Telescopes 1. They can collect far more light than the unaided eye 2. 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

Refracting Telescope

Reflecting Telescope

Mt Palomar 200" Reflecting Telescope

Multiple-Mirror Telescope Observatory in Mt. Hopkins, Arizona

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

Radio Telescope – very large telescope that picks-up radio waves emitted by quasars and pulsars The Very Large Array (VLA) in San Agustin, NM →→→→→ Arecibo in Puerto Rico (1000’ dia.)

Electromagnetic Spectrum The elecromagnetic The elecromagnetic spectrum includes spectrum includes all forms of radiation, all forms of radiation, 7% of which is visible 7% of which is visible light -- the radiation light -- the radiation to which our eyes to which our eyes are sensitive. are sensitive. The spectrum The spectrum up according to up according to the wavelength the wavelengthwavelength of the radiation. of the radiation.

Electromagnetic Spectrum

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 The faster the distance increases the greater the ‘Red Shift’ ‘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 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 The faster the distance decreases the greater the ‘Blue Shift’ ‘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

Parallax