 Pictures of telescopesPg. 96  TelescopesPg. 97

 B y the late 1920s, Edwin Hubble had been taking spectra and measuring distances to a large number of galaxies. From each spectrum he learned the galaxy’s redshift, which told him how fast it was moving away from Earth, then he compared that with the object’s distance. What he found set the stage for much of 20th- century cosmology: the farther away the galaxy, the faster it receded. This relation—that a galaxy’s speed is directly proportional to its distance—became known as Hubble’s Law. It was observational proof that we live in an expanding universe, and it helped lay the foundation for the big-bang theory of the universe’s origin.

 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

 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)

 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.

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.

Reflector telescope that observes in the near ultraviolet, visible, and near infrared spectra. The telescope is named after astronomer Edwin Hubble.

Mission type Space observatory OperatorNASANASA / LASPLASP SATCAT №34380 Website kepler.nasa.go v Mission duration Planned: 3.5 years Elapsed: 7 years, 2 months and 4 days (5/11/16)

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

 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.

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

 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.  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?