Exoplanets can be pretty wacky, at least compared to our own planet. Astronomers have recently found a new exoplanet that orbits so close to its star it seems to be evaporating under the intense heat.

Astronomers using the space-based Kepler telescope look for exoplanets by measuring the light reaching Earth from a distant star over the course of a month. A regular dimming in the light indicates that a planet is passing in front of it, much like how the Moon dims the light of the Sun during an eclipse. But the star KIC 12557548 has an unusual light pattern when viewed from Earth. Instead of a regular dim, astronomers found that the star’s light dimmed irregularly. Every fifteen hours, the shortest cycle for something orbiting a star ever observed, the light dimmed but the amount varied.

It didn’t look like a planet; planets are solid and regular. The observed interruption suggested something regular but variable was orbiting the star. Saul Rappaport, one of the astronomers on the team that made the discovery and professor emeritus of physics at MIT, thought it might be a pair of planets orbiting one another – like the Moon orbiting the Earth. That could explain why the light would dim differently each time the pair passed in front of the star. But this hypothesis didn’t match the data. A fifteen-hour orbit is just too short for two planets to be orbiting each other that way.

The team came up with a novel explanation based on their observations: the varying intensities of light could be caused by some kind of shape-shifting body. It had to be something changing, like dust coming off the planet in irregular amounts. They created a model of a planet with a dust trail densest right around the planet that dispersed as it moved away, sort of like the trailing tail of a comet. The model confirmed the irregular light pattern seen in the Kepler observations.

But how could dust just come off a planet like that? Rappaport and his team reasoned that the planet must have a low gravitational field, sort of like that of the planet Mercury, too weak to hold the gas and dust on its surface. It must also be extremely hot, somewhere in the realm of 3,600º F. That’s the how, but it didn’t explain where this gas and dust is coming from.

The team came up with two possible explanations. The dust might be ash coming from erupting from surface volcanoes, or it could be the result of metals vaporizing from the high temperatures that condense into dust and escape the weak gravity. Wither way, they believe the dust is made of sub-micron sized particles. Looking through the dust would be like looking through heavy smog.

This interesting, dissolving world isn’t likely to be around much longer. Based on calculation, the team suspect the planet will be completely disintegrated in just 100 million years. That might seem like a long time, but it’s like the blink of an eye in the universal time scale of things. Good thing it’s not a candidate planet for eventual human migration.

Connections:

• First Successful Tracking of Exoplanet Orbit
• Jupiter: Our Savior, Our Destroyer
• This Is Really Big