Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

Astronomy 101: Black holes

Astronomy magazine Senior Editor Richard Talcott introduces the Astronomy 101 video series with a look at one of the weirdest objects in the universe: black holes.
Black hole video still
Simply put, a black hole is a region of space-time where gravity is so strong that nothing can escape from it. This includes light, which travels at the cosmic speed limit of 186,000 miles per second. In a stroke of descriptive genius, American physicist John Wheeler coined the term "black holes" for these objects.

Although black holes lie at the frontier of astronomy, the idea such objects might exist stretches back more than 200 years. In the late 1700s, British professor John Michell and French astronomer and mathematician Pierre Simon, Marquis de Laplace, advanced the idea of what Laplace called "dark bodies." Using Newton's concepts of light and gravity, they reasoned that the gravitational pull of a massive star could grow large enough to prevent light from escaping. Unfortunately, Newton's theory could not describe what happens when gravity grows that strong.

Enter Albert Einstein. In 1916, his general theory of relativity put black holes on a firm footing. Using general relativity, which treats gravity as a distortion of space-time, physicists were able to describe black holes in gory detail. A key feature of a black hole is its radius. Scientists call this the "event horizon" because it marks the edge beyond which light cannot escape. Any event taking place inside the event horizon can never be glimpsed from outside. At the center of a black hole lies a point of infinite density called a "singularity."

The full text of this article is available to registered users of Astronomy.com. Register now!

Registration is FREE and takes only a few seconds to complete. If you are already registered on Astronomy.com, please log in below.
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

ADVERTISEMENT
ADVERTISEMENT
BoxProductcovernov

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook

Loading...