Year of the Comet
Comet C/2011 L4 (PANSTARRS)

PANSTARRS information

Comet C/2012 S1 (ISON)

ISON information

Ask Astro

Published: May 1, 2006
Black holes are regions where matter is extremely, mind-boggingly compressed into zero volume. According to Einstein's theory of general relativity, neither matter nor light can escape these dense objects. Hence, they are called black holes. However, the distance a black hole's strong gravity reaches is limited and is called the event horizon. Light is not emitted from the black hole itself but from an accretion disk of gas and dust that forms around a black hole far from its event horizon.
Subscriber-Only Content Subscriber Only Access
You are currently not logged in. This article is only available to Astronomy magazine subscribers.
Already a subscriber to Astronomy magazine?
If you are already a subscriber to Astronomy magazine you must log into your account to view this article. If you do not have an account you will need to regsiter for one. Registration is FREE and only takes a couple minutes.
Login   Register
Non-subscribers, Subscribe TODAY and save!
Subscribe
Get instant access to subscriber content on Astronomy.com!
  • Access our interactive Atlas of the Stars
  • Get full access to StarDome PLUS
  • Columnist articles
  • Search and view our equipment review archive
  • Receive full access to our Ask Astro answers
  • BONUS web extras not included in the magazine
  • Much more!
SEARCH SITE
Subscriber Only Access
Subscriber Only Content
Look for this icon. This denotes premium subscriber content. Learn more »
Become a Member of Astronomy.com
Register today for access to more valuable resource information.
Interact in our forums, comment on articles, receive our newsletter and much more!
Not a member?
Subscriber and Member Login
Password
Remember me