Eyeball Earths

Timerover51 · #1 November 15th, 2013, 02:09 AM

I found this interesting report online on "water-trapped" worlds, also called "eyeball Earths". being tidally locked Earth-sized planets orbiting a red dwarf star.

http://www.astrobio.net/exclusive/55...rapped-worlds-

What I thought was so interesting is that these type of planets are very close to the way Mercury is treated in GDW's Space: 1889 game. All you need to do is get a copy of Conklin's Atlas of the Worlds, along with a copy of the basic rules, and you are in business.

starship_captain62 · #2 November 15th, 2013, 03:11 AM

Just considering a few variations of this theme:

What about a planet on the outer edge of the habitable zone with only the part of the planet directly facing it's sun just warm enough to support life? Imagine the sun staying permanently overhead!

The exact opposite, where the planet is on the inner edge? Only a patch on the night side could then be habitable with it's residents enjoying a permanent night.

In the article referenced there is a painting of a theoretical planet with amoon orbiting a red dwarf. What if this planet was a gas giant and the moon was habitable? In this case the habitable moon would be tide locked to the gas giant. The moon now gets a 'day' every time it orbits the parent gas giant, but of course you could only see the gas giant from one heisphere of the moon.

Just some ideas for variationts on the night side Glacier/twiligbt temperate zone/ sunward facing desert theme.

**aramis** · #3 November 15th, 2013, 06:37 AM

Quote:

Originally Posted by starship_captain62

In the article referenced there is a painting of a theoretical planet with amoon orbiting a red dwarf. What if this planet was a gas giant and the moon was habitable? In this case the habitable moon would be tide locked to the gas giant. The moon now gets a 'day' every time it orbits the parent gas giant, but of course you could only see the gas giant from one heisphere of the moon.

Just some ideas for variationts on the night side Glacier/twiligbt temperate zone/ sunward facing desert theme.

The inbound face would likely not experience a whole lot of "Dark" - the relative size of the GG in the sky (30° or more), even if dim, would provide a considerable amount of light; twilight most of the time. The true "Dark" period would be when the star is eclipsed by the parent GG.

Also fun: A pair of close orbiting reds could produce up to about 1.4x the normal red star ecosphere radius (√2), and without the tidelocking. The resulting "dusky mid-day" would be relatively stable, brightest and warmest when neither star is in eclipse of the other, and coldest when the pair are in eclipse. Given the high likelihood of a resonant orbit, this could result in a pretty unified local calendar even without moons.

Actually, the overall ecosphere would probably be the average of eclipsed and non-eclipsed - so about 1.2x distances.

Timerover51 · #4 November 16th, 2013, 02:21 AM

Quote:

Originally Posted by starship_captain62

Just considering a few variations of this theme:

What about a planet on the outer edge of the habitable zone with only the part of the planet directly facing it's sun just warm enough to support life? Imagine the sun staying permanently overhead!

The exact opposite, where the planet is on the inner edge? Only a patch on the night side could then be habitable with it's residents enjoying a permanent night.

In the article referenced there is a painting of a theoretical planet with amoon orbiting a red dwarf. What if this planet was a gas giant and the moon was habitable? In this case the habitable moon would be tide locked to the gas giant. The moon now gets a 'day' every time it orbits the parent gas giant, but of course you could only see the gas giant from one heisphere of the moon.

Just some ideas for variationts on the night side Glacier/twiligbt temperate zone/ sunward facing desert theme.

I have already thought of the Gas Giant/Planet-sized satellite combination, as I thought that is what Regina is.

Carlobrand · #5 November 16th, 2013, 09:48 PM

Y'know, I've had Book 6 in hand for, well, close to three decades I guess, and it never occurred to me that Regina wouldn't have much of a night.

Timerover51 · #6 November 16th, 2013, 10:57 PM

Quote:

Originally Posted by Carlobrand

Y'know, I've had Book 6 in hand for, well, close to three decades I guess, and it never occurred to me that Regina wouldn't have much of a night.

I cannot remember if Regina is tidally locked or not, but either way, some portions of it would have a night. Either it would be the side that faced away from the Gas Giant if tidally locked, or the side not facing the Gas Giant if rotating.

Carlobrand · #7 November 17th, 2013, 01:42 AM

Lessee:

If I'm reading the table right, Regina orbits 55 radii from Assiniboia, a "large GG", therefore a gas giant of roughly Saturn-Jupiter size or larger. Without a mass, I don't think we can estimate an orbital period for Regina, but it's about twice as far out as Callisto from Jupiter, and Callisto's tidally locked, so maybe, especially if Assiniboia's significantly larger than Jupiter. Callisto runs a 16.7 day orbit.

On the other hand, if Regina's tidally locked with Assiniboia, then it's "day" with respect to its sun could be weeks to a month long. I can't find any mention of it being tidally locked or having a weeks-long day, and that would have distinct climate impacts on this "rich" world. I'd tend to make Regina have a more normal day to avoid potential canon conflicts. On the other, other hand, 3 of the four worlds orbiting Assiniboia inward from Regina boast habitable conditions, two of which are farm worlds, so either this tidal lock thing is irrelevant to climate - at least with respect to farming - or for some reason Assiniboia's moons aren't getting tidally locked.

55 radii from a 60 to 120 thousand kilometer radius sphere makes Assiniboia as seen from Regina a bit over twice the apparent diameter - there's a word for that, I know - of Earth's moon as seen from Earth. Lusor's brighter, but Regina/Assiniboia's farther out and in a habitable zone, so light level's roughly similar. Assiniboia's 8 times farther out than the moon but many times larger, twice the apparent diameter from Regina as I mentioned. So, bigger but not as bright? Which means Regina gets a dimmer "moonlit" night lit by a bigger but dimmer orb, but still a night - in fact, more night than we get here.

Best guess is you've got to be inside roughly 14 radii before your nights get brighter than Earth's moonlit nights. Redes, 3 radii from the GG, must have some interesting nights.

Okay, I don't feel so bad about not looking at the gas giant angle before now.

**aramis** · #8 November 17th, 2013, 03:49 AM

Quote:

Originally Posted by timerover51

I cannot remember if Regina is tidally locked or not, but either way, some portions of it would have a night. Either it would be the side that faced away from the Gas Giant if tidally locked, or the side not facing the Gas Giant if rotating.

Let's consider this a minute. Sunward is for this purpose 0° "true". When Regina is at 0°, regina's 275°-85° are in pretty close to full daylight, and it's getting about 16x (see below) the reflected light that we get from luna. Easily a dusk level. But the generated IR from the planet itself will make it warmer, too.

Luna is about 30° at ~385,000.km and is 3474 km diameter. 110.8:1
Assiniboia is a LGG, and regina is 55 radii away. Which means it's between 60,000 km and 120,000km radius, and so Regina is between 3.3Mkm and 6.6Mkm distant, and assinoboia is roughly 55:2 ratio, or 27.5:1 ... 4x the diameter, 16x the surface area.

The generated IR means that dark isn't going to be so cool, except when it's at 180° from the star. Plus, much of the time, there's an almost equally bright source - the companion star.

starship_captain62 · #9 November 17th, 2013, 04:52 AM

A number of years ago there were a series of posts called RICE papers where a detailed writeup of a world done. I have attempted one for an Eyeball planet over the last couple of days which was largely inspired by this discussion. As a newbie to COTI, how do I post this wruiteup? It is about 950 words and has a couple of maps. Should it be a word doccument or PDF? I think it might be a bit long just to copy/paste into the message board.

Cheers

Carlobrand · #10 November 17th, 2013, 09:46 AM

Quote:

Originally Posted by aramis

...Luna is about 30° at ~385,000.km and is 3474 km diameter. 110.8:1
Assiniboia is a LGG, and regina is 55 radii away. Which means it's between 60,000 km and 120,000km radius, and so Regina is between 3.3Mkm and 6.6Mkm distant, and assinoboia is roughly 55:2 ratio, or 27.5:1 ... 4x the diameter, 16x the surface area. ...

Dammitdammitdammit!!! I compared the lunar diameter to the GG's radius! Jeez, but I feel stupid now!