Google+ Hangouts On Air allows you to invite a speaker to your online course. Visit Google+ Hangouts On Air to learn more.

Here are the basics of starting a Google+ Hangout On Air in Canvas

The Google Hangout still has a 10-participant cap.
All participants must have a Google+ account.
The host of the On Air Hangout must have a YouTube account.
Participants are responsible for ensuring the content complies with the terms.
All broadcasts are automatically recorded and placed on YouTube.

Note: You can broadcast this live conversation to thousands since it will be likely they are sitting in the audience of a live performance. You should wait to start the On Air Hangout until right before the session is scheduled. The embed code is not available until the Hangout session has been started. For this reason, you may wish to place the live broadcast into Canvas as an Announcement.

Canvas Guide

How do I start a Google+ Hangout On Air in my Canvas course?