Page 1 of 1

### Super Earths

Posted: Tue Apr 16, 2013 3:32 pm
Anybody or any published material expand on the UWP to account for the super-sized "Earths" we're finding today? On a side note, any published material come up with a new solar system generation based on what we know today (and be outdated by tomorrow )?

I came up with an idea and wonder if it's a viable option: size codes B through L add 3200 per increment instead of 16, size codes M through W add 4800 per increment, and size codes X through Z add 6400 per increment. Size code Z then comes out to 115,000 kms (71539 miles for us yanks ) diameter, or just a tad over 9x the diameter of the Earth.

The next step would be to consider how this affects the atmosphere code and I have not yet given it much thought as yet.

A = 16000
B = 19200
C = 22400
D = 25600
E = 28800
F = 32000
...
L = 48000
M = 52800
...
W = 96000

### Re: Super Earths

Posted: Tue Apr 16, 2013 3:53 pm
How would they be determined?
3d6-3 would give a range of 0 to F, five more sizes added easily.

However the big question would be DM's for planet bigger then B so that you could get the chance of some normal Atmospheres, whilst also not getting an atmosphere G or higher. Of the top of my head a good modifier would be to put -5 on the atmosphere roll.

Example: F is rolled for Size. 15-7-5= +3 DM to atmosphere. Minimum on 2d6=3 would be 5 to F.
Would always going to have an atmosphere on these large planets of some kind, though the larger it gets the more likely the atmosphere isn't friendly in some manner of speaking, from needing breathing equipment to no chance of standard living on it.

### Re: Super Earths

Posted: Tue Apr 16, 2013 4:05 pm
GamingGlen wrote:Anybody or any published material expand on the UWP to account for the super-sized "Earths" we're finding today?

No because other than their size, nothing is known about them. We really know nothing about systems in general really. We have only studied one in any detail. So, we have wholly insufficient statistical data. You can make up whatever you want and it will be as accurate as anyone elses idea.

### Re: Super Earths

Posted: Wed Apr 17, 2013 2:34 am
F33D wrote:
GamingGlen wrote:Anybody or any published material expand on the UWP to account for the super-sized "Earths" we're finding today?

No because other than their size, nothing is known about them. We really know nothing about systems in general really. We have only studied one in any detail. So, we have wholly insufficient statistical data. You can make up whatever you want and it will be as accurate as anyone elses idea.
This is space opera. Why worry about reality?

### Re: Super Earths

Posted: Wed Apr 17, 2013 3:16 am
GypsyComet wrote:
F33D wrote:
GamingGlen wrote:Anybody or any published material expand on the UWP to account for the super-sized "Earths" we're finding today?

No because other than their size, nothing is known about them. We really know nothing about systems in general really. We have only studied one in any detail. So, we have wholly insufficient statistical data. You can make up whatever you want and it will be as accurate as anyone elses idea.
This is space opera. Why worry about reality?
That's my point. Make it fun and interesting.

### Re: Super Earths

Posted: Wed Apr 17, 2013 4:52 am
T5 does provide a mechanism for the smaller super-terrenes. I see the pan-thallasic option disappeared, though. A shame, that.

### Re: Super Earths

Posted: Thu Apr 25, 2013 3:22 am
F33D wrote:
GamingGlen wrote:Anybody or any published material expand on the UWP to account for the super-sized "Earths" we're finding today?
No because other than their size, nothing is known about them. We really know nothing about systems in general really. We have only studied one in any detail. So, we have wholly insufficient statistical data. You can make up whatever you want and it will be as accurate as anyone elses idea.
We know enough about the physics of our own planets to be able to extrapolate elsewhere. We do not know much specifically about those other planets, but we can make pretty good educated guesses about some of their properties. For example, knowing the orbital distance and the type of star and the size and mass of the planet can tell us about what the environment may be like there. Given physically reasonable assumptions about their composition and densities, we can say that they should have higher gravity than Earth, from which we can extrapolate how that may affect life on their surfaces. We can at least generalize based on that kind of logic, which will provide us with good educated guesses pending further data, which is better than nothing.

### Re: Super Earths

Posted: Thu Apr 25, 2013 3:53 am
Wil Mireu wrote:We know enough about the physics of our own planets to be able to extrapolate elsewhere. We do not know much specifically about those other planets, but we can make pretty good educated guesses about some of their properties. For example, knowing the orbital distance and the type of star and the size and mass of the planet can tell us about what the environment may be like there. Given physically reasonable assumptions about their composition and densities, we can say that they should have higher gravity than Earth, from which we can extrapolate how that may affect life on their surfaces. We can at least generalize based on that kind of logic, which will provide us with good educated guesses pending further data, which is better than nothing.
+1. Yes, we can make lots of interesting projections about these worlds. For starters, they're likely to be mineral rich and heavy with radioactives. Lots of geothermal activity, but probably low topological relief overall (big flat volcanoes). Rare earths might be common. Strong Van Allen belts, maybe heavy enough to hinder rather than aid surface communications. In fact, radiations of many sorts would be a hazard for most Terran kinds of lifeforms, to say nothing of suffocating gravity.

Likely they'd have reducing atmospheres heavier in hydrogen than our own, and probably suffering effects like Venus unless there's some satellite or somesuch to tear away atmosphere.

### Re: Super Earths

Posted: Thu Apr 25, 2013 4:13 am
Lemnoc wrote:+1. Yes, we can make lots of interesting projections about these worlds. For starters, they're likely to be mineral rich and heavy with radioactives. Lots of geothermal activity, but probably low topological relief overall (big flat volcanoes). Rare earths might be common. Strong Van Allen belts, maybe heavy enough to hinder rather than aid surface communications. In fact, radiations of many sorts would be a hazard for most Terran kinds of lifeforms, to say nothing of suffocating gravity.

Likely they'd have reducing atmospheres heavier in hydrogen than our own, and probably suffering effects like Venus unless there's some satellite or somesuch to tear away atmosphere.
Thick atmosphere may increase the greenhouse effect (simply because there's more atmosphere, so more chance for IR-radiation to be reflected back to the planet), so many may be hothouse worlds.

The lower density superearths could even be water worlds - earth-sized rocky planets planets covered in hundreds of kilometers of water and ice. Their atmospheres may contain a lot of H2O, which could be broken down by solar radiation into oxygen and hydrogen (the hydrogen would probably escape into space), so they may have a breathable atmosphere even if they have no life.
Definitely more fun than not thinking about it .

### Re: Super Earths

Posted: Thu Apr 25, 2013 6:57 am
GamingGlen wrote:A = 16000
B = 19200
C = 22400
D = 25600
E = 28800
F = 32000
...
L = 48000
M = 52800
...
W = 96000
Officially from canon sources (CT Book 6: Scouts):
Size R = Ring (as in rings of Saturn, not Ringworld or Halo)
Size S = Small planetoid (single to distinguish from Asteroid Belt)

### Re: Super Earths

Posted: Thu Apr 25, 2013 7:25 am
I have a smaller range because I included Gas Giants and other objects in my UWP Size Characteristic beyond the official two.Skipped I and O to maintain consistency with UWP convention, Left Z reserved for weird things (like a disc worlds in fantasy like campaigns)

Code: Select all

``````0	Asteroid Belt
1	1000
2	2000
3	3000
4	4000
5	5000
6	6000
7	7000
8	8000
9	9000
A	10000
B	11000
C	12000
D	13000
E	14000
F	15000
G	16000
H	17000
J	18000
K	19000
L	20000
M	21000
N	22000
P	23000
Q	24000
R	Ring
S	Small
T	Rosette
U	Small GG
V	Large GG
W	Brown Dwarf
X	Megastructure, non-functioning
Y	Megastructure, functioning
Z	Reserved``````

### Re: Super Earths

Posted: Thu Apr 25, 2013 1:21 pm
Wil Mireu wrote: Given physically reasonable assumptions about their composition and densities, we can say that they should have higher gravity than Earth, from which we can extrapolate how that may affect life on their surfaces.
We don't know what those 'reasonable assumptions' really are. Which is why they keep getting blindsided the more they can view.

Like I said earlier,

### Re: Super Earths

Posted: Thu Apr 25, 2013 2:53 pm
F33D wrote:We don't know what those 'reasonable assumptions' really are. Which is why they keep getting blindsided the more they can view.
Scientists really are not fumbling around in the dark as you seem to think they are. I do not know why you insist that too little is understood to make these extrapolations when that is not the case. You are simply wrong to state that. The same laws of physics apply across the universe - what we see here applies out there. We may not have Hot Jupiters and Superearths in our own system but there is no reason why we should be incapable of figuring out how they work (and before you claim otherwise, Hot Jupiters were predicted in the 1980s, and Superearths have never been considered 'impossible' so you cannot say that we were 'blindsided' by those).

You claim we don't know what those 'reasonable assumptions' about compositions and densities are. We do though, and it is easy to demonstrate that. We know that smaller planets close to the star should have a significant rocky and metallic component. We know the density of rocks and metals. We know how rocks and metals compress under pressure inside planets. Therefore we can use that to determine the masses and densities of planets given a range of planetary radii and internal structures, which we can then use to calculate the surface gravity.

We know that larger planets (superearths/sub-neptunes) can be made of rock/metal but it is also possible for them to have a significant volatile component (water, ices). The ones that have a higher volatile component will be waterworlds, and there will be enough water to reduce the planet's bulk density. So we can say that these waterworlds will have lower gravity than a superearth made entirely of rock and metal.

The point about 'reasonable assumptions' is that they are based on what we know about the universe, and we know enough that we can be justified in making them.

### Re: Super Earths

Posted: Thu Apr 25, 2013 5:05 pm
Wil Mireu wrote:Scientists really are not fumbling around in the dark as you seem to think they are. I do not know why you insist that too little is understood to make these extrapolations when that is not the case. You are simply wrong to state that. ....
Correct. Correct in all statements. Indeed, F33D, how do you think these worlds were discovered by Kepler observatory in the first place? It was designed to search for a series of theoretical principles. The fact that Kepler found these worlds demonstrates those assumptions are correct.

### Re: Super Earths

Posted: Fri Apr 26, 2013 5:17 am
Actually, researchers have been able to make some direct observations of the chemical composition of the atmospheres of the largest exoplanets by spectrographic analysis of the light curve generated when they begin and end a transit across their star. For example, see:

Analysis of Light Curves of Eclipsing Systems with Exoplanets: HD 189733 - arXiv:1201.4043v1 [astro-ph.SR] 19 Jan 2012

At the moment, this technique only works for gas giants, but it is still under development and scientists are confident that we will eventually be able to determine the chemical composition of the atmospheres of smaller planets. The exciting thing about this technique is that it might even allow us to measure temperature gradients between day and night and vertical atmospheric structure.

You might also be interested in this paper, although it is more speculative:

Miller-Ricci, E., Seager, S., & Sasselov, D. 2009 “The Atmospheric Signatures of Super-Earths: How to Distinguish Between Hydrogen-Rich and Hydrogen-Poor Atmospheres”, ApJ, 690, 1056-1067

Also keep in mind that if you know the size and mass of an exoplanet, you can calculate its average density - which gives important clues to its chemical composition. And if you have a rough idea of its escape velocity and average surface temperature, you can determine what chemicals cannot be in the atmosphere because they would have escaped into space.

This is an exciting area of study right now where the science is moving very quickly indeed...