The Speculist: I Remember When There Were Nine


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I Remember When There Were Nine

And in the little western Kentucky public library that I frequented when I was a boy, you could still find books that only listed eight. From a strictly local perspective, those formerly long-outdated books are once again up-to-date. Our solar system has only eight planets; the ninth got demoted a while back.

But back in those days, the number of planets in our solar system was equal to the number of known planets. That is no longer the case -- not by a long shot. According to NASA's PlanetQuest site, there are now some 264 known planets out there in the 'verse, though none have been declared officially earth-like. There are 227 stars that have been identified as having planets orbiting them. One of these, 55 Cancri, has five confirmed planets.

We've certainly come a long way. Uranus was discovered in 1781. Neptune was first spotted in 1846. Then Pluto came along in 1930, and was eventually de-planeted primarily because we were finding too many other objects that we would also have to count as planets if we continued to count Pluto. (Eris, for example, which is more massive than Pluto.)

So we had thousands of years of knowing only about the planets that can be seen with the naked eye, then along comes the telescope and we're finding a new one every 70-90 years. Pretty good progress, but it's nothing compared to what happened once astronomers started looking for evidence of extrasolar planets in the tell-tale wobble that a star displays when a planet orbiting the star tugs on it with its own mass.

The NASA site lists PSR 1257 as the first extrasolar planet to be discovered, in 1991. So while thousands of years of naked-eye observation followed by hundreds of years of peering through telescopes never even got us to double digits, a little over a decade and a half has us more than a quarter of the way to quadruple digits. And it's no understatement to say that we're barely scratching the surface. Look at what a limited space (relative to the rest of the galalxy) in which we are currently looking.


And don't forget, there may well be additional planets orbiting the stars around which we've already confirmed the presence of planets. The great age of planetary discovery is not yet even in its infancy, but perhaps we'll be there soon. We may well look back on the time when there were "only" 264 as not terribly different from the time when there were only nine.

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