Chapter 24 Sec. 1 Light Sec. 2: Tools of Astronomy

24.1 Electromagnetic Radiation Electromagnetic waves --> Range of electric and magnetic waves that travel through space transfer energy Classified based on wavelength travel through space travel at the speed of light—~300,000,000 m/s Include: Ultraviolet (UV) light=sunburns Infrared radiation=heat Visible light X-rays Microwaves Radio waves Gamma rays (CT scans)

Light is ... Nature of Light Behaves like a wave Similar to swells in the ocean Wavelength Distance from crest to crest Behaves like a particle Photon Small packet of light energy

Spectroscopy Spectroscopy Study of the properties of light that depend on wavelength Break light into the various colors, each with its own wavelength Three types of Spectra Continuous Absorption Emission

Spectroscopy: Continuous Uninterrupted band of light Emitted by an incandescent solid, liquid, or gas under pressure.

Spectroscopy: Absorption Continuous spectrum produced when white light passes through cool gas under low pressure.

Spectroscopy: Emission Series of bright lines of particular wavelengths produced by a hot gas under low pressure. Used to study the spectrum of a star: Spectral lines act as “fingerprints” Lines identify elements present  star’s chemical composition

Electromagnetic Spectrum: the continuum of radiation released by star --classified by wavelength (red longer, blue shorter) --wavelength=distance between the peaks on a wave --frequency=the # of waves that pass a point per second As wavelength decreases, freq. increases they are inversely proportional

Doppler Effect The Doppler Effect: Sound Waves Electromagnetic Waves Apparent change in frequency of electromagnetic or sound waves caused by the relative motions of the source of the observer. Used to determine whether a star or other body in space is moving away from or toward Earth. The Best Halloween Costume Ever

24.2 How Is This Used By Astronomers? Telescopes: Refracting telescope Reflecting telescope Both types have 3 properties that aid astronomers: Light-gathering power Resolving power Magnifying power Interferometry: combines several telescope images to make a very detailed image VLT (Very Large Telescope @ European Southern Observatory (reflecting)

Refracting Telescope Lenses bring light into focus Bends (refracts) light Objective lens produces image by bending light from distant object light converges @ area called focus (central point)

Refracting Telescope Yerkes Observatory Wisconsin 40” diameter lens 63’ long tube

Reflecting Telescope Reflects light off a concave mirror Focuses image in front of the mirror Advantages: Most large optical telescopes are reflectors Light does not pass through a mirror  glass for a reflecting telescope doesn’t have to be of optical quality

Reflecting Telescope Keck Telescopes Hawaii

Detecting Invisible Radiation Radio Telescopes Observations using radio wavelengths Focuses incoming radio waves on antenna Absorbs and transmits waves to amplifier

Radio Telescopes Advantages: Less affected by turbulence in the atmosphere, clouds and the weather No protective dome is required  reduces cost of construction Can “see” through interstellar dust clouds that obscure visible wavelengths

Space Telescopes Orbit above Earth’s atmosphere and thus produce clearer images then Earth-based telescopes Hubble Space Telescope 1st space telescope built by NASA Put into orbit around Earth April 1990 Other Space Telescopes Study X-Rays: NASA uses Chandra X-Ray Observatory (launched in 1999) Study Visible and Gamma Rays: Compton Gamma-Ray Observatory Infrared: James Webb Space Telescope

James Webb Space Telescope Infrared vision that will peer back over 13.5 billion years to see the first stars and galaxies forming out of the darkness of the early universe. Will launch in 2018 from European Spaceport located near Kourou, French Guiana on a rocket. (The mission lifetime is 5-10+ years.)