When you look up at the night sky, you see a lot of things glowing like stars, planets, and galaxies. So it might sound strange to hear that most of the Universe is actually dark. The truth is the protons, neutrons and electrons that make up everything we can see, and that means everything with telescopes we've got, accounts for only about 4% of the mass and energy of the Universe. The rest is dark and mysterious. More specifically, about 70% of the Universe is what is known as dark energy; about 26% is so-called dark matter. Modern day astronomers have developed many tactics to explore the dark Universe, including using telescopes like Chandra.

Cassiopeia A is the 300-year-old remnant created by the supernova explosion of a massive star. Each Great Observatory image highlights different characteristics of the remnant.?

Astronomy is truly in a golden age.? With a fleet of space-based observatories, including the Chandra X-ray Observatory, astronomers now have a suite of amazing tools to study the Universe.? Simultaneously to this bonanza in astronomy has been the growth and expansion of the Internet.? Think back to before 1990.? The Internet was barely a rumor and there were no Great Observatories!? But now people are taking advantage of these two seemingly separate advances to do some amazing things

Names in astronomy don't always tell the whole story. Let's take, for example, radio galaxies. Why, might you ask, would a Chandra podcast talk about such an object? The answer is that radio galaxies are, yes, very bright in radio emission. But they are also powerful emitters of X-rays, optical light and from other parts of the electromagnetic spectrum. More than that, they are important objects that really have played a very big role in how the Universe has evolved.

Black holes have a bad reputation. After all, something that could swallow you completely sounds pretty scary. They're invisible, so maybe there's one just around the corner and we dont know it! Also, arent they enormous vacuum cleaners capable of destroying anything that gets near them? Once the black hole starts pulling on something, isnt that just a one-way ticket to oblivion? Well, not all of these things are exactly true.

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