1. Space Science
Astronomy Chapter 26

2. What is Astronomy Chapter 26-1
Astronomy- Study of the stars, planets and other objects in space.
*Astronomy is one of the oldest sciences. Dates back to 2,000 B.C. century.
*Astronomers discovered the planets nearer the sun 5,000 years ago.
* Early civilizations relied on the science of astronomy for many things.
Modern Astronomy- Uses tools that can enhance the distances astronomers can observe.
* Modern astronomers study the universe. The universe is everything that exist
* Planetologist- Astronomers that study the solar system.
Solar System- Includes the Sun and all the bodies in space that orbit it.
Cosmologist- Astronomers that study how the Universe began and how it will end.
Historical Astronomers
*Aristotle- Claimed that the Earth was at the center of the universe. (Geocentric Theory)
*Copernicus- Suggested that the Sun was at the center of the Solar system. (Heliocentric Theory)
* Brahe, Kepler, Galileo, Newton supported Copernicus. Beginning of modern Astronomy.

3. Space Exploration Chapter 26-2
Galaxy- huge collection of stars, gas and dust that travels through space.
*Space age began in 1957, with the Russian space craft Sputnik.
*Goal of space exploration is to answer questions about the Universe.
How the Universe Formed- About 15 billion years ago a huge explosion called the Big Bang, was believed to have created distant galaxies.
*Hubble Telescope- Spaced based telescope that orbits the Earth. Launched in 1990.

4. Refracting Telescope Chapter 26-3
Refracting Telescope- telescope that uses convex lenses to produce enlarged images.
Convex Lens- lens that is thicker in the middle than it is at its edges.
* Galileo was the first person to look at objects in space through a telescope.
Refract- To bend light inward.
* The objective lens brings the light into the telescope.
* The eyepiece magnifies or enlarges the object being viewed.

5. Reflecting Telescope Chapter 26-4
Reflecting Telescope- telescope that uses a concave mirror to collect light.
Concave Mirror- mirror that curves inward.
* A reflecting telescope uses a mirror to redirect light.
* Newton(1668) made the first reflecting telescope. Used a mirror to collect the light and a convex lens to magnify the image.
Schmidt telescope- A reflecting telescope that uses a camera to take pictures of celestial bodies.

6. Radio Telescope Chapter 26-5
Radio Telescope- Non-optical telescope that can receive radio waves from sources in space.
* Stars like our Sun, can only be seen when it is dark. Clouds or light from the Sun and cities can block out or obscure star light.
* Stars send out visible light and all forms of electromagnetic radiation.

7. Radio Telescope
Radio telescope uses an antenna to collect and focus radio waves to a receiver.
Karl Jansky (1932) was the first person to listen to radio signals from space.
Advantages to using a radio telescope;
They can detect objects that reflecting and refracting telescopes cannot.
Can be used in any type of weather.
Can be used during the day.

8. Chapter 26-6 How Astronomers Measure Distances?
Light Year- unit of measurement equal to about 10 trillion Km or 6 trillion miles.
*Distance light travels in one year. (300,000 Km/sec. or 186,000 mi/sec)
*Measuring distance in space creates very large numbers.
*Light from the Sun takes about 8 minutes to reach the Earth.
Light from the North Star –Polaris takes about 700 years to reach the earth.
Parallax- apparent change in the position of a distant object when seen from two different positions.
*Astronomers use parallax to find the distances to stars.

9. Measuring Distance
Astronomical Unit- unit of measurement based on the Sun’s distance from Earth and equal to about 150 million Km.
* Varies based on the Earth’s position in its orbit. (1 AU= 150,000,000 Km). Used to measure planetary distances.
Parsec- Distance equal to 3.26 LY.