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Hot Planet

January 24, 2013

One of the smallest planets yet discovered around a “normal” star isn’t likely to be a popular destination for future star travelers. The planet is smaller than Earth, but it’s only a couple of million miles from its parent star. At that distance, its surface temperature is more than a thousand degrees Fahrenheit — so hot that the surface may be coated with molten rock.

The planet orbits the red-dwarf star Gliese 436, which is far smaller, fainter, and cooler than the Sun. Its surface is so cool that it emits most of its light in the infrared. Infrared wavelengths are tough to see from Earth because they’re absorbed by the atmosphere. So scientists were studying the star and another known planet with Spitzer Space Telescope, which is sensitive to the infrared.

Spitzer detected tiny dips in the star’s brightness. Astronomers realized those dips were caused by a planet passing in front of the star, briefly blocking some of its light. From that, they were able to measure the planet’s size, mass, and its distance from the star — compiling a thorough dossier with the help of infrared light.

Infrared provides the best views not only of cool stars, but of the gas clouds that are giving birth to stars, the cocoons of dust that are giving birth to new planets around stars, and many other objects. And the best way to study them all is with space telescopes. In fact, the first infrared space telescope was launched 30 years ago. More about that tomorrow.


Script by Damond Benningfield, Copyright 2012

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