Polaris is not one star but three, it has mysteriously brightened over the centuries, and its reign as the North Star is only a temporary accident of Earth's wobble.

Betelgeuse is a red supergiant so large its surface could stretch out past Mars, swallowing every rocky planet along the way, and its 2019-2020 dimming episode saw its brightness fall by more than two-thirds. Here is what the data actually shows.

Alpha Centauri looks like one bright point in the southern sky, but it is really three stars, one of them possibly hosting two small planets, first proven to circle each other by a comet-watcher in 1689.

A pulsar packs extreme density into a tiny, fast-spinning sphere that sweeps beams of radiation across the galaxy. Here is what decades of watching them tick has revealed.

A red giant is what happens when an aging star runs low on core fuel and balloons outward. The Sun will become one in a few billion years, swallowing the planets closest to it along the way.

White dwarfs are the collapsed cores left behind by dying stars, so dense that a teaspoon of their material would weigh several tonnes. Here is what makes them among the strangest objects in the galaxy.

A supernova can briefly shine billions of times brighter than the Sun, and the wreckage it leaves behind still puzzles astronomers decades later. Here are the facts behind the Universe's biggest explosions.

A neutron star packs more mass than the Sun into a sphere the size of a city, spins hundreds of times a second, and can carry a magnetic field strong enough to wipe a credit card from the Moon's halfway point. These are the facts behind the extremes.

Ceres was the first object ever found in the asteroid belt, mistaken at first for a new planet. It turned out to be a small, water-rich world with its own cryovolcano and a transient atmosphere of water vapor.

The asteroid belt between Mars and Jupiter is often imagined as a planet that never formed. In reality it's mostly empty space, holding barely 3% of the Moon's mass spread across up to 1.7 million asteroids.

Uranus is tipped over so far that it effectively rolls around the Sun on its side, giving each pole a 42-year day followed by a 42-year night. Here is what else makes this ice giant one of the strangest worlds in the Solar System.

An event horizon isn't a surface or a wall — it's the last point where escape is still mathematically possible. These are the facts behind the universe's strangest boundary, from its 1784 origin to the telescope that finally photographed one.