Giant Hurricane at Saturn's North Pole

Astronomers working with the Cassini spacecraft orbiting Saturn have taken a wonderful close-up picture in visible light of a giant storm at the exact North Pole of Saturn. On the FALSE COLOR image here, you can see the hurricane in red color right in the center. This giant storm is about 1250 miles wide (roughly 20 times the size of the eye of a typical earthly hurricane). Like sodas in the movie theaters, weather on the giant planets like Jupiter and Saturn comes only in super sizes .

(To be fair, this is not the first time we are seeing this storm. But now that summer sunlight is reaching the north pole of Saturn, we can actually see the storm in greater detail in visible light.)

Wind speeds at the edge of the storm are being measured at 330 miles per hour, so hold on to your hat if you intend to go windsurfing there.

Also on the current picture, in pale greenish color, you can see the mysterious hexagon of flowing gas that surrounds Saturn's north pole. This hexagon is about twice the size of planet Earth in diameter! The strange shape of this "jet-stream-like" feature is thought to be the result of complicated waves colliding in the upper atmosphere of the ringed planet.

Another storm is visible in teal color at the lower right, and -- in this false color view -- the rings of Saturn are an intense blue color in the upper right. (You can see the many ringlets that make up the rings. Bear in mind that each ringlet is composed of millions of chunks of ice, all staying in a regular traffic pattern around the equator of Saturn.)

Why is the image presented in false color? I think the Cassini astronomers themselves will be the first to tell you they make such images in part because they are beautiful. But also, in this case, color gives a sense of how high in the atmosphere you are looking. The reddish features are deeper down and the greenish ones float higher up.

Want to see the hurricane move? There is a wonderful short movie with good narration by astronomer Andrew Ingersoll that has been assembled at:http://photojournal.jpl.nasa.gov/archive/PIA14944_640.mov
(You will need the free Quicktime player on your computer to see it and a little time for it to load.)

For readers who are more technically oriented, a nice discussion of a possible explanation for why the jet stream takes the shape of a hexagon can be found in one of Emily Lakdawalla's columns at: http://www.planetary.org/blogs/emily-lakdawalla/2010/2471.html

Weather on a Star

Astronomers using both the Hubble and the Spitzer space telescopes have gotten an indication of weather in the atmosphere of a kind of "failed star" called a brown dwarf. Stars are so far away that, in general, they look like points of light, even in our biggest telescopes -- so this is quite an achievement.

Brown dwarfs (a name coined by Jill Tarter, the scientist on whom Jodie Foster's character in the movie "Contact" was based) are large balls of hot gas that "ain't got what it takes" to be a star. They don't have the mass to continue making energy on their own, so after a brief period of glowing from how compressed they get at birth, they just fade away. (I like to compare them to all the actors that come to Hollywood with high hopes, maybe get a role as an extra in a TV show, but never make it to be real stars.)

This particular brown dwarf (which doesn't have a name, only a long catalog number) was observed not in visible light but in "infra-red" or heat rays, which allow us to see cooler glows. Both the Hubble and the Spitzer can detect and measure infra-red waves, but they "see" them from different depths in the atmosphere of the star. Daniel Apai, one of the astronomers doing the work, compared this to medical imaging, where different kinds of instruments can see different layers of your body.

As shown in the accompanying artist's interpretation (NOT a photograph!), there appear to be huge and deep clouds in the star's atmosphere, some of them as large as planet Earth! They move around in the atmosphere as the star spins every 90 minutes or so. They may somewhat resemble the largest regularly scheduled cloud we know in the solar system, the Great Red Spot of Jupiter (see the beautiful image below, from the Galileo spacecraft which orbited Jupiter.)

But the temperature in a brown dwarf is not cool like the atmosphere of Jupiter, so the clouds are likely to be made of different stuff from clouds on Earth and Jupiter. What might condense into clouds in a region which is 1100-1300 degrees Fahrenheit (600-700 degrees Celsius) in temperature? Mark Marley, another scientist on the team, suggests they are "composed of hot grains of sand, liquid drops of iron, and other exotic compounds."

Isn't it amazing that we can now do weather reports from a star?