Pluto is a planet after all

[howabout]

I always thought it was but given the new views of its landscape and atmosphere can there be any doubt?

We have an historic observatory where we live and on open days we have Martian holidaymakers visiting so I worry my views are unduly coloured

I thought he was a dog

Pluto has always been a planet.

Ignore what the nasty bullies say!

80s child!

My dd1 just rolled her eyes at you. Years of Percy Jackson obsession reliably inform her that Pluto is named after the God of the Underworld - now going to have to check if Disney Pluto looks up to the planets or down to the underworld.

(Having read the Wikipedia article to refresh memory and appear well-informed...)

Pluto was named after the Greek God, and it's suggested that Disney was then inspired to use it for Mickey's dog. (Interesting trivia: the first two letters of Pluto are the initials of Percival Lowell, the discoverer).

If you agree that Pluto is a planet, do you think Eris is too? Eris is more massive than Pluto and orbits the Sun.

I don't think of it as a planet.

Fingers crossed for Pluto so we can resume all the proper earlier mnemonics. No Eris please, see above.

depends on the criteria which need to be satisfied in order for something to be categorized as a planet?

If Eris gets it what about Sedna? Anyway, bollix to the Kuiper belt objects planetary pedants, I grew up naming nine planets, so there.

While I have every sympathy with the "I grew up with nine planets" argument (me too!), it's a bit weak - those who grew up in the 1920s would have excluded Pluto on the same grounds.

With the discovery of Eris, astronomers at least tried to come up with a scientific (clear, objective) definition of a planet, and Pluto didn't meet it. It would seem that a scientific definition that did admit Pluto would also admit Eris.

Pluto has got the coolest orbit! It gets closer to the Sun than Neptune on occasion.
I love conic sections (geek!)

Yep, lovely bit of maths leading from the inverse square law for gravity to showing that where you have one massive object (ie the Sun) all other objects will follow paths that are conic sections (ellipses and hyperbolas in practice).

I believe the geometry / resonances of the situation ensure that even though Pluto's orbit comes inside Neptune's, there is no possibility of them colliding.

Wow Love the physical poetry of the universe.

All a problem with not being able to dominate his moon apparently

Yeah the barycentre of Pluto and his moon is outside of Pluto, which is unusual.
Told you I'm a geek!

I think its a planet. I am Scorpio and it was my planet, so clearly it must be one.

Yeah the barycentre of Pluto and his moon is outside of Pluto, which is unusual.

Yes, it's unique among planets. It doesn't take much thought to guess all the other planets with moons must have the barycentre well inside their surface. The Earth is the only one where I double-checked (as it has a relatively massive moon), but its b/c is about 1000 miles beneath Earth's surface.

dd1 informed me Mercury and Venus don't even have moons. According to the google oracle this is because they are so close to the sun any moons would have been sucked into it and destroyed.

I think the case for Pluto is getting stronger.

Haydee DH, dd2 and my big brother are all scorpios. When all 3 of them are in the house together sending them all off to their own planet is a pretty attractive option

I love that Pluto got downgraded. As a very cynical Scorpio it has given me lots of ammo to fight with astrologers.

I'm 59 and I had 9 planets for years.
I've heard the younger generation was careless but losing entire planets !
< grumpy old bag, slams thread door >

I try my best not to engage with my Scorpios MrsTerryPratchett. Volatile doesn't even start to cover it.

Moons of Mercury or Venus wouldn't get sucked into the sun. What would happen is that the sun's gravity would make their orbits unstable. They would most likely be ejected from orbit around Mercury or Venus. From there, they would likely be ejected from the solar system or crash into a planet.

What's Eris? I've never even heard of Eris?

Come back BigChoc. The campaign for reinstatement is alive and thriving in our household and I am only 47 with 3 dds to carry on the crusade. I blame the babyboomers for robbing future generations of their planets

geekmommy my geek gene is now well and truly engaged. Only just weaned myself off youtube tutorials on solar and lunar eclipses. Ejection from the solar system sounds like an even worse fate than relegation to dwarf status.

There's a question over whether Pluto and its moon Charon are actually two dwarf planets who are orbiting around both each other and the sun. Just to confuse things further

Apparently Pluto is classed as a dwarf planet and not a full planet because to be a full planet the object needs to have enough gravitational pull to form itself into a sphere and to be able to clear the surrounding area of other space debris. Or something like that

Eris is three times further from the Sun than Pluto, the most distant object in the Solar System apparently, and only discovered in 2005, so quite understandable if you'd missed it.

en.wikipedia.org/wiki/Eris_(dwarf_planet)

I happily learned the order of the NINE planets from the sun:

Mum Very Easily Made Jam Sandwiches Under No Protest
or
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto

Then in 2005, Mike Brown discovered Eris, further out from Pluto.
So, maybe add "Ever" to the end of the mnemonic and have 10 planets.

We happily chanted "your anus" at school for our favourite planet
Now the poor little tykes are taught "YOOR-an-us"
Where's the fun in astronomy lessons now ?