Either we have 10 planets or 8 now

[Rudey]

http://www.gps.caltech.edu/~mbrown/planetlila/

10 Planets? Why Not 11?
By KENNETH CHANG
PASADENA, Calif. - Between feedings and diaper changes of his newborn daughter, Michael E. Brown may yet find an 11th planet.

Once conducted almost exclusively on cold, lonely nights, observational astronomy these days is often done under bright California sunshine.

When he has a few spare minutes, Dr. Brown, a professor of planetary astronomy at the California Institute of Technology, downloads images taken during a previous night by a robotically driven telescope at Palomar Observatory 100 miles away. Each night, the telescope scans a different swath of sky, photographing each patch three times, spaced an hour and a half apart.

In any one of the photographs, a planet or some other icy body at the edge of the solar system looks just like a star. Unlike a star it moves between the exposures.

Dr. Brown's computer programs flag potential discovery candidates for him to inspect. He quickly dismisses almost all of them - double images caused by a bumping of the telescope, blurriness from whirls in the atmosphere or random noise.

Sometimes, like last Jan. 5, he spots a moving dot.

Dr. Brown had rewritten his software to look for slower-moving and more distant objects.

On that morning, he was sitting in his Caltech office - unremarkable university turf sparsely decorated with a not-full bottle of Jack Daniel's, a dragon mobile, a dinosaur toothbrush, a Mr. Potato Head and other toys and knickknacks that long predated parenthood - and re-examining images from nearly a year and a half earlier, Oct. 21, 2003.

The first several candidates offered by the computer were the usual garbled images.

Then he saw it: a bright, unmistakably round dot moving across the star field.

He did a quick calculation. Even if this new object reflected 100 percent of the sunlight that hit it - and nothing is perfectly reflective - it would still be almost as large as Pluto.

That meant, without any additional data, Dr. Brown knew he had discovered what could be the 10th planet.

-Rudey