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. Continue reading
What’s a nebula?
Well…you’re looking at one.
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.
But how come they look the way they do? Continue reading
What makes a star shine bright?
Much earlier on—probably months ago now—I explained how something called the proton-proton chain generates massive amounts of energy within stars, and enables them to fuel whole solar systems. That’s the battery of a star.
We’ll address the proton-proton chain later, when we start talking about star life cycles. We’ve still got some talk about nebulas and interstellar space to go before we get that far. For now, what’s important is that the proton-proton chain depends on high density.
That is, stars will have the strongest batteries if they have very dense interiors. It doesn’t really matter how dense their middles and atmospheres are. But conditions in their cores must be very dense.
You’ll find, if you study stars closely, that there is a definite relation between their densities, masses, and luminosities. Continue reading
What the heck is the average star like?
We’ve talked about a lot of stars over the past few weeks. We’ve discovered the vast distances between the stars, looked more closely at what really makes a star bright, and covered all kinds of ways to classify stars—from their spectral type to their luminosity class.
Most importantly, we’ve looked at the H-R diagram, the diagram that classifies stars by their color, temperature, composition, and luminosity…and relates those properties with many other features stars have.
We know what kinds of stars are out there. We know they range from thousands of times smaller than the sun to thousands of times larger. We know they range from desperately faint to incredibly luminous. We know they come in all the colors of the rainbow.
But how many blue stars are there? How many small stars are there? Are most of them small, or are there about the same number of small stars as large ones? Continue reading
Imagine a frisbee.
At the center of this frisbee lies the sun—our sun, for simplicity’s sake. And sprinkled around the surface of its disk are all nine…excuse me, eight…planets of the solar system, plus the dwarf planets, asteroids, moons, Kuiper belt objects, Oort Cloud objects, comets, cosmic dust…
Okay, I could go on, but I’ll stop there. You get the picture. The whole solar system is on this frisbee. It’s a flat plane, disk-like. There aren’t orbits that put the planets up in the air above or below the frisbee. They all lie, more or less, in the same basic plane.
Wait a second though…isn’t this post supposed to be about eclipsing binary stars? What the heck does our frisbee-like solar system have to do with that?
A lot, actually. Continue reading
Most of the time, when I publish posts on this blog, I choose a topic and write about it in the hopes that you’re curious about it. But I also want to know what you are curious about—always.
I want to call your attention to the “Got Questions?” link up in the menu.
This link will take you to a page that invites you to submit a question. Anything about science, anything you’re curious about, just type it out and hit “Submit!” My door is always open, so to speak—that page will always be available.
I’ll still send out posts like this one asking for your questions. But I want you to know that you never have to wait to ask a question. Science is all about being inquisitive, and you should never have to wait for me to prompt you. But you can, if you want 😉
Anyway, this is another “Science Questions” post—you’re welcome to ask whatever you want in the comments below. I’ll address your questions in the order they’re submitted and let you know when the post is published.
And please, by all means head over to my “Got Questions?” page. I want to know what you’re curious about. I want to answer your questions. Most of all, I want this blog to be a place where you feel free to wonder. A curious mind is a healthy thing!
Remember, everyone—there are no stupid questions, only stupid answers. I promise to answer anything you ask to the best of my ability.
Consider a solar system far different from our own. A solar system governed by two suns, and consisting of planets we can only dream of.
Would it surprise you to hear that, based on recent discoveries, that might actually be the norm?
The surroundings we grow up in determine our outlook on the world, and this is never more true than with our solar system. Our eight planets (though some would vehemently insist upon nine) and their parent star are all we know.
But what if I told you that most of the stars you see when you look up at the night sky have companions? And often, these companions are impossible to detect by visual means.
So how do we know they exist? Continue reading
Here’s a visual binary that just about stretches the limits of the definition. It’s a star, though you’ll never see it like this with the naked eye. Specifically, this is Sirius, the brightest star in the sky.
But if you look closely on the top left, you’ll see a tiny dot just peeking out from behind Sirius’s brilliance. That’s Sirius B, this bright star’s faint companion. Together, they’re known as Sirius A and Sirius B.
It’s tradition for astronomers to name all the stars in a system the same thing, but it also makes sense. Most of them aren’t obvious. You might look at some ordinary-looking star in the sky, say…Antares. But as it turns out, Antares has a barely-visible companion.
The visibility of visual binaries has a wide range. Consider the famous double star in the Big Dipper, Mizar. Continue reading
We know how big stars are; they range from the size of the Earth to over a thousand times the size of the sun (which is in itself over one hundred times the size of the Earth). We know they’re huge.
But how massive are they?
Yes, that’s a different thing.
A pingpong ball and a golf ball are close to the same size, but a golf ball is much more massive—in that it has more stuff in it. A pingpong ball is hollow and easily tossed; a golf ball has more matter in it and will hit the ground with a harder thunk.
Stars are similar. They have a wide range of sizes, but nothing I’ve described thus far has told us about their masses. That is, how much stuff is in them? Are they like puffy gaseous balls, or are they more dense, like planets?
The best way to learn about stars’ masses is by studying binary stars. But what exactly are binary stars? Continue reading
By now, I’ve introduced you to a lot of different ways to classify stars.
Months ago, I talked about the different spectral classes—O, B, A, F, G, K, and M. Even before that, I told you about apparent visual magnitude, our ranking system for how bright stars appear to the naked eye.
More recently, we explored absolute visual magnitude and the related absolute bolometric magnitude and luminosity. All these are related to a star’s actual brightness, not just how bright they seem to be from Earth.
And last but not least, we talked about the H-R diagram and how to rank stars by their luminosity classification.
In short, it may seem like sorting stars is a complicated business. But it’s not really. And here, I intend to give you an overview to put all this together. Continue reading