Nearest Star System Might Harbor Earth Twin
- Thread starter Andrew Boulton
- Start date
RandyT0001
SOC-13
The problem here is that the new planet is touted as being an 'Earth twin' which I think really pushes the probabilities. Now there might be a decent chance of a rocky planet located in the habitable zone of Alpha Centuri B but to stretch it into an 'Earth twin' which would require life to truly be deemed a 'twin' is a bit much.
YMMV
YMMV
To give you an idea of what the probabilities may be, I've modified the orbits of Traveller's standard orbits assigning each standard orbit to a range of distances from the primary. That is instead of these standard distances:
Orbit - AU
0 ----- 0.2
1 ----- 0.4
2 ----- 0.7
3 ----- 1.0
4 ----- 1.6
5 ----- 2.8
6 ----- 5.2
7 ----- 10
8 ----- 19.6
9 ----- 38.8
10 ---- 77.2
I use range bands:
Orbit - Inner - Outer
0 ---- 0.127 - 0.228
1 ---- 0.229 - 0.412
2 ---- 0.413 - 0.744
3 ---- 0.745 - 1.341
4 ---- 1.342 - 2.418
5 ---- 2.419 - 4.359
6 ---- 4.360 - 7.857
7 ---- 7.858 - 14.161
8 --- 14.162 - 25.523
9 --- 25.524 - 45.999
10 -- 46.000 - 82.901
The habitability zone for an Earthlike planet around a G2 V type star with a luminosity equal to that of our Sun is from 0.90 to 1.20 or thereabouts. To create an Earthlike planet, you need to have the right size, the right gravity, and the right amount of atmospheric depth and greenhouse effect. For Orbit band 3, you would generate a random number between 0.745 and 1.341 inclusive. smaller planets with thicker atmospheres would be further out while larger planets with thinner atmospheres would be closer to the primary to achieve the same average temperature. Under this system, generating a habitable planet is much less likely, and is probably closer to the truth of what's out there.
Orbit - AU
0 ----- 0.2
1 ----- 0.4
2 ----- 0.7
3 ----- 1.0
4 ----- 1.6
5 ----- 2.8
6 ----- 5.2
7 ----- 10
8 ----- 19.6
9 ----- 38.8
10 ---- 77.2
I use range bands:
Orbit - Inner - Outer
0 ---- 0.127 - 0.228
1 ---- 0.229 - 0.412
2 ---- 0.413 - 0.744
3 ---- 0.745 - 1.341
4 ---- 1.342 - 2.418
5 ---- 2.419 - 4.359
6 ---- 4.360 - 7.857
7 ---- 7.858 - 14.161
8 --- 14.162 - 25.523
9 --- 25.524 - 45.999
10 -- 46.000 - 82.901
The habitability zone for an Earthlike planet around a G2 V type star with a luminosity equal to that of our Sun is from 0.90 to 1.20 or thereabouts. To create an Earthlike planet, you need to have the right size, the right gravity, and the right amount of atmospheric depth and greenhouse effect. For Orbit band 3, you would generate a random number between 0.745 and 1.341 inclusive. smaller planets with thicker atmospheres would be further out while larger planets with thinner atmospheres would be closer to the primary to achieve the same average temperature. Under this system, generating a habitable planet is much less likely, and is probably closer to the truth of what's out there.
Actually it just says "spacecraft, such as the proposed Terrestrial Planet Finder, could be launched to find out more". That is, we could launch *telescopes* to study the planet remotely -- without actually going there.
Still, it would be a nice stimulus if we were to discover rocky world(s) around Alf Cen A or B. Knowing that there's an actual world to study there would help generate interest in developing interstellar probes. Especially if the world happened to be located in the Habitable Zone. Better yet, if it were likely to have liquid water. And oxygen lines in the spectra...
Hey, if we're gonna dream, do it in Technicolor, I say
Since were talking about the Alpha Centauri System, and this is in the gaming section, I just thought I'd mention the Alpha Centauri system I generated. Here it is.
The Alpha Centauri System
Orbit AUs/Satellites km -- Name ----------- UPP
Primary ----------------- Alpha Centauri A - G2 V
0.385 ------------------- Vulcan ---------- Y500000-0
0.805 ------------------- Lucifer ---------- YAB0000-0
1.250 ------------------- Mir -------------- B867600-8
1.250/513,696 ----------- Selene ---------- F300200-8
2.906 ------------------- Frost ------------ Y310000-0
23 +/- 12 AUs ----------- Alpha Centauri B
0.526 ------------------- Persephone ------ YAB0000-0
0.700 ------------------- Prometheus ------ X867600-8
2.143 ------------------- Hectate --------- Y200000-0
2.645 ------------------- Asteroids -------- Y000000-0
Details of the Mir/Selene System
Alpha Centauri Radius = 1.23 Sols
Alpha Centauri would appears to be 0.52 degrees in angular diameter Mir's sky. Earth's Sun by contrast appears as 0.53 degrees in angular diameter in Earth's sky.
I've arranged Mir's Moon, called Selene to be the same angular diameter in Mir's sky as appears Alpha Centauri A. Also since I wanted that moon to have an orbital period that was one twelveth a Mir year, I had to move the moon further out than the Distance of Luna from Earth, but to make it appear the same size as Mir's main sun, I had to make Selene 1.336 times bigger than Earth's moon, at a distance of 513,696 kilometers, and with a diameter of 4,645 kilometers or 2,886 miles. The surface gravity of Selene is at 0.223 of an Earth gravity or between a fifth and a quarter of an Earth gravity. The density of Selene is the same as Earth's Moon, and it has many of the same features, it is tidally locked to Mir, has Mares on the near side and is pockmarked by craters on the far side. Selene has effectively no atmosphere like Earth's Moon.
The system contains two garden worlds. The story of Mir is based in part on the Novel by Arthur C. Clarke and Stephen Baxter called Time's Eye. Mir is an artificial creation composed of many slices of Earth taken from many slices of Earth's history ranging from the years 2,000,000 BC to 2037 AD. Each slice is roughly triangular. Mir is 12,756 km in diameter, or 7,917.6 miles in diameter. with 196,941,384.7 square miles or surface area, each patch is a triangle equalateral triangle that's 4 1/3 miles on a side or about 9.3 square miles of area each. There are 20,971,520 such triangle patches taken from various eras in Earth's history between those two dates, most are semi random, some seem deliberately selected however, there are about 6 triangles forming a hexagon centered on Cape Canaveral Florida from March 10, 2037 AD, another such hexagon was taken from Washington DC from July 3, 1863, a third series of patches was taken from Berlin, Germany April 3, 1943. Alot of other patches were taken over oceans. The Titanic was snatched from its maiden and only ocean voyage in 1912 and this version of it missed its fateful rendevous with the ice berg, although many more ice bergs were sited by the crew, due to Mir's colder climate.
The event which delivered all these time slices is referred to as the discontinuity, some intelligence is suspected by all involved, although the aliens that did this have not yet shown themselve, it is generally believed that this is some sort of test or cosmic zoo set up by aliens with time travel capabilities. Oddly enough an American Moonbase of the same era as Cape Canaveral was patched onto Selene, along with a triangular section of lunar real estate surrounding it. The Moonbase has a mass driver and several Lunar Shuttles capable of reaching low Mir Orbit. Canaveral has for its part a fleet of scramjets capable of reaching the same orbit from the planet's surface.
The Alpha Centauri System
Orbit AUs/Satellites km -- Name ----------- UPP
Primary ----------------- Alpha Centauri A - G2 V
0.385 ------------------- Vulcan ---------- Y500000-0
0.805 ------------------- Lucifer ---------- YAB0000-0
1.250 ------------------- Mir -------------- B867600-8
1.250/513,696 ----------- Selene ---------- F300200-8
2.906 ------------------- Frost ------------ Y310000-0
23 +/- 12 AUs ----------- Alpha Centauri B
0.526 ------------------- Persephone ------ YAB0000-0
0.700 ------------------- Prometheus ------ X867600-8
2.143 ------------------- Hectate --------- Y200000-0
2.645 ------------------- Asteroids -------- Y000000-0
Details of the Mir/Selene System
Alpha Centauri Radius = 1.23 Sols
Alpha Centauri would appears to be 0.52 degrees in angular diameter Mir's sky. Earth's Sun by contrast appears as 0.53 degrees in angular diameter in Earth's sky.
I've arranged Mir's Moon, called Selene to be the same angular diameter in Mir's sky as appears Alpha Centauri A. Also since I wanted that moon to have an orbital period that was one twelveth a Mir year, I had to move the moon further out than the Distance of Luna from Earth, but to make it appear the same size as Mir's main sun, I had to make Selene 1.336 times bigger than Earth's moon, at a distance of 513,696 kilometers, and with a diameter of 4,645 kilometers or 2,886 miles. The surface gravity of Selene is at 0.223 of an Earth gravity or between a fifth and a quarter of an Earth gravity. The density of Selene is the same as Earth's Moon, and it has many of the same features, it is tidally locked to Mir, has Mares on the near side and is pockmarked by craters on the far side. Selene has effectively no atmosphere like Earth's Moon.
The system contains two garden worlds. The story of Mir is based in part on the Novel by Arthur C. Clarke and Stephen Baxter called Time's Eye. Mir is an artificial creation composed of many slices of Earth taken from many slices of Earth's history ranging from the years 2,000,000 BC to 2037 AD. Each slice is roughly triangular. Mir is 12,756 km in diameter, or 7,917.6 miles in diameter. with 196,941,384.7 square miles or surface area, each patch is a triangle equalateral triangle that's 4 1/3 miles on a side or about 9.3 square miles of area each. There are 20,971,520 such triangle patches taken from various eras in Earth's history between those two dates, most are semi random, some seem deliberately selected however, there are about 6 triangles forming a hexagon centered on Cape Canaveral Florida from March 10, 2037 AD, another such hexagon was taken from Washington DC from July 3, 1863, a third series of patches was taken from Berlin, Germany April 3, 1943. Alot of other patches were taken over oceans. The Titanic was snatched from its maiden and only ocean voyage in 1912 and this version of it missed its fateful rendevous with the ice berg, although many more ice bergs were sited by the crew, due to Mir's colder climate.
The event which delivered all these time slices is referred to as the discontinuity, some intelligence is suspected by all involved, although the aliens that did this have not yet shown themselve, it is generally believed that this is some sort of test or cosmic zoo set up by aliens with time travel capabilities. Oddly enough an American Moonbase of the same era as Cape Canaveral was patched onto Selene, along with a triangular section of lunar real estate surrounding it. The Moonbase has a mass driver and several Lunar Shuttles capable of reaching low Mir Orbit. Canaveral has for its part a fleet of scramjets capable of reaching the same orbit from the planet's surface.
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