Astronomers have, so far, discovered nearly 5,500 exoplanets—alien worlds orbiting alien stars—with over 7,000 candidate planets still waiting to be confirmed.
That’s a lot of planets.
We search for these distant worlds because we’re curious and we want to know what other planets are like. By understanding other worlds, we can better understand our own. But make no mistake: Scientists are humans, and we want the answer to one of the biggest questions of the scientific age: Are we alone?
We may get an answer soon. Our technology is just on the cusp of detecting exoplanetary biosignatures, telltale signs of life; for example, molecules in planetary atmospheres that could indicate the presence of biology. Until then, though, it’s useful to investigate everything we can about these planets and categorize them by their likelihood of supporting life.
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