How big can they get? What's the largest so far detected? Where does an 18 billion solar mass black hole hide?

We've never seen them directly...

yet we know they are there...

Lurking within dense star clusters...

Or wandering the dust lanes of the galaxy....

Where they prey on stars...

Or swallow planets whole.

Our Milky Way may harbor millions of these black holes...

the ultra dense remnants of dead stars.

But now, in the universe far beyond our galaxy, there's evidence of something even more ominous...

A breed of black holes that have reached incomprehensible size and destructive power.

It has taken a new era in astronomy to find them...

High-tech instruments in space tuned to sense high-energy forms of light -- x-rays and gamma rays -- that are invisible to our eyes.

New precision telescopes equipped with technologies that allow them to cancel out the blurring effects of the atmosphere...

and see to the far reaches of the universe.

Peering into distant galaxies, astronomers are now finding evidence that space and time can be shattered by eruptions so vast they boggle the mind.

We are just beginning to understand the impact these outbursts have had on the universe around us.

That understanding recently took a leap forward.

A team operating at the Subaru Observatory atop Hawaii's Mauna Kea volcano looked out to one of the deepest reaches of the universe...

And captured a beam of light that had taken nearly 13 billion years to reach us.

It was a messenger from a time not long after the universe was born.

They focused on an object known as a quasar... short for "quasi-stellar radio source."

It offered a stunning surprise...

A tiny region in its center is so bright that astronomers believe it's light is coming from a single object at least a billion times the mass of our sun...

Inside this brilliant beacon, space suddenly turns dark...

as it's literally swallowed by a giant black hole.

As strange as they may seem, even huge black holes like these are thought to be products of the familiar universe of stars and gravity.

They get their start in rare types of large stars... at least ten times the mass of our sun.

These giants burn hot and fast... and die young.

The star is a cosmic pressure-cooker. In its core, the crush of gravity produces such intense heat that atoms are stripped and rearranged.

Lighter elements like hydrogen and helium fuse together to form heavier ones like calcium, oxygen, silicon, and finally iron.

When enough iron accumulates in the core of the star, it begins to collapse under its own weight.

That can send a shock wave racing outward...

Literally blowing the star apart:...

a supernova.

At the moment the star dies, if enough matter falls into its core, it collapses to a point, forming a black hole.

Intense gravitational forces surround that point with a dark sphere... the event horizon... beyond which nothing, not even light, can escape.

That's how an average-size black hole forms.

What about a monster the size of the Subaru quasar?

Recent discoveries about the rapid rise of these giant black holes have led theorists to rethink their view of cosmic history.