Telescopes • They can collect far more light than the unaided eye • They can magnify very small images Different Types of Optical Telescopes (uses lenses and mirrors to gather and focus starlight) 1. refracting telescope – bends or refracts starlight through the first lens to focus the image through the second lens (the eye piece) 2. reflecting telescope – uses one large curved mirror to focus starlight 3. multiple-mirror telescopes – many reflecting mirrors working in unison to produce larger, higher resolution images
Telescopes (cont.)Famous Telescopes Schmidt Telescope – uses both reflecting mirrors and refracting lenses
Telescopes (cont.)Famous Telescopes Hubble Telescope – reflecting telescope orbiting Earth, has unparalleled resolution and usable for ultraviolet detection that is not possible from Earth’s surface
Other Types of Telescopes Spectroscope – uses a prism to separate visible light and determine the chemical composition of a star E.W. Maunder (at the eyepiece) and W. Bowyer observing with the half-prism spectroscope, c. 1894
Arecibo in Puerto Rico (1000’ dia.) Radio Telescope – very large telescope that picks-up radio waves emitted by quasars and pulsars The Very Large Array (VLA) in San Agustin, NM →→→→→
Electromagnetic Spectrum • The elecromagnetic spectrum includes all forms of radiation, 7% of which is visible light -- the radiation to which our eyes are sensitive. • The spectrum up according to the wavelength of the radiation.
Doppler Effect The apparent change in the wavelength due to an object's motion Sound: like the whistle on a train or a car horn as it goes past.
Doppler Effect Red shift – as an object moves away – the wavelength the star radiates gets longer… toward the RED end of the spectrum • The faster the distance increases the greater the ‘Red Shift’ The object is moving away from us
Doppler Effect Blue shift – as an object moves toward – the wavelength the star radiates gets shorter… toward the BLUE end of the spectrum • The faster the distance decreases the greater the ‘Blue Shift’ The object is moving toward US
Parallax the apparent displacement of an observed object due to a change in the position of the observer http://sci2.esa.int/interactive/media/flashes/2_1_1.htm