Subscribe to our free daily newsletters
. 24/7 Space News .

Subscribe to our free daily newsletters

UCLA professor proposes simpler way to define what makes a planet
by Staff Writers
Los Angeles CA (SPX) Nov 13, 2015

View of dwarf planet Ceres, based on images taken by NASA's Dawn spacecraft. Image courtesy NASA/Jet Propulsion Laboratory.

Since the late 1980s, scientists have discovered nearly 5,000 planetary bodies orbiting stars other than the sun. But astronomers are still working on what exactly we should call them. At an American Astronomical Society meeting, UCLA professor Jean-Luc Margot described a simple test that can be used to clearly separate planets from other bodies like dwarf planets and minor planets.

The current official definition of a planet, which was issued by the International Astronomical Union in 2006, applies only to bodies in our solar system, which Margot said has created a "definitional limbo" for the newly discovered bodies. A paper by Margot that has been accepted for publication in the Astronomical Journal proposes to extend the planet definition to all planetary systems.

The new approach would require only estimates of the star's mass and the planet's mass and orbital period - all of which can be easily obtained with Earth- or space-based telescopes. According to Margot's criteria, all eight planets in our solar system and all classifiable exoplanets - the large bodies that orbit stars other than our sun - would be confirmed as planets.

Margot, a professor of planetary astronomy, wanted to ensure that the new system would be easy to follow. "One should not need a teleportation device to decide whether a newly discovered object is a planet."

Some of the current confusion he's seeking to eliminate stems from the fact that the IAU's definition did not address how to classify exoplanets - that question was left for future consideration. Now, Margot argues, the recent flood of exoplanet discoveries should encourage the IAU to refine and extend the definition.

The IAU's definition is based primarily on the ability of a planet to "clear its orbit," meaning whether it can evacuate, accumulate or dominate small bodies in its orbital neighborhood. Margot's test can be used to determine whether a body can clear a specific region around its orbit within a specific time frame, such as the lifetime of its host star.

The test is easy to implement and it could immediately classify 99 percent of all known exoplanets. (Scientists do not currently have enough data to apply the test to the other 1 percent.)

When applied to our own solar system, the test clearly places the eight planets into one distinct category and the dwarf planets - Ceres, Pluto and Eris - into another.

"The disparity between planets and non-planets is striking," Margot said. "The sharp distinction suggests that there is a fundamental difference in how these bodies formed, and the mere act of classifying them reveals something profound about nature."

Margot also found that bodies that can clear their orbits, and therefore qualify as planets, are typically spherical. "When a body has sufficient mass to clear its orbital neighborhood, it also has sufficient mass to overcome material strength and pull itself into a nearly round shape," he said.

This is important because astronomers can't always see exoplanets well enough to accurately determine their shape, but they can almost always measure the parameters needed to apply Margot's criteria - and because the current IAU definition requires that a planet be nearly round.

Margot presented his proposal at the annual meeting of the AAS's Division for Planetary Sciences.

It is not known whether the new approach will be considered by the IAU, whose resolutions are typically crafted and reviewed by committees before members vote on them during a general assembly. The next IAU general assembly is scheduled for 2018.

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once

credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly

paypal only


Related Links
University of California - Los Angeles
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Previous Report
Distant world's weather is mixed bag of hot dust and molten rain
Edinburgh UK (SPX) Nov 04, 2015
Weather patterns in a mysterious world beyond our solar system have been revealed for the first time, a study suggests. Layers of clouds, made up of hot dust and droplets of molten iron, have been detected on a planet-like object found 75 light years from Earth, researchers say. Findings from the study could improve scientists' ability to find out if conditions in far-off planets are capab ... read more

Gaia's sensors scan a lunar transit

SwRI scientists explain why moon rocks contain fewer volatiles than Earth's

All-female Russian crew starts Moon mission test

Russian moon mission would need 4 Angara-A5V launches

Dust devils detected by seismometer could guide Mars mission

Amnesia Event Slows Down Opportunity Robotic Arm Work

Swiss Camera Leaves for Mars

NASA mission reveals speed of solar wind stripping Martian atmosphere

Orion's European module ready for testing

General Dynamics demos SGSS Command and Control Infrastructure for NASA

Orion Service Module Stacking Assembly Secured For Flight

Global partnerships in orbit support economic growth on and off the Earth

New rocket readies for liftoff in 2016

China's self-developed Mars probe to be on show

Could Sino-U.S. cooperation bring the Martian home?

China's scientific satellites to enter uncharted territory

Cygnus Starts Final Round of Processing for Station Cargo Delivery

US astronauts dodge ammonia on risky spacewalk

UK astronaut dreams of heavenly Christmas pudding

NASA drops Boeing from race for $3.5 billion cargo contract

LISA Pathfinder topped off for Vega launch that will test Relativity

Ariane 5 lofts dual birds

Rocket launch from Hawaii carrying UH payload experiences anomaly

Commercial Spaceflight Gets A Boost With Latest Congressional Moves

New Results from GPI Exoplanet Survey

Newfound Earth-size exoplanet may be an important milestone in search for alien life

UCLA professor proposes simpler way to define what makes a planet

Distant world's weather is mixed bag of hot dust and molten rain

Electron microscopy method sculpts 3-D structures at atomic level

BU Satellite Team Gets Big Boost from NASA

System helps novices design 3-D-printable robotic creatures

Queen's University professor to unveil self-levitating displays

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement