1. Astronomers Observe Light Radiated Toward Earth By Matter in Space 2. Light is Energy That is Radiated as a Wave with both Electric and Magnetic Properties 3. The Electromagnetic Spectrum Shows All Light Grouped in BANDS organized by wavelength Short wavelength High energy Long wavelength Low energy
All light travels through space at the same speed -- The Speed of Light -- 300,000 kilometer/second !!! The distance light travels in one year is called a Light Year -- about 10 trillion kilometers Our galaxy -- the Milky Way -- is about 100,000 light years in diameter and contains more than 200 billion stars!! The nearest star system to our Sun is Alpha Centauri -- about 4.2 light years away!! How many kilometers is that??
Fortunately, gamma rays, x-rays and much UV light are absorbed by Earth's atmosphere -- sparing us from harm Earth's atmosphere is transparent (like a window) only to certain bands, including: Optical Window – some UV light, all visible light and some infrared light Radio Window – some radio waves and some microwaves
Galileo Improved the Refracting Telescope to observe visible light Refractors use curved glass lenses to magnify objects up to 30x Visible light is refracted (bent) as it enters and exits a curved glass lens
-- visible light is refracted (bent) as it passes from air into materialof a different density. -- visible light is refracted (bent) as it passes from air into materialof a different density. -- white light bent by glass prism is spread into rainbow -- through water too! You can blend colors back into white light too!
-- Lenses can be arranged to refract (bend) lightin ways that make objects appear larger than they are. Convex Glass Lens -- The lens tricks the brain into thinking the object is larger than it is -- Object is magnified
Chromatic Aberration is a problem with refracting lenses -- white light is separated into colors of the rainbow -- creates image blurry with rainbows at edges
Sir Isaac Newton developed Reflecting lens Telescopes Reflector Telescopes usemirrors (instead of glass lenses) TwoAdvantages of reflecting telescopes: 1. No Chromatic Aberration – no separation of white light into colors of the rainbow 2. Mirrors weigh less than glass lenses Universal Law of Gravitation All objects in the universe exert a force on each other that is related to the mass of the two objects and the distance between them This force is gravity
Reflecting Telescope uses mirrors to gather and focus light Mirrors focus light by reflecting it, NOT refracting it
Since our atmosphere is transparent to Radio Waves we can position radio telescopes on Earth Arecibo Radio Telescope in Puerto Rico – located on a mountain and dug into the ground facing up so that it only detects radio waves from space, not radio waves emitted by radio stations. Radio waves are very long, so receiver must be very wide and it does NOT have to be a smooth surface
Arecibo also emits radio waves that bounce off near-Earth asteriods and back to the telescope so we can keep track of how close they come to Earth! Click here to see a radio image of an asteroid taken by the Arecibo radio telescope
The South Pole Telescope observesmicrowave light from space. It is located in Antarctica because the altitude is very high and the air is very dry. The atmosphere on mountain tops is much thinner and thus is more transparent tomicrowaves. Moisture in the air is a very effective blocker of microwaves.
Image of the “CosmicMicrowave Background” energyleft over from the formation of the Universe 13.75 billion years ago – aka, the “Big Bang”
Spitzer Space Telescope – designed to detect theinfrared light emitted by the cooler gas of Nebulas (the remains of supernovae) and the rings of Jupiter, Saturn, Uranus and Neptune Earth's atmosphere absorbs most infrared light, so infrared telescopes are designed to orbit Earth above the atmosphere
Hubble Space Telescope has orbited above Earth’s atmosphere for over 20 years – taking pictures of the visiblelight emitted and reflected by objects in space Although our atmosphere is transparent to visible light, Hubble takes much clearer pictures because it is above the atmosphere
Hubble Ultra Deep Field of the many Galaxies in our region of the Universe
SOHO Solar Space Telescope – detects UV lightemitted by the Sun SOHO helps astronomers predict dangerous "space weather" caused by massive ejections of particles and energy by the Sun. Space weather can cause satellites to fall out or orbit, expose airline passengers to be exposed to high doses of radiation and cause electrical blackouts on Earth.
Image of the UV light emitted by the Sun taken by the SOHO space telescope, showing a large ejection of energy and particles in the upper right quadrant of the Sun. Image is colorized to help us see different wavelengths within the band of UV light
Chandra Space Telescope Designed to detect X-raysemitted by the hottest objects in space such as neutron stars and black holes All space X-rays are blocked by our atmosphere
Infrared image of the famous “Crab Nebula” taken by the Spitzer Space telescope. It shows the cooler dust swirling around the remains of an exploded star Image of the same “Crab Nebula” taken by the Chandra X-ray telescope. The central white star spewing a jet of x-rays is clearly visible