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 GalaxyStandard 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