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Living in Space, Part 6 — Satellite Exploration: The Outer Planets
By Paul Mailloux/Danvers Herald columnist
Thu Sep 27, 2007, 05:18 PM EDT
Danvers -Beyond Mars are the outer planets. Distances are measured in hundreds of millions to billions of miles. While trips to Mars will be difficult for people, voyages farther out will take many years, both ways. As of now, our ships are too slow and conditions for humans to endure still have to be studied. Rockets will need to reach speeds of hundreds of thousands to millions of miles per hour. Do we have the will and the money? The cost will be astronomical. (Forgive the pun.)
Satellites and space probes have already studied the outer planets at a far reduced cost. In fact, they have been very cost effective.
This year, we not only celebrate 50 years of space exploration, but also 30 years since the launch of the Voyagers. Originally designed to last five years, both probes are still functioning beyond the orbit of Neptune in the Kuiper belt, where Pluto and Eris are. They were launched to fly by Jupiter and Saturn, but Voyager 2 was also sent to Uranus and Neptune. They proceeded to take thousands of photos of the outer planets and their moons, giving us much information concerning each planet’s surface conditions. We could see for the first time that all the outer planets have rings, not just Saturn.
For closer inspection of the Jupiter system, the Galileo probe was launched on Oct. 18, 1989. Galileo arrived at Jupiter on Dec. 7, 1995, entering orbit and dropping its instrumented probe into the giant planet's atmosphere. It made about 2 1/2 dozen orbits of Jupiter, usually flying close to one of its four major moons during each loop around the planet. Galileo discovered strong evidence that Jupiter's moon Europa has a melted saltwater ocean under an ice layer on its surface. The spacecraft also found indications that two other moons, Ganymede and Callisto, have layers of liquid saltwater as well. Other major science results from the mission include details of varied and extensive volcanic processes on the moon Io, measurements of conditions within Jupiter's atmosphere, and discovery of a magnetic field generated by Ganymede. The mission ended on Sept. 21, 2003, when the spacecraft plunged into Jupiter's atmosphere. This planned maneuver prevented the risk of Galileo drifting to an unwanted impact with the moon Europa, which may harbor a subsurface ocean.
To further investigate Saturn, Cassini was launched on Oct. 15, 1995 and entered orbit around Saturn on June 30, 2004. After leaving the Huygens probe on the moon Titan, Cassini is presently studying the rings and other moons of Saturn.
On Jan. 19, 2006, The New Horizons probe was launched to explore Pluto, its moons, and, possibly, other objects in the Kuiper Belt. Arriving in 2015, New Horizons will be the first probe to survey the Pluto area.
As you read the dates of launch and arrival for each mission, you get an idea of time and distance. Even within the Solar System, these worlds are far away.
In the south tonight, even though it is fall, you can still see the Summer Triangle of Vega, Deneb, and Altair. Deneb, which means in Arabic the tail, is to the left of bright Vega in the triangle. Deneb is the tail of Cygnus the Swan, which in our skies looks like a lower case printed t, or a sword, or a cross. In fact, sailors call Cygnus the Northern Cross. The “t” shape can be seen plainly, then think swan. Cygnus was actually, in the Greek myths, a disguise that Zeus, king of the Greek gods, wore so he wouldn’t scare us mortals.
The tip of the Summer Triangle, which points down, is the star Altair in the constellation Aquila the Eagle. Seeing an eagle in our skies is difficult, but bright Altair and the Summer Triangle are easier. Aquila worked for Zeus, delivering messages; but sometimes Aquila brought punishments to those who were naughty. Aquila brought the lightning bolt to those who displeased Zeus. So don’t be naughty, or Zeus will give you the ZAP!!!
Paul W. Mailloux is a retired teacher in charge of the Dunn Planetarium at Danvers High School, where the public is invited to learn more about the galaxies on Friday nights at 7 p.m. Tickets are $2.50. For more information, see the Internet, danvers.mec.edu and follow the Planetarium link.
