When the earliest astronomers and philosophers looked up at the night sky, they never could have imagined a sight like this.
What if I told you there are only four single stars in this image?
That’s right. Four.
The rest are whole galaxies, full of billions of stars.
You can tell the foreground stars from the galaxies by the diffraction spikes–astronomer speak for those four bright spikes of light. Can you find them?
Continue reading
Alright, people…time to finish off our exploration of the Milky Way Galaxy, our home in the cosmos!
For the past nine weeks, we’ve covered everything from how our galaxy was “discovered” to how it may have formed. But there’s so much more to explore–and, starting next week, we’ll begin covering the vast universe of galaxies beyond our own!
But before we do that…I want to wrap up our discussion of our own galaxy with an overview to tie the last nine posts together.
(By the way, has anyone noticed I actually managed to chug out a post a week for the entire Milky Way “module”? I’m a bit impressed with myself for that!)
Anyway…on to the Milky Way!
Continue reading
How big is our galaxy, anyway?
And more than that–how do we know?
Consider that we can’t really take a photo like this of our galaxy. We’re inside it, and space travel has not advanced to the point where we can leave it just yet. There’s no way we can get a camera out to take a picture from this perspective.
Most things in the universe–like stars, planets, and even other galaxies–can be measured using their angular diameters. That is, we use trigonometry to find their actual sizes based on how large they appear to us in the sky.
But that doesn’t work for an object that we’re inside of.
In order measure the size of our own galaxy, early astronomers had to get a bit creative–with variable stars.
Continue reading
Science at Your Doorstep 