Welcome to my blog! My name is Sean Raymond. I am an American astrophysicist living in Bordeaux (France). I study the formation and evolution of planetary systems (see my research website here). In my research I ask questions like:
- Where did Earth’s water come from?
- Which extra-solar planetary systems are the best for life?
- Can moons have their own moons?
- Why does our Solar System appear to be different than planetary systems around other stars?
As a science fiction-loving astronomer, I enjoy blending imagination with science. On this blog I sometimes create my own planetary systems (see for example, the ultimate Solar System series). Sometimes I evaluate the scientific validity of well-known settings from movies or books (such as Pandora, Arrakis, and more). And sometimes I try to figure out what it would feel like on a different planet, for example by understanding the day-night cycles in multi-star systems or by getting a feel for the climates of exotic worlds. I also describe the ways that planets are destroyed, based on my own research (see here) and sometimes break out Dr Seuss-style astronomy poems. I also just published a book of astronomy poems.
I am available to help out with ideas for books, movies, games or any other projects set on other planets. My specialties are:
- World building: creating scientifically accurate settings for storytelling
- Understanding what it would feel like to live on other (custom-built) worlds. How would the stars move? What would the weather be like?
- Testing the scientific validity of already-created settings.
Please contact me if you are interested in working with me. You can email me directly at rayray(dot)sean(at)gmail(dot)com.
Additional resources
- Amazon page of my new book, Black Holes, Stars, Earth and Mars: Astronomy poems for all ages
- Recordings of a couple of talks I’ve given: here is one for the general public and here is one for a somewhat technical audience.
- The MOJO videos on planet formation.
- My research website, which includes a list of my scientific publications and a CV
- Feel free to follow me on twitter (@sraymond_astro).
PLANETPLANET 
Hi Sean
An excellent blog that I have really enjoyed reading.
I have a few questions
How small of a red dwarf star can an earth sized planet orbit and receive the same solar flux as the earth before it becomes tidally locked and Stellar winds from the star become a problem?
Thanks Laintal
HI Laintal — good question.
Check out this image: http://sites.psu.edu/ceh5286/wp-content/uploads/sites/4579/2014/04/revised_ZAMS_grayscale.jpg
It shows how far away the habitable zone is (in grey) from its star for different kinds of stars (brighter stars are higher). To the left of the dashed line tides are strong enough to make a planet’s rotation locked so that it always shows the same face to the star. So this is important for stars as massive as about 60-70% the mass of the Sun.
Being tidally-locked is not necessarily bad for life. None of the ideas about tidally-locked planets — flares, stellar winds, etc — have been shown to be “nails in the coffin” for such planets. I think they are still good candidates for life. What I think is worth worrying about is tidal heating on these planets, which is stronger the farther to the left of the dashed curve your planet is. But tidal heating depends in large part on the other planets in the system — it’s not just a 1-planet thing.
Hi there,
I just found your blog after reading your recent Nautil.us article (“Reading Earth’s Destiny in the “Blood Spatter” Around Other Stars”). Seems promising. As I’m not a trained scientist I hope I’ll find useful and understandable pieces of information here 🙂
Thanks for sharing your work in this interesting field. I stay tuned via RSS syndication.
Really love reading your blog’s! They get my imagination going and get my curiosity of other star systems and their planetary systems going. I have to admit, I may not quite understand all the physics (a long time out of classrooms and a lot of new theories since I studied!), but you have a great knack for explaining that truly helps. Keep up the great work!
Great Blog! I found you doing research for my Sci Fi writing bug. I like your rogue planet theories and what they would look like.
I have a question:
In theory can there be a binary planet system where the two planets are lined up with their axis one atop another, like two spinning basketballs rotating the same direction together but not touching? The North and south poles would be opposite each other with the repelling force of magnetism offsetting the mutual pull of gravity. Instead of the common theory of Binary planets rotating around a center of gravity, mine would look like a dumbbell spinning on its axis. The ‘handle’ of the dumbbell being the offsetting forces of the pull of gravity and the push of the opposite poles.
Hi John, thanks for the question. Let me see — you basically want to use magnetism to offset gravity and create a binary planet. I don’t think this is plausible but I haven’t done the numbers. The magnetic forces involved would have to be titanic. Magnetic forces also require charge moving with respect to a magnetic field, so a static configuration wouldn’t work. It seems like an unstable equilibrium, even if you could get it to work. I can imagine magnetic forces playing a small role in a binary system, but relying on magnetism to counterbalance gravity seems like a very tall order… I’ll think more about this and I’ll get back to you if I have any more insights.
May I use your star system designs in a scifi setting?
HI Jacob — thanks for asking. I am happy to let anyone use these ideas for science fiction of any kind. And I’m happy to help with any specific issues you might have to make a setting as plausible as possible (astrophysically speaking, of course).
Thanks.
My hypothesis is that the magnetism keeps a smaller body from circling the larger planet in an orbit. Rather, the larger planet captures the smaller and holds it in a stationary orbit over one of the poles. They would be very close to each other. Not necessarily sharing atmospheres but that would be interesting too. The down side of a common atmosphere would be, that being that close together, there would be a danger of tidal earthquakes.
Hi Sean,
I really enjoyed reading this. It is making complicated stuff easier for us to get our teeth into. Humans are great and we need to show our greatness more often. Thank you for showing yours – a guiding star you are!
Thanks Patrick! That’s really nice of you to say.
Found your blog completely by accident while doing worldbuilding research. Absolutely essential reading for scifi writers, thank you so much! 😸
Thanks, I appreciate the comment!
I’ve been trying to figure out how to build a solar system for a sci-fi project I am working on, but it’s been hard to find tools to help me understand the minutia. I found a video about a 2-star system (https://vimeo.com/115945369) which I used as a basis – with some modifications like only 1 planet orbiting the yellow star and no moons), and have tried to assign things to the orbiting planet like how long is a day, year, season, etc… I dig mechanical stuff like this, but I am so far out of my bailiwick that it’s more frustrating than fun. I want to get this sort of stuff as right as I can based on what science knows so far.
Do you know of any software tools that will help me better model this sort of solar system and planetary orbits? Thanks!
check it https://www.youtube.com/watch?v=SaWLN0zf1aY and the channel.i love you blog.
Sean … I’m John in Salmon Arm, British Columbia, and I invite you to establish a rapport with me using my email jdublyuh@hotmail.ca – Because you live in France, and do what you do, WHY is it that you pursue your studies about space stuff, and mention ‘aliens’ when there is a perfectly legitimate website generated out of Switzerland where you can easily access ALL the truth necessary re: aliens! NO, the FIGU group is NOT a ‘cult’! It’s only people who are influenced by other religion[s] who make the claim that Eduard Meier is a fake. Get real with yourself, and permit yourself to use an open mind to explore the truth and reality that Meier really does liaise with advanced people of our own race! IF you do have a scientific approach to life, then you would do yourself good to investigate the following: https://www.figu.org/ – AND, if you continue to investigate, then I recommend this blog where people from around the globe contribute: https://theyflyblog.com/ – https://www.theyfly.com/
hi ; it’s really great blog ; and you have great imagination
i have question
let imagine that we are capable to make 2 rings of 42 earth like planets ; in each ring ; between the earth and mars ; can this disturb the orbit and the axial title of the two planets ; thank you
So — one ring of 42 Marses and another of 42 Earths, right? (Remember that planets within a given ring need to have the same mass.) As long as the rings of planets are far enough apart, their orbits won’t be strongly affected. In terms of axial tilts, I would not expect them to be strongly affected either.
1 26 21 Hello and god day, Lovely web page. Glad I found your site! Stay safe, keep calm, & ne well. Virginia
A common “extreme” environment considered in speculative evolution is space. Clearly space is rather inhospitable to life but, due to the presence of water, the two places that seem least inhospitable are icy planetary rings and comets. Icy rings are problematic though as they are just too cold to get liquid water. In contrast, comets can get quite warm close to perihelion but they are too far away from other comets to allow life to spread.
I then wondered whether it was possible to have the best of both worlds with an eccentric Jupiter (like HD 20782 b) with an icy ring that behaves like a “ring of comets”. Such a ring is similar to your engineered solar systems so I thought you may have comments on the plausibility and stability of this concept.
Also, you have a great blog and I have referred many people to it when answering world-building questions.