[Space] Making a solar system with 3 (semi-) habitable planets?

[vicky_molokh]

Greetings, all!

I'll admit that I experimented very little with GURPS Space's solar system / worldbuilding section, and am more blondie than geeky for the purposes of figuring it out with all the fine nuances. I'm currently re-reading the section and looking at the Handbook Of The Planets, but perhaps asking a question here might give a faster and/or more accurate answer.

I'm trying to get 3 planets (not moons) into a solar system, such that it contains at least the following planets:

• Nearest of the three has a Very Dense (but not Superdense) atmosphere with 5-10% Oxygen, an polar temperature no higher than 40-50°C (313-323°K), equatorial temperature as high as needed to make the planet 'work', and a gravity in the 0.8-1.2 range.
• The middle one basically earthlike garden for most purposes (75ish hydrographics, 0.95-1.05G etc.).
• The further of the three with at least a Thin atmosphere, at least some water on it, and a temperature range that falls within -20°C to +50°C (253°K to 323°K) in at least climate (doesn't need to have to be the whole planet, a single climate zone will suffice).

The Handbook seems good for quickly placing one planet in a system, but the problem is that I want to push in three adjacent ones . . .

Thanks in advance!