Astronomy Workshop Tools
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Astronomy Classroom
The closest star to the Earth is, of course, the Sun. But the next closest star is some 25 trillion miles away. How does scientific notation allow us to write down such immense quantities? Find out in the astronomy classroom.
| Astronomical Distances | Astronomical Sizes | Scientific Notation | Working With Equations | Universe Timeline |

Explore the Possibilities
Ever wonder what would happen if a rogue star entered our solar system? Or if an asteroid in orbit about the sun found a blue planet smack in its path? You can find out the answers to these questions and more as you explore the possibilities!
| Rogue Star | Solar System Collisions | Gravity Comparisons | Build Your Own Solar System | Earth's Season's |

Solar System Calculators
What's the length of day on Mars? Which planet has a density less than water? Is our moon the largest in the solar system? Compare the planets and moons by using these solar system calculators.
| Planetary Calculator | Satellite Calculators |
Solar System Viewers
Did you know that all the planets orbit the sun in the same direction? This picture lends support to the idea that the planets formed out of the same spinning disk around the Sun. Do moons also orbit their parent planets in the same direction? Find out by watching these worlds in motion!
| Solar Systems | Life of the Sun | Star Race |

Working With Orbits
The orbit of our Earth around the Sun is very nearly a circle, allowing Earth's tilt to control our seasons. Planets with elliptical orbits have more complicated seasons. What do the orbits of other solar system bodies look like? Find out in working with orbits.
| Orbital Elements | Solar System Orbits |

Orbital Integrators
Newton's Universal Law of Gravity allows us to predict the motions of all solar system bodies. Explore some of the consequences of this Law of Nature by applying it in different circumstances.
| Central Force Integrator | Three-Body Integrator | Planetary Satellite Integrator | Extrasolar Planetary Satellite Integrator |

Astronomy Classroom

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Astronomical Distances:

    This program is meant to help you get a feel for astronomical distances, which are large and difficult to comprehend. Imagine that you are in a spaceship. Choose your speed and see how long it takes to get to some of the most interesting places in the Universe! Let's Go!

Astronomical Sizes: 

    In order to understand the size of objects in the Universe it is helpful to scale them to a smaller size. For instance a pulsar is roughly the size of Washington D.C. But how big would a pulsar be if the Earth was the size of a baseball? Click here, Astronomical Sizes, to create scaled models of the Universe for yourself.

Scientific Notation:

    Scientific notation allows you to represent very large or very small numbers in a compact form. Your calculator converts to scientific notation when you multiply two very large numbers together. Practice working with Scientific Notation and quiz yourself!

Working With Equations:

    Many important laws of science can be written as algebraic equations with different variables representing different physical quantities. How do we decipher what an equation is telling us? One way is to determine how one side of the equation is affected when a variable is changed. Click here to practice Working With Equations.

Universe Timeline:

    When would the Earth have formed if the entire history of the Universe was squeezed into the length of a year? A week? A day? Just how long is two thousand years when compared with the history of life on Earth? Using the Universe Timeline you can explore the history of the cosmos in timescales you can actually have a feel for.


Explore the Possibilities
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Rogue Star:

    Have you ever wondered what would happen if another star came buzzing through the Solar System? Well, now you can find out! Pick a date, like your birthday, and send a star through the Solar System and see what kind of havoc you can create! Let's Rock and Roll! DEPRECATED

Solar System Collisions:

    What happens when a comet or an asteroid hits a planet? How big a crater does it make? Does Earth's atmosphere protect us? Send different objects hurtling toward your favorite planet and find out! Let 'Er Rip!

Gravity Comparisons:

    Your weight is affected by two things, your mass and the planet's surface gravity. If you were to visit the Moon, you would weigh six times less, without losing any mass. This is because the gravity at the surface of the Moon is smaller than on Earth. Want to try more? Click here to do some Gravity Comparisons.

Build Your Own Solar System:

    What makes a planetary system unique? The number of planets, their sizes, their orbits, and the properties of the central star are all important. This program allows you to customize your own Solar System and to observe its orbital dynamics. Find out whether life could exist in your creation. Build New Worlds!

Earth's Seasons:

    The variation of sunlight over the year determines what kind of plants and animals can live at different places on Earth. How many hours of sunlight does your home get at different times of the year? How about Alaska or the North Pole? What if the tilt of Earth were different? See what happens when you play with the Earth's Seasons! DEPRECATED

Solar System Calculators

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Planetary Calculator:

    Compare the sizes, spin periods, surface gravity, and other data for the eight planets of our Solar System plus dwarf planet Pluto. Convert to your favorite units and define your own formulae. Calculations are easy with the
    Planetary Calculator.

Satellite Calculators:

    Compare physical and orbital data for all satellites of the planets. Which moon is largest? Which has the strongest surface gravity? These calculators operate on multiple moons simultaneously making comparisons easy. Explore the Solar System's 70 largest and closest moons with the Regular Satellite Calculator and more than 100 more distant moons with the Irregular Satellite Calculator.

Solar System Viewers

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Solar Systems Visualizer

    The Solar System consists of rocky terrestrial planets, gaseous outer planets, asteroids, comets, and Kuiper Belt objects. All of these objects follow their own independent orbits around the Sun. Hundreds of satellites circle the planets, and hundreds of planets have been found around others stars. Watch the orbits of all of these objects with the Solar Systems Visualizer.

The Life of the Sun

    Since its birth 4.5 billion years ago, the Sun has grown slowly larger and brighter with each four Hydrogen nuclei that it fuses into Helium. Billions of years from now, it will swell into a red giant and engulf the inner planets. Using up the last of its nuclear fuel, the Sun will finally collapse into an Earth-sized white dwarf. Animate the Sun!

Historical Viewers

    Planetary Orbits: Our Solar System! Satellite Orbits: Show me the moons!
    Planetary Orbits: Other Solar Systems DEPRECATED

Star Race

    Which stars burn though their fuel fastest? Enter stars of different masses into the Pan-Galactic Star Race and find out!

Working With Orbits

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Orbital Elements

    An asteroid or comet moving subject to the Sun's gravity has an orbit shaped like a circle, an ellipse, a parabola, or a hyperbola. What type of orbit depends on the value of the orbital elements, quantities that determine the size, shape, and orientation of the orbit in space. Use these two orbital viewers to see how the appearance of an orbit depends on the values of the orbital elements.

    Orbits in a plane: Orbital Elements (2D)
    More General Orbits: Orbital Elements (3D)

The Solar System

    Watch several planets in our Solar System simultaneously orbit the Sun. Change the orbital parameters of an additional object - an asteroid or a comet - to see what types of orbits are possible. In the real Solar System, objects on crossing orbits will eventually collide (Pluto and Neptune are an exception; if you watch them move you'll notice that they never come close to one another).
    Inner Solar System (with Asteroid)
    Outer Solar System (with Comet)

Changing the Elements

    An orbit can be represented by a position and velocity vector, or by a set of six orbital elements that describe the size, shape, and orientation of the orbit in space. Use this tool to convert between the two.

    Changing the Elements

Orbital Integrators
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Central Force Integrator

    A central force, F(r), is one that is directed radially toward or away from a fixed point. Orbits in time-independent central force fields conserve both orbital angular momentum and energy. Explore the types of orbits that result from these strange force laws!

    Newtonian Gravity F(r) = -GM/r2
    2D Harmonic Oscillator F(r) = -r
    General Central Force Integrator

Three-Body Integrator

    How does a small object orbit in the combined gravity field of two large objects?

    Watch an asteroid in the Sun- Jupiter system (2D orbits and 3D orbits)!
    Investigate planetary orbits around a Binary Star (2D orbits and 3D orbits)!
    Find Solar System stability zones with the
    Lagrange Point Explorer

Satellite Integrator

    How far away can our moon be before the sun's gravity pulls it away into heliocentric orbit? Why don't we find any satellites in the solar system that orbit over their planets' polar regions? Answer these questions and more by investigating satellite orbits around different planets!

    What if the Moon's orbit were ...

    Twice as large?
    Tilted by 90 degrees?

Extrasolar Planetary Satellite Integrator

    Most of the planets discovered outside our solar system as of 2003 are gas giants not unlike our very own Jupiter and Saturn. These planets have no solid surfaces, as they're made almost entirely of gas. However, could these planets have moons orbiting around them? Would such orbits be stable? Answer these and other questions as you investigate satellite orbits around extrasolar planets!

    Transiting Planet HD209458b

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