stars, galaxies, and the universe chapter 21.1 & 21.2
TRANSCRIPT
Stars, Galaxies, and the
UniverseChapter 21.1 & 21.2
Telescopes• Electromagnetic Radiation
- energy that can travel through space
in the form of waves
• Electromagnetic Spectrum
- the entire range of radiation
Telescopes
• Telescopes are instruments that collect and focus light and other forms of electromagnetic radiation.
• Telescopes make distant objects appear larger and brighter
Telescopes
• 3 kinds of telescopes
- Optical telescopes
1) Refracting telescopes
– use convex lenses
The larger the lens, the stronger the telescope
Largest Refracting Telescope
The Great Paris Exhibition Telescope of 1900
1.25 m diameter
Telescopes
2) Reflecting Telescopes
- use concave mirrors
The larger the mirror, the stronger the telescope
Largest Reflecting Telescope
Large Binocular Telescope
Mount Graham International Observatory, Arizona
Two 8.4 m diameter
Subaru Telescope
Hawaii
8.2 m diameter
Telescopes
- Radio Telescopes – devices used to detect radio waves from objects in space
The larger the dish, the stronger the telescope
Telescopes
Largest radio telescopes
Arecibo, Puerto Rico
1,001 ft
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
Characteristics of Stars
• Constellations –
imaginary patterns
of stars in the sky
Classifying Stars
• Stars are classified using color and temperature
Hottest
Coldest
Classifying Stars
Stars are classified using size
Classifying Stars
Stars are classified according to composition
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
Brightness of Stars
Apparent Brightness- how bright a star appears from Earth
Brightness of Stars
Absolute Brightness- how bright a star would be at a standard distance
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
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
Hertzsprung-Russell Diagram
Plotting of stars on a graph based on temperature and absolute brightness
Used to understand how stars change over time
