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X-Ray Astronomy V
To the eye alone, Orion may be the most impressive of all the constellations. It consists of a bright rectangle of stars with a “belt” of three stars in the middle, and a massive stellar nursery along the hunter’s sword.
If we could view the constellation in X-rays, though, it would look even more impressive. That’s because it’s home to a superbubble — a globule of million-degree gas that spans hundreds of light-years. At such high temperatures, the gas emits most of its energy as X-rays.
It’s known as the Orion-Eridanus Superbubble because it spans two constellations. Its distance is a little uncertain, but it’s probably more than a thousand light-years.
A recent study found that the superbubble may consist of a series of bubbles within bubbles. The bubbles are created by young, massive stars. The stars produce intense winds of hot gas. And at the ends of their lives, the stars explode as supernovae. The blasts expel enormous amounts of gas. The gas expands rapidly, so it quickly fills a large volume. Smaller bubbles eventually merge to form the superbubble.
As the gas expands, it runs into clouds of colder, denser material. That causes some of those clouds to collapse and give birth to new stars. Over the last 12 million years or so, the superbubble has given birth to as many as a hundred stars that could someday explode as supernovae. And 10 to 20 stars have already done so — keeping the superbubble going.