Mercury-sized exoplanet is being vaporized into a cloud of gas

Something very strange is happening around the star KIC 12557548. Its light dims every 15 hours, as though a planet is orbiting around it...except the dimming varies wildly each time around. A planet is being vaporized before our eyes.

According to researchers led by Saul Rappaport of MIT, the star's orbital companion is a rocky planet about twice the mass of Mercury orbiting at just a hundredth the distance between the Sun and Earth, a distance known as an astronomical unit (AU). For the sake of comparison, Mercury even at its closest approach to is always at least 0.3 AU from the Sun. At such a tiny distance, this planet would roast at 2,000 Kelvin, which would easily be hot enough to vaporize the common minerals that make up rocky planets.

The idea of a vaporizing planet isn't new - astronomers discovered a gas giant being pulled apart by its star back in 2003, which you can see in the artist's conception up top. But this is the first time we've spotted a solid, rocky planet being destroyed in this way. The planet is kicking up massive quantities of vaporized rock and dust, forming a thick cloud that would vary in density over time, thus explaining why the amount of light from KIC 12557548 keeps varying so much.

If this discovery holds up, then this is easily the tiniest exoplanet spotted by Kepler or any other planet-hunting survey, and indeed it's way below the usual lower limit for what our current technology can detect. That's where the cloud comes in. It blocks way more light than the planet itself would, allowing us to see it at all.

The planet, whose cloud may actually possess a comet-like tail, will likely last for about 200 million years - hardly anything in cosmic terms - before being completely destroyed. Mercury may also await a similar fate when our Sun runs out of fuel and expands into a red giant -before it's swallowed up by our bloated future Sun, Mercury might go through a similar vaporization process.

Via arXiv. For more, check out New Scientist. Artist's conception of Planet HD 209458b by ASA, European Space Agency, Alfred Vidal-Madjar (Institut d'Astrophysique de Paris, CNRS).