Login
Copyright

The Nucleus of a Galaxy

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: The Spiral Arms of the Milky Way Galaxy

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 A Dormant Volcano
  • 0:27 The Nucleus of Our Galaxy
  • 1:34 What's Inside the Nucleus
  • 4:18 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
Create an account to start this course today
Try it free for 5 days!
Create An Account

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Artem Cheprasov
This lesson will explore our galaxy's nucleus. Namely, we will find out how we can peer inside using radio waves and infrared, and what that and X-rays tell us about the cool thing that's located inside of it.

A Dormant Volcano

A dormant volcano is a volcano that hasn't erupted in a long time. It may have been a big and powerful rumbling thing back in its day, but no longer is, although it may become active again. At the center of our galaxy, the Milky Way, there is something big, rumbling in its own way, and it is considered to be dormant. This lesson will tell you what that thing is as we look inside the nucleus of our galaxy.

The Nucleus of Our Galaxy

Our galaxy is a barred spiral galaxy, a type of galaxy that has a bar-like elongated nucleus with spiral arms jutting out from the bar. About two-thirds of all spiral galaxies are barred spiral galaxies. The very center of our galaxy is called the nucleus, or central bulge. There is some pretty crazy stuff that happens here. And if you've seen other lessons on galaxies you're probably too aware of the fact that we can't see much of it. At least not with any visible light - that kind of stinks.

The reason we can't see it is for the same reason you can't see very far in a dust storm. Just picture riding through a desert when one kicks up. It'll become almost as dark as night even if the sun is still shining. When light travels through space, it also encounters space dust and gas. This stuff will block and scatter light. In fact, the amount that's blocked is insane. If a trillion photons of light left the center of our galaxy, guess how many would reach Earth? One puny photon, that's it.

What's Inside The Nucleus?

This means we must use a sort of X-ray vision to see through all of this dust, except it's not always X-ray vision; it's also radio vision and infrared vision. What I mean is, we use radio waves and infrared to see through the dust. Short-wavelength X-rays can penetrate the interstellar matter (the dust and the gas) as well. The reason we can't see through the dust using visible light is because wavelengths about the same size as the diameter of a speck of dust, like that of visible light, will be scattered or absorbed by the dust. Longer wavelengths will be able to pass right through.

Observations using infrared and radio waves show us that the nucleus has a lot of crowded stars orbiting at a high velocity. There are so many stars, they heat up the surrounding dust, which then emits very strong infrared radiation. Furthermore, radio maps of the center of our galaxy revealed a lot of different radio sources, but one stood out above the rest. It is Sagittarius A*, or Sgr A*. A very powerful radio source lying in the galactic nucleus.

What could possibly be emitting all that radio energy? Well, we also know X-ray emissions come from Sgr A*. Observations have shown us that Sagittarius A* is about one astronomical unit in diameter (the average distance between Earth and the sun) and has four million solar masses, yet it produces a lot of radio and X-ray energy for its size. What could be that small, yet produce relatively so much energy? The only reasonable answer seems to be a supermassive black hole.

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

Register for a free trial

Are you a student or a teacher?
I am a teacher
What is your educational goal?
 Back

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

Earning College Credit

Did you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2,000 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 free for 5 days!
Create An Account
Support