The Solar System
The Solar System
Goals: Seeing the size and scale of the Solar System and the extent of the farthest spacecraft; understand light-travel time and distance.
Before starting, turn on: stars, mwVis
You will be using: solsys, probes, 1lmo, constel, 1ly, clip command
Turn on the Solar System orbits. Because the orbits are so close to the Sun in the parsec-scaled Milky Way Atlas, you need to perform some maintenance in Partiview to view them.
Adjust the Clipping Planes to See Objects Right Next to You
In computer graphics, programs regulate what the computer must draw and keep track of to improve their performance. If you think of your view as a pyramid in which you are looking through the apex, the sides of the pyramid are defined by the field of view. Set the field of view to small values and less information is drawn, your pyramid is narrow. What about the sides parallel to your screen? These boundaries are set by the near and far clipping planes.
When you start the Milky Way Atlas, the near clipping plane, which sets where the apex of the pyramid is located, is set to 0.1 parsec (0.326 light-years). Objects closer than this will not be drawn. Similarly, the far clipping plane, the base of the pyramid, is that distance beyond which nothing is drawn. In the Milky Way Atlas this value is set to 1 million parsecs (3.26 million light-years). To see these current values, type clip in the Partiview Command Line and it will return # clip 0.1 1e+06.
Let's alter the planes to bring those objects right in front of us into view. Type the command
clip 0.0001 1e5setting the near and far clipping planes to 0.0001 and 100,000 parsecs, respectively. (Note that some systems, particularly Macintosh, cannot handle a near clipping plane of less than 1, so this may not work on your computer. You may need to adjust the clipping plane values to remove unwanted flashing.)
Now you should see the orbits of the planets drawn on the sky.
Viewing the Solar System in the Milky Way Atlas
Pull back slowly (hold the right mouse button down and move the mouse to the left) until the Sun pops into view, then stop (click the mouse). Turn off the glare of the Sun by selecting stars as the active group and pressing the Polygon Toggle Button.
In this group you will find the orbits of the rocky, inner planets huddled around the Sun: Mercury, Venus, Earth in blue, and Mars in red. Beyond these are the gaseous planets Jupiter, Saturn, Uranus in green, and Neptune in blue. Finally, we have Pluto, the small icy body that's smaller than our Moon and whose orbit is inclined to the plane of the Solar System by 17o.
The Farthest Man-Made Objects
Turn on the space probes. These four trajectories show the paths of the Pioneer and Voyager spacecraft from their launch date to the year 2050. Voyager 1 was launched in 1977 and explored Jupiter and Saturn before it was tossed out of the Solar System as if with a slingshot by Saturn's gravity. Voyager 2 explored Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989) before leaving the Solar System.
Labels on the trajectories mark the years as well as the light-travel time. You may be familiar with the light-year, the distance light travels in one year. Similarly, a light-day is the distance light travels in one day. At 300,000 km/sec (186,000 miles/sec) and with 86,400 seconds in one day, that distance equals 26 billion kilometers (16 billion miles). A table of the relationship between light-travel time and distance can be found in “Light-Travel Time and Distance.”
Let's get some perspective. Turn on the 1-light-month grid (1lmo) and pull back from the Solar System a bit. This group consists of green rings and faint blue lines. These form a grid that is aligned with the Galactic plane and is a measure of light-travel time. The first ring out from the Solar System is 1 light-day from the Sun. The Voyager and Pioneer space probes are the farthest objects we have sent into space. Launched nearly 30 years ago, they will reach this 1-light-day mark in another 40 years.
While you're here, you can see the inclination of the Solar System to the grid and, therefore, to the Galactic plane. You saw this before with the coordinate grids; now you can see the Solar System orientation in relation to that plane.
Continuing to fly away from the Sun, you now see the entire light-month grid split into 4 light-weeks. Restore the stellar polygons so the stars' luminosity is represented accurately. Also turn on the constellations and return to more reasonable clipping planes with the command
clip 0.1 1e6
Turn on the 1-light-year grid (1ly) and now you see the light-months stretch across space. You also begin to see the constellation lines distort, revealing those stars that are nearby. You will explore these nearby stars in the next tutorial.
© 2002-2005 American Museum of Natural History
Last Modified: 2007-12-19 by Brian Abbott