Astro 1 – Section 2 The Astronomical Universe The Astronomical Universe Professor: Robin CiardulloTime: TTh 2:30 – 3:45 Office: 519 Davey LabPlace: 121 Sparks Office Hours:TTh 4:00 – 5:00 Phone: Text: Astronomy - A Beginner’s Guide, by Chaisson & McMillan Class Web Site: Grades Policy: 50% midterms 25% final 25% homework

Keys to Success Attend class, and ask questions! Skim the material before the lectures, and review the notes afterward. All the notes and the class slides will be posted on the web. Don’t concentrate on facts. Instead, consider the class as an exercise in learning the process of scientific thinking. Learn from the tests and the homework. The questions you miss may appear later on!

Homework (Almost) weekly set of five difficult questions, posted on-line. Check the course web-site for the due dates! Work together!!! Ponder, discuss, and argue! You may submit the homework multiple times. Only the last submission will count. Submit the homework on time! No submission means negative points! You don’t have to get all the answers correct. If you’re getting ~ 70% right, you’re doing “A” work!

Observing Project Observe the sunset (beginning and end of semester) Observe the Moon (one time) Observe planets, stars and constellations (one time) Observe through a telescope  Telescopes are open on the roof of Davey Lab (M-Th)  Telescopes are open to everyone until Sept 27  After Sept 27, you can only observe during certain dates (determined by the first initial of your last name) Assistance for observing is available on the roof of Davey Lab Monday through Thursday (starting next week). In addition, the Astronomy Dep’t and the Penn State Astronomy Club sponsor a telescope open house every (clear) Friday. Detailed information is available on the class web-site

The Astronomy Diagnostic Test (ADT) The University wants everyone to fill out a brief (40 minute!) online questionnaire through Angel. This survey won’t be graded, but participation will count towards your homework grade. Since the purpose of the ADT is to find out how much astronomy you know before taking the course, you should not study for this. Just answer the questions the best you can. The link will disappear two days after the first class.

Visual and Historical Astronomy STRUCTURE OF COURSE

HISTORY OF ASTRONOMY

Visual and Historical Astronomy Gravity STRUCTURE OF COURSE

GRAVITY

Gravity STRUCTURE OF COURSE Light

LIGHT

Gravity STRUCTURE OF COURSE Light Stars

STARS

The Milky Way Gravity STRUCTURE OF COURSE Light Stars

THE MILKY WAY

The Milky Way Gravity STRUCTURE OF COURSE Light Stars Galaxies

GALAXIES

Gravity STRUCTURE OF COURSE Light Stars Galaxies The Universe

THE UNIVERSE

Gravity STRUCTURE OF COURSE Light Stars Galaxies The Universe The Solar System

THE SOLAR SYSTEM

Gravity STRUCTURE OF COURSE Light Stars Galaxies The Universe The Solar System Life, the Universe and Us

LIFE IN THE UNIVERSE

The Sky and the Motions of the Earth

The Celestial Sphere Geocentrially speaking, the Earth sits inside a celestial sphere. Fixed on the sphere are stars.

Constellations Constellations are patterns of stars that the eye picks out. The stars are usually not near each other; they just lie in the same direction. Historically, the brightest stars are stars of the 1 st magnitude. The next brightest are stars of the 2 nd magnitude. The faintest stars one can see by eye are 6 th magnitude. (The biggest telescopes can reach m = 26 or so.)

Orion, the HunterLeo, the Lion Cygnus, the Swan Scorpius, the Scorpion Antlia, the Air PumpPuppis, the Poop Deck

Diurnal Motion The Earth’s axis of rotation also defines some places on the celestial sphere. The celestial North pole is over the Earth’s north pole. The celestial equator is the extension of the Earth’s equator. The meridian divides east from west on the sky.

Diurnal Motion Each day, the Earth rotates once (west-to-east) on its axis. This causes us to face different directions and see different stars. The stars’ daily (diurnal) motion reflects the Earth’s spin.

Risings and Settings The spin of the Earth causes the stars to appear to rotate about the celestial pole. Some stars are circumpolar and never set, while others dip below the horizon. Which stars are which depends on where you are on Earth. The 2 nd magnitude star Polaris happens to be very near the North celestial pole.

The Yearly Motion In addition to rotating, the Earth also revolves about the Sun. As the Earth revolves the Sun is projected in front of different constellations at different times of year. The path the Sun takes across heavens is called the ecliptic. The constellations which the Sun passes through are zodiac constellations. Because the Sun is bright, we can only see some constellations at certain times of year.

The Seasons Since the plane of the ecliptic is tilted 23.5° with respect to the celestial equator, we have seasons.

The Motion of the Sun From the Geocentric point of view, the Sun moves from the northern part to the southern part of the sky with the seasons. When the Sun is furthest north (south), it’s the summer (winter) solstice. When the Sun crosses the celestial equator, it’s the vernal (or autumnal) equinox.

Next Time -- Sun, Earth and Moon