Yeah…we’re talking about the Orion Nebula again. I know, we already took a tour through the Orion constellation in my last post…but there’s still more to cover about how stars come to life, and Orion is still the best case study I know.
So…hold up a second. Contagious star formation? What’s that supposed to mean? I mean, usually, when you think about “contagion,” you think of catching diseases from others around you. So…can stars get sick?
Well, no. Stars are pretty good at maintaining their own homeostasis, something I’ll explain in a later post. By “contagious” star formation, I mean that star formation can trigger more star formation.
Take a wild guess: What do you think this image is showing you?
If you said it looks like a giant black hole in space, I don’t blame you. I also don’t blame you if you thought it looks like a giant outer space blob…and the funny thing is, that’s actually closer to the truth.
This isn’t a hole in space. We can’t see any stars in this region, but not because there aren’t any. In fact, there are just as many there as there are flanking the giant space blob.
What you’re seeing is evidence of the vast interstellar medium, the galaxy’s backstage. The interstellar medium is the stuff between the stars, often invisible since it’s not hot enough to produce its own light.
Sometimes we can see it as a pale blue reflection nebula, or a bright pink emission nebula. But in this case, we’re looking at a dark nebula—visible only because it blocks the light from stars beyond it. It appears to be a hole in space.
It’s closer to being an outer space blob. But what exactly is it?
What you see here is the Trifid Nebula, a vast cloud of gas and dust in space.
In my last post, we explored why it looks the way it does. We discovered that the pink hues of emission nebulae are caused when extremely hot nearby stars “excite” the gas of the nebula itself to emit its own light, which our eyes perceive as pink.
The haze of blue to the right, on the other hand, is the result of light from hot young stars nearby getting scattered among the nebula’s dust particles. It looks blue for the same reason the sky looks blue. We call nebulae like this reflection nebulae.
And the black wisps of dark nebulae are hardly as ominous as they look; they’re simply ordinary clouds of gas and dust, ordinary nebulae, that we can only see because they’re silhouetted by brighter objects in the background.
But nebulae, for all their different names, are actually a heck of a lot more similar than you might think.
Okay, okay, I know. You want to know what that actually is. You want to know why it’s there. You want to know why there are colors in space…and why you’ve never noticed such a thing in your own night sky before.
Nebulae are the stuff between the stars. They’re the galaxy’s backstage. They’re the only visible evidence of a vast expanse of gas and dust between the stars, completely invisible to the human eye, called the interstellar medium.
Nebulae are the sites of star birth. Planets form from the dusty particles present in these glowing space clouds. They’re the galaxy’s way of replenishing itself. And they’re pretty cool to look at, too.