As Carl Sagan memorably reminds us, we’re not leaving Earth anytime soon. But as Carl Sagan also memorably reminds us, that’s no reason not to keep learning about how we could leave Earth for other worlds someday. That’s what NASA’s Kepler Mission is about: identifying other planets in distant solar systems — some of which might be Earthlike. Kepler has already identified 1,235 candidate systems using an orbiting telescope, and this infographic shows all of them to scale with our own pale blue dot.
Through the chart, we also learn about Kepler’s process.
Actually, in this graphic, our native star is the pale dot, Jupiter is the black speck on its face, and Earth is a microscopic pinpoint (so small you can’t even see it here without zooming way in) — that circle off in the upper right corner, separated from the rest, is the Sun drawn to scale with the other stars in the Kepler collection. Each of them has at least one planet orbiting it, depicted as a small black shadow against the disc of its parent star. That’s actually how NASA finds these planets in the first place — by observing what are called “transits,” when the light of the star is briefly and infinitesimally dimmed by an orbiting planet passing in front of it. (There are myriad other, more complicated ways of detecting exoplanets, but this is the most easily intuitable one.)
NASA’s infographic looks simpler than it is. Besides showing over a thousand planets and stars to scale in one easily understandable image (no mean feat in itself), we also learn about Kepler’s process — the “transit” concept. The scale illustrations and color-coding also impart valuable information in aggregate: With one glance, we learn that the average solar system seen by Kepler has a pale, yellowish star roughly the size of our own, with at least one giant planet roughly the size of Jupiter.
“No duh,” you might think — didn’t the Copernican principle already predict that? Yeah well, predictions are one thing but hard data is something else: The fact that many of these “just like us” solar systems exist at all, much less line up with what appear to be habitable conditions on an orbiting planet, was (and still is) hotly contested. But looking at this image, it’s hard to deny: there really may be “other Earths” out there.
But how can we be sure? That’s Kepler’s real mission: to refine these twelve hundred candidate worlds down to a handful of sure things. Of these twelve hundred worlds, 54 were initially announced by NASA to be in the habitable zone — that is, in the “Goldilocks” sweet spot that can support Earth-like life. (Some of them may have since been ruled out by other observations, but that’s the ballpark.) Spectrometers can tell us amazingly detailed things about the conditions on a planet light-years away, and Kepler may just prove that there’s a place out there for us, if — as Carl Sagan memorably said — we can get there without destroying ourselves here first.