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

PANSTARRS information

Comet C/2012 S1 (ISON)

ISON information

How-To
E-mail Article to a FriendPrint ArticleBookmark and Share

Observing Basics: Distances in Space

Light's constant speed helps astronomers and observers better understand the vastness of our universe.
By Michael E. Bakich
Light travels at a constant speed of 299,702,458 meters per second (186,282 miles per second). That's equal to more than 670 million mph (1.08 billion km/hr). So the distance light travels in a year is known as the light-year, and it's equivalent to 5.88 trillion miles (9.46 trillion km).
stardome330
Expand your observing at Astronomy.com

StarDome

Check out Astronomy.com's interactive StarDome to see an accurate of your sky. This tool will help you locate this week's targets.

Intro to the Sky: Get to know the night sky
Learn how to use star charts, find constellations, and observe the brightest objects in your night sky with in this handy reference section.

The Sky this Week
Get a daily digest of celestial events coming soon to a sky near you.

Observing Talk
After you listen to the podcast and try to find the objects, be sure to share your observing experience with us by leaving a comment at the blog or in the Reader Forums.

Other Observing Basics videos
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