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NGC 6388 Animations
Click for low-resolution animation
Tour of NGC 6388
Quicktime MPEG With closed-captions (at YouTube)

The destruction of a planet may sound like the stuff of science fiction, but a team of astronomers has found evidence that this may have happened in an ancient cluster of stars at the edge of the Milky Way galaxy. Using several telescopes, including NASA's Chandra X-ray Observatory, researchers have found evidence that a white dwarf star — the dense core of a star like the Sun that has run out of nuclear fuel — may have ripped apart a planet as it came too close.

How could a white dwarf star, which is only about the size of the Earth, be responsible for such an extreme act? The answer is gravity. When a star reaches its white dwarf stage, nearly all of the material from the star is packed inside a radius one hundredth that of the original star. This means that, for close encounters, the gravitational pull of the star and the tides associated with it are greatly enhanced. For example, the gravity at the surface of a white dwarf is over ten thousand times higher than the gravity at the surface of the Sun.

Chandra's excellent X-ray vision enabled the astronomers to determine that the X-rays from NGC 6388 were not coming from a black hole at the center of the cluster, but instead from a location slightly off to one side. This ruled out a central black hole as the source of the X-rays, so the hunt for clues about the nature of the X-rays in NGC 6388 continued. Monitoring NGC 6388 with the Swift telescope, astronomers watched as the source become dimmer over 200 days. The rate at which the X-ray brightness dropped matched theoretical models for the disruption of a planet by the gravitational tidal forces of a white dwarf. Astronomers will continue to study NGC 6388 in order to learn everything they can about this interesting object on the outskirts of our Milky Way galaxy.
[Runtime: 02:22]

(Credit: NASA/CXC/A. Hobart)


Click for low-resolution animation
The Teeny Tiny Planet Destroyer
Quicktime MPEG With closed-captions (at YouTube)

If you're a fan of science fiction, you'll have seen some pretty crazy things, up to time travel and the destruction of entire planets! We saw poor Spock's home planet Vulcan destroyed in Star Trek, and in Star Wars Princess Leia's home planet of Alderaan was blown to smithereens.

Does the destruction of planets really happen in the Universe, or is this just science fiction?

Astronomers have recently discovered evidence that a planet may have been destroyed in our very own Galaxy. Even scarier, it appears to have been destroyed by a star that was once like our own Sun!

When a star like our Sun runs out of fuel to burn, its outer layers drift away into space, leaving just the very centre. For this star, and the Sun, that will be a ball about the size of Earth (over a million times smaller), which is hot, dense and really bright. This is called a white dwarf star.

It was a white dwarf star like this that ripped apart the planet. But how could such a teeny tiny star be responsible for such a violent act?

The answer is gravity. The gravity at the surface of a white dwarf is over 10,000 times higher than the gravity at the surface of the Sun.

One day, the planet appears to have strayed too close to the star and was ripped apart. Parts of it were then gobbled up by the white dwarf.
[Runtime: 01:59]

(Credit: NASA/CXC/April Jubett)



Return to NGC 6388 (April 16, 2015)