After being in print for twenty years, the Chronological Encyclopedia of Discoveries in Space, covering everything that was learned on every single space mission in the 20th century, has finally gone out of print.
Behind The Black, c/o Robert Zimmerman
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"Useful to space buffs and generalists, comprehensive but readable, Bob Zimmerman's Encyclopedia belongs front and center on everyone's bookshelf." -- Mike Collins, Apollo 11 astronaut
"The Chronological Encylopedia of Discoveries in Space is no passionless compendium of information. Robert Zimmerman's fact-filled reports, which cover virtually every spacecraft or probe to have ventured into the heavens, relate the scientific and technical adventure of space exploration enthusiastically and with authority." -- American Scientist
Astronomers have discovered an additional twenty moons orbiting Saturn, bringing the total known to 82, three more than the 79 moons known to circle Jupiter.
Each of the newly discovered moons is about five kilometers, or three miles, in diameter. Seventeen of them orbit the planet backwards, or in a retrograde direction, meaning their movement is opposite of the planet’s rotation around its axis. The other three moons orbit in the prograde—the same direction as Saturn rotates.
Two of the prograde moons are closer to the planet and take about two years to travel once around Saturn. The more-distant retrograde moons and one of the prograde moons each take more than three years to complete an orbit.
The astronomers have also created a contest allowing the public to help name these new moons.
I will make one prediction: They are going to find many more.
In fact, Saturn’s rings and its numerous moons raise the question of what defines a moon. At present, a moon is defined as any object orbiting a planet, regardless of size. With Saturn’s rings however we have millions of objects orbiting that planet, many very tiny. It seems we have never put a size limit on the definition of a moon, and really need to.