XPost: sci.space.tech   
   From: baalke@zagami.jpl.nasa.gov   
      
   Spotlight: Tiny Measurement Gives Big Boost to Planet Hunt   
   Written by Randal Jackson/Planet Quest   
   Jet Propulsion Laboratory, Pasadena, Calif.   
   July 22, 2003   
      
   Even though astronomers have discovered more than 100 planets around   
   stars other than the Sun in recent years, the "holy grail" of the   
   search -- an Earth-sized planet capable of supporting life -- remains   
   elusive. The main problem is that an Earth-like planet would be much   
   smaller than any of the gas giants detected so far (see illustration   
   at right).   
      
   Planets orbiting other stars are too dim to be observed directly, but   
   scientists infer their presence by the tiny gravitational "wobble"   
   they induce in their parent stars. Observed from tens of light years   
   away (one light-year is 5.88 trillion miles), this movement becomes   
   very tiny indeed. The smaller the planet, the less the star parent   
   wobbles.   
      
   To detect the stellar wobble caused by a planet as small as Earth,   
   scientists need an instrument of almost unbelievable sensitivity --   
   one that could measure an angle just one-tenth the width of a hydrogen   
   atom. That's about 1 millionth of the width of the thickest human   
   hair.   
      
   Or look at it this way: Let's say there's an astronaut standing on the   
   moon, wiggling her pinky. You'd need an instrument sensitive enough to   
   measure that movement from Earth, a quarter million miles away.   
      
   Is such precision possible? After a six-year struggle, engineers at   
   the Jet Propulsion Laboratory recently proved that the answer is yes.   
      
   Such sub-atomic measurements were conducted for the first time ever   
   within a vacuum-sealed chamber called the Microarcsecond Metrology   
   Testbed.   
      
   By doing this, the engineers proved they can measure the movements of   
   stars with an astonishing degree of accuracy never before achieved in   
   human history.   
      
   The testbed, which resembles a shiny silver submarine, is jammed with   
   mirrors, lasers, lenses and other optical components. Because even   
   small air movements can interfere with the measurements, all air is   
   pumped out of the chamber before each experiment is run. Laser beams,   
   moving mirrors and a camera are used to help detect movements of an   
   artificial star, which simulates the light that would be emitted by a   
   real star.   
      
   The instrument that engineers have demonstrated in the laboratory will   
   become the heart of a revolutionary new space telescope known as the   
   Space Interferometry Mission.   
      
   "Six-and-a-half years ago, this technology was unproven and   
   unsubstantiated," said Brett Watterson, the mission's deputy project   
   manager. "It was just a remote possibility that we could do it. It was   
   through ingenuity, insight, leadership and sheer perseverance that the   
   team was able to overcome these difficult technological challenges."   
      
   NASA recently gave the go-ahead for the second stage of development   
   for the mission, which will not only be able to search for Earth-like   
   planets around other stars, but will also measure cosmic distances   
   several hundred times more accurately than currently possible.   
   Scheduled to launch in 2009, it will scan the heavens for five years   
   and provide astronomers with the first truly accurate road map of our   
   Milky Way galaxy.   
      
   "This is a historical time that we're intimately involved with,"   
   Watterson said. "Unlike any other culture in history, we have the   
   technological means, the budget, and the will to determine the   
   occurrence of Earth-like planets orbiting other stars. Everyone on the   
   team is aware of their role in this pivotal stage in the search for   
   life elsewhere in the universe."   
      
   The Space Interferometry Mission is managed by JPL as part of NASA's   
   Origins program.   
      
   Written by Randal Jackson/Planet Quest   
   Jet Propulsion Laboratory, Pasadena, Calif.   
      
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