Sean Raymond (planetplanet.net)
@planetplanet.bsky.social
Building crazy planetary systems on my blog planetplanet.net. Solar System formation. Exoplanets. Free-floating planets and interstellar objects. Astronomy poem book: http://amzn.to/3muytqo He/him.
Here's a teaser: me on the beach showing how a basketball does not match 'Oumuamua's light curve!
My favorite was the "making a comet" demo with dry ice, or maybe going to check out the Vera Rubin telescope in Chile.
My favorite was the "making a comet" demo with dry ice, or maybe going to check out the Vera Rubin telescope in Chile.
November 18, 2025 at 11:27 AM
Here's a teaser: me on the beach showing how a basketball does not match 'Oumuamua's light curve!
My favorite was the "making a comet" demo with dry ice, or maybe going to check out the Vera Rubin telescope in Chile.
My favorite was the "making a comet" demo with dry ice, or maybe going to check out the Vera Rubin telescope in Chile.
New animation of the ultimate engineered solar system for a talk I'm giving tomorrow at a sci-fi convention in Lithuania.
It has 400 rocky planets in the habitable zone of a single Sun-like star
It's perfectly stable (I simulated it out to about a billion years)
planetplanet.net/2017/05/03/t...
It has 400 rocky planets in the habitable zone of a single Sun-like star
It's perfectly stable (I simulated it out to about a billion years)
planetplanet.net/2017/05/03/t...
October 10, 2025 at 1:51 PM
New animation of the ultimate engineered solar system for a talk I'm giving tomorrow at a sci-fi convention in Lithuania.
It has 400 rocky planets in the habitable zone of a single Sun-like star
It's perfectly stable (I simulated it out to about a billion years)
planetplanet.net/2017/05/03/t...
It has 400 rocky planets in the habitable zone of a single Sun-like star
It's perfectly stable (I simulated it out to about a billion years)
planetplanet.net/2017/05/03/t...
Here's something new and weird -- eccentric rings of co-orbital planets.
They are stable indefinitely, from an orbital point of view.
Could they actually form and exist?
planetplanet.net/2025/09/02/e...
They are stable indefinitely, from an orbital point of view.
Could they actually form and exist?
planetplanet.net/2025/09/02/e...
September 2, 2025 at 9:17 PM
Here's something new and weird -- eccentric rings of co-orbital planets.
They are stable indefinitely, from an orbital point of view.
Could they actually form and exist?
planetplanet.net/2025/09/02/e...
They are stable indefinitely, from an orbital point of view.
Could they actually form and exist?
planetplanet.net/2025/09/02/e...
Flashback to 2012 when I ate the Sun
(Photo from the top of Vulcano in Sicily)
(Photo from the top of Vulcano in Sicily)
August 29, 2025 at 3:03 PM
Flashback to 2012 when I ate the Sun
(Photo from the top of Vulcano in Sicily)
(Photo from the top of Vulcano in Sicily)
Like dinosaurs, Saturn and Jupiter roamed
They sculpted this system that humans call home
The gas giants roared, the system unstable
An ice giant planet fell right off the table!
A whole ring of comets was launched to the stars
The planets — bombarded — still bear the scars.
They sculpted this system that humans call home
The gas giants roared, the system unstable
An ice giant planet fell right off the table!
A whole ring of comets was launched to the stars
The planets — bombarded — still bear the scars.
June 28, 2025 at 10:56 PM
Like dinosaurs, Saturn and Jupiter roamed
They sculpted this system that humans call home
The gas giants roared, the system unstable
An ice giant planet fell right off the table!
A whole ring of comets was launched to the stars
The planets — bombarded — still bear the scars.
They sculpted this system that humans call home
The gas giants roared, the system unstable
An ice giant planet fell right off the table!
A whole ring of comets was launched to the stars
The planets — bombarded — still bear the scars.
I know this is getting kind of ridiculous, but I just think it's amazing that this sort of system can exist.
It reminds me of amazing balancing rock piles. Although co-orbital rings of planets are much more stable, because they can survive perturbations, at least up to a point.
It reminds me of amazing balancing rock piles. Although co-orbital rings of planets are much more stable, because they can survive perturbations, at least up to a point.
June 5, 2025 at 4:44 PM
I know this is getting kind of ridiculous, but I just think it's amazing that this sort of system can exist.
It reminds me of amazing balancing rock piles. Although co-orbital rings of planets are much more stable, because they can survive perturbations, at least up to a point.
It reminds me of amazing balancing rock piles. Although co-orbital rings of planets are much more stable, because they can survive perturbations, at least up to a point.
A quick update about co-orbital rings of planets.
This setup -- with 42 planets (each the same mass as Earth) sharing an orbit that is the same average distance as Earth (1 au) but super-eccentric -- is stable for at least 5 million years. (I'm running it out to a billion years to test)
This setup -- with 42 planets (each the same mass as Earth) sharing an orbit that is the same average distance as Earth (1 au) but super-eccentric -- is stable for at least 5 million years. (I'm running it out to a billion years to test)
June 5, 2025 at 3:53 PM
A quick update about co-orbital rings of planets.
This setup -- with 42 planets (each the same mass as Earth) sharing an orbit that is the same average distance as Earth (1 au) but super-eccentric -- is stable for at least 5 million years. (I'm running it out to a billion years to test)
This setup -- with 42 planets (each the same mass as Earth) sharing an orbit that is the same average distance as Earth (1 au) but super-eccentric -- is stable for at least 5 million years. (I'm running it out to a billion years to test)
Blog post on #planetplanet about the paper: (Exo)Planet Nine strikes back!
planetplanet.net/2025/05/27/e...
3/
planetplanet.net/2025/05/27/e...
3/
May 27, 2025 at 1:20 PM
Blog post on #planetplanet about the paper: (Exo)Planet Nine strikes back!
planetplanet.net/2025/05/27/e...
3/
planetplanet.net/2025/05/27/e...
3/
Hello what have we here?
I didn't think this would be stable, but it is! (Planets are 1 Earth-mass each)
I didn't think this would be stable, but it is! (Planets are 1 Earth-mass each)
May 26, 2025 at 7:32 PM
Hello what have we here?
I didn't think this would be stable, but it is! (Planets are 1 Earth-mass each)
I didn't think this would be stable, but it is! (Planets are 1 Earth-mass each)
Another interesting result: Pluto has a ~5% chance of going unstable in the next 5 billion years. That's 2x higher than for any of the planets (Mercury being most vulnerable), and infinitely higher than previously thought (odds previously thought to be zero)
(Here's one example from the paper)
(Here's one example from the paper)
May 13, 2025 at 8:53 AM
Another interesting result: Pluto has a ~5% chance of going unstable in the next 5 billion years. That's 2x higher than for any of the planets (Mercury being most vulnerable), and infinitely higher than previously thought (odds previously thought to be zero)
(Here's one example from the paper)
(Here's one example from the paper)
Now to our paper. The key result is that stellar flybys are the main threat of dynamical instability to the planets for the next 4-4.5 billion years. After that, internal chaos is more important. (And then the Sun will go red giant...)
May 13, 2025 at 8:53 AM
Now to our paper. The key result is that stellar flybys are the main threat of dynamical instability to the planets for the next 4-4.5 billion years. After that, internal chaos is more important. (And then the Sun will go red giant...)
Fun fact: if you throw darts completely randomly at a regulation dartboard, it will take ~199 to hit the outer bullseye and 1261 to hit the inner bullseye!
May 13, 2025 at 8:53 AM
Fun fact: if you throw darts completely randomly at a regulation dartboard, it will take ~199 to hit the outer bullseye and 1261 to hit the inner bullseye!
While I'm at it, here's me with a space cat in Osaka the week before!
January 1, 2025 at 12:10 PM
While I'm at it, here's me with a space cat in Osaka the week before!
Selfie from my wonderful day at JAXA with @elizabethtasker.bsky.social a couple weeks ago.
(also, happy new year!)
(also, happy new year!)
January 1, 2025 at 12:08 PM
Selfie from my wonderful day at JAXA with @elizabethtasker.bsky.social a couple weeks ago.
(also, happy new year!)
(also, happy new year!)
A few more examples:
Earth implanted into the Oort cloud
An instability that left just one planet standing
A system with all planets lost.
Earth implanted into the Oort cloud
An instability that left just one planet standing
A system with all planets lost.
November 22, 2023 at 3:10 PM
A few more examples:
Earth implanted into the Oort cloud
An instability that left just one planet standing
A system with all planets lost.
Earth implanted into the Oort cloud
An instability that left just one planet standing
A system with all planets lost.
Here's 3 examples: In the first, there's little action (weak flyby)
In the second, the ice giants are lost
In the third, the giant planets are perturbed, then that perturbation is transmitted to the terrestrials, leading to Mercury hitting the Sun and a Mars-Venus collision
In the second, the ice giants are lost
In the third, the giant planets are perturbed, then that perturbation is transmitted to the terrestrials, leading to Mercury hitting the Sun and a Mars-Venus collision
November 22, 2023 at 3:09 PM
Here's 3 examples: In the first, there's little action (weak flyby)
In the second, the ice giants are lost
In the third, the giant planets are perturbed, then that perturbation is transmitted to the terrestrials, leading to Mercury hitting the Sun and a Mars-Venus collision
In the second, the ice giants are lost
In the third, the giant planets are perturbed, then that perturbation is transmitted to the terrestrials, leading to Mercury hitting the Sun and a Mars-Venus collision
Here’s the experiment we performed.
We started with the present-day Solar System, then zoomed a star past the Sun, to see how the planets’ orbits responded over the next 20 million years. We did this 12,000 times.
We started with the present-day Solar System, then zoomed a star past the Sun, to see how the planets’ orbits responded over the next 20 million years. We did this 12,000 times.
November 22, 2023 at 3:07 PM
Here’s the experiment we performed.
We started with the present-day Solar System, then zoomed a star past the Sun, to see how the planets’ orbits responded over the next 20 million years. We did this 12,000 times.
We started with the present-day Solar System, then zoomed a star past the Sun, to see how the planets’ orbits responded over the next 20 million years. We did this 12,000 times.
Let’s zoom out.
As the Sun orbits within the Galaxy, stars fly by. There is a 1% chance that a star will pass within 100 au (1 au = Earth-Sun distance) of the Sun in any billion year period. That's close enough to affect the planets’ orbits
As the Sun orbits within the Galaxy, stars fly by. There is a 1% chance that a star will pass within 100 au (1 au = Earth-Sun distance) of the Sun in any billion year period. That's close enough to affect the planets’ orbits
November 22, 2023 at 3:07 PM
Let’s zoom out.
As the Sun orbits within the Galaxy, stars fly by. There is a 1% chance that a star will pass within 100 au (1 au = Earth-Sun distance) of the Sun in any billion year period. That's close enough to affect the planets’ orbits
As the Sun orbits within the Galaxy, stars fly by. There is a 1% chance that a star will pass within 100 au (1 au = Earth-Sun distance) of the Sun in any billion year period. That's close enough to affect the planets’ orbits
Life on Earth is doomed. In 1 billion years, the Sun will be 10% brighter and Earth won’t be able to cool fast enough to maintain a stable energy balance.
Earth will exit the habitable zone. Runaway greenhouse. No more liquid water (or beer).
Earth will exit the habitable zone. Runaway greenhouse. No more liquid water (or beer).
November 22, 2023 at 3:06 PM
Life on Earth is doomed. In 1 billion years, the Sun will be 10% brighter and Earth won’t be able to cool fast enough to maintain a stable energy balance.
Earth will exit the habitable zone. Runaway greenhouse. No more liquid water (or beer).
Earth will exit the habitable zone. Runaway greenhouse. No more liquid water (or beer).
T minus 2 hours to a new blog post. Paper to follow on arxiv tomorrow
Here's a teaser in gif form
Here's a teaser in gif form
November 21, 2023 at 5:12 PM
T minus 2 hours to a new blog post. Paper to follow on arxiv tomorrow
Here's a teaser in gif form
Here's a teaser in gif form