How I Killed Pluto and Why It Had It Coming by Mike Brown Read Free Book Online Page A

the astronomical world. At one time, all astronomy libraries had a wall full of cabinets containing fourteen-inch-square prints that together made up the complete Palomar Observatory Sky Survey. Each print, when pulled out of its special protective envelope, shows an area of the skythat looks about as big as your fully outstretched hand held at arm’s length. It takes 1,200 of those prints to cover the whole sky, from Polaris, the North Star, all the way down to the Southern Cross.
    As a graduate student, I had been instructed in the arcane mysteries of the correct use of the Palomar Observatory Sky Survey, which was simply called POSS by the cognoscenti. First, you go to the astronomy library and open the big cabinets; then, based on the sky coordinates of where you want to be looking, either you find the library ladder and climb to the top (if you’re looking in the far north), or you sit on the floor (for the farthest southern objects), or, if you are fortunate enough to be looking for something directly overhead, you can stand comfortably and look straight ahead. With luck, you will find that the prints are stacked in the order they are supposed to be in, from pictures of the sky farthest to the east to pictures of the sky farthest west. If you’re unlucky, the one picture you’re looking for will be the only one out of place, and your search might take an hour. When you find the picture you want, you pull it out, set it on the large library table, put your face down close to the picture to see the millions and millions of stars and galaxies, and use the jeweler’s loupe to find the precise area of the sky you’re looking for. Finally, you pull out a custom-built Polaroid camera from its case, point it at the spot you’ve identified, and take an instant picture of a postcard-sized section of the sky survey print. That Polaroid print is now your personal road map.
    For decades, astronomers carried these Polaroids with them to telescopes all around the world. When you commanded your large telescope to point to the spot in space in which you were interested and you looked at the TV screen, you were usually greeted by a fairly unremarkable field of stars. The Polaroid pictures were the only way to know that the unremarkable field youwere looking at was the one in which you could find the galaxy or the nebula or the neutron star you were looking for. In the control room of any telescope at any night of the year, you could find an astronomer or a group of astronomers holding a Polaroid print and staring at the TV screen. Often the actual image of the sky from the telescope was flipped or upside down and no one could ever remember which particular way this combination of instrument and telescope flipped images, so there would always be a time in the night when three or four astronomers would be squinting at a little screen full of stars, holding a little Polaroid picture full of stars, and turning the picture sideways and upside down until someone exclaimed, “Ah ha! This star is here, and that little triangle of stars is here and we’re in just the right place.” These days the technique is mostly simpler—the Palomar Observatory Sky Survey pictures are all quickly available over the Internet, and the cabinets full of prints are gathering dust; but because you can’t take the computer screen and turn it sideways or flip it over, the little group of three or four astronomers is now more often than not standing with their heads cocked in all possible combinations of directions until the lucky one exclaims, “Ah ha!” and then all heads immediately tilt to that direction.
    Though the 48-inch Palomar Schmidt was famous to astronomers the world over, I had not even considered it worthy of thought, for one good reason: The telescope still used relatively primitive photographic technology to take pictures. Astronomers a generation before me all learned photographic astronomy: how to load film in the dark, how to ride in a