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back to article Hubble finds fifth moon orbiting Pluto

The Hubble Space Telescope has found yet another moon orbiting what used to be the last planet in the Solar System. The moon, the fifth that's been spotted orbiting Pluto, is an irregularly shaped lump around 6 to 15 miles across and orbits in a plane 58,000 miles around the dwarf planet. It was spotted in nine images taken with …

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the New Horizons probe, which carries some of the ashes of Pluto's discoverer Clyde Tombaugh

...what a superb tribute!

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Trollface

Re: The ashes of Pluto's discoverer Clyde Tombaugh

Will they be thrown overboard at some point, to lithobrake (icebrake?) on Pluto's surface?

Also, when do we get to rename one of Pluto's moons as 'Mass Relay'?

It was in Mass Effect so it must be true...

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Silver badge

Re: the New Horizons probe, which carries some of the ashes of Pluto's discoverer Clyde Tombaugh

So now it's been found, what do we do with it?

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Headmaster

Ahem...

"Eventually the New Horizons probe ... will become the furthest man-made object to travel from Earth".

Nope. It's velocity is already less than that of Voyager I by 2 km/s and it will only slow down further as it goes through termination shock and loses the solar wind from its' sails. It will never catch up with Voyager.

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Anonymous Coward

Re: Ahem...

"Eventually the New Horizons probe ... will become the furthest man-made object to travel from Earth".

Nope. It's velocity is already less than that of Voyager I by 2 km/s and it will only slow down further as it goes through termination shock and loses the solar wind from its' sails. It will never catch up with Voyager."

Not unless a galactic zargon beam intercepts Voyager 1 and destroys it - with all life on board.

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Always has been..

a planet, always will be.

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Stop

Re: Always has been..

@Dave Ross

>>Always has been.. a planet, always will be.

What about Eris? similar size to pluto, similar orbit, is that a planet? and then there's the slightly smaller Makemake, is that a planet? smaller still, but of a similar factor, then there's Haumea, Sedna, 2007 OR(10), Quaoar and Orcus, are they planets? do we have 15 planets? in the solar system (and still counting)?

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Boffin

Moon vs really big asteroid

When does an orbiting asteroid become big enough to become a moon? Enquiring minds must know.

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Re: Moon vs really big asteroid

If it's orbiting a planet then might be moon.

If it's orbiting some random lump of rock in a highly elliptical orbit...

that was named after a fictitious dog...

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Bronze badge

Re: Moon vs really big asteroid

Moons orbit planets, asteroids orbit the star, comets sell shoddy electrical merchandise.

Otherwise, there's little difference.

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Coat

Re: Moon vs really big asteroid

> If it's orbiting a planet then might be moon.

But Pluto isn't a planet, so none of them are moons!

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Headmaster

Re: Moon vs really big asteroid

Pluto is a dwarf planet ergo it is a planet

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Joke

Re: Moon vs really big asteroid

So the new moon should then be called Snow White, to follow the Disney tradition?

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Anonymous Coward

Re: Moon vs really big asteroid

"But Pluto isn't a planet, so none of them are moons!"

Yes it is. Dwarf planets are a category of planets. You wouldn't say that a hatchback or city-car 'wasn't a car', would you?

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IT Angle

Re: Moon vs really big asteroid

A better analogy would be trying to categorise a Reliant Robin, I think.

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Re: Moon vs really big asteroid

According to New Scientist, "Pluto may not be a planet any more, but the discovery of its fifth moon means it can boast more satellites than the inner four planets combined."

-- http://www.newscientist.com/article/dn22052-discovery-of-fifth-moon-reignites-pluto-planet-debate.html

I agree it should be a planet, but that doesn't make it one.

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Go

You go to Pluto

Looking at "Charon (green) rocks Pluto's world". Why does it look like the two repel each another? Shouldn't Pluto be @ the other side of the red circle? (180° further along its orbit, yadda yadda).

I'm no scientist and this won't really affect at what time I break open my lunch tin. But .... Enquiring minds must know.

<=== Boldly go where no-one else bothered to go before.

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Boffin

Re: You go to Pluto

"Shouldn't Pluto be @ the other side of the red circle?"

No. Since this is an Olympic year, you will forgive the athletic analogy. Think of Pluto as the hammer-thrower, and Charon as the hammer.

Got it?

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If Pluto were positioned on the perihelion...

They both orbit around their common center-of-mass. At no time can that center of mass be on Pluto's far-side away from Charon.

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Alien

Gotta be the first to say it...

Thats no moon.......

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Re: Gotta be the first to say it...

That's no planet either........

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Anonymous Coward

"an irregularly shaped lump around 6 to 15 miles across"

So THAT'S where John Prescott went!

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Re: Moon vs really big asteroid

The definition of planet is that it is in orbit around the Sun, has sufficient mass to assume aroughly spheroid shape and has "cleared the neighbourhood" around its orbit.

Where there are two bodies rotating round each other, the planet is the one where the centre of gravity is below its surface. (another nail in the coffin for pluto).

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Anonymous Coward

Re: Moon vs really big asteroid

The people who wrote the definition and defined Pluto as a dwarf planet disagree with your armchair observations...

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Gold badge

Re: Moon vs really big asteroid

So imagine the scenario where there are two jupiter sized bodies orbiting each other. With the centre of gravity between them, neither is a planet? Since neither is orbiting a planet, neither is a moon? Does that make them fekin giant asteroids? (If so, how many shots does it take to make them disappear on my Atari?)

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Joke

Re: Moon vs really big asteroid

>how many shots does it take to make them disappear on my Atari?

Probably the whole bottle :D

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Headmaster

Re: Moon vs really big asteroid

Actually that's still under contention. The definition you quote was made up by astronomers (those who study stars), but a lot of the the planetologists (those who study _planets_) don't agree with that new definition. See http://greatexperiments.wordpress.com/2012/04/14/what-is-a-planet-the-planetologists-speak/ There are other places out there that discuss this, I first heard about the controversy in an interview of a planetologist.

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Image processing

Can anyone say why the centre part of the image has a nice black background with no artefacts/noise, etc. ? (If anyone answers just saying photoshop, without saying why it's done I'm not going to buy them a pint)

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Silver badge

Re: Image processing

Complete guess, the glare of the much larger Pluto and Charon obscures reflections from the smaller moons. So the area containing the two main bodies has been partially obscured.

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Pint

«After blasting past Pluto the New Horizons probe will fly on

to investigate objects in the Kuiper Belt with its infrared and ultraviolet spectrometers, a multi-colour camera, two particle spectrometers and a space-dust detector.» Not a chance ! When it discovers those «Russian dolls», it's not going to go anywhere, but break out the samovar and invite the dolls to tea....

Henri

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