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Earth’s Nearest Exoplanet Might Not Be Habitable



Exoplanet discoveries are always exciting — to find a place outside our solar system that could potentially support life or future human colonization is science fiction becoming a reality. Most of these planets are hundreds or even thousands of lightyears away, making it impossible to reach them with our current levels of technology, but it’s fun to dream.

Some scientists thought our closest exoplanet “neighbor” Proxima B might be habitable for humans in the future, but that might no longer be an option. Why is Proxima B no longer on the “to-visit” list?

Where Is Proxima B?

First, where is our nearest interstellar neighbor?

If you ask Google, the answer you get looks like gibberish — RA 14h 29m 43 sec | Dec -62° 40’ 46”. Those are the planet’s interstellar coordinates, but if you’re not an astronomer or an astrophysicist, the numbers probably don’t mean much.

Proxima is also called Proxima Centauri B and is in orbit around Proxima Centauri, a red dwarf star in a massive triple-star system. What makes it so exciting is its location — it’s only about four lightyears from Earth. While that’s still a staggering 25 million miles away, Proxima B is still one of the closest exoplanets researchers have discovered.

The triple-star system the planet calls home isn’t the best place for planets, though — and Proxima B might not be able to support life anymore.

The Worst Sunburn Ever

Have you ever thought of stars as having a personality? Well, Proxima Centauri has a bit of a temper. In March 2017, the star released an enormous solar flare, making its surface more than 1,000 times brighter for a few seconds before it dimmed. While it created an amazing light show for observing astronomers, it also probably took Proxima B off NASA’s “to-visit” list.

M-Class red dwarf stars like Proxima Centauri tend to be extremely volatile, and while this is the first flare of this size we’ve observed, they may be common in that solar system. The short flare bombarded the surface of the planet with 4,000 times more radiation than normal. These flares are capable of ripping a planet’s entire atmosphere away, making it entirely uninhabitable.

NASA’s research has shown the flares emitted by Proxima Centauri tend to drain Proxima B’s atmosphere roughly 10,000 times faster than the atmosphere drain we experience on Earth. Similar phenomena have occurred on Earth — in 2014, two massive solar flares from our own sun, known as coronal mass ejections (CMEs), drained electrons from affected areas. These areas rebounded within a few days, but the CMEs we experienced were orders of magnitude less powerful than the flare that cooked Proxima B.

The biggest question now is how fast the planet can recharge its atmosphere, and whether this process is happening faster than the solar flares can burn it away. If the planet can rebound quickly enough, it could still potentially support life, but it may not be the best option for future human colonization.

Other Neighbors Might Provide More Hope

All is not lost, though — a newly discovered dust ring in the Proxima Centauri system suggests Proxima B may have interstellar neighbors in the same system, some that might be in a more ideal place for a visit from future humans. The Breakthrough Starshot project is planning on sending solar-sail-equipped microprobes into the Proxima Centauri system in the not-too-distant future to analyze the dust field and get a better look at our closest neighbor. The project will give us a better idea whether the star system is capable of supporting life —and whether or not we should be looking to visit Proxima Centauri in the near future.

Even if Proxima B turned out to be totally cooked by the solar flares of its nearby star, this discovery gives us a better idea of the kind of solar system we need to look for in the future once we start truly taking our first steps as a species into interstellar space. We just might want to pack the SPF 1,000,000 for our visit to Proxima B.


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