Over the past decade, researchers have been puzzling through Pluto’s mysteries. Meanwhile, the New Horizons probe heads for interstellar space.

Ever since the International Astronomical Union recognized Haumea and Makemake as dwarf planets in 2008, University of Maine ...

Among them, "Tombaugh Regio," the official name for the heart-shaped crater on the dwarf planet's surface, which honors Clyde Tombaugh. He is the American astronomer who discovered Pluto in 1930.

But the heavenly body – possibly a dwarf planet à la Pluto – isn't a frequent visitor. Located beyond Neptune, its extreme orbit circumnavigates the sun once every 25,000 years, taking it ...

Pluto, the largest of those dwarf planets, has a diameter of about 1,477 miles. Don't miss out on what's happening! Stay in touch with breaking news, as it happens, conveniently in your email inbox.

An artist's illustration depicts the massive, slow impact that likely created a heart-shaped feature on Pluto's surface early in the dwarf planet's history.

Almost 10 years ago, a NASA spacecraft was able to take several photos of Pluto, known for decades as a planet before it was reclassified as a dwarf planet in 2006.