Skip to main content

Pluto Planethood Debate Tonight! Here's How to Watch Online

Pluto used to be a full-fledged planet, and then in 2006 it wasn't. But the debate over  its status continues, and you can watch one discussion live tonight. 

The International Astronomical Union's 2006 decision to demote Pluto to a "dwarf planet" takes center stage in a debate at 8 p.m. EDT (0000 April 30 GMT) by the Philosophical Society of Washington in Washington, D.C. You can watch live here, in the window above, or directly from the PSW Science group here.

Alan Stern, the principal investigator of the New Horizons mission that flew past Pluto in 2015, has been a fierce advocate of Pluto remaining a planet. He will battle it out with Ron Ekers, a past president of the International Astronomical Union (IAU) who led the organisation from 2003 to 2006, when Pluto's demotion occurred. The IAU is the international body that governs the naming of celestial objects.

Stern will discuss what he sees as scientific issues surrounding the definition for the term "planet," and he will propose a newer definition that is more inclusive of small bodies such as Pluto. Ekers will argue in favor of the IAU definition, which has a distinct taxonomy for little worlds that are far out in the solar system in a region known as the Kuiper Belt.

The push to give planethood back to Pluto accelerated after the New Horizons flyby of the object, which revealed that Pluto had mountains, vast seas and other complex features. Stern argues that its geology is more reminiscent of a planet's than a smaller world's geology. 

Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.   

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at:

Elizabeth Howell

Elizabeth Howell is a contributing writer for who is one of the few Canadian journalists to report regularly on space exploration. She is the author or co-author of several books on space exploration. Elizabeth holds a Ph.D. from the University of North Dakota in Space Studies, and an M.Sc. from the same department. She also holds a bachelor of journalism degree from Carleton University in Canada, where she began her space-writing career in 2004. Besides writing, Elizabeth teaches communications at the university and community college level, and for government training schools. To see her latest projects, follow Elizabeth on Twitter at @howellspace.