Siraj’s Planet Y search started about a year ago when he was trying to find out whether the shape of the Kuiper Belt is flat. “The planets of the solar system have slight tilts up and down, but ...

Astronomers are investigating a potential hidden planet, dubbed Planet Y, far beyond Neptune. Its gravitational pull is ...

Our solar system now, once again, officially consists of only eight planets. Although largely debunked, speculation continued ...

Earth has a newly-discovered neighbor in the solar system. But the heavenly body – possibly a dwarf planet à la Pluto – isn't a frequent visitor. Located beyond Neptune, its extreme orbit ...

comets and dwarf planets (including Pluto) that orbit the sun beyond the eight known planets — but has so far evaded ...

Scientists have detected methane gas glowing faintly above Makemake, an icy dwarf planet smaller and farther than Pluto in space. Until now, Pluto was the only object that far out in the solar system ...

A recent research paper suggests that a planet may exist far beyond Neptune — less than 20 years after the previous ninth planet, Pluto, was demoted. That research paper, accepted last month for ...

Your 1996 column on the mysterious giant Planet X some astronomers thought might lurk beyond Pluto is in need of an update. In particular, you should tell the story of the dwarf planet Eris, whose ...

(CNN) — The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have ...