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Explorations: Stars, Galaxies, and Planets
Thomas Arny, University of Massachusetts



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What Do Professors Think?

Interactives Like No Other

McGraw-Hill is proud to bring you an assortment of outstanding Interactives like no other. These Interactives offer a fresh and dynamic method to teach the astronomy basics. Each Interactive will allow students to manipulate parameters and gain a better understanding of topics such as Blackbody Radiation, The Bohr Model, Retrograde Motion, and the H-R Diagram by watching the effect of these manipulations.

Each Interactive will include an Analysis Tool (interactive model), a Tutorial describing its function, Content describing its principle themes, related Exercises, and Solutions to the exercises. Plus you'll be able to jump between these Exercises and the Analysis Tools with just the click of the mouse.

To run the interactives you will need Microsoft Internet Explorer 5.5 or later or Netscape 6. If you are using MAC OS 9.1 or lower you will need to download the free DMR or JAVA (MJR 2.2.5). If you are running a Windows-based Operating System, try using Internet Explorer 6.0, which can be downloaded free at If you are using Netscape go to to download a free version of 6.2.1.


Blackbody Radiation

In the Blackbody Radiation Interactive, students can manipulate the scroll bar in the upper right corner and see how temperature influences the size and luminosity of stars. In the scroll bar in the bottom portion of the Interactive, users can see how temperature of stars affects its wavelength.

The Bohr Atom

The Bohr Atom Interactive illustrates the concept of emission and absorption spectra as well as Kirchoffs Laws by having students "Build an Atom." Students can construct an atom with energy levels corresponding to different colors of light. By heating a gas of these atoms or shining a continuum light through them students will construct different spectra.

Retrograde Motion

This Interactive illustrates how the different planetary orbital velocities lead to “looping” or retrograde motion in the night sky. The Interactive will show the view at successive times from the Earth as well as from a “birds-eye” perspective in space. Users will be able to manipulate the size of planetary orbits, plus be able to view the retrograde motion from different perspectives, like what the retrograde motion of Earth looks like from Mars.

Solar System Builder

This Interactive will allow students to build their own solar system by placing planets of different masses at different locations and watching these systems evolve. Choose from a Sun and Earth system; our solar system up to Saturn; or 2,000 randomly-selected systems. Watch how a Hot Jupiter interacts with a Mercury-sized planet, or how Saturn interacts with a Mars-sized planet. What will happen? Check out the Interactive and see for yourself.


The Cosmology Interactive allows you to play with the equations for the evolution of the Universe. You will see how the universe might evolve under certain parameters, such as the Hubble Constant and the density parameter Omega. You will see a representation of the Universe's evolution in terms of the expansion or collapse of a uniform distribution of galaxies in a window viewer in the upper right. Notice how the color of the galaxies change from red when they are expanding away from each other (redshifting) to blue (blueshifting) when they collapse back towards each other in Omega > 1 Universes.

H-R Diagram

Manipulate the properties of a star (luminosity and temperature) and see how the star evolves along its evolutionary path at a rate determined by its nuclear burning timescale. As the star evolves, its color and size will change.

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What do professors think?

"I loved it. I have been looking for something similar for some time but haven't found anything quite this good delivered on the Internet." -- Larry Sessions, The Metropolitan State College of Denver

"This is a very useful introduction to Blackbody Radiation. I loved the (Interactive)." - Parviz Ansari, Seton Hall Univ.

"I would definitely incorporate this applet into an introductory astronomy class to help students understand the issues of emission and absorption lines." - Anna Jangren, Wesleyan Univ.

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McGraw-Hill would like to thank Adam Frank, professor at the University of Rochester, Rochester, NY and President of Truth -N- Beauty, as well as the other employees of Truth-N-Beauty, especially, Ted Pawlicki and Carol Latta. McGraw-Hill also would like to thank the reviewers of these Interactives:

Peter Becker, George Mason Univ.

Parviz Ansari, Seton Hall Univ.

Larry Sessions, The Metropolitan State College of Denver

Donald Terndrup, The Ohio State Univ.

Anna Jangren, Wesleyan Univ.

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