GALAXIES These are galaxy clusters and separate galaxies taken by long-range telescope. The area of the sky covered is less than the diameter of the moon.

Light year: ______________________________________ ________________________________________________ Light moves at a velocity of about 180,000 miles each second (300,000 km each second). One light year is equal to 5,880,000,000,000 miles Milky Way Galaxy is about 150,000 light-years across. Andromeda Galaxy (one of our nearest neighboring galaxies) is 2.3 million light-years away. Center of the galaxy is approximately 30,000 light years away. DISTANCE IN THE UNIVERSE Unit of distance (NOT TIME). It is the distance that light travels in one year.

Astronomical Unit: _________________________________ ___________________________________________________ It is approximately 93 million miles. Mercury is about 1/3 of an AU from the Sun. It is not big enough when we talk about anything outside of our solar system. Light minute – ________________________________________ Sun is approximately 8.3 light-minutes away Light second – _________________________________________ Moon is approximately 1.3 light-seconds away. distance light travels in a vacuum in one minute. distance light travels in a vacuum in one second Average distance between the Earth and the Sun.

Galaxies: _____________________ _____________________________ ______________________________ Billions of stars, dust, and gas held together by gravity ________________ was an astronomer in the 1920s who gathered many pictures of galaxies noticed they all didn’t look alike decided to classify them by the way they looked into 3 types “E” or _____________________ “S” or _____________________ “SB” or ____________________ Elliptical Spiral Barred Spiral Edwin Hubble

HUBBLE TUNING FORK DIAGRAM

3 types of galaxies wasn’t enough, so Hubble furthered divided the galaxies by variations within each galaxy type For “E” or ____________________ he looked at the amount of flattening (elongation/roundness) Divided into E0 to E5 For “S” or ____________________ he looked at how tightly the arms were wound around the bright center Divided into Sa, Sb, or Sc For “Sb” or ____________________ he looked at the increased openness of the arms (spiral arms) Divided into SBa, SBb, or SBc Elliptical Spiral Barred Spiral

1.Elliptical: __________________________; have an elliptical shape that ranges to nearly spherical, and lack spiral arms most abundant type

2.Spiral: typically disk-shaped; Somewhat greater concentration of stars near their centers, often containing _________________ __________________________. arms of extending from their central nucleus

3.Barred Spiral: type of spiral galaxy Has the stars arranged in the__________________, which rotates as a rigid system shape of a bar

4. Irregular: lack symmetry account for only 10 percent of known galaxies

The Milky Way: __________is only one of 200 billion stars in the Milky Way It is a large, disk-shaped, ______________________ about 100,000 light-years wide and about 10,000 light-years thick at the center (central bulge) There are 3 distinct spiral arms of stars Sun spiral galaxy

The sun is positioned on one of these arms about 2/3 of the way from the galactic center, at a distance of 30,000 light-years. Scientist suspect there is a super massive ______________ at the center of the galaxy It takes over 200 million years for the sun to revolve around the galactic center. black hole

II. The Expanding Universe A. The Big Bang Theory: ____________________________ ________________________________________________ Idea that all matter began in an infinitely small point and exploded out in all directions

B. Doppler Shift 1. red shift: ______________________________________ _________________________________________________ 2. blue shift: _____________________________________ ____________________________________________________ Galaxies moving away from us should show a shift in their spectrum toward the red end Galaxies moving toward us should show a shift toward the blue end of the spectrum

Since the spectrum for all galaxies show a ________________ from Earth, we assume the universe is ___________________ Red shift expanding