Elliptical orbit and how seasons would be affected

[CosmicAdam]

TL;DR Summary

Identifying the type of orbit a planet would need in order to have more than 4 seasons

Trying to establish the conditions needed in order for a planet to have more than the standard 4 seasons. I may be wrong for assuming an elliptical orbit is required, but could make sense in order for there to be two winters for example.

 

[scottdave]

There is more than just orbit which has an affect on the seasons.

 

[MikeeMiracle]

It is the tilt of the planet together with it's orbit which cause the seasons we are familiar with. Using your analogy, we would probably end up with 2 of each season per solar year though if it was really eliptical, the temperature variations would likely prohibit the creation of life due to the extreme variations experienced.

 

[sophiecentaur]

if it was really eliptical, the temperature variations would likely prohibit the creation of life due to the extreme variations experienced.

A highly eccentric orbit could well make life difficult but highly eccentric orbits can be short lived in the presence of other planets (instability). Only arrangements like our Solar System are likely to last long enough to get life going, I think. An orbit would need to be in the Goldilocks zone.

Eccentricity and tilt can have similar effects but a tilted circular (almost) orbit has the advantage of causing large temperature variations near the poles without the whole Earth suffering at the same time - our equatorial regions get about the same day length all the time but the poles have long periods of continuous day and night.

These variations are pretty good stimuli to promote evolutionary change along with the beneficial effects of the tides, due to the Moon's significant mass. (Tidal pools are great for bringing sea organisms onto land when they'd probably prefer to stay aquatic and not bother.)

 

[Dragrath]

A highly eccentric orbit could well make life difficult but highly eccentric orbits can be short lived in the presence of other planets (instability). Only arrangements like our Solar System are likely to last long enough to get life going, I think. An orbit would need to be in the Goldilocks zone.

Eccentricity and tilt can have similar effects but a tilted circular (almost) orbit has the advantage of causing large temperature variations near the poles without the whole Earth suffering at the same time - our equatorial regions get about the same day length all the time but the poles have long periods of continuous day and night.

These variations are pretty good stimuli to promote evolutionary change along with the beneficial effects of the tides, due to the Moon's significant mass. (Tidal pools are great for bringing sea organisms onto land when they'd probably prefer to stay aquatic and not bother.)

It might be worth mentioning that eccentricity variation can be maintained long term if you have a multi planet system that is locked in a type of mean orbital resonance known as a laplace resonance this is the mechanism that maintains Io's extreme volcanic activity as the tidal forces of Jupiter try and circularize the orbit while the combined tidal interactions of Europa and Ganymede restore that eccentricity. Similar dynamics have been observed in a number of multi planet systems around other stars with the most famous example being the TRAPPIST1 system where a whopping seven planets are locked in resonance.

Now it is worth noting that thus far the only examples we have are close into their host star or planet which in the case of say the type G5 main sequence star K223 with four subneptune worlds in a 8:6:4:3 resonance with periods of 7.3845, 9.8456, 14.7887 and 19.7257 days respectively are going to be decidedly uninhabitable.

Even the so called potentially habitable zone worlds of TRAPPIST1 are problematic as they are very close to their M dwarf star so close that simulations suggest any magnetospheres of planets inside the outer habitable zone boundry which would be needed to protect them from the stars radiation would also be close enough to the star's coronal activity that plasma loops and streamers within the stars corona could potentially directly reconnect with any planetary magnetospheres of such planets. Such events would trigger the release of rapidly heated plasma onto the planets poles as the energy formerly in the magnetic loops gets injected into the plasma which is deposited straight onto the unfortunate planets magnetic poles. While this is I stress just a model at this point it might even be related to the identity of those enigmatic extreme M dwarf Super flares. Regardless even if coronal death loops don't exist in reality regular flare events are more than enough to sterilize and evaporate any volatiles from such close worlds blasting them off into the stellar wind.

However I don't know if this is an intrinsic characteristic of such systems or an observational bias since all such systems aside from Jupiter's Galilean moons have been detected via the transit method which is biased to close in planets and some models for the formation of our solar system suggest that the giant planets were once in such a resonance. Without further observations that are more sensitive to more distant planetary systems or new methods of solar system archeology that can help distinguish between formation models within our own solar system, since other models such as a purely chaotic system also can reproduce observations, it will be hard to gauge whether such an arrangement can exist in the habitable zone of a G type star.

Additionally given how early we are in the game of planet finding around other stars I expect there to be some mechanisms we probably haven't even thought of yet.

 

[sophiecentaur]

@Dragrath . An interesting post with good information. I have to wonder if the length of time that we have had to observe these things (including Jupiter's system) is long enough to consider them 'stable' in any sense. I guess ring systems and spiral galaxies suggest that a form of stability can exist when there are enough objects involved - a sort of macroscopic behaviour like vortices - but could a simple system of large moons be stable?
Playing with on-line multi body simulations always seems to end quite quickly with one of the objects leaving the screen. (I well realize the limitations of simulations.)

 

[Dragrath]

@Dragrath . An interesting post with good information. I have to wonder if the length of time that we have had to observe these things (including Jupiter's system) is long enough to consider them 'stable' in any sense. I guess ring systems and spiral galaxies suggest that a form of stability can exist when there are enough objects involved - a sort of macroscopic behavior like vortices - but could a simple system of large moons be stable?
Playing with on-line multi body simulations always seems to end quite quickly with one of the objects leaving the screen. (I well realize the limitations of simulations.)

Indeed N body simulations are hard hence why they are one of the defining examples of a chaotic system usually requiring a large ensemble of high accuracy of simulations. From what I have read resonant systems typically form via inward disk migration and probably only persists in a small number of systems. For example if a resonance formed among the giant planets of our solar system it broke down billions of years ago not long after the formation of the solar system with Jupiter and Saturn left just out of resonance. Moreover Jupiter's moon Ganymede seems to be getting pushed further away by the net tidal interactions such that it likely no longer receives enough tidal effects to heat its interior.

An interesting result of the Cassini mission regarding ring systems is of course their ephemeral nature having likely formed in the last billion years and being unlikely to last more than another 250 Ma given the current rate of mass loss so I'm not actually sure ring systems can persist over the timescales presumably needed for a habitable system and while galaxies structure is persistent as has been the asteroid and perhaps the more tenous rings of the other giant planets they are all notably far more diffused systems of lots of objects with large seperations.

 

[snorkack]

Summary:: Identifying the type of orbit a planet would need in order to have more than 4 seasons

Trying to establish the conditions needed in order for a planet to have more than the standard 4 seasons. I may be wrong for assuming an elliptical orbit is required, but could make sense in order for there to be two winters for example.

It is not clear "planet" would have the same number of seasons!
Earth and Mars are on low eccentricity orbit. With the result that the brightness of Sun varies by close to sine wave. And insolation due to orbital tilt is also close to sine wave except at high latitudes with stuff like cutoff at polar night. Sum of two sine waves at same period is another sine wave at the same period. At present, coincidentally both Earth and Mars have perihelion close to solstice.

If a planet had a bigger eccentricity, the brightness of Sun would get less harmonic. With a short and sharp maximum near perihelion.
If one hemisphere had the sharp perihelion insulation maximum overwhelming the general insulation minimum due to winter solstice and the other had the perihelion on top of the general insulation maximum, you could have two summers on one hemisphere and only one on the other.