But even as the Keck was capturing first light, CARA had even more innovative plans in mind. They would build a twin of the Keck and then be able to combine the images from both instruments. This would give them a telescope not just twice as big, but due to a unique characteristic of optics, one as big as the distance between the two instruments. In the case of the twin Kecks, that would be 85 meters (280 feet). A mirror that size would resolve things never seen before. It would resolve planets around other stars.
Keck II was completed in 1996. Since then, the primary mission of the twin Kecks has been to search for extrasolar planets. And it has found them—at least evidence they exist. No images have been seen, but their affect on their star has been measured, and the twins have imaged a dust cloud around a star that astronomers are certain is the birthplace of planets. It may even contain at least protoplanets now.
The Kecks however have imaged a brown dwarf orbiting a small, dim red star. The dwarf is at about the distance of Neptune. They have also imaged the indications of the massive black hole at the center of our galaxy. Of course, you can't 'see' the black hole, as no light can escape from it. What the photo shows is the swirl of stars and gas around it.
The twins work together using a technique called interferometry, in which two light beams are combined. Astronomers do not actually produce an image in this way, but create interference rings as the two beams go in and out of sync. In this way they can measure the size of stars, their rotation, and other characteristics.
This method was invented by Thomas Young in 1805, in an attempt to prove whether light was a wave or a particle. He used two slits in cardboard to produce the interference rings. In the late 1800s, Abraham Michelson improved on the technique with his interferometer and used it in the famous Michelson-Morley experiment in 1887 that proved that the speed of light was constant. It was on that experiment that Albert Einstein built his Special Theory of Relativity.
The Keck interferometer is far more complex, with the light beams traveling between the two instruments in a circuitous path through the complex.
The Keck twins continue their work today, now in concert with the Gemini telescope, an 8 meter monolithic mirror on the same complex as Keck. Yet, even this monolithic mirror was constructed using Jerry Nelson’s segmented technique. Many octagonal segments were fused together to make a single blank. In the photo below, the Kecks are on the far end of the cinder cone. The Gemini is the silver dome. The small dome is a 3.6 meter scope jointly operated by Canada, France and Hawaii.
Today, the 21st century giants such as the Giant Magellan and the Thirty Meter Telescope, and even others to come, use some form of Nelson’s astounding idea of individual segments and position actuators to create telescopes larger than George Hale and George Ritchey could ever have imagined.
