When the Earth was struck by a Mars-sized planet in its early history, it ejected a debris cloud that led to the formation of the Moon. In the beginning, the Moon was extremely close to the Earth, but then conservation of angular momentum led to the Moon drifting away from the Earth - it's still doing it today. Because the Earth was covered in oceans of magma, researchers think the Moon moved quickly away from the Earth, getting to 25 Earth radii within 100,000 years.

Interstellar objects visit our solar system all the time. A new study shows they likely come in streams of sibling objects from the same star system.

A survey of high velocity clouds in the galactic halo of the Milky Way finds that they make up less of our galaxy's mass than we had previously thought.

Type Ia supernovae are crucial to our understanding of cosmology. But we still don't fully understand what causes them.

Observations from the Dark Energy Spectroscopic Instrument suggest that the rate of cosmic expansion may be changing over the time. While this wouldn't rule out general relativity, it opens the door to modified gravity models, which may better match the data.