Looking Up – Bob Eklund

GJ-1132bScientists have discovered a new exoplanet that, in the language of “Star Wars,” would be the polar opposite of frigid Hoth, and even more inhospitable than the deserts of Tatooine. But instead of residing in a galaxy far, far away, this new world is, galactically speaking, practically next door.

The new planet, named GJ 1132b, is Earth-sized and rocky, orbiting a small star located a mere 39 light-years from Earth, making it the closest Earth-sized exoplanet yet discovered.

Scientists from The Massachusetts Institute of Technology (MIT) have determined that the planet is a roasting 440 degrees Fahrenheit, and is likely tidally locked, meaning that it has a permanent day and night side, presenting the same face to its star, much like our Moon is locked to the Earth.

Because of its scorching temperatures, GJ 1132b most likely cannot retain liquid water on its surface, making it uninhabitable for life as we know it. However, scientists say it is cool enough to host a substantial atmosphere.

It is also close enough to Earth that scientists may soon be able to find out much more about its characteristics, from the composition of its atmosphere to the pattern of its winds—and even the color of its sunsets.

“If we find this pretty hot planet has managed to hang onto its atmosphere over the billions of years it’s been around, that bodes well for the long-term goal of studying cooler planets that could have life,” says Zachory Berta-Thompson, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research. “We finally have a target to point our telescopes at, and [can] dig much deeper into the workings of a rocky exoplanet, and what makes it tick.”

Berta-Thompson and his colleagues discovered the planet using the MEarth-South Observatory, a Harvard University-led array of eight 40-centimeter-wide robotic telescopes located in the mountains of Chile. The array monitors small, nearby stars called M dwarfs, which are scattered all over the night sky. Scientists have determined that these kinds of stars are frequently orbited by planets, but haven’t yet found Earth-sized exoplanets that are close enough to study in depth.

Since early 2014, the telescope array has been gathering data almost every night, taking measurements of starlight every 25 minutes in search of telltale dips in brightness that may indicate a planet passing in front of a star.

On May 10, one telescope picked up a faint dip from GJ 1132, a star located 12 parsecs, or 39 light-years, from Earth.

The robotic telescope immediately started observing GJ 1132 at much faster 45-second intervals to confirm the measurement—a very slight dip of about 0.3 percent of the starlight. The researchers later pointed other telescopes in Chile at the star, and found that indeed, GJ 1132’s brightness dimmed by 0.3 percent every 1.6 days—a signal that a planet was regularly passing in front of the star.

“We didn’t know the planet’s period from one single event, but when we phased many of them together, this signal popped out,” Berta-Thompson says.

Based on the amount of starlight the planet blocks, and the radius of the star, scientists calculated that planet GJ 1132b is about 1.2 times the size of Earth. From measuring the wobble of its host star, they estimate the planet’s mass to be about 1.6 times that of Earth.

By calculating the size of and proximity to its star, the group came up with an estimate of the planet’s average temperature: a scorching 440 degrees Fahrenheit.

 

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