Many humans think of space as empty or, perhaps, as a vacuum that's filled with nothingness. It turns out, according to scientists, that the space between planets is actually filled with asteroids, comets, and space dust. "The voids between stars in our galaxy can be filled with tenuous clouds of gas and other molecules." But what about the space, the void, that lies between galaxies? Are they filled with "stuff" too?
You might expect the answer to be no; that it's just empty space. But that's just not true. Just as the rest of space has "stuff" in it, so does the intergalactic space. "In fact, the word 'void' is now normally used for giant regions where NO galaxies exist, but apparently still contain some kind of matter." I don't know about you, but I was stunned to learn that space is filled with things! I was kind of expecting that there would be vast areas of nothingness. You might be asking, "So what is between those galaxies?" I know I was curious. I checked it out and here's what I learned.
Clouds of hot gas can be found sometimes. These clouds occur when galaxies interact and collide. "The material gets 'ripped away' from the galaxies by the force of gravity, and often enough it collides with other material. That gives off radiation called x-rays." It turns out that these clouds aren't the only things found between galaxies. Some of the other "stuff" is dim and difficult to see but is thought to be cold gases and dust.
The Palomar Observatory in California has an instrument called the Cosmic Web Imager (I sure love that name!) that has been used to see that dim material floating around beyond our galaxy. It's called dim matter because it isn't bright like stars or nebulae, but it isn't so dark, either, that it cannot be detected. The Cosmic Web Imager looks for this matter in the "intergalactic medium or IGM" and charts where it is most abundant and where it isn't.
Astronomers are interested in where this cosmic web of material comes from, where it's headed, how warm it is, and how much of it there is. They find it by looking for hydrogen, the main element in space because it emits light at a specific ultraviolet wavelength called Lyman-alpha. Since Earth's atmosphere blocks light at ultraviolet wavelengths, it makes seeing Lyman-alpha more easily observable from space. This means that most instruments used to observe this dim matter but be above Earth's atmosphere.
"The study of intergalactic stuff continues to unfold much like a detective novel. There are a lot of clues about what's out there, some definite evidence to prove the existence of some gases and dust, and a lot more evidence to gather." The Cosmic Web Imager, and other instruments like it, uncover clues about happened very long ago. The next step is to "follow the evidence" to figure out exactly what's in the IGM (intergalactic medium) and, hopefully, discover even more distant objects. All of this information can help us learn more about what happened in the early universe, billions of years before our planet and star even existed.
I hope you are as intrigued by space as I am. It is hard to fathom the depth and distance of outer space. It is endless and contains things we may never find out. But it is always fascinating and for whatever reason, the more we learn about outer space and galaxies "far far away" the more we want to know. Space is truly the last frontier and one that we may never be able to tame.
Tomorrow's a special day for all you creative types...and that means everyone, so please come back and I promise you a fun blog on living creatively. So, until tomorrow, I wish you