This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights. The size of the solar system is defined by the volume ...

To be a planet, NASA says an object must be big enough that its gravity has cleared away any other objects of a similar size ...

WASHINGTON, May 30 (Reuters) - Scientists have identified an object about 435 miles (700 km) wide inhabiting the frigid outer reaches of our solar system that might qualify as a dwarf planet, spotting ...