1. Unit 3 Astronomy

2.  Spectroscope: An instrument that separates light into its component colors  Similar to what a glass prism does to light  Dark lines are missing wavelengths that replace colors absorbed by elements in the cooler outer layers of the star  Each element and type of star has a unique pattern

3.  Red-shift: displacement of spectral lines of distant stars toward the red end of the spectrum; Doppler shift  Evidence that distant galaxies are moving away from us  The more distant the galaxy, the greater the red shift

4. Sample Regents Question  In the diagram below, the spectral lines of hydrogen gas from three galaxies, A, B, and C, are compared to the spectral lines of hydrogen gas observed in a laboratory. A) Galaxy B is moving away from Earth, but galaxies A and C are moving toward Earth. B) Galaxy A is moving away from Earth, but galaxies B and C are moving toward Earth. C) Galaxies A, B, and C are all moving away from Earth. D) Galaxies A, B, and C are all moving toward Earth.

5.  Two scientists in the 1960s pointed a sensitive receiver toward space and picked up an annoying background radiation, which was the sound of the birth of the universe  The use of the Hubble Space Telescope and other instruments have led to the predicted age of the universe: 13.7 billion years

6. Size of the Universe  Light-year: the distance light can travel in 1 year, which is about 6 trillion kilometers  It is assumed that no object or energy can travel faster than light  Light travels so fast that it could circle the Earth 7 times in 1 second  The universe is thought to be about 25 billion light-years in diameter

7. The Future  Some astronomers think the universe will keep expanding forever  Others think that gravity will eventually cause the collapse of the universe in a big crunch  Recent observations have led to the belief that the universe is expanding at an accelerating/speeding up rate

8. Unit 3- Astronomy

9. Structure of the Universe  The universe includes everything we know and don’t know

10. Galaxy  Galaxy- includes billions of stars and various amounts of gas and dust  Each galaxy will have over 100 billion stars, and there are billions of galaxies  Type of galaxy is based on shape: elliptical (football-shaped), irregular, and spiral  The Milky Way galaxy is a spiral galaxy, which has over 200 billion stars

12.  Along with the Earth rotating on its axis and revolving around the sun, the Earth is also revolving around the center of the Milky Way galaxy  Period of Revolution Around the Milky Way: 220 million years  Neighbor: Andromeda Galaxy  Takes 2 million years for the light from Andromeda to reach us  Andromeda is one of about 30 galaxies in our local group

14. Solar System  Solar System- includes a star (like the Sun) and those celestial objects bound to it by gravity

15. SAMPLE REGENTS QUESTION  In which one of the following lists are celestial features correctly shown in order of increasing size? A) universe -> galaxy -> solar system -> planet B) galaxy -> solar system -> universe -> planet C) planet -> solar system -> galaxy -> universe D) solar system ->galaxy -> planet ->universe

16. DON’T FORGET UGSS!  Universe (largest)  Galaxy  Solar System (smallest)