http://www.rssboard.org/rss-specification 720 http://ecuip-xtf.lib.uchicago.edu/xtf/search?f4-type%3DObservation;f5-associated-Lesson%3DX-ray%20Impact;expand%3Dsubject;f6-spectral-Type%3DOptical Results for your query: f4-type=Observation;f5-associated-Lesson=X-ray Impact;expand=subject;f6-spectral-Type=Optical Thu, 01 Jan 1970 12:00:00 GMT http://ecuip-xtf.lib.uchicago.edu/xtf/view?docId=grxr/HorseheadNebulaSpaceTelescope/HorseheadNebulaSpaceTelescope.dc.xml The Horsehead Nebula is one of the most identifiable nebulae because of the shape of its swirling cloud of dark dust and gases, which resembles to a horse's head when viewed from Earth. http://ecuip-xtf.lib.uchicago.edu/xtf/view?docId=grxr/HorseheadNebulaSpaceTelescope/HorseheadNebulaSpaceTelescope.dc.xml Thu, 01 Jan 1970 12:00:00 GMT http://ecuip-xtf.lib.uchicago.edu/xtf/view?docId=grxr/optical-crab/optical-crab.dc.xml The Crab Nebula, some 6,000 light years from Earth, is the remnant of a supernova explosion. It was seen on Earth in the year 1054. At the center of the bright nebula is a rapidly spinning neutron star, or pulsar, that emits pulses of radiation 30 times a second. This view shows the Crab in the optical wavelength. http://ecuip-xtf.lib.uchicago.edu/xtf/view?docId=grxr/optical-crab/optical-crab.dc.xml Thu, 01 Jan 1970 12:00:00 GMT