At this time next year, NASA's probe New Horizons will fly by the planet-like object Pluto and discover more about the icy ball. The last time scientists reached for a major solar system body was Voyager 2's flyby of Neptune in 1989.

Data from New Horizons might reignite the debate about Pluto's interstellar status.It was back in 2006 when - what was thought to be the furthest planet in our solar system - Pluto was demoted to a "dwarf planet." Pasadena astronomer Mike Brown of Caltech played a major role in reclassifying little Pluto.

His team had found that Pluto was not the largest object in the faraway Kuiper Belt - the ring of icy bodies in orbit beyond Neptune.

Guests:

Mike Brown, Professor of Planetary Astronomy, Caltech; Author, “How I Killed Pluto”

Sean Carroll, Senior Research Associate in Physics at California Institute of Technology