rings
esiegel | June 30, 2012"Don't go around saying the world owes you a living. The world owes you nothing. It was here first." -Mark Twain
So, you've been around a while, seen all sorts of things, and learned an awful lot about the world, solar system and Universe that we live in. But how well do you know it, really?
Image credit: NASA / Lunar and Planetary Laboratory.
To scale and in order, these are the eight planets you know so well. There are the four rocky worlds of our inner solar system: Mercury, Venus, Earth, and Mars, and the four gas giants that dominate the outer solar system: Jupiter, Saturn, Uranus, and…
krandall | February 10, 2011By Dr. Ignacio Mosqueira, an astrophysicist at the Carl Sagan Center for the Study of Life in the Universe, SETI Institute, and Gail Jacobs
Ignacio Mosqueira works with Paul Estrada to piece together the way in which giant planets - such as Jupiter and Saturn -- and their moons and rings formed. Ignacio notes that making moons is similar to forming planets. Understanding moons may have something to tell us about the possible habitats for life, since large moons could, in principle, have both the liquid water and atmosphere necessary for the kind of diverse biology we see on planet Earth.…
krandall | July 23, 2010By Dr. Mark R. Showalter
Planetary Astronomer at the Carl Sagan Center for the Study of Life in the Universe, SETI Institute
In 1609, Galileo introduced to the world his new invention, the astronomical telescope. It opened up new opportunities to explore a territory that all prior generations had regarded as familiar--the night sky. In short order, he was making major discoveries. But the sky is very big and Galileo's telescope was very small. He had to choose his targets carefully.
In that context, Saturn was nothing special, the least of the known planets, just a bright point in a black…
sb admin | June 22, 2010by Nathalie A. Cabrol
I realize how immodest the title of this first blog may sound and it is certainly not my intention to convince anybody that I will answer this question in the limited space allowed here or even in a lifetime. My hope is, instead, to stir thoughts and invite an exchange of diverse perspectives to make this a thread that we can all pull from time to time. It is an immense subject debated in an abundant literature, but discussing it is certainly not the exclusive privilege of those called explorers. All beings, from the greatest minds to the simplest forms of life on this…
esiegel | May 6, 2008(This is adapted from my public lecture, Afraid of the Dark: How We Know What We Can't See.)
Let's go back over 200 years ago, to 1781. William Herschel (left) discovered the planet Uranus, noticing that an object, as bright as a star, was actually moving relative to the other stars. The other five inner planets (besides Earth) were known for over 2000 years before that. But it was thought for a long time that Saturn was the farthest one.
But it clearly isn't; as you can see with modern telescopes, Uranus is a super-interesting planet, rotating on its side, surrounded by rings and moons.…