Feeds

Solar system to get new planets?

IAU sets criteria for planetary club membership

Beginner's guide to SSL certificates

If astronomers approve a new proposal for a definition of a planet, not only will Pluto retain its status as the ninth planet, but the solar system will gain three more.

The question of Pluto's planethood has been the subject of a long-running, and ultimately frustrating debate. Frustrating, because until now there has been no officially accepted definition of a planet.

Step forward the massed ranks of the International Astronomers Union (currently having its regular, once-every-three-yearly, knees-up in Prague) with the following definition, hammered out over two, very long, years:

"A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet."

This means anything massing more than 5x1020kg with a diameter greater than 800 km will automatically count as a planet of some kind. But borderline cases, the IAU stresses "would have to be established by observation".

The definition also sets out a class structure for different kinds of planets, to distinguish between the inner planets and ore distant bodies in less circular orbits. Thus, anything with an orbit longer than 200 years would be classed as a "pluton". Two of the three new planets would fall into the pluton category.

Qualifying orbiting bodies include the lovely 2003 UB313, otherwise known as Xena. However, now that official planethood beckons (even if it is a kind of lesser, plutonic planethood) the warrior princess might just end up being renamed. Officially, of course, it still carries its 2003 Ub etc moniker. Nice.

Ceres and Charon* will also join the list. Twelve other candidate planets are on the IAU's watch list.

The astronomers will actually vote on the definition on 23 August. ®

* Bootnote: Yes, we spotted that, too. Although the definition rules that objects that are satellites of other planets are not planets themselves, a footnote adds:

"For two or more objects comprising a multiple object system, the primary object is designated a planet if it independently satisfies the conditions above. A secondary object satisfying these conditions is also designated a planet if the system barycentre resides outside the primary. Secondary objects not satisfying these criteria are "satellites". Under this definition, Pluto's companion Charon is a planet, making Pluto-Charon a double planet."

As a result, you will probably start to see Charon being referred to as Pluto's companion rather than its moon.

Choosing a cloud hosting partner with confidence

More from The Register

next story
Renewable energy 'simply WON'T WORK': Top Google engineers
Windmills, solar, tidal - all a 'false hope', say Stanford PhDs
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
Post-pub nosh neckfiller: The MIGHTY Scotch egg
Off to the boozer? This delicacy might help mitigate the effects
The next big thing in medical science: POO TRANSPLANTS
Your brother's gonna die, kid, unless we can give him your, well ...
I'M SO SORRY, sobs Rosetta Brit boffin in 'sexist' sexy shirt storm
'He is just being himself' says proud mum of larger-than-life physicist
NASA launches new climate model at SC14
75 days of supercomputing later ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
prev story

Whitepapers

Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
5 critical considerations for enterprise cloud backup
Key considerations when evaluating cloud backup solutions to ensure adequate protection security and availability of enterprise data.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Managing SSL certificates with ease
The lack of operational efficiencies and compliance pitfalls associated with poor SSL certificate management, and how the right SSL certificate management tool can help.