A100 Solar System Today’s APODAPOD  Read Chapter 1 in text – History of Astronomy  Rooftop, Kirkwood Sessions TONIGHT  1 st Homework due Friday (get it on Oncourse) The Sun Today Wednesday, Sept. 10 & Friday, Sept. 12

Kirkwood and Rooftop Sessions Kirkwood Observatory –Open 9:30-11:30 PM (about 30 minutes) –West end of Dunn’s Woods, near 4 th & Indiana Rooftop – Swain West –9 PM –Elevator to 3 rd floor, follow signs to roof –Rain date Sept. 11 PRINT WORKSHEETS FROM ONCOURSE (SYLLABUS TOOL) BEFORE YOU COMEONCOURSE

SPECIAL Opportunities! SCOPEOUT in Cincinnati: Sept. 13 – –Phil Plaitt (Bad Astronomy) Astronomy Day – Stonebelt Stargazers – Sept. 13 –Wal-Mart in Bedford, 4-8 PM

Jupiter & the Moon in Sagittarius Sept 9Sept 8 Just look south… Jupiter is the brightest object in the southern sky

Finding Polaris Find the Big Dipper in the northwestern sky Sky chart for 9 PM TONIGHT Find an open area away from nearby lights where you have a good view of the sky North South Big Dipper’s on its side in the northwestern sky

Finding Polaris To find Polaris: find the Big Dipper follow to Polaris the Big Dipper is ALWAYS up in Indiana!

The Celestial Sphere The stars all appear to lie on a large sphere surrounding the Earth (the celestial sphere) Really, the stars are all at different distances

The Local Sky An object’s altitude (above horizon) and direction (along horizon) gives its location in your local sky

Our view from Earth: Stars near the north celestial pole are circumpolar and never set. All other stars (and Sun, Moon, planets) rise in east and set in west. Celestial equator A circumpolar star never sets This star never rises in Indiana

Altitude of the celestial pole = your latitude

Why do the constellations we see depend on latitude and time of year?  They depend on latitude because your position on Earth determines which constellations remain below the horizon.  They depend on time of year because Earth’s orbit changes the apparent location of the Sun among the stars.

The sky changes as Earth orbits the Sun  As the Earth orbits the Sun, different constellations are visible at night  At midnight, the stars on our meridian are opposite the Sun in the sky

Vocabulary Review oConstellation oEcliptic oEquator oCelestial sphere oLatitude oLongitude o Meridian o Zenith o Horizon o Altitude o North and south celestial poles

Visualizing Space

Expert Methods for Visualization  Draw diagrams  Use 3d models  Use visualization software If you have a chance, visit a planetarium…

Visualize the Earth from Space Pretend you are Superman! What do you see? –Earth –Moon –Sun –Stars Copyright 1980 by DC Comics Inc.

Welcome to Outer Space!

Which of the following four diagrams most accurately depicts the Earth's orbit around the Sun?

The Solar System from Overhead space.jpl.nasa.gov

The Solar System from “Overhead” Earth’s Orbit –91,369,000 miles on Jan 4 (minimum) –94,776,000 miles on July 4 (maximum) –average distance is 92,918,000 miles –Varies +/- about 2% from a perfect circle

Basic Ideas The Earth orbits the Sun in one year (revolves) The Earth spins around once each day (rotates) The Moon orbits the Earth about once a month (revolves)

The Earth and Moon from Mars Where are Mars, Earth the Moon and the Sun?

Visualizing the Earth in Space: What causes the Seasons…?

The Earth has seasons because…? The Earth moves closer to or farther from the Sun - it’s closer in the summer and farther in the winter. True or False?

December Weather Bondi Beach - Sydney, Australia IU’s Rose Well House

When is the Earth closest to the Sun? A. Winter B. Spring C. Summer D. Fall

Visualizing Seasons – What really happens? Textbook applet: cause_of_seasons.htm

Which of the following best explains why it is hotter in Indiana in June than it is in December? A The Sun gives off more heat energy in June. D Earth is closer to the Sun in June. B The Northern Hemisphere is closer to the Sun in June. C The Sun is higher in the sky and and provides more hours of daylight in June.

With thanks to Bill Watterson, 1990

Visualizing the Moon

Galileo Galilei's "The Phases of the Moon" Image courtesy of Biblioteca Nazionale Florence, Italy How can we understand the phases of the Moon as it circles around the Earth?

What causes the Moon to change its appearance in this way? A.As the Moon orbits Earth, Earth's shadow covers the Moon. B.Clouds block part of the Moon from our view so it is full sometimes and covered other times. C.As the Moon orbits Earth, the part of the Moon facing Earth is facing away from the Sun. Sometimes the Moon looks like this And sometimes the Moon looks like this

The Earth and Moon from Space

Thinking about the Moon How much of the Moon receives sunlight at a given time? Always half the Moon? Sometimes more or less than half? Why? During new moon (when the moon appears dark) is sunlight falling anywhere on the Moon's surface? If not, why not? If so, why don't we see it? Is the Earth or the Moon closer to the Sun at new moon? Which is closer to the Sun at full moon?

The Moon moves in its orbit about 12 degrees per day It rises about an hour later each night. Why?

Bring the perspective back to Earth Ansel Adams; copyright © 2000 George Eastman House, Rochester, NY

Understanding the Moon in the Sky I’m really way off to the right

Now I’m right here!

Moon and Venus before Dawn Where are the Earth, Moon and Sun in 3-dimensional space? Where is Venus?

The Libration of the Moon

One question I’ve always had about astronomy is…

ASSIGNMENTS this week  Read Chapter 1, History of…  Kirkwood Obs. TONIGHT  Rooftop Sky Viewing TONIGHT  1 st HW due Friday Dates to Remember