Solar System has 8 planets instead of 9 — IAU official vote
Pluto loses its status as a planet, declared officially by International Astronomical Union (IAU) today on Aug 24, 2006 after several years of debate since its discovery in 1930.
Definition of a Planet
- must be in orbit around a star while not itself being a star
- must be large enough in mass for its self-gravity to overcome rigid body forces so that it assumes a… nearly round shape
- has cleared the neighbourhood around its orbit
With this definition, Pluto was automatically disqualified because its oblong orbit overlaps with Neptune’s.
Some Facts about Pluto
- A “demoted” planet
- Named after underworld god
- Average of 5.9bn km to Sun
- Orbits Sun every 248 years
- Diameter of 2,360km
- Has at least three moons
- Rotates every 6.8 days
- Gravity about 6% of Earth’s
- Surface temperature -233C
- Nasa probe visits in 2015
- Why the name “Pluto”? Read more…
Astronomers meeting in the Czech capital have voted to strip Pluto of its status as a planet.
About 2,500 experts were in Prague for the International Astronomical Union’s (IAU) general assembly.
The scientists rejected a proposal that would have retained Pluto as a planet and brought three other objects into the cosmic club.
Pluto has been considered a planet since its discovery in 1930 by the American Clyde Tombaugh.
The ninth planet will now effectively be airbrushed out of school and university textbooks.
“The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune,” said the IAU resolution, which was passed following a week of stormy debate.
*** *** ***
They agreed that to qualify as a planet, a celestial body must be in orbit around a star while not itself being a star. It also must be large enough in mass “for its self-gravity to overcome rigid body forces so that it assumes a… nearly round shape, and has cleared the neighbourhood around its orbit.”
Pluto was automatically disqualified because its oblong orbit overlaps with Neptune’s.
It will now join a new category of “dwarf planets”.
*** *** ***
Named after the god of the underworld in Roman mythology, Pluto orbits the Sun at an average distance of 5.9 billion kilometres (3.7 billion miles) taking 247.9 Earth years to complete a single circuit of the Sun.
An unmanned US spacecraft, New Horizons, is due to fly by Pluto and the Kuiper Belt in 2015.
Read more on: bbc.co.uk
See the official IAU’s voting result for Pluto’s planetary status.
Email This Article
| 28812 Views |Permalink
RSS feed
Barry said,
August 24, 2006
Isn’t Neptune also disqualified, then, because its orbit overlaps with Pluto’s?
“Pluto was automatically disqualified because its oblong orbit overlaps with Neptune’s.”
Korayem said,
August 24, 2006
Pluto is disqualified because its orbit is also oblong (not nearly circular) and tilting (not horizontal), I think.
Yummy Tofu said,
August 24, 2006
Let’s call it “Planetoid.”
dave hudson said,
September 7, 2006
as usual some pompous self righteous panel of so called experts take it upon theirselves to alter what has been an accepted fact for decades to suit their own narrow minded views on what is correct
runiks said,
December 4, 2006
it is disqulified because it didn’t clear its neighborhood…. as you can see its orbit overlaps neptune…. clearing neighborhood means having dominion in magnitude , mass especially
runiks said,
December 4, 2006
it is not disqulified because of the second criterion infact pluto meets the first and the second but fails for the last requirement
Cheyenne said,
April 25, 2007
Good web site
Cheyenne said,
April 25, 2007
Pluto not a planet????? Hmmmm…
Cheyenne said,
April 25, 2007
Poor Pluto!!!!!
Franky said,
June 11, 2007
if you wanna be a planet, you gotta learn how to fend for yourself, and stop overlapping other planets’ orbits. Get your mass up pluto, then you’ll get your title back, but not any flimsy old rock can be named a planet, know what im saying? no offense pluto, you’re cute and everything, but you’re just not up to par with the rest of the planets… survival of the fittest. lol, im stupid. but it’s kinda true.
Francisca Tapia said,
June 23, 2007
This is really intresting, love it!
Jonny said,
July 23, 2007
i think even Quaoar be a dwarfplanet. Eris is the biggest with i think 2700 km, also little smaller then Moon. Then is Pluto with 2400 km, ½ of Mercury. Sedna is not a dwarfplanet, but is something else. Sedna are 1800 km, ¾ of Pluto. And Quaoar and Charon(Pluto moon?) are 1200 km, ½ of Pluto and 2/3 of Sedna. Ceres are 1000 km, and the smallest dwarfplanet. It have circa 1/3 of asteroids mass i THINK.
neshelle said,
October 4, 2007
It’s cool learning that pluto is gone but,we have to get use 8 planets now.U feel me!
Ciara said,
October 20, 2007
Boo ho you got moved to dwarf planets so whatever grt over it!!!
jen said,
November 13, 2007
i wish someday,,i could live in venus
smart said,
November 19, 2007
pluto not being a planet ! the new horizon will give more news in 2015
kiluah said,
December 2, 2007
i think pluto is consider as a planet..because of its orbit roling in our solar system,,how the scientist say that the pluto is not a planet??please make me an answer…send a best answer in my email adrss….
this web needs more detail said,
February 27, 2008
this web realy has no detail about the s system
bryani woods said,
March 11, 2008
i wosh i could vist plutoooooo!
camelia said,
March 21, 2008
I love the planet satuarn it’s my favortie.
lolajamaican said,
March 24, 2008
i love jupiter and us to l;ove pluto but it is now a bwarf planet alonge with three other booooo
Teresa said,
March 27, 2008
We do not have 8 planets we have 12, we just have three drawf planets they are still planets. TRUST ME MY SCIENCE TEACHER TOLD ME!!!!!!!!!
lolajamaican said,
March 28, 2008
pluto is plain or shall i saY A DWARF planet
dedpigeon said,
April 12, 2008
You mean the earth is not flat?!
dementria said,
May 7, 2008
This will take some geting used to..after all these years. I think every celestial body (except stars, comets, asteroids ect) should be considered a planet including all the kuiper belt objects…
Denequa said,
May 7, 2008
Ummm…i was shock when i saw this wesite saying that there’s only 8 planets…OMG!! pluto has been demoted and i hope it come back to being a planet….WHEN I GET OLDER I WANNA BE AN ASTRONAUT!!!
SAHIL SANDHU said,
May 28, 2008
I LOVE PLUTO. I HOPE IT WILL BE SOON BACK AS A PLANET
Rohini said,
June 3, 2008
Pluto we really miss you. maybe not a planet anymore , but never miss hope to become one again
dolphin said,
September 19, 2008
WE MISS U PLUTO!!!!!!!!!