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Author Topic: Best Earth Similarity Indexes?  (Read 1888 times)

Element29

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Best Earth Similarity Indexes?
« on: November 26, 2017, 04:56:19 PM »
Hello,

I don't know if a thread like this exists. I tried to create a planet between Earth and Mars which is rather similar to Earth.

The results are the planet Somnia and its moon Oneiroi. The names are from the Greek and Roman representation of dreams.

Somnia: http://www.bilder-hochladen.net/files/big/c4q7-pg-8c99.png
Oneiroi: http://www.bilder-hochladen.net/files/big/c4q7-pk-b627.png

Somnia has an impressive Earth Similarity Index of 0.95. The temperature are between 15 and 18°C (59/64,4°F), atmospheric pressure, gravity and whatever is exactly like on Earth. It's has 1.33x the size of Earth, a 24-hour day and needs 1.4 years or 512 days as one year. The magnetic field is similar to Earth. There a two main problems: To reduce the gravity, the panet is completely created from silicates. The average relative temperature is about -60°C / -76°F, this is probably too low.

Oneiroi has an Earth Similarity index of 0.89, which is still very good. The temperatures are the same as on Somnia. It is 37x larger than the moon and has an 48-hour day. Otherwise there would be a bound rotation, and doubling the time makes calculating easier. It also needs about 30 days for one rotation. To increase the gravity, Oneiroi has a large iron core. I can't really tell the distance between it and Somnia, so I don't know if this is a problem.

Here is a view of the magentic fields and the position, both objects are in the Goldilocks zone.

http://www.bilder-hochladen.net/files/big/c4q7-ph-1d31.png
http://www.bilder-hochladen.net/files/big/c4q7-pi-eaee.png

But like the names say, something like just is just a dream - or a Universe Sandbox 2 project file.
Is it possible somehow to declare Oneiroi as a true moon of Somnia?

Greets, Element29.
« Last Edit: November 26, 2017, 05:10:22 PM by Element29 »

Austritistanian

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Re: Best Earth Similarity Indexes?
« Reply #1 on: November 29, 2017, 02:08:57 AM »
Oneiroi is too large in comparison to Somnia to be considered as a moon. We don't currently have a definition for what makes something a moon, but my preferred definition is for the moon to be small enough that the barycenter would be located inside the parent planet. Because Oneiroi is too large compared to Somnia, the barycenter would be located above the surface of Somnia, making it a binary planet. Similar to Pluto and Charon, where Charon is too large compared to Pluto and their barycenter is above Pluto's surface.