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.
Here is a link to the original article, by Ozsvart et al: arxiv.org/pdf/2509.04165
arxiv.org
October 19, 2025 at 3:01 PM
Here is a link to the original article, by Ozsvart et al: arxiv.org/pdf/2509.04165
The main challenge is the alternating prograde and retrograde rings of planets.
To build a single ring, I think you's need to pass through a horseshoe constellation phase (see planetplanet.net/2023/04/20/c...) and then damp out the librations. Obviously not feasible for humanity at the moment....
To build a single ring, I think you's need to pass through a horseshoe constellation phase (see planetplanet.net/2023/04/20/c...) and then damp out the librations. Obviously not feasible for humanity at the moment....
Constellations of co-orbital planets – planetplanet
planetplanet.net
October 10, 2025 at 5:40 PM
The main challenge is the alternating prograde and retrograde rings of planets.
To build a single ring, I think you's need to pass through a horseshoe constellation phase (see planetplanet.net/2023/04/20/c...) and then damp out the librations. Obviously not feasible for humanity at the moment....
To build a single ring, I think you's need to pass through a horseshoe constellation phase (see planetplanet.net/2023/04/20/c...) and then damp out the librations. Obviously not feasible for humanity at the moment....
I guess it would be transits, not eclipses, but if the planets had moons they would also be blocking the light from the other planets all the time. A very astronomically-engaging place to be!
October 10, 2025 at 2:55 PM
I guess it would be transits, not eclipses, but if the planets had moons they would also be blocking the light from the other planets all the time. A very astronomically-engaging place to be!
See for example this paper : ui.adsabs.harvard.edu/abs/2009ApJ....
Tidal Limits to Planetary Habitability
The habitable zones (HZs) of main-sequence stars have traditionally been defined as the range of orbits that intercept the appropriate amount of stellar flux to permit surface water on a planet. Terrestrial exoplanets discovered to orbit M stars in these zones, which are close-in due to decreased stellar luminosity, may also undergo significant tidal heating. Tidal heating may span a wide range for terrestrial exoplanets and may significantly affect conditions near the surface. For example, if heating rates on an exoplanet are near or greater than that on Io (where tides drive volcanism that resurfaces the planet at least every 1 Myr) and produce similar surface conditions, then the development of life seems unlikely. On the other hand, if the tidal heating rate is less than the minimum to initiate plate tectonics, then CO<SUB>2</SUB> may not be recycled through subduction, leading to a runaway greenhouse that sterilizes the planet. These two cases represent potential boundaries to habitability and are presented along with the range of the traditional HZ for main-sequence, low-mass stars. We propose a revised HZ that incorporates both stellar insolation and tidal heating. We apply these criteria to GJ 581 d and find that it is in the traditional HZ, but its tidal heating alone may be insufficient for plate tectonics.
ui.adsabs.harvard.edu
September 9, 2025 at 8:16 PM
See for example this paper : ui.adsabs.harvard.edu/abs/2009ApJ....
Thanks!
If there was a very large amount of internal heat flux from tidal dissipation, it would likely be bad for habitability if the planet is close to the inner edge of the habitable zone, or good if it's beyond (colder).
The planet's orbit would also change (slowly) due to tidal dissipation.
If there was a very large amount of internal heat flux from tidal dissipation, it would likely be bad for habitability if the planet is close to the inner edge of the habitable zone, or good if it's beyond (colder).
The planet's orbit would also change (slowly) due to tidal dissipation.
September 9, 2025 at 8:15 PM
Thanks!
If there was a very large amount of internal heat flux from tidal dissipation, it would likely be bad for habitability if the planet is close to the inner edge of the habitable zone, or good if it's beyond (colder).
The planet's orbit would also change (slowly) due to tidal dissipation.
If there was a very large amount of internal heat flux from tidal dissipation, it would likely be bad for habitability if the planet is close to the inner edge of the habitable zone, or good if it's beyond (colder).
The planet's orbit would also change (slowly) due to tidal dissipation.
It would be interesting to see what the mass ratio threshold is for stability -- does it have to be 1.000000 or could it be 1.01, 1.1, 2., ...?
September 3, 2025 at 9:43 PM
It would be interesting to see what the mass ratio threshold is for stability -- does it have to be 1.000000 or could it be 1.01, 1.1, 2., ...?
Ask away. In terms of stability, eccentric rings are clearly stable for billions of years if left undisturbed. I wrote a paper about the dynamical stability of the circular-orbit case when it's perturbed -- it's more robust than you might think.
ui.adsabs.harvard.edu/abs/2023MNRA...
ui.adsabs.harvard.edu/abs/2023MNRA...
Survival and dynamics of rings of co-orbital planets under perturbations
In co-orbital planetary systems, two or more planets share the same orbit around their star. Here we test the dynamical stability of co-orbital rings of planets perturbed by outside forces. We test tw...
ui.adsabs.harvard.edu
September 3, 2025 at 4:20 PM
Ask away. In terms of stability, eccentric rings are clearly stable for billions of years if left undisturbed. I wrote a paper about the dynamical stability of the circular-orbit case when it's perturbed -- it's more robust than you might think.
ui.adsabs.harvard.edu/abs/2023MNRA...
ui.adsabs.harvard.edu/abs/2023MNRA...
I haven't studied that carefully for eccentric rings. For circular rings of planets, I wrote a paper about it. The punchline is that they're pretty robust. When kicked, these systems often transition to a horseshoe state, unless they're kicked really hard...
ui.adsabs.harvard.edu/abs/2023MNRA...
ui.adsabs.harvard.edu/abs/2023MNRA...
Survival and dynamics of rings of co-orbital planets under perturbations
In co-orbital planetary systems, two or more planets share the same orbit around their star. Here we test the dynamical stability of co-orbital rings of planets perturbed by outside forces. We test tw...
ui.adsabs.harvard.edu
September 3, 2025 at 4:18 PM
I haven't studied that carefully for eccentric rings. For circular rings of planets, I wrote a paper about it. The punchline is that they're pretty robust. When kicked, these systems often transition to a horseshoe state, unless they're kicked really hard...
ui.adsabs.harvard.edu/abs/2023MNRA...
ui.adsabs.harvard.edu/abs/2023MNRA...
That's a great idea to check!
September 3, 2025 at 4:16 PM
That's a great idea to check!
Me neither -- it's really tricky to understand why our results are different. Either taking the Moon quadrupole into account is critical, or sampling different possible configurations for the flyby is essential.
July 10, 2025 at 6:25 PM
Me neither -- it's really tricky to understand why our results are different. Either taking the Moon quadrupole into account is critical, or sampling different possible configurations for the flyby is essential.