# Describe the Universe

## What is Astronomy?

Astronomy is the study of the universe in which astronomers have discovered the mysteries in space. Astronomers have discovered new plants, stars, black holes, and nebulas. The famous inventor Galileo was the one who invented the telescope in the mid 1609. Astronomers have named our years on how we go around the sun in 365.25 days. Astronomers can also predict when asteroid will hit us.

## Objectives

1. Describe characteristics of the universe in terms of time, distance, and organization.

2. Identify the visible and nonvisible parts of the electromagnetic spectrum.

3. Compare refracting telescopes and reflecting telescopes.

4. Explain how telescopes for nonvisible electromagnetic radiation differ from light telescopes.

## Describe The Electromagnetic Spectrum

Electromagnetic is all of the frequencies or wavelengths of electromagnetic radiation. Both visible and invisible light have to travel in wavelengths and at the same speed. The shortest wavelengths are invisible and so as the longest wavelengths. The shortest wavelength in the visible light is blue and violet, while the longest wavelengths of light are red and orange. In 1800, scientist Sir Fredrick William Herschel discovered infrared radiation.

## Compare The Refracting And Reflecting Telescopes

Refracting telescopes is a telescope that uses a set of lenses to gather and focus light from distant objects. Reflecting telescopes is a telescope that uses a curved mirror to gather and focus light from distant objects. The problem about refracting telescopes is that the lens focuses different colors of light at different distances. Another problem is that it is difficult to make very large lenses of the required strength and clarity. Refracting and reflecting telescopes have to gather and focus light to analyze.

## Invisible light and Visible light Telescopes

Invisible light telescopes are different from visible light telescopes. The telescopes we have here on earth are all around us. There are two types of telescopes, refracting telescopes and reflecting telescopes. The problem about refracting telescopes is that the lens focuses different colors of light at different distances. Another problem is that it is difficult to make very large lenses of the required strength and clarity. The reason they build space based telescopes is that the ones on earth have to deal with the atmospheres getting on the way.

## Spaced Based Telescopes

Spaced based telescopes can absorb visible and invisible electromagnetic radiation without the obstruction of the earth's atmosphere. The Chandra X-Ray Observatory makes remarkably clear images using x-rays from objects in space. The Compton Gamma Ray Observatory is no longer in space, but it detected gamma rays from objects, such as black holes. The Spitzer Space telescope was launched in 2003 to detect infrared radiation.