Dana Berry/MIT

The Closest Exoplanet So Far Has Been Discovered, And It's Got Astronomers Excited

12 NOVEMBER 2015

An international team of researchers has discovered a new exoplanet that's much, much closer than any previously found, close enough that we can study its potential atmosphere.

 

Bearing the slightly wordy name of GJ 1132b, the new neighbour is a rocky, Earth-sized planet that's located only 39 light-years away from us in the Vela constellation, which is visible from the southern hemisphere. 

The planet circles a small red M-dwarf star called GJ 1132 (which is where GJ 1132b gets its creative name), which is only one-fifth the size of our Sun. It's a much cooler and fainter star, but the exoplanet orbits so close to it, the surface temperatures reach an eye-watering 260°C (500°F).

The planet is estimated to be only 16 percent larger than Earth. "GJ 1132b's average density resembles that of the Earth, and is well matched by a rock/iron bulk composition," the researchers note in a letter published in Nature.  

Even though it's so hot, the planet is cooler than many other balls of fire we've found in our search for exoplanets, in fact it’s cool enough to have a substantial atmosphere, which has astronomers excited.

“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,” MIT astronomer Zachory Berta-Thompson told Jennifer Chu at MIT News. “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.” 

The team, led by MIT researchers, found GJ 1132b using the MEarth-South Observatory, an array of eight 40-cm large robotic telescopes in the mountains in Chile, where some of the best astronomy takes place. This array is built specifically to monitor the abundant M-dwarf stars in the night sky, and look for any dips in brightness that might indicate an exoplanet. 

On May 10 this year, one of the telescopes detected a faint dip from GJ 1132, and immediately started taking measurements every 45 seconds for confirmation. You can watch a cool time-lapse of this discovery below: it's all business as usual, telescopes scanning all over the sky, until one of the robots stays transfixed on the data blip that turned out to be a new, exciting exoplanet.

The researchers employed other nearby telescopes to confirm the discovery, and found that every 1.6 days GJ 1132 would dim by 0.3 percent, which is the tell-tale sign of a regularly passing planet. 

“What is tremendously exciting to me is that this planet could be a real ‘cousin’ of Venus and Earth,” astronomer Jonathan Fortney told MIT News. 

“I think that this planet’s atmosphere, when we are able to try to determine what it is made of, will be an interesting data point in understanding the diversity in atmospheric composition for Earth-sized planets. In our solar system, we only have two data points: Earth and Venus. Before we can understand habitability, I think we need to understand the range of atmospheres that nature makes, and why.”

Meanwhile GJ 1132b has already been pronounced “arguably the most important planet ever found outside the solar system”, thanks to an accompanying article in Nature by astronomer Drake Deming.

As The Guardian's science editor Ian Sample reports, "the planet will become a prime target for future [observatory] missions too, including the James Webb Space Telescope, which is expected to launch in 2018, and the Giant Magellan Telescope, which is due to start operations in Chile in 2025."