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 learnt
My Very Early Morning Jam sandwich Usually Nauseates People.
Which doesn't sound as good without the P, so of course Pluto is a planet.

"My Very Educated Mother Just Showed Us Nine Planets"

Interesting commentary on the changing role of women.

I would have to add Eventually to my mnemonic as it sometimes takes me a while to get round to the enquiring minions.

The dds spent an afternoon with their teacher coming up with their own versions and then made posters. Poetry, art and astronomy all at once - Scottish curriculum for excellence in practise. I don't think my primary school days were as much fun even allowing for the day I got iron filings all over the magnet.

"Eris - a personification of strife and discord" Doesn't sound like she should be allowed in the club.

Yes, even at school I was a militant feminist and objected, but - at a Girls' Grammar - they just laughed. GRRRR

It's not baby boomers who killed Pluto. Mike Brown, the astronomer who discovered Eris and who wrote a book about his involvement in demoting Pluto, was born in 1965. He's just over the line into Generation X. The book is called How I Killed Pluto And Why It Had It Coming, and is a fun read.

It's actually rather hard to throw something into the Sun. The Sun just isn't that big compared to the size of a planetary orbit. If you miss by a little bit, the object usually gets a gravitational slingshot and is generally ejected from the solar system. Ejection is the usual fate for the smallest object in a three-body system where the orbits aren't stable.

You should be careful excluding Eris from things. That didn't end so well in Greek mythology. The fallout ended up causing the Trojan War.

The definition of a planet has nothing to do with surface features. Lots of moons in the solar system have very interesting surface features. Mimas is a moon of Saturn that looks like the Death Star, Io is a moon of Jupiter that is covered in volcanoes, Europa is another moon of Jupiter that we think has a liquid ocean. And then there's Saturn's moon Iapetus, which is just plain weird. Those objects all have interesting surfaces, but nobody is arguing that they are planets.

Having a moon doesn't qualify an object as a planet, either. In the 90's, we found that a fairly small and very non-spherical asteroid called Ida has a moon, Dactyl.

Mike Brown is the same vintage as my big brother then. That explains everything. I think you should write a book on all this geekmommy Obviously I can't bring myself to engage with the Pluto killer no matter how fun and entertaining.

Planet: Officially definition

agreed 2006 by the International Astronomical Union (IAU):

1. it must orbit the Sun.
2. it must be big enough for gravity to squash it into a round ball
3. it must have cleared other objects out of the way in its orbital neighborhood. The issue for Pluto is that being in the Kuiper belt, the unlucky bugger has billions of objects to either pull in, or shove out into space.

The IAU claims Pluto is now in a new class of objects called "dwarf planets."

< picks splinters out of IAU arse >

I think Pluto has shifted loads of objects and has earned its full planet status

< proudly moons thread with pristine Big Choc arse >

It's a dwarf planet. Still technically a planet, but not in the same category as other planets. :)

The great thing about science is that it's always changing when new information is discovered.

Having an atmosphere can't qualify an object as a planet- Saturn's moon Titan has one.

There is historical precedent for demoting an object from planet status. The dwarf planet Ceres was considered a planet from its discovery in 1801 until the 1850's. By then, lots of other objects had been found in similar orbits between Mars and Jupiter, so it was reclassified as an asteroid, then as a dwarf planet in 2006.

Astronomers have nothing to do with astrology, and in fact calling an astronomer an astrologer is a good way to piss them off. You might also end up getting a lecture about why astrology is BS, depending on the astronomer and his or her mood. The ones who are professors at universities (at least in the US) Anyway, there's a historical precedent for demoting an object here, too- the moon was and is considered a planet by astrologers. It rules Cancer, IIRC.

It's kind of hard to make a logical argument as to why Pluto should be a planet but Eris and Ceres shouldn't. Eris is bigger than Pluto. Ceres is smaller, but there's really nothing special about Pluto's size. Ceres is spherical due to its own gravity, just like planets are. Ceres has some interesting surface features, too. Using Pluto's size as a cutoff is arbitrary. Scientists tend not to like arbitrary definitions. And we're now using the word "planet" to talk about objects outside our solar system. The arbitrariness of Pluto's size as a cutoff would be obvious there.

We can't know how many objects Pluto or Ceres has ejected from the solar system- they're gone into interstellar space or they've crashed into Pluto or Ceres and are now part of them. Even if you could see the objects in interstellar space (which is tricky in and of itself, since planets don't emit their own visible light), it would be hard to know if they were ejected by Pluto or Ceres.

geeky - I thought I read that Eris is smaller than Pluto, but it has a greater mass.

If you include Ceres or Eris, the mnemonic has to change. If we include any new objects or demote any, the number will of course change.

I bought a book for DD titled "Eight Spinning Planets". Maybe they are starting to teach kids differently in school.

howabout, I'm flattered, but 3 yo DD and 3 month old DS barely let me read a book these days, let alone write one. If the book isn't divided upinto small segments that don't take much time to read each one, forget about it.

DadDadDad, you're right. Pluto's size has been a subject of debate for decades, though, so I wouldn't be that surprised to see changes in the estimate of the radius for Eris or any other Kuiper Belt Objects. The masses are easier to measure in both cases, since they both have moons. You can find a planet's mass pretty easily from the orbit of its moon.

Why is makemake called makemake?

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?

Pluto's size has been a subject of debate for decades

Clearly size does matter.

Makemake is named after an Easter Island deity. They name these objects after deities, and using only Roman or Greek deities is a bit Eurocentric, plus they might run out of names that way. Quaoar, Haumea, and Sedna are also named after deities from various mythologies.

Thanks - I was right in thinking it wasn't Greek

They used some Greek and Roman deity names on asteroids, which of course brings them closer to running out.

The problem Pluto has is that it's orbit is, I believe, locked to that of Neptune's in some way. This means that it isn't the gravitationally dominant body in its orbit.

Clare and the Reasons have a stab at explaining this here:

At least they weren't debating the size of Uranus

I'm old too: but surely it's "Maths Very Easily Makes Jack Sleep Until Next Period"?! When did jam creep into it?!

Mike Brown in particular was interested in getting some less Eurocentric names given to dwarf planets and Kuiper Belt Objects. The person who discovers the object gets to name it.

I always thought that you had to clear your own orbit to be a planet. I feel sorry for Pluto but love that science clearly demonstrates the ability to say, ah fuck with what everyone thought, we've changed our minds.

A friends son just discovered a new planet. It hasn't been named yet (actually he discovered it over a year ago but it's just been confirmed)

Guess it'll be something to put in his personal statement!

I feel Pluto doesn't get a fair deal < indignant >

Having to clear its orbit with all the Kuiper Belt junk flying around is so much tougher work than those drawling dilettantes like Mars, Venus, Earth

Fair Planetary Status for Pluto NOW !
< snarls at Terrans >