A Planet is being Vapourized by its Home Star

At least once a month we hear of a new exoplanet with a strange and amazing story.  From the ‘Super-Saturn’ ringed world to Magnetic Fields to systems of three Earths, there is an abundance of planets and strange systems.

The latest weird discovery brings us to a star 1,500 light years away in the constellation Cygnus.  The small-Mercury sized planet it hosts orbits in only 16 hours, bringing its surface temperature to over 1,800 degrees celsius.  This amount of heat is enough to vapourize rock, and so the star is literally roasting the planet and blasting away its surface.  The dust liberated from the planet is trailing behind it as it orbits, resulting in a comet-like trail.

Image credit: Maciej Szyszko.

Even though the planet is very small, the dust cloud from its vapourized surface is large enough to block out 1% of the host star’s light.  This is the same as if a Jupiter-sized planet was orbiting in its place.  Without the massive dust cloud its unlikely we would be able to find such a small planet.

The William Herschel Telescope’s ULTRACAM was used to study the dust cloud, which blocks a slightly larger fraction of the star’s blue light than red light.  This is similar to the Earth’s atmosphere scattering blue light, causing a sunset to appear red. The exact color-dependence of the scattered dust can reveal the size of the grains, and even their composition.  Determining the dust composition, as the astronomers hope to with future observations, will give us the composition of the planet’s surface, a first in exoplanet astronomy.

I’ve said it before, and it will ring true for years to come.  This is the most exciting time for planetary scientists and astronomers, and centuries from now it will be remembered as the beginning of humanity’s understanding of planetary systems beyond our own.


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