The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

Mars is chilly, Earth moderate, while Venus scorches, and Mercury fluctuates With an average temperature of about -224°C (-371°F), Uranus takes the top spot as the coldest planet in the solar ...

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Aside from the solar system once again having nine planets—which it had before Pluto’s demotion in 2006—the discovery of a distant Earth-mass planet would have profound implications for ...

Yes, six planets will be visible in the January night sky. And yes, they'll be in a line. But because planets always appear in a line from our Earth-bound vantage, the alignment isn't anything out ...