If you were hoping to see the “mini moon,” you’ve probably been disappointed. But experts say the asteroid was an important milestone in planetary defense research.

A small asteroid called 2024 PT5 will temporarily orbit Earth this fall. Here's what it looks like and whether it will be visible to the naked eye.

As Earth continues its timeless journey around the Sun, it is not alone in its celestial voyage. Our faithful Moon has always given us company. In an exciting new development, scientists have detected a temporary “second moon” orbiting Earth—an asteroid named 2024 PT5,