How do we know what we know about the universe? By studying the energy ( light ) emitted by objects in space. What do we call all the energy/light we receive from space? The Electromagnetic Spectrum http:/www.electro-optical.com/images/em_spect.gif What forms of energy/light can actually reach most of the Earth’s surface? VISIBLE LIGHT RADIO WAVES SOME ULTRAVIOLET LIGHT http:/wwwspitzer.caltech.edu/Media/guides/images/transmission.jpg What tools do we use to observe these forms of energy that reach the Earth’s surface? * Telescopes* What types of telescopes do we use to observe visible light? Optical Telescopes: Refracting Reflecting Refracting Telescope (Google-Images-Refracting Telescope) This tool uses a convex lens (objective) to collect and bend light coming from an object. Reflecting Telescope ( Google-Astro-canada.ca) This tool uses a concave mirror (objective) to collect visible light. What is used to collect radio waves? The radio telescope. Radio Telescope (AOL- Images-Radio Telescope) This tool collects radio waves using an antenna. One advantage this tool has over optical telescopes is that it can be used during the day, even if it is cloudy. The largest telescope used on Earth is this type. (Clip artJ0195812.wmf ) Why do astronomers use more than one type of telescope to observe energy/light coming from space? Most telescopes are only designed to detect a particular portion of the Electromagnetic Spectrum (EMS). Due to the Earth’s atmosphere, not all telescopes work best placed on the surface of the Earth. ( Water vapor interferes with infrared, ozone blocks most of the ultra-violet, the atmosphere absorbs or scatters most x-rays and gamma rays.) How do astronomers best detect parts of the EMS which do not entirely reach the surface of the Earth? ORBITING SATELLITES (AOL-Images-Telescopes) (AOL-Images-Satellites ) What parts of the EMS are best detected from space due to a lot of interference from the Earth’s atmosphere? http:/wwwspitzer.caltech.edu/Media/guides/images/transmission.jpg CONCLUSION: Infrared Ultra-Violet X-Ray Gamma Ray How are they detected? INFRARED Using optical reflectors with heat detectors. Ultra-Violet, X-Rays and Gamma Rays • Data is sent back from telescopes placed in space and then sent to receivers on the ground for computer analysis. • Due to the high energy of X-Rays and Gamma Rays, they cannot be directly collected since they go right through the telescopes. As a result, new technology has been developed to measure their presence indirectly.