1. Stars, Galaxies, and the Universe
Chapter 21.1 & 21.2

2. Telescopes Electromagnetic Radiation
- energy that can travel through space
in the form of waves
Electromagnetic Spectrum
- the entire range of radiation

3. Telescopes
Telescopes are instruments that collect and focus light and other forms of electromagnetic radiation.
Telescopes make distant objects appear larger and brighter

4. Telescopes 3 kinds of telescopes - Optical telescopes
1) Refracting telescopes
– use convex lenses
The larger the lens, the stronger the telescope

5. Largest Refracting Telescope
The Great Paris Exhibition Telescope of 1900
1.25 m diameter

6. Telescopes 2) Reflecting Telescopes - use concave mirrors
The larger the mirror, the stronger the telescope

7. Largest Reflecting Telescope
Large Binocular Telescope
Mount Graham International Observatory, Arizona
Two 8.4 m diameter
Subaru Telescope
Hawaii
8.2 m diameter

8. Telescopes
- Radio Telescopes – devices used to detect radio waves from objects in space
The larger the dish, the stronger the telescope

9. Largest radio telescopes
Arecibo, Puerto Rico
1,001 ft

10. Telescopes
Observatory – a building that contains one or more telescopes
Usually located on mountain tops or in space
Hubble space telescope is a reflecting
(optical) telescope

11. why do we study the stars?

12. Characteristics of Stars
Constellations –
imaginary patterns
of stars in the sky

13. Classifying Stars Stars are classified using color and temperature
Hottest
Coldest

14. Classifying Stars
Stars are classified using size

15. Classifying Stars
Stars are classified according to composition

16. Brightness of Stars
The brightness of a star depends on both its size and temperature
A large star may look bright, even though it is relatively cool, because of its size
A small star may look bright because it is hot

17. Brightness of Stars
Apparent Brightness- how bright a star appears from Earth

18. Brightness of Stars
Absolute Brightness- how bright a star would be at a standard distance

19. Measuring Distances to Stars
Light-year – distance light travels in a year
- used to express distance
between stars
-speed of light = 300,000 km/s
1 light-year is about
9.5 million million kilometers

20. how to measure extreme distances

21. Measuring Distances to Stars
Parallax – the apparent change in position of an object when you look at it from different places
Parallax can be
used to
measure stars
that are only a
few hundred
light-years
away

22. What is Parallax? - YouTube

23. Hertzsprung-Russell Diagram
Plotting of stars on a graph based on temperature and absolute brightness
Used to understand how stars change over time