Add to table of contents:  Pictures of telescopesPg. 82  TelescopesPg. 83

 Hubble’s Law – the speed of a galaxy is directly proportional to its distance from earth. v = H 0 r v = velocity H 0 = Hubble’s constant = 20Km/s Mly(mil. light yrs) r = distance

How an optical telescope works  gathers light through the objective (mirror or lens)  bigger is better because it gathers more light  ability to see faint objects increases proportionally with the square of the radius of the objective  focuses light  viewed through an eyepiece (changing the eyepiece changes the magnification)

Telescopes  1. Optical – detects visible light. A. Refracting (objective is a lens) - needs lots of light to work - good for viewing the moon and “close” planets.

Refractors (glass lens)

Types of telescopes B. Reflecting (objective is a mirror) - best for seeing objects in space that don’t emit very much light. - almost all major telescopes are reflecting ones.

Reflectors (mirror)

Hubble Telescope Launched by Space Shuttle Discovery, 1990 Reflector telescope that observes in the near ultraviolet, visible, and near infrared spectra. The telescope is named after astronomer Edwin Hubble.

2. Radio telescope – detects long wavelength radio waves. -Focuses radio waves on an antenna then converted to pictures.

Types of telescopes  3. X-ray and gamma ray – detects short wavelength waves.  X-ray telescopes help astronomers study the sun, supernova, and other stars.  Gamma ray telescopes study supernovae, pulsars and black holes.

Chandra X-ray Telescope - Launched by Space Shuttle Columbia in 1999 This is a model! Real one is over 10,000lbs! Predicted to last 5 years, but it is still working today! Tycho Supernova seen in x-ray light

Compton Gamma Ray Telescope Launched by Space Shuttle Atlantis 1991 o June 4, 2000 it ended its mission. It was too big too completely burn up upon re- entry into Earth’s atmosphere so NASA controlled the re-entry before it fell by itself and directed the re-entry so it would fall into the ocean. o 1 st to detect gamma rays bursts from space lasting from a fraction of a second to many minutes. There is no clear scientific consensus as to their cause.

** All telescopes work best outside Earth’s atmosphere because it distorts light and radiation! Why else?

Attach pictures of telescopes to page 82.  Then Work on Review Sheet.