The Highly Conspicuous Rings of Proxima c

Hello, friends!  As you know, Saturn is a really pretty planet.  That’s not an opinion.  It’s a scientific fact.  But in the solar system right next door to our own, there is a planet even prettier than Saturn.  As you can see in the highly technical diagram below, the planet Proxima Centauri c may be the brightest, shiniest, prettiest planet known to human science!

The last time I wrote about Proxima Centauri c, the planet was only suspected to exist, based on circumstantial evidence.  But according to this press release, Proxima c’s existence is now confirmed.  Additional data about the planet was found in archived Hubble Space Telescope images dating back to the 1990’s.

However, certain details about Proxima c remain difficult to explain.  Most notably, the planet (as observed in infrared light) appears to be way, waaaay brighter than we would expect, based upon its estimated mass (approximately seven times the mass of Earth).  In my highly technical diagram, I tried to make Proxima c look as bright and shiny as possible, but I’m starting to think I didn’t make the planet bright and shiny enough!

According to this paper on Proxima c’s infrared signature, one possible explanation is a “conspicuous ring system” that’s reflecting a whole lot of extra sunlight.  If that’s the case, Proxima c really would be a stunningly beautiful sight, with wide, glorious rings that would put the rings of Saturn to shame.  However, that same paper offers other possible explanations that sound far more grim.  Something horrible may have happened to Proxima c and/or its moons.  But I’ll save that for Friday’s episode of Sciency Words.

P.S.: If you own a backyard telescope or a pair of binoculars and want to see Proxima c for yourself, well… you can’t.  But if you have access to a high powered astronomical observatory, there’s a really interesting technique that can help you find Proxima c and planets like it.  Science communicator Elizabeth Tasker has written an excellent article about that.  Click here!

How Proxima b Lost Its Ozone Layer

Hello, friends!

Today we’re visiting Proxima Centauri, one of three stars in the Alpha Centauri system, the star system right next door to our own.  And it turns out Proxima has at least one planet.  Not only that: Proxima’s planet is orbiting within the habitable zone.  That planet may have liquid water on its surface, and perhaps even life!

Proxima’s planet, known officially as Proxima b, orbits about 0.05 AU away from its star.  That puts Proxima b closer to its star than Mercury is to our Sun.  But that’s okay.  Proxima Centauri is much smaller, dimmer, and colder than our own Sun, so everything balances out.

But I have bad news.  The temperature might be right for life, but the radiation environment is all wrong.  Proxima Centauri is a very angry little star.  It’s much angrier than our Sun.  Solar flares, solar wind, and solar radiation are a whole lot worse than anything Earth would normally have to worry about.

In March of 2016, Earth-based astronomers observed a “superflare” on Proxima Centauri.  As you can see in the highly technical diagram below, that superflare would have done serious damage to Proxima b’s ozone layer (assuming Proxima b had an ozone layer in the first place).

According to this 2018 paper on ozone loss, if superflares like that are normal for Proxima Centauri, we should expect Proxima b to lose 90% of its ozone layer in just five years (again, assuming Proxima b had an ozone layer in the first place).  Without an ozone layer, incoming ultraviolet radiation would thoroughly sterilize Proxima b’s surface (much like it does on Mars).

And it gets worse.  Earth’s magnetic field deflects a lot of harmful solar and cosmic radiation away.  But according to this 2016 paper on space weather, Proxima b’s magnetic field (assuming Proxima b has a magnetic field) is taking a real beating.  The magnetic field would be badly weakened and compressed.  As a result, Proxima b’s atmosphere would start eroding away, due to the solar wind, and if those UV rays haven’t already killed everything on the surface, all that solar and cosmic radiation would have a chance to finish the job.

Even the most extreme of extremophiles here on Earth would have a tough time surviving on Proxima b.  But the situation is not hopeless.  That 2016 paper on space weather and that 2018 paper on ozone loss both acknowledge that there are still plausible scenarios where life could evolve and thrive on Proxima b.  But in order to do it, the Proxima b-ians must have done one of two things:

  • Life on Proxima b must be very specifically adapted to that radiation environment, or…
  • Life on Proxima b must have found a good hiding place, perhaps deep underwater or underground, where the radiation can’t reach it.

Next time on Planet Pailly, it’s a bird!  It’s a plane!  It’s… oh no, it’s a killer asteroid!!!

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?

Dancing with the Binary Stars

Hello, friends!

Today I just want to share a thing that came up during my research for last week’s episode of Sciency Words.  It has to do with our next-door neighbors, the Alpha Centauri star system.

Alpha Centauri is, famously, the nearest star system to our own Solar System.  As such, Alpha Centauri gets a lot of love from science fiction writers.  So many space aliens come from there, and so many human space adventurers will be heading Alpha Centauri’s way, just as soon as we invent faster-than-light technology.

Alpha Centauri is also, famously, a binary star system: two stars locked in orbit together1.  But the way the Alpha Centauri binary is portrayed in science fiction is… well, I think a lot of Sci-Fi writers get this wrong.  I know I’ve gotten it wrong in the past.

Which brings me to the thing I want to share with you today.  It’s a simple but absolutely perfect visualization of the way Alpha Centauri A and B dance around their common center of mass (a.k.a. their barycenter).

Image courtesy of Wikipedia.

In my experience, a lot of science fiction writers make it sound like Alpha Centauri A and B are right next to each other.  They make it sound like you could stand on the surface of a planet, look up, and see two suns side by side, like you’re Luke Skywalker watching the double sunset on Tattooine.

But even at closest approach, Alpha Centauri A and B are approximately 11 astronomical units apart (roughly equivalent to the distance between the Sun and Saturn).  And at maximum separation, they’re approximately 36 astronomical units apart (roughly equivalent to the distance between the Sun and Pluto).

Yes, watching a double sunset like that scene in Star Wars would be incredible.  But this figure-eight dance that happens in Alpha Centauri (and in many other binary star systems too) is even more amazing, in my opinion.

Next time on Planet Pailly, we’ll meet some insects who would really appreciate it if we’d change their name already.

1 Umm, actually Alpha Centauri has three stars: two Sun-like stars in the middle and a tiny red dwarf star orbiting much farther out.

Proxima Centauri Has a Planet!

Ohmigod, ohmigod, ohmigod!

Okay, calm down, James. Breathe. Breathe.

Okay. Let’s take a look at Alpha Centuari, a binary star system located within a mere 5 light-years from Earth. In the bottom corner of the image, you can see a red dwarf star called Proxima Centauri, which is believed to be a companion to the Alpha Centauri pair. And in orbit of Promixa, you can see… you can see… ohmigod!

Ag16 Alpha Centauri

Apparently the European Southern Observatory (ESO) has discovered a planet orbiting Proxima. Not only that, it’s an Earth-like planet. And furthermore, it’s within Proxima’s habitable zone. This according to an unnamed source in a German newspaper.

The ESO is a highly respected, extremely trustworthy astronomical institution. As for unnamed sources… okay, let’s put our skeptical hats back on.

Let’s also remember that Earth-like planets are not necessarily all that Earth-like. For the last few weeks, I’ve been blogging from the surface of Titan, which is often described as one of the most Earth-like worlds in the Solar System. And let me tell you, it is miserable here. I guess there could be life on Titan, but not life as we humans understand it.

Mars is also sometimes described as Earth-like, and believe it or not, so is Venus.

Ag16 Earth-like Worlds

Supposedly the ESO will release its official findings at the end of August. Until then, we’ll just have to sit back, wait patiently, and stay skeptical.

P.S.: Ohmigod! Proxima Centauri might have… might… I can’t even! OH MY GOD!!!


Earth-like Planet Around Proxima Centauri Discovered from Universe Today.