Q: How many real objects are there in SpaceEngine, and how many are generated by the program?
A: The entire Hipparcos catalog of stars, as well as all known extrasolar planets, over ten thousand galaxies, and all of the most prominent objects in our Solar system are included. This adds up to over 130 000 objects. As for procedural objects, there are more galaxies and star systems in SE than exist in reality in all of the observable universe.
Q: May I make a video with SpaceEngine or use screenshots or skyboxes made with SE for my own use?
A: Yes, you may use SpaceEngine products for non-commercial use as long as you cite SpaceEngine as the source for those assets. Please see the license page for full details.
Q: Why are there some gigantic dwarf stars, and small giant stars?
A: The Hipparcos-based star catalog that SpaceEngine uses contains some errors and missing data. If you find a real star which seems to have erroneous data, please post its name in this thread, this will make it much easier to fix the stars in the future.
Q: Why is Vega binary, but 40 Eridani is solitary? Is it a bug?
A: This is not a bug. SpaceEngine currently has an incomplete catalog of binary stars, so it makes some real binary/multiple stars are still represented as a solitary. But you make contribute to the development of the program by making a script for a binary or multiple star which are not represented in SE.
Q: Why do stars like Eta Carinae and Deneb have such low luminosities?
A: Most of the light from these stars is blocked by interstellar dust before it reaches Earth, so these stars do not look as bright as they really are. When these stars are put into SpaceEngine using their apparent magnitudes, it gives them low luminosities. Unfortunately, SE cannot simulate interstellar extinction, so it is impossible to have their luminosities be correct without making them look unrealistically bright in the sky.
Q: How can an Ice Giant be “Hot”? This makes no sense. Is it a bug?
A: “Ice Giant” is a scientific term for a planet that has a mass between 10 and 50-70 Earth masses and composed primarily of water, ammonia and methane. These substances in the planet’s interior are in the form of a high pressure high-temperature modification of ice, so the planet is called an “Ice Giant”. Surface temperature doesn’t matter.
Q: How can an Oceania be “Hot”? This makes no sense. Is it a bug?
A: “Oceania” is a scientific term for a planet up to 10 Earth masses and composed primarily of water. Surface temperature doesn’t matter. On a hot oceania, water in the upper atmosphere is in the form of hot vapor, but farther down it smoothly transitions into a liquid state under high pressure. Even deeper it turns into a solid state called ice VII.
Q: How can I add my own objects to SpaceEngine, or modify existing ones?