It could be something even cooler.
Gravity makes the Earth round.
It defied the odds to discover thousands of planets.
Short answer: Because we changed the definition of the word “planet” to better fit its meaning.
More than a light Venusian breeze.
Something's got the Kuiper belt's rocks off, and there's a scramble to find it.
Another day, another hypothetical object on the outskirts of the solar system.
So hot right now.
More exciting news about cold, dead rocks
Three of them may be habitable
Scientists aren't just jerking you around—this is about something more than your childhood nostalgia
New evidence suggests it could be a rogue planet captured by our sun
Konstantin Batygin is one of the 10 most brilliant people of 2016
Now to figure out if it has liquid water. Or an atmosphere.
Where can I find a planet like that?
And it's still not Pluto
How skeptical should we be, and how will we find out if this mystery planet is really out there?
Scientists are hot on the trail of our solar system's 9th planet
Bring an umbrella
Short answer: It depends who you ask
This Mars-sized exoplanet is a big deal
And he thinks the upcoming flyby will prove it
This year's missions to the outer solar system are set to shake up the planetary family tree
The Dawn spacecraft arrives at Ceres this March, and it could be the most surprising space mission in decades