Unit 3 Astronomy

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

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

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.

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

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

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

Unit 3- Astronomy

Structure of the Universe

The universe includes everything we know and don’t know

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

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

Solar System

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

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

DON’T FORGET UGSS!

Universe (largest) Galaxy Solar System (smallest)