Hubble Deep Field: How a Photo Revolutionized Our Understanding of the Universe

Hubble Deep Field: How a Photo Revolutionized Our Understanding of the Universe — page 5
you want to do this 2 he cordially asked PICKING THE PATCH Some technical problems had to be overcome in order to take the Hubble Deep Field HDF photograph One was getting around the many stars and other objects in the Milky Way in order to see galaxies lying far outside our local galaxy Bob Williams and the other scientists who helped him take the HDF solved this problem by choosing a tiny patch of sky in the constellation Ursa Major Because of the location only a handful of stars inside the Milky Way would block the view of deep space The target patch was also chosen because it is in a continuous viewing zone in relation to the Hubble Space Telescope’s orbit Such a zone is a place in the sky where the space telescope can see and take photographs without Earth’s getting in the way Williams and his colleagues realized that NASA had already eliminated the problem of taking long-exposure photos from a space platform moving at high speeds As Earth travels around the sun views from the planet of various objects in space are constantly changing Because Hubble is in Earth’s orbit whatever spot in the sky it sees also appears to be constantly and quickly changing position How then could astronomers keep Hubble’s onboard camera focused on a spot long enough to take a long exposure picture NASA scientists overcame this challenge by developing sophisticated computer software It compares the position of the target spot in the sky with certain guide stars and calculates tiny course corrections for the camera several times per second Once the camera is locked on the guide stars Hubble would barely wobble off its target According to a NASA book about the space telescope it is like holding the beam of a laser pointer all day on the face of a dime located 200 miles away 1 The Hubble Space Telescope floats gracefully above Earth But regardless of how many other scientists cautioned Williams he continued on He believed that the proposed photo would reveal at least some galaxies Now that Hubble’s optics were as good as new he reasoned they might be able to pick up the light of faint galaxies