MIT astrophysicist Sara Seager on newly discovered exoplanet Proxima b

The planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our Solar System, is seen in an undated artist's impression. REUTERS

By now you’ve heard we’ve got a new neighbor — at least, one we’ve just discovered. A neighbor that’s about 25 trillion miles away.

When scientists announced the discovery of Proxima Centauri b in August, the small exoplanet made headlines for its potential to sort of, maybe, possibly be able to sustain life. Orbiting Proxima Centauri, the closest star to our sun, Proxima b occupies the “Goldilocks zone” where temperatures are not too hot or too cold for liquid water to form — a necessary component for life.

Promising. But what might it like on this far-flung exoplanet?

MIT astrophysicist Sara Seager wrote an article for Quartz at the news organization’s request, speculating what human existence on Proxima b might look like. For starters, we’d all be much older — one year on the exoplanet equals 11 Earth days. We’d also probably weigh more since, as Seager writes, the planet may have a higher surface gravity.

What’s more, the view wouldn’t ever change. In all likelihood, Seager wrote, Proxima b is “tidally locked,” meaning the planet rotates on its axis once every time it orbits around a star. So the planet presents the same face to the star at all times, the same way our moon presents the same face to the earth. On Proxima b, one side of the planet would always be day, while the other would always be night.

Of course, these are hypotheses. Scientists still don’t know anything about the exoplanet’s atmosphere or its exact size and density. But using a detection method called radial velocity, which depends on the movement of an orbiting object, researchers were able to determine the minimum mass of the planet (at least 30 percent greater than that of the Earth) which led them to believe it probably has rocky terrain and isn’t a gas giant like Jupiter, said Seager, an expert on exoplanet research.

Here’s where it gets really tricky. Radial velocity detection works because a planet and star orbit a common center of mass, but the planet’s relatively tiny gravitational pull can cause the much bigger star to move slightly or “wobble” around that center of mass. The star’s movements can be observed on Earth as colors of light on the visible spectrum. Scientists then measure the star’s motion by noting the color changes. Redder means the planet is moving away from the Earth, blue means it’s moving closer.

But while radial velocity has been an extremely effective way of identifying exoplanets, it has its drawbacks. There’s a lot of ambiguity, Seager said. It’s as if the planet were a person jumping trillions of miles away.

“Imagine if you were jumping up and down,” Seager said in an interview. “I would see you better at different times because you’re not just jumping straight up and down but also toward me and away from me.”

In other words, using this method, astronomers can only measure an object as it moves closer and farther from Earth. If it appears to maintain the same distance, the colors of light won’t change — and the planet will go undetected.

Finding Proxima b is only the beginning. Scientists will now try and learn more about its atmosphere and size. They’ll also start looking for other exoplanets in the same system now that they know Proxima Centauri has at least one orbiting planet. Seager thinks the media attention is playing a major role in these discoveries.

“The hype works both ways. People are getting excited — young people who wanted to work flooded the field,” she said. “Many of the best and brightest young minds are getting into exoplanets.”