Mirror Earth

Mirror Earth by Michael D. Lemonick Read Free Book Online

Book: Mirror Earth by Michael D. Lemonick Read Free Book Online
Authors: Michael D. Lemonick
divided the world into good guys and bad guys, and the bad guys included some of the world’s most eminent scientists. These would eventually include, once he signed on with Geoff Marcy, many of their professional colleagues. He thought nothing of describing senior astronomers at places like Caltech and Cornell and especially Harvard as evil, or cowardly, or even mentally ill. He would say these things openly, and later on, when Marcy and Butler finally began making discoveries and getting some public recognition, he would sometimes even say them to reporters.
    Nevertheless, Butler was very good at his job. He spent more than a year hanging out with chemists, trying out one element or compound after another, looking for the ideal reference gas to use for finding planets. Ultimately, he settled on iodine. It was not only safe, but it also had an enormous number of spectral absorption lines that spanned the visible spectrum all the way from red to violet. That would give each measurement plenty of cross-checks. The lines created by hydrogen fluoride, by contrast, were not only fewer in number, but they also bunched up in a small part of the visible-light spectrum.
    So Marcy and Butler built what they called an “iodine cell” to attach to the Hamilton Spectrograph at Lick Observatory near San Jose, and began using a small telescope to take data on relatively bright, nearby Sun-like stars, looking for wobbles. They didn’t have the software yet to analyze their observations; the spectrum of iodine was so horribly messy that they couldn’t disentangle its spectrum on their images from the spectra of the stars. But Butler was also a talented software writer, so while they continued to take unreadable measurements, he worked on code that might someday make sense of them.
    In the end, it took him six years. “It’s my Rembrandt,” Butler told me in 1996. “It’s as close to great art as I’ll ever get.” Even then, however, Marcy and Butler could get to a precision of only twelve meters per second—still not good enough to find an alien Jupiter. The Hamilton Spectrograph, built by Steven Vogt, Geoff Marcy’s thesis adviser in grad school at Santa Cruz, was now the limiting factor. Vogt had to upgrade the device, and then Butler had to rewrite his software to account for the upgrade. Finally, Geoff Marcy, Paul Butler, and Steven Vogt, their new collaborator, were able to measure the wobbles of stars to within an astonishing and unprecedented three meters per second. They could find a planet like Jupiter.

Chapter 3

HOT JUPITERS: WHO ORDERED THOSE?
    After Geoff Marcy and Paul Butler had all the kinks worked out in their hardware and software, the only thing standing in their way was time. It takes Jupiter eleven years to orbit the Sun just once. If you were an alien astronomer looking toward our solar system using an iodine cell and the Hamilton Spectrograph, it would take you eleven years to watch the Sun move toward you, then away, then back in a single orbital cycle. And if you were a really careful alien astronomer, who didn’t want to risk the embarrassment of making a discovery that turned out to be wrong, you’d want to see not just one, but at least two or three cycles to convince yourself you really were seeing a planet and not, say, some weird pulsation of the star itself.
    Geoff Marcy knew very well that astronomers had fooled themselves about planets before. The best-known example was the “discovery” of planets around a nearby star known as Barnard’s Star, by Swarthmore College astronomer Peter van de Kamp in the 1960s. What van de Kamp thought was aside-to-side motion in the star, caused by a planet, was actually a change in his telescope—a minuscule repositioning of a lens when the telescope was refurbished. The slight change in focal length made Barnard’s Star appear to move, and van de Kamp interpreted the motion as the tug of a

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