Basic Information
A HabStar is a star defined as being likely to produce habitable worlds for life similar to what has evolved on earth. This distinction is being made by our current SETI program, so we don't yet know which HabStars will actually have life or planets. Currently, we just play the odds. Assuming that life exists elsewhere in the universe, and that it has much in common with life here, chances are it'll be in orbit around one of the 17,000 HabStars that SETI has identified.
Such stars are classified as F V, G V, or K V Stars, having temperatures between 7,000 K and 4,000 K, and lifespans of at least a few billion years. Other star classes are too hot, too cold, or too short lived to be likely to produce life as we know it.
HabStars emit enough radiation to promote the conversion of oxygen into ozone, but not so much radiation that they inhibit life. They need to be non-variable stars, with stable "habitable zones" where liquid water can exist on planetary surfaces. If they exist in binary or multiple star system, the companion star(s) need to be very distant so that they don't disrupt the formation or orbits of planets around the HabStar.
HabStars have a certain amount of elements other than Hydrogen and Helium in their mix. Those two elements are the most common ones in the universe, but a variety of heavier elements are needed to support life. If a star has other elements in it (which we can detect based on spectrographic analysis), then it's likely that terrestrial planets formed in it's system, composed from those same elements. The existence of elements other than the first two within a star or system is sometimes referred to as High Metallicity.
To qualify as a HabStar, a star needs to be at least 3 Billion years old. Otherwise it won't have been around long enough to form stable planets.
Interestingly, our Sun, while certainly a HabStar, is not of the specific category of stars perhaps best suited to supporting life. Some data suggests that K V Stars might be able to support life for far longer periods than our sun is. Therefore, not all HabStars need be exceedingly like our earth.
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Game and Story Use
- Great place to put an alien homeworld. It makes them share at least some needs with humanity, which may contribute to understanding, or to competition for resources.
- If a universe / setting has other Hypothetical types of biochemistry, then the definition of HabStar may need to be expanded or discarded all together. What's good for oxygen-breathing, water-drinking, carbon-based life here on earth might not be the same as what fosters silicon-based life. It may well prove the later is more common in the galaxy.