An atom consists of a heavy center, called the nucleus, made of particles called protons and neutrons. An atom has lighter ...

So, the hydrogen and helium atoms formed during recombination, when the cooler temperature allowed electrons to fall into orbits. But you, I and almost everything on Earth is made of many more ...

Most of the universe's hydrogen and helium atoms formed around 400,000 years after the Big Bang, which is the name for when scientists think the universe began, about 14 billion years ago.

Most of the universe’s hydrogen and helium atoms formed around 400,000 years after the Big Bang, which is the name for when scientists think the universe began, about 14 billion years ago.

Miguel Claro captured the Orion Constellation glowing red due to hydrogen gas, as seen from the Dark Sky Alqueva Reserve in ...

The precursors of heavy elements might arise in the plasma underbellies of swollen stars or in smoldering stellar corpses.