Why a dying star winds up looking like a puffball

Even in death, stars are stunning.

Instead of just fading into the darkness, a dying star actually explodes in what is called a supernova. But the remains of the supernova do something equally beautiful and impressive: They glow. In fact, they look like this puffy, glowing celestial jellyfish:

That's the remnant of SN 1572, otherwise known as the Tycho Supernova, located some 13,000 light years away from Earth in the Milky Way. Like the luminescence of other remnants, its glow has always baffled scientists... until now.

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Using an X-ray satellite, researchers at the Harvard-Smithsonian Center for Astrophysics have been able to identify the first clear example of collisionless electron heating, the cause of the SN 1572's glow.

After a supernova, the dying star's core begins to collapse, sending out an initial shockwave. And, curiously, a reverse shockwave forms alongside. The propelling shockwave travels at Mach 300 and the reverse shockwave, which pulls leftover material back into the center, travels at Mach 1000.

Like a light bulb, those materials heat up and produce X-rays, which the scientists are able to view as stripes. This shockwave pulley system can last a few hundred years.

And just because the remnant of the Tycho Supernova is too pretty to pass up, here's the star seen using a composite X-ray with infrared and optical shots: