I have recently found myself developing a new world, not for any particular story, but just for its own sake. I have been thinking of elements of this world for some time now, and I am now putting them together. A major feature of the world is similar to something brought up in a post by fayanora
in which a world orbits a star in a binary system and passes between them in its orbit. This world is similar in that it is in a trinary system with a central white star (not large enough to be called a white giant, but larger than Sol) and two orange dwarves.
The stars pull the planet into a highly eliptical orbit, but the main effects are the geological activity caused by the tidal forces and the radical seasonal climate of this world. Volcanic and seizmic activity is constant. What caused so much catastrophe in Japan last month is a normal day there. There are volcanoes everywhere, and there is no part of the planet where you will not find lots of hydrothermal vents.
In addition, because of the eliptical orbit and the lack of axial tilt, seasons are the same in both the northern and southern hemispheres. Because of the air and water currents, the temperature difference in latitude is not as great as on Earth. In summer the planet is hot enough to make Death Valley seem cool. At the end of summer there is a massive planetwide storm causing global flooding. Then there is a brief sub - summer (a severely hot summer by Earth standards) and then the first of four separate but short winters. Before each there is a massive superstorm which freezes the planet. It is somewhat similar to the storms in the film "The Day After Tomorrow". Immediately afterward, there is a return to mild weather. At the end of the first (and third) winter, when it is closer to one of the dwarves, there is a shift to moderately hot weather, then another winter. At the end of the second (and fourth) winter, there is a sudden heat wave, and another episode of flooding. The waters drain quickly, though, and then there is the long summer. There are two super - summers, two less extreme summers, four winters (really, just sudden freezes and then the recovery period), and two inter - winter "sub - summers" a year, but the extreme summers are longer than all of the other seasons combined. In the winter, the oceans freeze. In the summer, temperatures can get over 80 Celcius/176 Fahrenheit, from the equator to the poles.
The planet is tropical except for about 1 percent of the year, so all life just goes dormant for that period, or takes refuge underground. The entire planet is a honeycomb of caves, and most are extremely warm due to hydrothermal vents. The planet has extremely variable topography. The tallest mountains reach more than 25 miles, and there are areas of the ocean that are equally deep. There are a lot of strange rock formations, and much of the surface looks almost like the interior of a cave, but scaled up. There are vertical fomations which look almost like stalagmites, but they are the size of skyscrapers. There are also a lot of "mushroom mountains", inverted rock formations created by sediment accumulating in a massive hydrothermal vent. Essentially, the whole planet is Yellowstone meets the rainforests of northern Australia, meets the Amazon, meets Hawaii, in terms of geology and climate.
In terms of biology, it is in some ways very different than Earths, but in other ways it is very similar. If the first organisms on Earth had taken a different path, perhaps they would be the same. The kingdoms are mostly different. There is an entire kingdom for chemoautotrophs, and they are macroscopic. There are chemoautotrophs that are as large as trees, but they look more like some types of coral. These live both underwater and on land. There are large photoautotrophs, plant analogs, but they are a lot more colors than green, since the light is constantly changing color due to certain biologically - produced particulates in the air. There are organisms which are both chemoautotrophs and photoautotrophs, and there are bacteria - analogs which are more like depictions of nanotech swarms; they propel themselves through the atmosphere or oceans, and display collective intelligence (comparable to the average large mammal). There are two animal - analog kingdoms; one that is comparable to animals in the sense that it is heterotrophic and mostly motile, and another that is motile but still autotrophic. There is also a kingdom of organisms that switch from motile to sessile and vice versa, and tend to rely on symbiosis with other organisms. These are somewhere between plants, animals, and the large chemosynthetic organisms.
There are lots of intelligent and technological species. There are many species with technology as advanced as that of humanity or more. Over time, these species have formed a single global "civilization of civilizations", much like the modern global society on Earth. The difference is that this society is 1.) environmentally sustainable, 2.) polyspecific, and 3.) more advanced than humanity in some ways, most notably biotechnology, large - scale engineering, and (in some ways) spaceflight.
I still have not come up with a name for this planet. Somewhere in the recesses of my mind the name Xuxa emerged (with that particular spelling), but I looked it up just to find out if I had heard it somewhere, or if I had just come up with it and forgot (since it sounds Mayan) and it turns out that it is actually a name in some parts of Latin America, so I am back to the drawing board.
There is a lot more I have come up with concerning this little planet, but I am going to get some sleep for now.