Monday, November 30, 2015

Villanova Astronomer Helps Find Distant Earth-Sized Planets

NASA defines life as a self-replicating system that can evolve through natural selection. So the search for life is the search for evolution, and two new planets bring them closer.

Villanova Astronomer Helps Find Distant Earth-Sized Planets


Big, gaseous planets are becoming a commonplace finding in our galaxy, but until now astronomers had never detected a body as small as our Earth orbiting another star. Two new planets announced today matter in the search for life because they are small enough to have a solid surface. They are too close to their sun to have liquid water, but astronomers are optimistic that more habitable worlds will be found soon.    

On Tuesday I caught up with Villanova astronomer Andrej Prsa, who was part of the team announcing the planets. They were detected with a space telescope called Kepler, launched in 2009 with the express goal of finding other earths.

Prsa’s job is to make sure Kepler is detecting real planets and not reacting to false alarms. The astronomers don’t actually see any of these planets but indirectly detect their presence by monitoring stars for tiny periodic dips in brightness. These dips are indications that planets are passing in front and creating mini-eclipses. (The image is an artist's reconstruction)

The newly announced planets only dim the stars by 100 parts per million, said Prsa, but measuring such minuscule changes is within Kepler’s ability.  The project has led to announcements of hundreds of “candidate planets,” he said, but astronomers have high standards of evidence when it comes to naming a true discovery.

To tell which candidates are real, the astronomers watch them for a few orbits to make sure the dimming really is periodic. And they have to rule out the possibility that they’re seeing the effects of a series of stars eclipsing each other.

That means the easiest planets to pin down are ones that orbit fast. The new planets, called Kepler 20e and Kepler 20f, orbit every 6.1 days and 19.6 days. They are 1000 light years away. With its much longer orbit, a distant twin to Earth would have to be watched for more than three years.  

The new planets are part of an unusual solar system that contains five planets with orbits smaller than Mercury’s. To find planets at more temperate distances, Prsa said, they need to convince NASA to extend their mission. It would seem like an easy sell, but Prsa said anything is possible.



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About this blog
Faye Flam - writer
In pursuit of her stories, writer Faye Flam has weathered storms in Greenland, gotten frost nip at the South Pole, and floated weightless aboard NASA’s zero-g plane. She has a degree in geophysics from the California Institute of Technology and started her writing career with the Economist. She later took on the particle physics and cosmology beat at Science Magazine before coming to the Inquirer in 1995. Her previous science column, “Carnal Knowledge,” ran from 2005 to 2008. Her new column and blog, Planet of the Apes, explores the topic of evolution and runs here and in the Inquirer’s health section each Monday. Email Faye at Reach Planet of the at

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