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In the past 20 years, astronomers have found hundreds of planets scattered across the galaxy. Some of them, like Kepler-452b, are thought to be remarkably like our Earth: similar in size and orbiting in a zone warm enough to sustain life. The thing is, most of these are impossibly far away. It takes light — the fastest thing in the universe — 1,400 years to reach Kepler-452b. We can never travel there.
That’s why today’s announcement from the European Southern Observatory and the Pale Red Dot project is so damn exciting: Astronomers have discovered a new, potentially habitable planet circling Proxima Centauri, the closest star to our own.
This is likely the nearest planet outside our solar system that we’ll ever find. What’s more, it should, in theory, be warm enough for liquid water — and warm enough for life.
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"This rocky world is a little more massive than the Earth and is the closest exoplanet to us — and it may also be the closest possible abode for life outside the Solar System," the ESO explains in its announcement of the discovery, which was published in the journal Nature.
Proxima Centauri is a smaller, cooler star than our sun. But the new planet, Proxima b, orbits about eight times closer to its star than Mercury does to the sun, the team that led the discovery said in an Reddit Ask Me Anything session. That keeps it warm in a cold solar system.
It’s about 1.3 times more massive than Earth, and it’s believed to only expose one side of its surface to the light (kind of like how on Earth we only ever see one side of the moon). A year on Proxima b is about 11.2 days long. If you were standing on Proxima b, you’d be basked in red light from the star. The Atlantic reports that if there were plant life on the planet, it would probably be crimson-colored to best absorb the rays.
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Above, you can see just how close Proxima b is to its star, in the narrow band of green that represents the area where life could, hypothetically, live.
The discovery is the culmination of years of observations by a group of scientists under the banner of the "Pale Red Dot" initiative. ("Pale red dot" is a nickname for Proxima Centauri.) Basically, astronomers pointed telescopes at Proxima Centauri and were searching for signs a planet was influencing the quality of light emanating from the star. From those changes in light, they can then calculate basic features of the planet, such as its size and orbit.
There are some reasons to be doubtful that Proxima B could sustain life
Proxima b is at the right distance and temperature to support life, but other hazards may lurk that could make life impossible. For example, orbiting so close to a star could expose the planet to deadly levels of radiation. "Despite the temperate orbit of Proxima b, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star — far more intense than the Earth experiences from the Sun," ESO explains.
"Life on such a planet would probably have to shelter underground or under water if it exists," Lisa Kaltenegger, director of Cornell University’s Carl Sagan Institute, says in an email press statement. (She was not involved with the discovery.) "Or develop a method to shelter from the flares and its temporary high UV radiation."
Could we ever get there? Maybe!
At 4.2 light-years away, Proxima b is still incredibly distant. The rocket that took men to the moon reached a speed of 24,500 miles per hour. At that speed, it would take more than 130,000 years to reach Proxima b. Humanity itself might not last that long.
But there may be a way to send something there.
In April, Russian billionaire Yuri Milner and super-famous physicist Stephen Hawking announced they had an idea to send teeny, tiny spaceships to Alpha Centauri, the next closest star after Proxima.
They call their initiative the Breakthrough Starshot, and it involves propelling space vessels the size of postage stamps to 100 million miles per hour — 20 percent of the speed of light.
At that speed, one of these "nanocrafts" could reach Alpha or Proxima Centauri in about 20 years. And because radio communications travel at the speed of light, it would only take an additional four years or so for the data from the mission to reach Earth.
Hawking and Milner think it's possible to design such tiny spaceships because of Moore's law, which dictates that microchips will keep getting smaller and more powerful. "This creates the possibility of a gram-scale wafer, carrying cameras, photon thrusters, power supply, navigation and communication equipment, and constituting a fully functional space probe," the Breakthrough Starshot website explains.
This work is all preliminary. There are a lot of problems Starshot will have to figure out before it can get off the ground. Here’s one, described in Ars Technica today: At speeds of 20 percent the speed of light, it’s possible the spacecraft could be destroyed by a single atom.
But here’s the thing: It’s at least in the realm of possibility — thanks to human ingenuity and imagination — to travel to this strange new world. And that’s exciting.
