INTRODUCTION TO ASTRONOMY Overview FRONTIERS IN ASTRONOMY PHYS 271

North America Landsat Satellite Images

Earth from SPACE APOLLO 17 IMAGE

Earth and Moon From Galileo Spacecraft on way to Jupiter

Comparison of Earth and Moon Relative Diameters Earth ~ 8000 miles, Moon ~ 2160 miles

Distance to the Moon About 240,000 miles (similar to the Diameter of Saturn’s Rings)

The Moon Mare Orientale: a large lunar crater on the East Limb (edge). ~ 700 miles Diameter

The Sun Much larger than the Planets

The Sun The Chromosphere with a large Prominence (~ 864,000 miles in Diameter)

The Corona in X-Rays Active regions (solar activity)

The Astronomical Unit Average distance between Sun and Earth ~ 150 million Kilometers or 93 million miles

Size of the Sun 109 times the diameter of Earth

Relative Size of the Planets Pluto smaller than the Moon

Orbits of the Planets Eccentricity and inclination of Pluto’s Orbit!

The Sky – Celestial Sphere North and South Celestial Poles The Celestial Equator

Rotation or Spin Rotation of the Earth - time scale Day 24 hours with respect to the Sun

Rotation of SKY – Star Trails 23 hours and 56 minutes, diurnal motion

Diurnal Motion Near Horizon Western or Eastern Horizon

Circumpolar Stars or constellations They never set, 23 hours 56 minute clock

Revolution The orbit of the Earth (sky changes)

Constellations Chance alignments in different directions

Summer Triangle Looking in different directions from Sun

Winter Constellations Use your imagination – anthropomorphic

Stars very far away Pleiades (A star cluster size of full Moon)

Milky Way – Our Galaxy Looking toward Andromeda Nebula

About 200 billion stars Some close, some intermediate, some far

Andromeda Galaxy Nearest Major Galaxy – 2.7 million Light Years distant

Clusters of Galaxies 100s or 1000s of individual galaxies!

Giant Elliptical Galaxy Standard Candles Dominates Centers of most Clusters Among Brightness Objects we know

Clusters more and more remote Billions of light years distant

Hubble Deep Field Smallest blue objects more than 10 billion light years distant