Now it's the age of the Universe which seems to get older by a billion years every few years. Heck when Einstein made his discovery that light bends due to gravity, the entire universe was considered to be the Milky Way. Professor Hubble changed that. Now I believe each point of light in this map is a galaxy.

Quick Hive Poll!

How many planets do we have in our solar system? I say 9.

 

[3dcheapskate]

Actually, based on current naming conventions it would be Earth b.

Awwww! And I was just about ready to believe that the IAU WGPSN were the ultimate, topmost, highest authority when it came to naming big-lumpy-type things whizzing around the Solar System. (Which leads nicely into my next guess: The Moon, the Sun, the Galaxy, and the Universe, with the initial capital letter and preceding 'the' being the clincher in each case.
Personally I now prefer S/-1000000 E 1 for the moon (sorry, I meant the Moon). I understand that this is the standard format for temporary designations, and since I'm still really not 100% sure of the ultimate, official, rubber-stamped, name for the Moon I feel safer sticking with a temporary name. S/ indicates it's a satellite, -1000000 is the year it was discovered (I have to admit that I've been a tad arbitrary with the actual year, and I feel that a nice round number sounds less pretentious in this case. After all, if I used -1000029 everybody would probably think I was an idiot!), E that it's a satellite of the Earth, and 1 that it's the first satellite - I think that means first in terms of discovery date?)

By the way - has anybody read A Wreath Of Stars by Bob Shaw ?

 

[3dcheapskate]

Quick Hive Poll! How many planets do we have in our solar system? I say 9.

That's easy - 9. Or 8. Or maybe 10 or more. That we currently know of, of course. Not counting Niburu.