Pluto loses planet status - Nature
The quote of the day is the recent newsrelease by Nature:
"Dwarf stars are stars. Dwarves are people," reasons Donald Lubowich, coordinator of astronomy outreach for Hofstra College of Liberal Arts and Sciences in Hempstead, New York. So as far as he is concerned, Pluto — the 'dwarf' planet — is still a planet. (Nature)
It makes me feel a bit better to hear this... Unfortunately, that's not what IAU explained after their vote.
Did anyone notice how the media is confused about how to present the news in simple words?
I still haven't heard a single good news report either on TV or on the Radio.
There has never been so much confusion!
|Published online: 24 August 2006; | doi:10.1038/news060821-11 |
Pluto loses planet statusTense debate ends with a definition of 'planet'.
Astronomers have been battling over the concept of what defines a planet all week at the general assembly of the International Astronomical Union (IAU) in Prague (see our conference newsblog for a blow-by-blow account).
In the end it was decided that to qualify as a planet in orbit around our Sun, a chunk of rock must have been made round by its own gravity; have cleared its neighbourhood of other debris; and not be a satellite of another planetary body.
Mercury, Venus, Earth, Mars, Jupiter, Uranus and Neptune all fulfil these criteria. But Pluto is just one of many bits of icy debris in orbit at the edge of our Solar System, known as trans-neptunian objects. Pluto's membership of the trans-neptunians disqualifies it from being a fully fledged planet because it has not 'cleared its orbit'.
Instead, Pluto is one of a new category of object to be known as 'dwarf' planets (which, not to be confusing, don't fall under an umbrella term of 'planets', and must, by definition, be written with single quote marks around 'dwarf'). These objects satisfy the other criteria, in being round and not a satellite. Ceres, which lies in the asteroid belt between Mars and Jupiter, is also now a 'dwarf' planet.
'Dwarf' planets in Pluto's neighbourhood, including the object nicknamed Xena (UB313), will be given a category of their own. But the IAU's most recent suggestion, that these be named 'plutonian objects', was narrowly voted down, by 186 votes to 183.
This move had been intended to soften the blow of Pluto's demotion. "There is a large Pluto fan club out there that is going to be incensed by our actions," Owen Gingerich, chair of the planetary definition committee, had warned earlier in the week. The rejection of 'plutonian objects' not only disappoints Pluto fans, it also means the category remains nameless.
That astronomers would reach any consensus at all on the concept of a planet looked unlikely earlier this week.
A draft definition issued on 16 August (see 'Planets are round. Will that do?') had received a hostile reaction: it was debated in lively sessions in which astronomers accused IAU officials of keeping them in the dark, and proposing something "silly".
The resolution had to be changed many times before astronomers were even happy voting on it.
But despite the successful vote and the IAU's best efforts at clarity, it seems there is still scope for some confusion. Already at the conference there are hints of problems.
"Dwarf stars are stars. Dwarves are people," reasons Donald Lubowich, coordinator of astronomy outreach for Hofstra College of Liberal Arts and Sciences in Hempstead, New York. So as far as he is concerned, Pluto — the 'dwarf' planet — is still a planet.
Follow the debate on our newsblog.