Astronomy / Space New Horizons - First Photos of Pluto

[Ram Paige]

...there's some debate as to wether our own moon is technically a dwarf planet too

Uh, no there isn't.

Unless you include the tinfoil hat crowd. There is no debate, that's just silly.

A moon is categorized as a body orbiting a larger host planet. Even dwarf planets have moons, Pluto has several but we don't call them dwarf planets.

Our moon is just that, a moon. Nothing more.

 

[Ambroza]

Uh, no there isn't.

Unless you include the tinfoil hat crowd. There is no debate, that's just silly.

A moon is categorized as a body orbiting a larger host planet. Even dwarf planets have moons, Pluto has several but we don't call them dwarf planets.

Our moon is just that, a moon. Nothing more.

Actually yes, there is. Have you ever heard of a binary planet system? They are present in the game.

 

[SirFreddie]

Actually yes, there is. Have you ever heard of a binary planet system? They are present in the game.

Yes. And as the moon circles the Earth the Earth circles the Moon and the Sun in its way circles both of them... I'ts called Physics

 

[Ram Paige]

Trolls, the lot of you.

While binary systems do exist, their defined differently and I won't go into what has already been clearly established.

 

[Windscreen Smudge]

Yes. And as the moon circles the Earth the Earth circles the Moon and the Sun in its way circles both of them... I'ts called Physics

Given your avatar I don't feel that we can trust your opinion on this matter to remain unbiased.

 

[Ambroza]

Trolls, the lot of you.

While binary systems do exist, their defined differently and I won't go into what has already been clearly established.

That's the thing, binary planet systems aren't very well defined, which is why this debate exists. Our moon is much larger than any other moon we've observed yet. The Moon doesn't orbit the center of the Earth, rather, both the Earth and Moon orbit a point somewhere in the Earth's mantle.

 

[HarlequiNQB]

That's the thing, binary planet systems aren't very well defined, which is why this debate exists. Our moon is much larger than any other moon we've observed yet. The Moon doesn't orbit the center of the Earth, rather, both the Earth and Moon orbit a point somewhere in the Earth's mantle.

Actually the Moon is the 5th largest known planetary satellite; Ganymede is about three times it's size. What the moon is, is the largest moon we know of in ratio to the planet it's orbiting, being about a quarter of the size of Earth (though it's mass is much lower than a quarter of Earth's - I forget exactly how much, like 0.0123456789 of Earth's, but that seems far too pat). To be fair though, the number of known planets with moons isn't particularly high - so its a bit like saying 'Jupiter is the largest planet we know of' 60 years ago; we have since discovered far, far more massive planets, so Jupiter wasn't the best example of a large planet, just the best we had at the time.

Yes, the Moon and Earth do orbit around a point somewhat offset from the centre of the planet - so does every planet/moon system (unless there is some interesting planet with moons spaced in such a way that their gravity cancels out this little offset) - It's just that with the Moon being so large compared to the Earth it's a little more offset than most. That doesn't make it a binary planet necessarily, although I have heard it described that way (allegedly the European Space Agency has used the term unofficially, but I don't know the exact circumstances of that).

For me at least the point of rotation of the two bodies together would need to be somewhere between the two bodies for me to say "These are twin bodies." I'm not in charge of definitions though, so who knows, it may happen one day though. For the time being it's a moon, by virtue of it being it's name, and the very thing we defined moons from in the first place

 

[Ram Paige]

^^ Ninja'd but basically this. Titan, a moon of Saturn, is actually bigger than Mercury - a planet.

 

[adoredtv]

Actually the Moon is the 5th largest known planetary satellite; Ganymede is about three times it's size.

No it's only about half as big again. 5,268 km vs 3,474 km = 52% larger.

For me at least the point of rotation of the two bodies together would need to be somewhere between the two bodies for me to say "These are twin bodies." I'm not in charge of definitions though, so who knows, it may happen one day though.

What about when a larger "moon" orbits a smaller "planet" due to mass? That'll be rare but possible I guess.

 

[gamecat]

The Moons orbital center point is only slightly off.

 

[Undecided]

No it's only about half as big again. 5,268 km vs 3,474 km = 52% larger.

52% in radius. It's over 3 times its size in volume.

These things happen when people measure "bigness".

 

[adoredtv]

52% in radius. It's over 3 times its size in volume.

These things happen when people measure "bigness".

Yes good point. Based on the rest of his comment about the moon "being a quarter the size of Earth" I thought it clear that he meant diameter/radius.

 

[AsukaZ]

The first photos of Pluto are upon us..!

Oh cool I remember when this was launched.
I put a countdown timer on a mayspace page then, It's probably still going.
I haven't been on myspace in ages.

 

[Dakron Nova]

I have to ask. I am not a telescope type person but if Hubble can see "billions and billions" of stars at great distances why is it that it takes a murky looking puddle picture of a planet in our own system?

According to NASA its all to do with size and distance, although Pluto is close (relatively) its very small so size/distance means its ratio is tiny compared to other items hubble looks at.

 

[Ram Paige]

"Pluto is so small and distant that the task of resolving the surface is as challenging as trying to see the markings on a soccer ball 60 kilometers away." - NASA

 

[tdquasar]

Yes. And as the moon circles the Earth the Earth circles the Moon and the Sun in its way circles both of them... I'ts called Physics

That's a quite simple model. Actually they all orbit around the center of mass of the system. Which is also just a model and you can go even deeper if you wish.

 

[Alatar]

Pluto isn't a planet because it didn't clear its orbit of other objects just like ceres didn't and unlike the 8 planets that did.

And it's hard to see because it's incredibly small in the sky. Stuff like nebulae and galaxies might be far away but they're also incredibly big so they take up a reasonable portion of the night sky. The Orion nebula for example is actually sometimes hard to image with a telescope because it's too big in the sky. But pluto is really small so taking a photo is hard. And the meh magnitude doesn't make it easy either.

 

[knowles2]

Pluto isn't a planet because it didn't clear its orbit of other objects just like ceres didn't and unlike the 8 planets that did.

Actually that isn't true, Earth hasn't cleared it orbit, the Earth passed through several asteroid fields which is why we have meteor storms.

 

[Ram Paige]

Actually that isn't true, Earth hasn't cleared it orbit, the Earth passed through several asteroid fields which is why we have meteor storms.

Actually, that isn't accurate at all. We have meteor showers for a variety of reasons, but 'passing through several asteroid fields' in not one of them.

1 - There is only one main asteroid belt, located between Mars and Jupiter.
2 - Earth's orbit does not cross the asteroid belt.
3 - Meteors and meteorites vary in size from grains of sand to the size of a bus. Most aren't larger than a marble or an ice cube.
4 - Most meteors on Earth are the result of Earth passing through the remnants of comets that have orbited the Sun.
5 - Earth has quite effectively cleared its orbit and has for several hundred million years.

What @Alatar is referring to is the third rule of planetary classification and his statement is exactly accurate. Where Pluto resides, within the Kuiper Belt, there are swarms of bodies meandering about. The 'larger' bodies have only just begun to 'mop up'.

This accretion process takes much longer as you get further from your host star as the distances are much, much more vast.

 

[nexxo]

According to NASA its all to do with size and distance, although Pluto is close (relatively) its very small so size/distance means its ratio is tiny compared to other items hubble looks at.

[video=youtube;dS12p0Zqlt0]https://www.youtube.com/watch?v=dS12p0Zqlt0[/video]