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An artist’s conception provided by NASA shows GJ 1132b (foreground), a rocky planet similar to the Earth in size and mass, orbiting a red dwarf star.
An artist’s conception provided by NASA shows GJ 1132b (foreground), a rocky planet similar to the Earth in size and mass, orbiting a red dwarf star.Dana Berry/SkyWorks/NASA via AP

For decades, astronomers have studied faroff stars and planets in the Milky Way galaxy, never finding an Earth-sized, star-orbiting planet close enough to study in depth.

But now, scientists say, they've discovered a new planet, just 39 light years away, that offers an exciting research opportunity.

"We've learned in the past about the forest of planets out there. The one planet that we just found, it's like it's a tree just a few feet away from us. It's just one lone tree by itself, but you can see it in so much detail," said Massachusetts Institute of Technology researcher Zachory Berta-Thompson.

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The new planet, called GJ 1132b, is a rocky exoplanet (a planet that orbits a star other than our Sun). Berta-Thompson discovered GJ 1132b with his team of MIT and Harvard University researchers in May, and their findings were published Wednesday in the science journal Nature.

The research is a piece of the MEarth Project, a Harvard-led research project that started in 2008 with telescopes in Arizona, Berta-Thompson said. Six years ago, a year into the project, the researchers made their first exoplanet discovery — GJ 1214b, an exoplanet whose size is between the sizes of Earth and Neptune.

Through a newer project with telescopes installed in the mountains of Chile, Berta-Thompson and his team found GJ 1132b.

"By studying this new world, I'm optimistic we'll learn a little more about how planets work and bring us a little closer to that big exciting question of empirically figuring out whether life is out there in the galaxy," he said.

With 500-degree Fahrenheit temperatures, GJ 1132b is likely uninhabitable by life as we know it, but Berta-Thompson said its proximity to Earth would allow researchers to study it in greater depth than any other previously discovered exoplanet.

"What is great about a close star is that it's relatively bright," he said. "So because it's so nearby and so bright, we can point ... big telescopes at this star and at this planet and learn more."

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In studying the planet's 1.6-day orbital period and its gravitational pull on its star, researchers have been able to calculate the planet's mass, radius, and density. The density, Berta-Thompson said, indicates the planet is composed of mostly rock and iron, like Earth.

Now, astronomers are hoping to learn more about the planet's atmosphere.

"If you have a mass and radius for a planet, that's great, but it's just a nondescript sphere," he said. "If you could study its atmosphere and figure out what molecules are in its atmosphere … then that really kind of turns this world from a nondescript sphere into a world, like a place you could imagine standing or walking around."

Berta-Thompson said the research on exoplanets will continue to expand with the construction of two new telescopes within the next decade — the James Webb Space Telescope scheduled to launch in 2018 and the Giant Magellan Telescope in Chile, where construction began on Wednesday.

The MEarth-South telescope array in Cerro Tololo in Chile monitors the brightness of small nearby stars.
The MEarth-South telescope array in Cerro Tololo in Chile monitors the brightness of small nearby stars.Jonathan Irwin

Felicia Gans can be reached at felicia.gans@globe.com. Follow her on Twitter @FeliciaGans.