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The International Astronomical Union has unveiled a contest called NameExoWorlds that gives the public and astronomy groups a role in naming planets and stars beyond the solar system.

It's the latest chapter in a years-long controversy over how celestial objects are classified and named.

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The IAU has presided over the planet-naming process for nearly a century, but in recent years it's been facing challenges to its authority. For instance, a commercial venture called Uwingu currently lets Internet users suggest informal names for extrasolar planets and other celestial features such as Martian craters for a fee.

NameExoWorlds was created as a response to such challenges. In partnership with Zooniverse, a citizen-science organization, the IAU has drawn up a list of 305 well-characterized exoplanets in 206 alien solar systems. Starting in September, astronomy clubs and other nonprofit organizations can register for the opportunity to select planets for naming.

In October, the IAU plans to ask the registered organizations to vote for the 20 to 30 worlds on the list that they want to name. Starting in December, those groups can propose names for the worlds that get the most votes, in accordance with the IAU rules for exoplanets. Each group will be allowed to name only one exoplanet.

Starting in March 2015, the list of proposed names will be put up for an Internet vote. The top-rated names will be validated by one of the IAU's working groups, and announced during a special public ceremony at the IAU General Assembly in Honolulu in August 2015.

The popular name for a given exoplanet (Vulcan, for instance) won't replace the scientific name (40 Eridani A b, hypothetically speaking). But it will carry the IAU seal of approval, unlike Uwingu's names.

"The IAU is excited that the general public will be able to participate in this new and ambitious global challenge," the organization said in a news release issued Wednesday. "Other contests may be organized after 2015."

Flash interactive: How exoworlds are found

The 305 planets on the list represent just a fraction of the more than 1,800 exoworlds that have been detected to date. Thousands more could be identified by the time the IAU's NameExoWorlds process has run its course, thanks to planet-hunting efforts such as NASA's Kepler mission.

Planetary scientist Alan Stern, the chief executive officer and co-founder of Uwingu, said the IAU was taking the wrong approach. "They just can’t seem to get out of the elitist rut, thinking they own the universe," Stern told NBC News in an email.

"Uwingu's model is, in our view, far superior and far more democratic," he said. "People can directly name planets around other stars at Uwingu, with no one having to approve the choices. With 100 billion-plus planets in the galaxy, why bother with committees of elites telling ordinary people what they do and don't approve of?"