TelescopesTELESCOPES ALLOW US TO

STUDY SPACE FROM EARTH!!!

History

• Galileo Galilei (1564-1642)• 1st telescope invented in Holland in 1609• Galileo learned of this and made his own: small 30X scope • Observed the moon and “began” the modern age of

Astronomy where measurement was more important than philosophy

• moons orbiting Jupiter• phases of Venus• craters on the moon• sunspots

Galileo noticed

This was strong evidence that Copernicus was right although Galileo wasn’t willing to die for it. The sun was the center of the solar system!

Lenses• The lens in your eyes works like a glass lens. The light bends

as it goes through a different medium.

• Light rays are bent when they intersect glass; a curved surface can produce an image.

• In your eye, the image is then focused at the retina.

How does this apply to telescopes?• If you had a bigger eye, you could collect

more light from the object. This image could be magnified so it stretches out over more pixels in your retina.

• In a telescope, two pieces make this possible:• the objective lens (refractor telescopes) or primary

mirror (reflecting telescopes)• the eye piece

Not everything is visible…

• Many modern day telescopes do not use visible light to collect images.

• Radio telescopes, x-ray telescopes and infrared (IR) telescopes have become a staple of modern day astronomy, producing some amazing images.

www.yorku.ca/eye/spectrum.gif

How a telescope works• TELESCOPE: a device that gathers

electromagnetic radiation

• VISIBLE LIGHT TELELSCOPESREFLECTING TELESCOPE REFRACTING TELESCOPE

Uses a mirror to collect light

Light bounces off 2 different mirrors

Newton’s Telescope

Uses a glass lens to collect light

light travels in a straight line

Galileo’s telescope

Famous Optical Telescopes on Earth

• Keck Telescope-Mauna Kea HawaiiMirror is 10 meters wide

• Kitt Peak ObservatoryTuscon, AZhttp://www.noao.edu/outreach/kptour/

Very Large Array (VLA)radio telescopes in New

Mexico, signals are combined to produce

clearer images

RADIO TELESCOPESShow where radio waves are being emitted by objects in space

Has a dish & antenna ; Need to very BIG because radio waves are so long

Very little interference

Problems with earth-based telescopes

• Earth’s atmosphere reflects certain wavelengths– x-rays, gamma rays and most UV light is not

transmitted by our atmosphere

• Earth’s atmosphere blurs images– the bending of light by the atmosphere depends on the

temperature of the “air”

– “twinkling” (shimmering) effect

• “Light pollution”• Solution? Put the telescope in space. HUBBLE

Light Absorbed by Earth’s Atmosphere

Telescopes in SPACE• Hubble Space Telescope-

reflecting telescope– Placed in orbit in 1990– Collects visible light, infared, &

ultraviolet

• Chandra X-ray Observatory 1999

• Compton Gamma-Ray Observatory 1991

• Spitzer (infared) 2003

Disadvantages of space-based telescopes

• Expensive to launch and maintain

• Difficult to repair

• Low lifetime

Spitzerhttp://www.jwst.nasa.gov/Jame Webb Telescope 2014