Every big galaxy appears to keep one of these monsters at its heart, some weighing billions of times more than the Sun. Here is what a decade of direct imaging has taught us about them.

Black holes were doubted by Einstein himself, bet against by Stephen Hawking, and finally photographed in 2019. These are the strangest verified facts about the universe's one-way doors.

The Andromeda Galaxy is the nearest major galaxy to the Milky Way, first described in 964 CE, and it is on a collision course that will merge the two galaxies in about 4.5 billion years.

The Eagle Nebula is the star-forming region around the cluster NGC 6611, famous for the Pillars of Creation -- towers of gas and dust that Hubble and James Webb have photographed again and again.

Galaxies range from dwarfs with under a thousand stars to supergiants with a hundred trillion, and the observable universe may hold as many as two trillion of them.

The Milky Way is a barred spiral galaxy holding 100 to 400 billion stars, with a supermassive black hole at its center that astronomers finally photographed in 2022.

A nebula is a vast cloud of interstellar gas and dust that can either give birth to new stars or mark the death of an old one, and its many types get their names from very different physics.

The Orion Nebula is the closest region of massive star formation to Earth, bright enough to see with the naked eye, and home to nearly 700 stars still being born within it.

Asteroids are far stranger than leftover space rubble. Some carry their own moons, some are held together by almost nothing, and a few have been visited, sampled, or even landed on by spacecraft.

Comets are frozen leftovers from the birth of the Solar System, small enough to hide in a city yet capable of growing a glow bigger than the Sun. Here is what actually happens inside one.

The point farthest from Earth's center isn't Mount Everest, the ocean floor recycles itself every 200 million years, and the planet's magnetic shield is already fading. Twenty things about home you probably didn't know.

Enceladus, a small moon of Saturn barely a seventh the size of our own Moon, is covered in fresh clean snow and vents 250 kilograms of water vapor into space every second — enough to build an entire ring of Saturn.