School of Physics, UNSW,
Michael Burton at the South Pole
|March 15||An overview of the Universe|
|March 29||Observing or Astronomy with a Computer|
|April 5||Astronomy with a Computer or Observing|
As a result of the huge demand for popular astronomy courses at US universities and colleges there are a number of superb textbooks on astronomy, updated almost annually, which contain fantastic images, associated CDs and other teaching resources. They are generally written at a descriptive level, with mathematical equations placed inside text boxes. Such books will make an excellent reference source and can be used by a wide range of students and educators. You can order these books through the UNSW bookshop. Some suitable books, and web addresses for further information, include:
|Australian Sky and Telescope||http://www.austskyandtel.com.au|
|Sky and Space||http://www.skyandspace.com.au/public/home.ehtml|
This article by Andrew Fraknoi and Sherwood Harrington of the Astronomical Society of the Pacific is a great background piece. Take a trip from Earth to the farthest reaches of the Cosmos! Extracts from it are given below:
THE SOLAR SYSTEM
To begin at home, our Earth is a member of the family of planets and moons known as the solar system. Orbiting our star, the Sun, are nine planets and their more than 40 satellites, each a unique world with its own special characteristics. Assorted cosmic debris - in the form of comets, asteroids, and smaller chunks called meteoroids - also share our system with us.
THE MILKY WAY GALAXY
Beyond the solar system, there is a vast expanse of space, with an occasional grain of dust or elemental atom floating in the dark emptiness. The nearest other star system - Alpha Centauri, best seen from the Earth's southern latitudes - is so far away that Voyager, the fastest spacecraft our species has built, would take about 100,000 years to reach it. Even beams of light, which travel at a phenomenal one billion kilometres an hour, take a little over four years to make the journey between these two systems.
BEYOND THE MILKY WAY
Beyond our own Galaxy lie even larger and emptier regions of what we call "intergalactic space". These areas are so unpopulated that on average you might run across only a single atom in every cubic metre of space. Accompanying our Milky Way are several small "satellite" galaxies, the largest of which are the Magellanic Clouds. They are 150,000 to 200,000 light years away and give astronomers (in the Southern Hemisphere, where the clouds are visible) an excellent opportunity to study another system of stars that has evolved more or less separately from our own.
THE LARGEST OF SCALES
Very recently, astronomers have discovered
that even the grand groups of galaxies are not randomly distributed. Galaxy
groups seem strung out in vast rounded filaments, separated by enormous
voids with relatively few galaxies. This structure, which we are just beginning
to glimpse, may hold important clues to the unimaginably violent processes
that created the universe.
At that time, the free quarks became confined in neutrons and protons. After the universe had grown by another factor of 1,000, protons and neutrons combined to form atomic nuclei, including most of the helium and deuterium present today. All of this occurred within the first minute of the expansion. Conditions were still too hot, however, for atomic nuclei to capture electrons. Neutral atoms appeared in abundance only after the expansion had continued for 300,000 years and the universe was 1,000 times smaller than it is now. The neutral atoms then began to coalesce into gas clouds, which later evolved into stars. By the time the universe had expanded to one fifth its present size, the stars had formed groups recognisable as young galaxies. When the universe was half its present size, nuclear reactions in stars had produced most of the heavy elements from which terrestrial planets were made. Our solar system is relatively young: it formed five billion years ago, when the universe was two-thirds its present size. Over time the formation of stars has consumed the supply of gas in galaxies, and hence the population of stars is waning. Fifteen billion years from now stars like our sun will be relatively rare, making the universe a far less hospitable place for observers like ourselves.
From The Evolution of the Universe by P. James E. Peebles, David N. Schramm, Edwin L. Turner and Richard G. Kron, Scientific American Special Edition, 'The Magnificent Cosmos', March 1998.
Stars form from condensations within huge interstellar gas clouds. These contract due to their own gravitational pull. The star settles down to a long period of stability while the hydrogen at its centre is converted into helium with the release of an enormous amount of energy. This stage is called the main-sequence stage, a reference to the classical Hertzsprung-Russell (HR) diagram, which relates the stellar temperature (or colour) to the luminosity (or 'magnitude'). Most stars lie in a well-defined band in the HR diagram and the only parameter that determines where they lie is the star's mass.
The more massive a star is the quicker it 'burns' up its hydrogen and hence the brighter, bigger and hotter it is. The rapid conversion of hydrogen into helium also means that the hydrogen gets used up far sooner for the massive stars than for the lighter ones. For a star like the Sun the main-sequence stage lasts about 10 billion years whereas a star 10 times as massive will be 10,000 times as bright but will only last for 100 million years. On the other hand, stars a tenth the mass of the Sun have a lifetime far greater than the current age of the Universe!
Stars do not all evolve in the same way. Once again it is the star's mass that determines how they change. Stars similar in mass to the Sun 'burn' hydrogen into helium in their core during the main-sequence phase but eventually there is no hydrogen left there to provide the necessary radiation pressure to balance gravity. The core of the star thus contracts until it is hot enough for helium to be converted into carbon. The hydrogen in a shell continues to 'burn' into helium but the outer layers of the star have to expand. This makes the star appear brighter and cooler and it becomes a 'red giant'.
During the red giant phase a star often loses much of its outer layers, blown away by the radiation coming from below. In the more massive stars the carbon may be 'burnt' to even heavier elements but eventually all energy generation will fizzle out and the star will collapse to what is called a 'white dwarf', if its mass is less than five times that of the Sun.
There are very few stars with masses greater than this but their evolution ends in a spectacular fashion. They go through their evolutionary stages very quickly compared to the Sun. They expand enormously, becoming red 'supergiants'. During this stage many different chemical elements will be produced in the star and the central temperature will approach 100 million Kelvin.
For elements of lower atomic number than iron the addition of more nucleons to the nucleus releases binding energy and so yields a small contribution to the balance inside the star between gravity and radiation. However, to add nucleons to an iron nucleus requires energy and so once the core of the star has been converted to iron no more energy can be extracted. The star's core then has no resistance to the force of gravity and it contracts rapidly. The protons and electrons combine to produce a core composed of neutrons and a vast amount of gravitational energy is released. This energy is sufficient to blow away all the outer parts of the star in a violent explosion and the star becomes a supernova. The light of this explosion shines as bright as an entire galaxy for a few days. During this phase all the elements with atomic weights greater than iron are formed in the expanding shell and are blown out into interstellar space. The central core of neutrons is left as a neutron star, which could be a pulsar, or even collapse to a black hole.
What is remarkable about this process is that the first stars were composed almost entirely of hydrogen and helium, without oxygen, nitrogen, iron, or any of the other elements that are necessary for life. These were all produced inside massive stars and then spread throughout space by such supernovae events. We are made up of material that has been processed at least once, and probably several times, inside stars-we are 'stardust'.
Adapted from Royal Greenwich Observatory Information
Leaflet No. 7: 'What is a Star?' http://www.nmm.ac.uk/server/show/conWebDoc.299
Planetary structure is determined by chemical differentiation whilst the planet is still molten. Dense elements sink to the core of the planet and light elements rise to the surface. After the planet cools and solidifies this internal structure remain frozen.
Our solar system consists of the Sun; the nine planets, sixty-six satellites of the planets, a large number of small bodies (the comets and asteroids), and the interplanetary medium. The inner solar system contains the Sun, Mercury, Venus, Earth and Mars and the outer solar system contains Jupiter, Saturn, Uranus, Neptune and Pluto.
The orbits of the planets are ellipses with
the Sun at one focus, though all except Mercury and Pluto are very nearly
circular. The orbits are all more or less in the same plane (called the
ecliptic), and are in the same sense. All but Venus and Uranus also rotate
in the same sense as the orbit.
The Sun's output is not entirely constant.
Nor is the amount of sunspot activity. There was a period of very low sunspot
activity in the latter half of the 17th century called the Maunder
Minimum. It coincided with an abnormally cold period in northern Europe
sometimes known as the Little Ice Age. Since the formation of the solar
system the Sun's output has increased by about 40%. It is now about 4.5
billion years old and will continue to radiate "peacefully" for another
5 billion years or so (although its luminosity will approximately double
in that time). But eventually it will run out of hydrogen fuel and be forced
into radical changes, which will result in the total destruction of the
Earth (and probably the creation of a planetary nebula).
The Earth's surface is very young. In the relatively short (by astronomical standards) period of 500 million years or so, erosion and tectonic processes destroy and recreate most of the surface and thereby eliminate almost all traces of earlier geologic surface history (such as impact craters). Thus, the very early history of the Earth has mostly been erased. The Earth is about 4.6 billion years old, but the oldest known rocks are about 4 billion years old and rocks older than 3 billion years are rare. The oldest fossils of living organisms are about 3.5 billion years old. There is no record of the critical period when life was first getting started.
Earth has a modest magnetic field produced
by electric currents in the core. The interaction of the solar wind, the
Earth's magnetic field and the Earth's upper atmosphere causes the auroras.
The Earth's magnetic field and its interaction with the solar wind also
produce the Van Allen radiation belts, a pair of doughnut shaped rings
of ionized gas (or plasma) trapped in orbit around the Earth, extending
from 7,500 km to 40,000 km in altitude.
Web Sites of Interest
Department of Astrophysics, University of New South Wales
One of Australia's leading university research
groups in astronomy, with particular strengths in star formation, cosmology,
infrared astronomy, millimetre-wave astronomy and Antarctic astronomy.
School of Physics, University of New South Wales
One of Australia's premier physics groups,
undertaking a wide range of research activities, including condensed matter
physics, biophysics, environmental physics and astrophysics.
Astronomical Society of Australia
The society for professional astronomers in Australia.
Australian Astronomy Portal
Run by the Astronomical Society of Australia, a starting point for learning about astronomy in Australia.
Anglo Australian Observatory
Australia's national optical / infrared observatory.
Includes an excellent source of astronomical images taken by David Malin.
Australia Telescope National Facility
Australia's national radio observatory.
Hubble Space Telescope
Home page for the Hubble Space Telescope,
including access to all the news releases, pictures and extensive educational
NASA (National Aeronautics and Space Administration)
Starting point for a truly vast ranges of resources!
Of particular interest might be the link to Human
(b) Educational Resources
A set of web-based activities designed for classroom use. Includes
AstroCappella is a marriage of astronomy and music, developed by astronomers and professionally recorded by the Chromatics. It includes the following downloadable songs:
Lecture notes for a complete astronomy course, together with images, from Nick Strobel of Bakersfield College. A quite remarkable resource. It contains the following sections:
Astronomy Picture of the Day
Updated daily - a picture of somewhere interesting
in the Universe, with a brief description from a professional astronomer.
Earth and Moon Viewer
See any part of the Earth and Moon, at any time of the day or night, from space! You can view the Earth as a map, as it is seen from the Sun or the Moon, above any particular location, or from a satellite. This is a great piece of software to play with!
Great Debates in Astronomy
Classic debates in astronomy on major issues. A useful reference not only for the subject at hand, but for the history of science, and also for understanding the working of the scientific method. Debates include:
Imagine the Universe
A service from the high-energy astrophysics
group at NASA's Goddard Space Flight Center. The site is dedicated to a
discussion about our Universe; what we know about it, how it is evolving,
and the kinds of objects and phenomena it contains. Just as importantly,
it also includes discussion on how scientists know what they know, what
mysteries remain, and how we might one day find the answers to them.
This is a demonstration page of various physics
and astronomy Java applets from the University of Oregon Physics Department.
They recommend a minimum size of 800x600 to view these resources. The Java
applets which are referenced have been certified to work under Netscape
version 3.0 (and higher) on a Windows 95 platform or in the SUN/Solaris
OS. Java under Netscape on a Mac still exhibits problematical behaviour.
Please be patient when loading the applet pages - if funny behaviour occurs
under Windows95 try flushing Netscape's Cache. Note that hitting the reload
button will often cause the applet to be repainted incorrectly. This behaviour
is beyond their control. In this case it's best to go back to the demo
page, flush the cache, and click on the applet link again. Referenced animations
are all in MPEG format so an MPEG viewer is required to view them.
NASA tracking software J-track allows you to see where any satellite is at any time! It works using java applets, so should work on your machine once you download the database. In particular, you can find out where the Hubble Space Telescope, the Mir space station, the Space Station and the Space Shuttle (during missions) are right now, watch their progress across the surface of the Earth and see when they will next be visible from your location. The 3D version is particularly useful for illustrating orbital mechanics, by observing the distribution of satellites used for specific purposes (eg astronomy-IUE, HST, ROSAT, Chandra; communications, iridium, military-GPS; weather-GOES).
http://liftoff.msfc.nasa.gov/RealTime/JTrack/Spacecraft.html Satellite location over Earth map
|Click on craft||Change orbital data in lower right|
|Ctrl+Click on craft||Toggles on/off ground trace|
|Shift+Click on craft||Goes to web page about craft|
|Click+hold on map||Display first visible at longitude|
http://liftoff.msfc.nasa.gov/RealTime/JTrack/3D/JTrack3D.html 3D distribution of satellites
|Click on satellite||show trace|
|Click in list||show trace|
|Drag||rotate in 3d|
Origins Program (NASA)
The Origins Program is funded by NASA for the scientific study of the long chain of events from the birth of the universe in the Big Bang, through the formation of galaxies, stars and planets, the chemical elements of life to the profusion of life on Earth and possibly elsewhere. This link is the public gateway to the program. There are fact sheets on the following:
Project Astro (Astronomical Society of the Pacific)
Astronomers and educators as partners for learning. Project ASTRO began in 1993 as a pilot project in California, pairing professional and amateur astronomers with the classroom. It combines the expertise of educators and scientists in a long-term collaborative. The partners are trained together in workshops that emphasise hands-on activities with family and community involvement. Some sample classroom activities include:
Project CLEA (Contemporary Laboratory Exercises in Astronomy)
Project CLEA develops laboratory exercises that illustrate modern astronomical techniques using digital data and colour images. They are suitable for high schools. Each CLEA laboratory exercise includes a dedicated computer program, a student manual, and a technical guide for the instructor. The CLEA labs run under Windows on PC's, or on Macintosh computers (but work best on PC's). The exercises can be down-loaded for free. Of particular interest may be the following exercises:
Relativity on the World Wide Web
http://www.math.washington.edu/~hillman/relativity.html (broken link)
A starting point for learning about Relativity, with a comprehensive listing of sites on the subject. Broken down into three main sections:
The Science Education Gateway is a collaborative NASA project, which brings together the expertise of NASA scientists, science museums, and educators to produce Earth and space science curricula for classroom and public use via the World Wide Web. This SEGway web site is designed to help teachers locate and identify the resources they can use best and that fit their local curriculum and National Science Education Standards. Web-projects are divided into three main categories, each containing several web-based tutorials:
Solar System Exploration
Lesson plans from NASA JPL (some need to be down-loaded in PDF format) regarding the Solar System. These may help you find ways to integrate the study of Space Science into the curriculum. The lesson plans are classified by grade level.
Royal Greenwich Observatory Information Leaflets
An excellent source of concise information about a wide variety of astronomical topics. The notes are divided into the following sections, each containing many leaflets within them:
The Astronomy Café
Ask the Astronomer! Sten Odenwald will attempt
to answer your question on astronomy. There is also an archive of questions
that he's answered. There's a good chance he may already have answered
yours! Get your pupils to send him a question!
The Nine Planets
The Nine Planets is an overview of the history,
mythology, and current scientific knowledge of each of the planets and
moons in our solar system. Each page has text and images, some have sounds
and movies, and most provide references to additional related information.
The Universe as Humans see it
http://www.geocities.com/Athens/Atlantis/7119/UniPicture.htm (link broken)
A short synopsis of our changing view of
the Universe, including a brief overview of the ideas of the Greeks (Aristotle
and Ptolemy) and the Renaissance astronomers of Europe (Copernicus, Kepler,
Newton), followed by a more in-depth view of 20th century cosmology,
including the expanding universe, the steady-state universe and the Big
Treasure Trove of Science
Eric Weissen's encyclopedia of science, with particular
volumes for physics and for astronomy. A comprehensive reference source.
A searchable directory of images, visualisations and animations of the Earth. Contains some truly spectacular images of the Home Planet, and helps one to appreciate the fragile beauty of the Earth as well the interconnected ecology of its parts. Created from a range of satellites operating as part of NASA's "Mission to Planet Earth". Divided into several sections:
Welcome to the Planets
This is a collection of many of the best
images from NASA's planetary exploration program.
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