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Kate Becker
Kate Becker
Kate Becker

Am I normal?

You might say that the years between age 13 and age 23 are one long, angsty investigation of this question.

And yet humans on planet Earth have been asking a similar question for far longer: Are we normal? Is our planet ordinary, or is our solar system a cosmic weirdo?

Finally, we may be on the verge of an answer. In the last 20 years, astronomers have confirmed the existence of more than 750 planets and more than 100 multi-planet systems beyond our solar system. Though many of these systems look very different from our own, with massive gas planets circling their stars even more tightly than Mercury orbits our sun, the better our telescopes get at discovering these systems, the more familiar they look.

Earlier this month, astronomers announced that they may have even found a solar system more plentiful in planets than ours. The star HD 10180, about 130 light-years from Earth, was already known to have as many as seven planets.

But by rooting through data from the High Accuracy Radial Velocity Planet Searcher, an extremely precise spectrometer installed on a telescope at La Silla Observatory in Chile, astronomers believe they've found traces of two more planets, bringing the total up to nine and surpassing our own solar system's eight. (That's not counting Pluto, of course.)


The family of planets around HD 10180 might not look much like our planetary family. Most of the "siblings" are far more massive than Earth, and seven of the nine are in orbits even tighter than the Earth's. Yet the discovery, if it is confirmed, tells us that our big planetary family isn't a cosmic freak. It's pretty normal.

At the same time, astronomers have discovered that another defining feature of our solar system -- the fact that the planets' orbits are roughly aligned in a single plane, like tracks on a record -- is also the norm and not the exception. They compared planetary data from the Kepler Space Telescope, which can only spot planets if their orbits happen to be neatly aligned with our line of sign, with data from HARPS, which can pick out planets in a wide range of orbital tilts. The results suggest that most solar systems have neatly aligned orbits, just like ours.

This means that our solar system is normal-looking (a relief for any teenager). But it also means something deeper. The orbital alignment that we see today is a relic of the way that our solar system formed in a swirling pancake of dust and gas. So, seeing other "flat" solar systems means that even the formation of our solar system was ordinary. We've been normal since we were born.

And as for life? We don't yet know whether life is the norm or the exception. Even if we one day find evidence that microbes flourished on Mars or beneath the ice of Enceladus, we may not know for a long time whether intelligent life -- the kind of life with which we could have a conversation -- is commonplace or eccentric.

In that, we are perpetual teenagers: Hoping, on one hand, to be truly special -- and fearing, on the other, that we might turn out to be just that.