SWAS Spacecraft
The Submillimeter Wave Astronomy Satellite
(SWAS)
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Wide-field Image of Comet Hale-Bopp's Ion Tail This pseudo-color image of Comet Hale-Bopp (1995 O1) was obtained with a Takahashi 8-inch wide-field telescope at Lowell Observatory on 9 April 1997 by David Schleicher and Tony Farnham. Mounted piggy-back on the Hall 42-inch (1.1-m) telescope, the Takahashi yields a several degree field-of-view when coupled with a 2048x2048 CCD. Trimmed as shown, the image is 2.6 degrees by 3.1 degrees in size or 9.7 million km by 11.6 million km (5.9 million miles by 7.1 million miles) at the distance of the comet from Earth. A narrowband filter was used to isolate light emitted by carbon monoxide ions (CO+) at a wavelength of 4266 Angstroms. This is the blue ion or plasma tail of the comet, which points away from the sun because the solar wind flowing from the sun traps and carries charged particles with it. Note the various detailed structures visible in the ion tail caused by the changing solar wind. A faint, diffuse dust tail is also visible, caused by sunlight reflected by dust grains. Other notes: The heliocentric distance of the comet (distance from the sun) was 0.925 AU (139 million km or 86 million miles). The geocentric distance (distance from Earth) was 1.432 AU (215 million km or 133 million miles). Solar phase angle is 44 deg (the sun is between us and Hale-Bopp, with the tails pointing away from us). Credit line should indicate "Lowell Observatory Photograph."



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