Exploring Mysterious Stars in The Universe - Are There Other Planets Like Earth?

We begin the search on familiar ground. On this planet, currently our sole example of a life-bearing world, the need for water is non-negotiable. So astronomers search the cosmos for similar environments. Around almost every “normal” star, including our sun, we can draw a band of potential habitability: the right distance and temperature for liquid water to exist. The key, of course, is a planetary surface where the water could pool. Both stars and planets come in many types and sizes, and the interplay of these factors determines the extent and influence of this “habitable zone.”

A giant, hot-burning star’s habitable zone would be found at a much greater distance than that of a smaller, cooler stellar dwarf. And if we stick with the plan—hunting first for what we know—then small, rocky worlds are our best bet for finding evidence of life as we know it (we’ll talk about “life as we don’t know it” in the next section).

So the ideal candidate is an Earth-sized, rocky world nestled comfortably within its star’s habitable zone—though scientists’ understanding of what makes up a habitable zone continues to evolve.

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