The First Galaxies Form

In the early stages of our Solar System, there were three life-friendly planets: Venus, Earth, and Mars. Only Earth thrived. Here's why.

The Earth that exists today wasn't formed simultaneously with the Sun and the other planets. In some ways, we're quite a latecomer.

It took 9.2 billion years of cosmic evolution before our Sun and Solar System even began to form. Such a small event has led to so much.

Early on, only matter and radiation were important for the expanding Universe. After a few billion years, dark energy changed everything.

Our own galaxy, the Milky Way, is both completely normal and absolutely remarkable in a number of ways. Here's the story of our cosmic home.

On the largest cosmic scales, galaxies line up along filaments, with great clusters forming at their intersection. Here's how it took shape.

Life became a possibility in the Universe as soon as the raw ingredients were present. But living, inhabited worlds required a bit more.

Today, the star-formation rate across the Universe is a mere trickle: just 3% of what it was at its peak. Here's what it was like back then.

Earth wasn't created until more than 9 billion years after the Big Bang. In some lucky places, life could have arisen almost right away.

As early as we've been able to identify them, the youngest galaxies seem to have large supermassive black holes. Here's how they were made.

For 550 million years, neutral atoms blocked the light made in stars from traveling freely through the Universe. Here's how it then changed.

Even after the first stars form, those overdense regions gravitationally attract matter and also merge. Here's how they grow into galaxies.

The first stars in the Universe were made of pristine material: hydrogen and helium alone. Once they die, nothing escapes their pollution.

The first stars took tens or even hundreds of millions of years to form, and then died in the cosmic blink of an eye. Here's how.