Space Technology Telescopes Chapter 18 Section 2

Telescopes Telescope— an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation. These can be used by professional astronomers or amateur stargazers.

Optical Telescopes Optical telescopes are the most common type of telescope. Used to study visible light from objects in the universe. Makes it possible to see millions of stars and other objects in space (You can only see 3,000 stars without a telescope).

How Does an Optical Telescope Work? An optical telescope collects visible light and focuses it to a focal point for observation.

2 Types of Optical Telescopes 1. Reflecting 2. Refracting

Reflecting Telescope Reflecting telescope— an optical telescope that uses a curved mirror to gather and focus light from distant objects The light is reflected from a curved mirror to a flat mirror. The flat mirror focuses the image and reflects the light.

Refracting Telescope Refracting telescope— an optical telescope that uses a set of lenses to gather and focus light from distant objects The objective lens bends light that passes through it and focuses the light,

Optical Telescopes and the Atmosphere Light gathered by the telescopes on Earth is affected by the atmosphere. Pollution and light from large cities causes faint objects to be less visible. For this reason optical telescopes are placed on mountaintops where pollution and lights are less visible.

Optical Telescopes in Space Scientists have put telescopes in space to avoid interference from the atmosphere. Ex: The Hubble Telescope is an optical, reflecting telescope. It uses mirrors.

The Electromagnetic Spectrum Scientists discovered that visible light isn’t the only form of radiation. 1852—James Clerk Maxwell proved that visible light is just part of the electromagnetic spectrum. Electromagnetic spectrum— all of the frequencies or wavelengths of electromagnetic radiation

Detecting Electromagnetic Radiation Each color of light is a different wavelength of electromagnetic radiation. Humans see from red light to blue light. Visible light is only part of the electromagnetic spectrum. Radio waves, microwaves, infrared light, ultraviolet light, X rays, and gamma rays are all invisible.

Weird Science Shortly after Marconi invented the radio in the 1890’s, people became interested in listening for messages from intelligent life in the universe. In 1901, a reward of 100,000 franks was offered to the first person to communicate with aliens.

Nonoptical Telescopes Used to study invisible radiation, light we don’t see. The entire electromagnetic spectrum is used because different types of radiation reveal different clues about the objects being studied. Examples of light we don’s see. It is detected as heat/radiation: radio waves, x-rays, microwaves, gamma rays and ultraviolet rays. 2 examples of Non-optical Telescopes: Radio (land-based) and X-ray (Space-based).

Radio Telescopes Radio telescopes detect radio waves. These are much larger than optical telescopes because radio waves are 1 million times longer than the optical wavelength.

Linking Radio Telescopes Astronomers link radio telescopes together. When linked together, they work like a giant telescope. Very Large Array (VLA) has 27 radio telescopes spread over 30 km.

Nonoptical Telescopes in Space Because most electromagnetic waves are blocked by the Earth’s atmosphere, sciences have placed telescopes in space. Chandra X-Ray Observatory— space- based telescope that detects X-rays. Some x-ray telescopes can detect something the size of a Frisbee on the surface of the sun.

KNOW THIS!! Reflecting telescopes use mirrors. Refracting telescopes use lenses. Optical telescopes collect visible light. Non-optical telescopes collect radiation that is not visible to the eye, radio waves for example. Land-based telescopes are located on Earth. Space-based telescopes are located in space. The Hubble is an example of a space-based telescope. Telescopes are placed in orbit in space to avoid atmospheric interference like pollution and light from cities.