Why isn't there an endless variety of planet sizes in the universe? Why are most planets like those in our solar system: small and rocky, or big and gaseous? 

A report suggests that snakes – the Chinese krait and the Chinese cobra – might have been the original source of the coronavirus that's triggered an outbreak of deadly infectious respiratory illnesses in China this year.

This Arctic whale has the only spiral tooth found in nature. But there’s more to the narwhal than its unique tusk.

The pace of archaeological discoveries has picked up in recent decades, helping to refine the human story.

"Anybody besides me notice that the past two decades have been nameless?"

How did whales that feed on tiny prey evolve into the largest creatures on Earth? And why don't they get even bigger?

There's a supermassive black hole - 4 million times our sun's mass - in the center of our Milky Way galaxy. Astronomers who've measured star movements near this central black hole are now saying there might be a 2nd companion black hole near it.

The burning rainforest releases black carbon into the atmosphere, which, according to a growing number of scientific studies, directly contributes to the melting of glaciers.

White Island is one of several volcanoes in New Zealand that can produce sudden explosive eruptions at any time. An Earth scientist explains why.

We know of a couple of dozen so-called "stellar-mass" black holes in our Milky Way galaxy. They tend to be between about 5 and 20 times as heavy as our sun. This new black hole - in a distant spiral arm of the galaxy - is 70 times as heavy as the sun.