27 Jan 2008
People steeped in public education swim in a swirling sea of buzzwords and phrases. One of those phrases is "scientific literacy." It seems that we Americans are a wee lacking in the area of scientific literacy, knowledge of the basic terms and facts from the land of science. But we do not have to belong to the Club of Illiteracy, oh no! We can rise above that. So, in addition to the usual sky information that we normally see here in this column, maybe this year we can, on occasion, devote some time to laying down a solid foundation in the grand science of astronomy.
Which planets have rings? Well, of course we know that Saturn has rings. For hundreds of years it was the only planet with rings. But recently we have discovered that Saturn's neighbors, the so-called gas giants, also have rings. But they are so faint they weren't discovered until a short time ago.
Uranus was the first planet after Saturn to show us its rings, although we first had to pry the fact from it. In the mid-70's astronomers observed that distant stars would flicker just before and after Uranus passed in front of them. The reason must have been faint rings cutting off the starlight. In 1986, the spacecraft Voyager 2 flew by Uranus and sure enough, there were the nearly imperceptible rings.
It turned out Jupiter had them, too. They were discovered in Voyager 1's flyby in 1979. But don't expect to see them with your backyard telescope. They are essentially made of dust. Only the biggest scopes here on Earth can catch a glimpse of them.
Then, not to be left out, Neptune revealed his rings. Suspected to exist by the same flickering of stars as Uranus' rings showed us, Voyager 2 confirmed them in 1989. It appears that all the big guys - not just Saturn - wear rings.
What is the hottest planet? Most would suspect, intuitively, that the planet closest to the Sun would be the hottest, to wit, tiny Mercury. And Mercury is hot, to be sure - very hot. At its equator it can get to 800 degrees Fahrenheit.
But even as hot as that little guy is, it isn't the winner. Venus is actually hotter - averaging almost 900 degrees Fahrenheit.
But how can a planet more than 50 million kilometers father away from the sun than Mercury be hotter? Because Venus is swaddled in an atmospheric blankie. Poor Mercury has no atmosphere to hold onto the heat, which is why its dark "nighttime" side gets to 300 below.
But Venus has an extremely thick carbon dioxide atmosphere. And carbon dioxide has a notorious ability to hold on to heat; it is the prime suspect in global warming here. This is precisely what is happening on Venus, the warmest planet in the solar system.
How does the sun burn? It was believed since time immemorial that the sun was hot because it was burning stuff, just like fires do here on earth. But if that were what was happening it would have had only tens of thousands of years of stuff to burn, not b-zillions. There had to be another, more efficient way. It took Einstein and his contemporaneous colleagues to figure this one out.
A group of really smart people of his time discovered that the nucleus of an atom stores a wealth of energy, a great wealth, a fortune. It seems that if we rip apart giant nuclei, or smash together very tiny ones, a tremendous amount of energy is liberated.
That is what happens up there in the sun. At its very hot and high-pressure center - the core - tiny little hydrogen nuclei are forged together to form helium. In the process, a prolific amount of energy is released and eventually makes its way to the sun's surface, released now into space.
There is enough hydrogen left at the core for our sun to burn nicely for several billion more years. No need to feed those flames, all is well.
Feel a little more "literate"? Hope so.
Until next time, clear skies!
13 Jan 2008
This Monday marks the anniversary of an historic event in interplanetary space travel. It was a mere three years ago when the Huygens probe landed on Titan, the largest and arguably the most mysterious of Saturn's sixty moons.
The probe was named for Christian Huygens, a Dutchman of extraordinary talents. Neither he nor the namesake probe are well known by the general public, but both played an important role in moving us forward in this discipline of astronomy.
Huygens lived in the 17th century, the real kickstart century for the scientific revolution. He was well educated in... well, a lot of things. He studied law and mathematics at first but eventually wandered into physics and astronomy. He dabbled with and invented and engineered two types of instruments that play huge roles in astronomy: clocks and telescopes. He was a man of many hats. In the truest sense of the term, he was an educated person.
More specific to what we are talking about now, it was in the late 1650's that the overactive Huygens developed a better way to grind lenses and with these constructed some wonderful telescopes. He used his refined telescopes to confirm that Saturn's strange and unexplained rings were not appendages growing out the side of Saturn, nor were they one solid disk of material. They were collections of innumerable "rocks" orbiting about the planet.
Moreover, with his scopes he discovered a moon around Saturn, a behemothic moon later christened Titan.
As time went on and telescopes got better, it became clear that Titan was a special satellite. It was more than 1000 miles larger across than our own moon. It is even larger than Mercury. But what set it apart was not just its extra large girth - it was a moon with an atmosphere.
Before we sent the Cassini-Huygens spacecraft there, not much was known of Titan. Its hazy atmosphere prevented scientists from seeing the surface. What was below? Was there just a rocky surface? Were there lakes and oceans of methane as predicted by temperature and pressure data?
When NASA sent the Cassini spacecraft to Saturn in the 1990's they efficiently decided to kill two birds with one stone. On board the massive Cassini spacecraft they would piggyback a smaller bundle of instruments - a bundle with a parachute.
This probe, named Huygens, would be released from Cassini to fall onto Titan, recording the whole journey along the way.
Well, three years ago Huygens fell to its destination and landed on the mystery moon, dropping through the haze and landing successfully on its surface. What Huygens and the Cassini spacecraft flying above discovered was not exactly what planetary scientists were hoping for.
It had long been thought that Titan might be covered in shallow seas of methane and ethane, hydrocarbons which are gases on our planet, but which on bitter cold Titan would be liquid.
Although Huygens snapped some pictures of what seemed to be liquid-worn terrain, the oceans were not to be found. Such is science; sometimes revealing the truth about something can take some the fun out of it.
Huygens also sent back images from the frozen surface itself, and eerie place surrounded in a kind of "sand" made of water ice.
The little trooper of a spaceprobe breathed its last after just an hour and a half on the surface. But Cassini, the mothership that brought Huygens to Titan, is still making the papers, sending back those incredible images of Saturn and snapping pictures of Saturn's moons as it flies by them. Just last week Cassini flew by Titan again, revisiting Huygens' final resting place.
If you can, take a virtual trip to Titan and Saturn at saturn.jpl.nasa.gov, and see the images both spacecraft have sent back. And if you can, grab a telescope this season and discover for yourself both the ringed giant Saturn and tiny Titan next to it, just as a young Christian Huygens did over 350 years ago.