Copyright

Important Points on the Celestial Sphere

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: The Cycle of the Seasons in Astronomy

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:01 The Celestial Sphere
  • 0:37 Horizon, Zenith, & Nadir
  • 1:47 The Celestial Equator,…
  • 3:00 Lesson Summary
Add to Add to Add to

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Login or Sign up

Timeline
Autoplay
Autoplay
Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Artem Cheprasov
This lesson will discuss some important points and lines located on the celestial sphere, including the zenith, nadir, celestial equator, meridian, and north and south celestial poles.

The Celestial Sphere

If you could just imagine for a second being transported inside of a snow globe, what would it look like? I don't think it'd look any different to you than if you were to walk outside right now and look at the sphere-ish looking thing that surrounds you, the sky. Well, you only see half of a sphere, but you know another half exists down below you. People in Brazil and Australia also have a snow-globe or dome-shaped sky as much as anyone in Europe or the U.S.

The imaginary sphere that surrounds the Earth is called the celestial sphere, and it's a useful tool used to reference real and imaginary points on the sky.

Horizon, Zenith, and Nadir

As I just recently said, at any location on our planet, you'll only see half of the celestial sphere. We'll follow an image on-screen for an observer in North America to explain the reference points on the celestial sphere that are commonly used.

The celestial sphere
Diagram of the celestial sphere points

The half of the celestial sphere you see is bounded by the horizon, the boundary between Earth and the sky. This celestial horizon is best seen when you have an unobstructed view of the sky, such as in a vast, flat, and open plain or when you're in the middle of the ocean. As you stand outside, if you look straight up, you'll be looking at the zenith, the point in the sky directly overhead. Do not get the zenith confused with looking north. Looking straight up is not the same thing as looking north.

Conversely, if you could look through the Earth, right underneath where you stand, you'd be looking towards the nadir, the point on the celestial sphere directly opposite the zenith. Again, this is not the same thing as saying you are looking south. As seen on the screen, the nadir and the cardinal direction of south are not the same points.

The Celestial Equator, Poles, & Meridian

The point on the celestial sphere directly above the Earth's North Pole is known as the north celestial pole, and not surprisingly, the point on the celestial sphere directly below the Earth's South Pole is the south celestial pole.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create An Account
Support