Sciency Words: Necroplanetology

Hello, friends!  Welcome back to Sciency Words, a special series here on Planet Pailly where we talk about those weird words scientists use.  Today on Sciency Words, we’re talking about:


I’d like to introduce you to a very special exoplanet, one of the very first exoplanets to be photographed by a telescope (by the Hubble Space Telescope, in fact!).  Its name is Fomalhaut b.  Its also known as Dagon, and here’s what it looks like…

Oh no!  What happened!?!

The prefix “necro-” comes from a Greek word meaning dead.  So necroplanetology refers to the study of planets and planetary bodies that are… dearly departed.  The term was first introduced in this 2020 paper, published in The Astrophysical Journal.

That 2020 paper describes a white dwarf star designated WD 1145+017.  A white dwarf is, as you may already know, the stellar remnant left behind after the death of a sun.  WD 1145+017 appears to have some debris orbiting it: the wreckage of a destroyed planet (or planets).

Finding planetary debris like that is an incredible opportunity for astronomers.  Like forensic scientists studying blood splatters at a crime scene, astronomers can observe this sort of planetary debris to determine how planets die, and they can also learn more about what the interiors of planets must have been like before their deaths.  That’s what the study of necroplanetology is all about!

Potential subjects of necroplanetological research include WD 1145+017, KIC 8462852 (a.k.a. Tabby’s Star), Oumuamua, Alderaan, and Fomalhaut b.  In the case of Fomalhaut b, the planet sure did look like a planet when its discovery was announced in 2008 (though Fomalhaut b appeared to be unusually bright at that time, given its estimated mass and other characteristics).  But since then, Fomalhaut b seemed to fade and disperse, suggesting that rather than observing a planet, we’ve been observing the debris field left behind after a recent planetary collision.

And another possible subject of necroplanetological research may be Proxima Centauri c.  As I told you in Wednesday’s post, Proxima c appears to be a lot brighter than we’d expect, given its estimated mass and other characteristics.  As this paper suggests, that excess brightness could be caused by a “conspicuous ring system” reflecting lots and lots of sunlight.  But that same paper also draws the unavoidable analogy with Fomalhaut b.  We may not be looking at a planet after all.  We may be looking at an expanding debris field left behind by a recent planetary collision.

We’ll have wait and see if Proxima c starts to fade and disperse, like Fomalhaut b did.  Personally, I hope that doesn’t happen.  But if it does, the destruction of a planet in the star system right next door to our own will be an incredible opportunity for necroplanetologists.

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!

If Proxima c Exists, It Must Be Beautiful!

Hello, friends!

For over a week now, I’ve been teasing you with promises of a very pretty picture of a very pretty planet.  Proxima Centauri is already known to have at least one planet, named Proxima b.  Now a second planet, Proxima c, may have also been discovered.

So how do we know Proxima c is there?  Well, we don’t.  I would be an irresponsible science blogger if I didn’t make this 100% clear: astronomers do not know for certain if Proxima c exists.  The evidence, as it currently stands, is highly circumstantial.

  • First off, we have the possible detection of asteroid belts encircling Proxima Centauri.  The presence of asteroid belts would imply the presence of planets, since it would take a planet’s gravity to keep the gaps between those asteroid belts clear.
  • Second, as reported in this paper, we have the possible detection of a “compact source” of thermal emissions.  There could be multiple explanations for this, but one possibility is a planet with a large, Saturn-like ring system.
  • Lastly, according to this paper, Proxima Centauri is wobbling in place.  That sort of wobbling in a star usually means a planet’s gravity is tugging on that star.  Usually.

As I said, all this evidence is highly circumstantial.  Proxima Centauri is known to have extremely violent solar flares, which may also explain why the star is so wobbly.  And that compact source of thermal emissions could be lots of things other than a planetary ring system (it might even be an error in our data).  And as for Proxima’s asteroid belts, we haven’t confirmed those exist yet.  It would be premature to say anything about possible planets based on possible asteroids.

But as this article from Scientific American explains it, all this circumstantial evidence seems to be lining up in such a way that you have to go hmmm.  If Proxima Centauri’s wobbles are caused by a planet, astronomers can make an educated guess about where that planet must be located.  And that location lines up with that compact source of thermal emissions.  And that compact source of thermal emissions is right where a planet would need to be to keep the gap between the asteroid belts clear. Coincidence? Well, maybe.

Again, this is highly circumstantial evidence.  It will take a lot more observation and data analysis to determine whether or not Proxima c is really there.

But for a planet that may not exist, we know an awful lot about what Proxima c should be like.  Based on Proxima Centauri’s wobbliness, we know Proxima c must be more massive than Earth, but less massive than Neptune.  We also know it must be very cold.  It’s a long way away from the habitable zone.  Due to Proxima Centauri’s intense solar flare activity, we’d expect Proxima c to have some crazy bright aurorae.  Oh, and as we already established, Proxima c would have a large, Saturn-like ring system.

In short, Proxima c sounds like it must be a very pretty planet.

If it exists.  Which is still a pretty big if.

Quick programming note: I’m going to take a few days off from blogging.  I’ll be away on a trip to visit family.  My grandmother is turning 100 years old this weekend, so it’s going to be a party!

I’ll be back some time next week with updates about my book and an announcement about this year’s A to Z Challenge.  See you soon!

Touring Proxima Centauri’s Asteroid Belts

Hello, friends!

As you know, sometimes things don’t go according to plan.  For today’s post, I was planning to draw a really pretty picture of a really planet—a planet that astronomers may (or may not) have found in the Proxima Centauri system.  But as I did my research about this possible planet, I realized I needed to draw something else for you first.

As reported in this 2017 paper, temperature readings indicate that Proxima Centauri may have at least one and as many as three asteroid belts.  Based on what I’ve read, it sounds like the presence of these belts has not been definitively proven yet.  But no one seems to be able to definitively disprove them either.

So here is a map of everything we currently know or suspect exists in the Proxima Centauri system.

As you can see, the planet Proxima b is in an extremely tight orbit around its star.  But since Proxima Centauri is much smaller and cooler than our Sun, Proxima b is technically in the star’s habitable zone.  Click here for my post on whether or not Proxima b could actually support life.

Beyond the orbit of Proxima b, we find our first possible asteroid belt.  In that 2017 paper I cited above, this innermost belt is described as the warm dust belt.  It appears to be located approximately 0.4 AU away from its star (roughly equivalent to the orbit of Mercury in our Solar System).

A little farther out, we find a second possible asteroid belt, which the authors of that 2017 paper describe as the cold dust belt.  Remember: we suspect these dust belts exist because of temperature measurements, hence the names.  The cold dust belt appears to be spread out between 1 AU and 4 AU (roughly equivalent to the space between the orbits of Earth and Jupiter in our Solar System).

And then farther out still, there appears to be a third belt, referred to as the outer dust belt (in my opinion, it should have been named the colder dust belt).  The outer dust belt appears to be located approximately 30 AU away from its star (roughly equivalent to the orbit of Neptune).

I want to emphasize again: as far as I can tell from my own research, no one has definitively proven or disproven these dust belts exist.  All we have are some temperature measurements that suggest something might possibly be there.

But if all those dust belts do exist, that tells us there should be planets orbiting in the gaps between the belts.  It would take a planet’s gravity to keep those gaps empty.  And now that you know that, I think we’re ready to take a closer look at Proxima c.

Except tomorrow is Insecure Writer’s Support Group day, so our trip to Proxima c will have to wait.  But I promise the wait will be worth it.  Science predicts that if Proxima c really exists, it must be the most gorgeous planet you’ve ever seen!

Next time on Planet Pailly, the unexpected benefits of having your manuscript edited.