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Rocky Earth-sized exoplanet found orbiting a nearby red dwarf star

Astronomers are eager to get a peek at its atmosphere

There’s a new exoplanet on the galactic map. A rocky planet roughly the same size and density of Earth has been discovered orbiting a nearby red dwarf star, thanks to new data gathered by telescopes in Chile. Located 39 light-years from our Solar System, it's the third-closest transiting exoplanet we know about.

Scientists are particularly excited about this planet as they think it’ll be a lot easier to study than other rocky planets that have been found. That’s because the star it’s orbiting is relatively small. Right now, it's difficult to study Earth-sized exoplanets found around large stars like our Sun because those giant stars are so incredibly luminous that they completely drown out nearby objects, making any orbiting planets hard to see. Red dwarf stars, however, are much fainter and smaller — about 10 to 20 percent the size of our Sun — making this new planet much more visible.

This planet will be a lot easier to study

And since the star system is so close, scientists think they will be able to study this planet in even greater detail. The next closest Earth-sized planet around a red dwarf is located 127 light-years away — too far for scientists to characterize the planet. But due to the proximity of this new world, there's hope of figuring out the gases that comprise its atmosphere. "This will probably be our first opportunity to study the atmosphere of a rocky planet outside our Solar System," said Zach Berta-Thompson, an observational astronomer at MIT, who made the discovery.

The planet was first spotted by the MEarth-South telescope array in Chile, and is described today in a study published in Nature. The MEarth-South telescopes found the planet by studying the brightness of various stars in the night sky. Using data gathered by this array, scientists noticed a red dwarf that would lose about .33 percent of its brightness every 1.6 days. That suggested that something small was passing in front of the star, blocking a little bit of its light in a routine pattern.

The MEarth-South telescope array, located on Cerro Tololo in Chile. (Jonathan Irwin)

Based on those measurements, Berta-Thompson and his team figured out that the red dwarf had an orbiting exoplanet, with a radius 1.2 times that of Earth's. The object, named GJ 1132b, is most likely made up of rock and iron, and it's about as dense as our planet is.

However, chances are GJ 1132b wouldn't be a very comfortable place to live. The exoplanet is much closer to its host star than our planet is to the Sun. Its temperature ranges between 278 and 572 degrees Fahrenheit, which is hot enough to boil any liquid oceans away. "It's so close, the coolest its atmosphere gets is about as hot as your oven can get in your kitchen," said Berta-Thompson. GJ 1132b also receives 19 times more radiation than we receive here on Earth.

Chances are GJ 1132b wouldn't be a very comfortable place to live

Despite its inhospitable nature, the planet is still cool enough to support a complex atmosphere, which scientists are eager to study. Berta-Thompson says they hope to analyze the light from the red dwarf as it passes through the "edges" of GJ 1132b. Light wavelengths change when they pass through different types of gases, so by observing the various wavelengths in the exoplanet's atmosphere, scientists can figure out its gaseous composition. "Basically we want to peer over the shoulder of someone on the planet who is watching the sunset and see what color the sunset is," said Berta-Thompson.

The gases in an exoplanet's atmosphere could provide clues as to what the planet holds — such as the presence of extraterrestrial life. Earth's atmosphere is comprised of 20 percent oxygen, for example, which stems primarily from photosynthesis and biological processes. If abundant amounts of oxygen or other gases associated with biology are present in an atmosphere, it could indicate that lifeforms are on the surface below. It's one of the main tools planetary scientists use when looking for life. "If we want to detect life on an exoplanet, the only chance is through the atmospheric spectrum," said Drake Deming, an astronomy professor at the University of Maryland, who wrote an accompanying article in Nature about the discovery. "You can’t send a probe there, and you can’t see down below to the surface. All we have access to on extrasolar planets is the outer edges."

While it's unlikely that GJ 1132b has any life on its surface, studying its atmosphere will provide good practice — in case we find another rocky Earth-like planet in a much more habitable area of space.