Unlike Earth, the moon no longer has a core-generated magnetic field. On our planet, the movement of liquid iron in the outer core generates a global magnetic field. This so-called geodynamo works on a similar principle to a bicycle dynamo, which converts mechanical motion into electrical energy. “Today, there is an ongoing heated debate as to whether the moon also operated a dynamo in the past,” says Xi Yang, a Ph.D. student in the Department of Earth and Planetary Sciences at ETH Zurich. This is because analyses of rock samples brought back to Earth by the Apollo astronauts are contradictory.

If you want to understand the origins of black holes, Yale astronomers say, you need to look beyond the centers of galaxies and start searching in the nooks and crannies. That’s where you’ll find the “wanderers”—black holes whose journeys may tell the story of how the first black holes formed.

Asteroids don’t come with a warning label that they might one day hit Earth. While we don’t know of any currently on course to do so, we are finding thousands of new ones each year, and there’s always a chance that one could.