Why Haven’t We Found Planets in Alpha Centauri?

Hello, friends!  Today I’d like to take you on a quick tour of the Alpha Centauri star system, the Solar System’s next door neighbors.

Alpha Centauri consists of three stars.  Two of those stars orbit in a tight binary formation, sort of like this:

Animation courtesy of Wikipedia.

The third star is known as Proxima Centauri.  It’s a tiny red dwarf star, orbiting very far away from that central binary pair.  Proxima is known to have at least one (possibly two) planets, but we’ll visit Proxima’s planets in a future post.

Today, I really just want to focus on Alpha Centauri A and B, the two stars in that central binary, to see if they have any planets.  In 2012, astronomers announced the discovery of a planet orbiting Alpha Centauri B, but that discovery turned out to be a ghost in the data.  Otherwise, astronomers have found nothing out there.

Over the last decade or so, we’ve found so many exoplanets, both near and far.  Given how close-by Alpha Centauri is, you’d think we would have found something there by now.  It’s enough to make you wonder if, maybe, there’s nothing to find.  But it turns out there’s a very good reason why we’re having so much trouble finding Alpha Centauri’s planets.

As Alpha Centauri A and B move through their figure-eight orbital paths, sometimes they’re close together, and sometimes they’re far apart.  Over the past decade or so, it just so happens that they’ve been very close together, at least from our vantage point here on Earth.  Even with all the advanced planet hunting techniques we’ve developed in the past ten years, the double glare of those two stars would’ve concealed any signs of a planet from our view.

But that’s about to change.  In February of 2016, Alpha Centauri A and B were as close together as they’ll get (as seen from Earth).  They’ve been moving away from each other ever since, and according to this article from Scientific American, 2020 is the magical year when A and B are finally far enough apart that our telescopes can observe them separately.

Based on the metallicity of those two stars, they should be just as capable of forming planets as our own Sun.  Planetary orbits would be stable up to 2.5 astronomical units away from either star, according to Scientific American (our entire inner Solar System could fit comfortably inside that 2.5 A.U. radius).  And computer simulations produce many plausible scenarios where Earth-like planets could exist in the Alpha Centauri binary.

In some of those computer simulations, an Alpha Centaurian planet might be even more suitable for life than Earth!  So stay tuned.  In the next few years, we may finally get news about habitable planets—or even a superhabitable planets—in Alpha Centauri.

Next time on Planet Pailly, how are you preparing for the robot rebellion?

2 thoughts on “Why Haven’t We Found Planets in Alpha Centauri?

    1. The Solar System is much bigger, yes. I’m referring only to the inner Solar System. The orbits of Mercury, Venus, Earth, and Mars could fit comfortably within that 2.5 AU radius.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.