ASTR178 Other Worlds Week 1, August 2 A/Prof. Orsola De Marco dergraduate/units/ASTR178/

ASTR178 structure 7 weeks, 21 hours for the Solar System (by Orsola De Marco) 3 weeks on the details of the Sun and Solar System formation (by Andrei Gilchrist) 3 weeks on extrasolar planets (by Mark Wardle)

Assignments (25%) 3 assignments handed to students via website returned via collection boxes. Content of assignments discussed in class on following Monday upon request. AssignmentValueTo studentsdeadline 15%6 August 4pm13 August 4pm 210%3 September 4pm17 September 4pm 310%29 October 4pm12 November 4pm

Practical (10%) There is one practical posted on the website. You can do it in your own time on any clear night between two specified dates There is a minimum requirement of 5 observations between August 24th and September 11th Due in on September 11 You do not need to go to the Observatory, but we will reserve two evenings for you to visit if you wish

Tutorials (15%) Tutorials start week 2. Check what group you are in, and in which weeks and day your group goes to tutorial. Each student goes to only 4 tutorial classes. Tutorial class 1: Discuss the lay out of a 5 minute presentation, techniques and technology to present and topics. Tutorial class 2-4: Present or listen to the presentations on a topic of your choice with relevance to this course.

Exam (50%) Regular 3 hour exam. Format likely some multiple choice, some short answers.

Office hours Office Hours: best way to contact me: Second best, make an appointment via . Third best come to my office right after class. If you really must, come any time. READ YOUR UNI !!!!!!!!!!! It is the way I talk to you. Not reading your is no excuse not to have heard from me (check your unit works – did you get my test message on 30 July 2010?)

For me to know … Raise your hands if: You are a Physics of Astronomy Major Have you taken an Astronomy course before?

A sense of place

A sense of history

A sense of heritage

The Big Picture Astronomy to create a sense of belonging that has a wider meaning. Take a look at the short essay by Sandy Faber in the course book “Universe”.

Course Outline 1. The Solar System in context and the celestial sphere 2. Why the night sky looks the way it does. Early observers and the scientific method. 3. The terrestrial planets: Earth 4. The terrestrial planets: Mercury, Venus and Mars. 5. The gas giants: Jupiter, aurorae and tides. 6. The gas giants: Saturn, Uranus and Neptune and their rings.

In this class Space and time: sizing up the Universe. The Solar System in context Units Angular separations and sizes What are constellations Earth spin, daily motion, night and day, timezones. Earth Orbit around the Sun, yearly motion, different stars appear overhead on different months. The celestial sphere, north and south, the nightly motion of stars. Latitude and longitude on Earth and how to tell Latitude by the stars

Units of the Universe (length) Units of the Cosmos: – Solar Radius (Ro) – The astronomical unit (AU) – light years – parsec (=3.26 ly; pc) – centimeter (!) The Scientific notation: –1 = 10 0 –10 = 10 1 –100 = 10 2 –100,000 = 10 5 –When using cm, you see a lot of, e.g., !

Units of the Universe (time) Units of the Cosmos: – Year – Second The Scientific notation: –When using the second, you see a lot of, e.g., 10 9 yr = 1 Gyr

Units of the Universe (mass) Units of the Cosmos: – Solar masses – Jupiter masses – Earth masses – Gram The Scientific notation: –When using the gram, you see a lot of, e.g., gr = 1 Msun

And while we are at it … prefix multipliers: 10 = deca 100 = hecto 1000 = kilo (K) 1,000,000 = 10 6 = million = mega (M) 10 9 = billion = giga (G) = triollion = tera (T) = million trillion (?) = peta (P) (exa zetta yotta)

And since we are having so much fun…. prefix multipliers: 0.1 = deci 0.01 = centi = milli (m) = = a millionth = micro (  ) = a billionth = nano (n) = a triollionth = pico (p) = a millionth trillionth (?) = femto (f) (atto zepto yocto)

Another tool of the trade: angular separations

The scales of the Universe

Earth Radius: km or 6.4 x 10 8 cm (Concept of approximation)

Sun Radius 696,000 km or 6.96 x cm or 1 Ro ~100 x Earth

Jupiter Radius 69,911 km or 6.99 x 10 9 cm or ~0.1 Ro ~10 x Earth

Solar System Radius (Pluto) 40 AU 6.0 x 10 9 km 6.0 x cm 40 x Earth-Sun

Our Galaxy Radius ~15,000 pc or 15 kpc 4.6 x cm 7.7 x 10 7 x SS

LMC: 50 kpc SMC: ~60 kpc M31: 2.5 Mpc Virgo Cluster: 18 Mpc Other Galaxies

The Solar System in context

Timescales Supernova implosion (last phases): seconds. Planetary orbits: days … years … decades. Lifetime of the Sun: 10 billion year. Lifetime of a 100 solar mass star: few million years. Age of the Universe 13.7 billion years.

Orienting yourself in the night The first thing you need to do in order to start understanding our place in the Universe is to look up!

The Constellations Stars in a constellations are not grouped in space, they are close because of chance alignment.

Constellations Names and the Zodiac Many constellations were named by the Greeks (including some southern ones which were more northern 2000 years ago). Constellations names are usually Latin (e.g., Centaurus). Stars in a constellation are called with Greek letters according to their brightness (  being the brightest), followed by the constellation name in the genitive (e.g.,  Centauri, also abbreviated  Cen). The horoscope…

The day: The spin of Earth

The year: The orbit of Earth

The night sky over the year

The celestial sphere is an imaginary sphere centered on the Earth, whose poles are the same as the Earth’s poles and whose equator is the projection of Earth’s equator.

The North Celestial Pole

The South Celestial Pole To find South at night, look for the South celestial pole and draw a line down to your horizon. That is South.

At the North Pole: how do stars move during the night?

And at the Equator?

And where is this observer?

Latitude and Longitude What is the reference frame? Latitude: equator Longitude: the Greenwich meridian.

Measuring Latitude Your latitude North/South is the same as the altitude of the North/South celestial pole (easy to measure in the North, where Polaris marks the spot!)

Key Ideas Astronomy, Science, and the Nature of the Universe: The universe is comprehensible. The scientific method is a procedure for formulating hypotheses about the universe. These are tested by observation or experimentation in order to build consistent models or theories that accurately describe phenomena in nature. Observations of the heavens have helped scientists discover some of the fundamental laws of physics. The laws of physics are in turn used by astronomers to interpret their observations. The Solar System: Exploration of the planets provides information about the origin and evolution of the solar system, as well as about the history and resources of Earth. Stars and Nebulae: Studying the stars and nebulae helps us learn about the origin and history of the Sun and the solar system.

Galaxies: Observations of galaxies tell us about the origin and history of the universe. Angular Measure: Astronomers use angles to denote the positions and sizes of objects in the sky. The size of an angle is measured in degrees, arcminutes, and arcseconds. Powers-of-Ten Notation is a convenient shorthand system for writing numbers. It allows very large and very small numbers to be expressed in a compact form. Units of Distance: Astronomers use a variety of distance units. These include the astronomical unit (the average distance from Earth to the Sun), the light-year (the distance that light travels in one year), and the parsec. Key Ideas

Constellations and the Celestial Sphere: It is convenient to imagine the stars fixed to the celestial sphere with the Earth at its center. The surface of the celestial sphere is divided into 88 regions called constellations. Diurnal (Daily) Motion of the Celestial Sphere: The celestial sphere appears to rotate around the Earth once in each 24- hour period. In fact, it is actually the Earth that is rotating. The poles and equator of the celestial sphere are determined by extending the axis of rotation and the equatorial plane of the Earth out to the celestial sphere. The positions of objects on the celestial sphere are described by specifying their right ascension (in time units) and declination (in angular measure). Key Ideas

Some sample questions and answers

What lengths are most conveniently measured in astronomical units (AU)? A.Distances on the Earth B.Distances within the solar system C.Distances between stars in our Galaxy D.Distances between galaxies E.Only the largest distances in the universe Q1.5

What lengths are most conveniently measured in astronomical units (AU)? A.Distances on the Earth B.Distances within the solar system C.Distances between stars in our Galaxy D.Distances between galaxies E.Only the largest distances in the universe A1.5

What lengths are most conveniently measured in units of nanometers (10 −9 m)? A.Distances between the planets B.Distances between cities on Earth C.Dimensions of the human body D.Wavelengths of visible light E.Diameter of an atom Q1.6

What lengths are most conveniently measured in units of nanometers (10 −9 m)? A.Distances between the planets B.Distances between cities on Earth C.Dimensions of the human body D.Wavelengths of visible light E.Diameter of an atom A1.6

What is the approximate diameter of our Galaxy, the Milky Way? A.50 × 10 6 km B.50 astronomical units C.50 light-years D.50 kiloparsecs E.10 million light-years Q1.8

What is the approximate diameter of our Galaxy, the Milky Way? A.50 × 10 6 km B.50 astronomical units C.50 light-years D.50 kiloparsecs E.10 million light-years Q1.8