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A technical point was correctly stated in Planets defy what ought to be there by Seth Borenstein (NEWS 29, February 22, 2007), but was incorrectly noted in the caption that explained the NASA released artist’s conception of exoplanet HD209458b. The caption should have read “900 trillion miles from Earth” not “900 trillion light years from Earth”. Through measurements made by the Wilkinson Microwave Anisotropy Probe (WMAP) the age of our universe is estimated to be (13.7 ± 0.2) billion years. In other words, It takes about 13.7 billion years for light to traverse the distance of our currently perceived Universe. An object at a distance of 900 trillion light-years would correspondingly take 900 trillion years for its light to reach Earth. As this time far exceeds the estimated age of the Universe, any light emitted from such an object would not yet have reached our planet. The conversion is one light-year equals 5.88 trillion (5,880,000,000,000) miles. Applying this conversion to the estimated age of our universe gives a crude estimate of its size (13.7 billion years times 5.88 trillion miles per year): 80,600,000,000,000,000,000,000 miles. This letter has not been edited.
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