In my continuing theme to explore all things exoplanet this week, I want to give a shoutout to Eos magazine for celebrating exoplanets in their August issue. It is packed full of stories, some of which we’re covering here on Daily Space. It’s definitely worth a look at their website to see all the fantastic writing being done, including by Weekly Space Hangout journalists and CosmoQuest-a-Con guests Kimberly Cartier and Morgan Rehnberg.

Earlier this week, I talked about some of the strange atmospheric conditions and possible weather on hot Jupiters – places where the rain is composed of iron, rubies, sapphires, and other materials not usually thought of as liquid molecules. Honestly, I love thinking about fascinating possibilities for exoplanets. These worlds must be a science fiction writer’s dream. You may not be able to host human life on them, but you sure can be creative about other forms of life and their adaptations.

However, the press releases about all these individual worlds might be overshadowing the forest for the trees, so to speak. In a story titled “Exoplanets in the Shadows”, Damond Benningfield takes a look at research areas that are as interesting, if not more so, than all these individual exoplanets we keep reporting on.

First up, necroplanetology. That’s an awesome name. It’s the study of dead or dying planets, mostly in orbit around white dwarfs, the very hot but no longer fusing cores of stars. Scientists have managed to detect planetary debris orbiting such stars, which were destroyed by the star’s gravity. Taking spectra of these white dwarfs has revealed calcium, magnesium, iron, and other heavier elements. These are all too heavy to remain on the surface of the white dwarf and so would sink into the core over time. To see them in the spectra means they arrived recently as rubble from the planets broken up in the system. This also means that planets can survive as a star goes through expansion during the red giant phase. And we can use this debris to get a glimpse at the inside of planets.

Another area of research involves stars whose brightness slowly changes over time. For example, Boyajian’s Star dimmed and brightened in an unusual pattern, which some people hoped might be a sign of a megastructure around the star and a signal of a technologically advanced alien civilization. More practical hypotheses now involve dust because, of course, dust or maybe even disintegrating exomoons falling in toward the star. And this study gives us another cool new word: necrolunarology.

On top of these two unusual realms of study, scientists are also intrigued by planets orbiting pulsars. These planets have basically been offered a second chance at life. And then there are rogue planets, which are difficult to detect since they’re not orbiting a star and therefore aren’t reflecting a star’s light and are also quite cold. The Gaia spacecraft is proving very capable of finding such planets. Plus we need to understand how rogue planets form — do they form independently of a star system the way stars form with a collapse of interstellar dust? Or are they more likely booted from their original star system due to gravitational interactions with other planets or nearby stars?

There is just so much to talk about when it comes to exoplanets as groups and not just individual discoveries. It’s overwhelming and wonderful, and we’ll keep bringing you all the news we can get our hands on. Tomorrow, I’ll look at some more oddball exoplanets.

More Information

Exoplanets in the Shadows (Eos)