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:

NECROPLANETOLOGY

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.