Did Earth Look Like “Gliese 436B” Before Evolution?

A planet that is the size of Neptune, is losing its atmosphere, meanwhile forming a fat, comet like tail. The planet is 33 times closer to its parent star than Earth orbits the Sun. Using the Hubble Space Telescope’s light –splitting ultraviolet spectrograph, astronomers caught the sight of the planet called Gliese 436b, located at a distance of about 30 light years from Earth, in the constellation Leo. They saw it as it passed in front of its parent star on the dates of December 2012, June 2013 and June 2014.

NASA’s Chandra X-ray Observatory, a telescope specially designed to detect X-ray emission from very hot regions of the Universe such as exploded stars, clusters of galaxies, and matter around black holes, made similar observations during the last two transits.

David Ehrenreich, with the Observatory of the University of Geneva, and colleagues wrote in this week’s Nature, that the scientists found a huge and asymmetrical spike of hydrogen, most likely caused by a massive hydrogen cloud surrounding and trailing the planet.

The intense radiation from the parent star is burning off the hydrogen from the planet’s atmosphere. The parent star is a red dwarf that is less than half as big as the sun. The planet orbits just 2 million miles from its host star. By comparison, the Earth, is about 93 million miles from the sun.

“The ultraviolet transits repeatedly start about two hours before, and end more than three hours after the approximately one-hour optical transit,” Ehrenreich and colleagues wrote. That means the cloud is about 50 times bigger than the parent star.

As the star pushes on the escaping hydrogen it forms a tail due to the ultra violet light, which causes it to spiral out, added Peter Wheatley, with the University of Warwick and a co-author of the paper.

436b is losing more than a ton of hydrogen every second from its atmosphere, estimation by scientists. That works out to about 0.1 percent of its total mass every billion years.

“Overall, we estimate that it may have lost up to 10 percent of its atmosphere over the past several billion years,” Enrenreich said in a statement.

The planet is a long way from losing its atmosphere completely, but scientists are wondering if they’ve caught sight of a so-called “Hot Super-Earth” in the making. These are rocky planets several times the mass of Earth that are in close orbits around their parent stars.

This new research provides a theory for the existence of even more massive planets with once-thick gas atmospheres that burned away over the eons.


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