Notes

•
Energy that travels through space in the form of waves is called Electomagnetic Radiation.
EM radiation does not require a medium.
•
All of the various types of EM radiation from the longest wavelengths to the shortest wavelengths is the EM Spectrum.
•
The only radiation from the the EM spectrum that we can see is called visible light .

•
Telescopes are instruments that collect and focus light and other forms of EM radiation.
•
A telescope that collects and focuses visible light is called an optical telescope . The two major types of optical telescopes are refracting telescopes and reflecting telescopes.

•
A refracting telescope uses convex lenses to gather and focus light.
•
Galileo is credited with having used a refracting telescope first to view the sky.

•
A reflecting telescope uses a curved mirror to collect and focus light. The largest telescopes are reflecting telescopes.
•
In 1668, Isaac Newton is credited with building the first reflecting telescope.

•
A radio telescope is a device used to collect radio waves that come from objects is space. Most radio telescopes have large, curved surfaces like dishes.
•
Radio telescopes can combine multiple dishes to form one larger dish.

The Arecibo radio telescope in Puerto Rico was built into a natural bowl in the ground.
It is 305 meters in diameter and is the largest single radio telescope in existence.
The Very Large Array
(VLA) in New Mexico is a set of 27 radio telescopes that can be maneuvered and combine together to form one radio telescope
25 kilometers in diameter.

•
Telescopes have also been developed to look at all parts of the EM spectrum.
•
Telescopes can now see into the infrared, microwave, X-ray, ultraviolet, and Gamma rays of the EM spectrum.

•
An observatory is usually a building that has one or more telescopes. Some observatories are not in buildings, because they are in space.
•
Why would we want to have observatories in space? What does
Earth have/not have that would make telescopes on the surface undesirable?

The James Webb Space
Telescope will replace the
Hubble. It will have a mirror of nearly 21 feet and is intended to look far enough into the universe to see galaxies, stars, and even planets in the process of forming.
The Hubble Space Telescope was put up in 1990 and is intended to last until 2014. It has a nearly 8 ftwide aperture (opening) and has taken the most clear pictures of space.

•
Because it is very expensive to put observatories into space, many telescopes are still Earth-bound.
•
But because of light pollution, air pollution, and atmospheric interference, where is the best place to install these large telescopes?

The Giant Magellan
Telescope will eventually be the world’s largest optical telescope. It’s mirror will have an 24.5 meter diameter and will sit at Las Campas Peak,
Chile at 2,550 meters above sea level.
The Keck observatory is a two-telescope observatory at an elevation of 4,145 meters at the summit of Mauna Kea in Hawai’i. Each mirror is 10 meters across, making them the 2nd largest optical telescopes on the planet.

http://www.nature.com/news/specials/hubble/slideshow
.html
http://store.discovery.com/telescopes/index.php?v=dis covery_telescopes&nvbar=Telescopes http://media.skyandtelescope.com/documents/AboutSc opes.pdf
http://stellarium.org
/