Astronomy Picture of the Day 11-14-03

Explanation: Every day is a cloudy day on Jupiter, the Solar System's reigning gas giant. And swirling cloud tops are all you see in this stunningly detailed true color image, a portion of a large digital mosaic portrait of Jupiter recorded from the Cassini spacecraft during its Jovian flyby in December 2000. The smallest features visible are about 60 kilometers across. Jupiter's composition is dominated by hydrogen and the clouds contain hydrogen compounds like ammonia, hydrogen sulfide, and even water. A truly giant planet, Jupiter's diameter is over 11 times the diameter of Earth and the smallest storms visible in the Cassini Jupiter portrait are similar in size to large terrestrial hurricanes. Now traveling beyond Jupiter, the Cassini spacecraft is scheduled to reach the Saturnian system in July of 2004.

The active regions on the Sun are rotating back into view, and appear to still be capable of producing strong flares and CMEs.
That's sunspot group 484 back for another round.

Below is the Sun at a wavelength of 284 Angstroms (extreme UV light). Looks like that area is still busy!

Compare that with the following image at 171 Angstroms (extreme UV):

Saturn Covers a Star
By Roger W. Sinnott

The 8.4-magnitude star follows this apparent track behind Saturn, as seen from anywhere on Earth, but the time it will reach a particular ring or gap could vary up to 10 minutes or so, depending on your location. (Remember to subtract 5 hours from UT for EST, 8 hours for PST.) Sky & Telescope illustration by Steven Simpson.

Late Friday night, November 14–15, Saturn and its ring system glide right in front of an 8.4-magnitude star in Gemini. Observers with large enough telescopes — ideally 8-inch or larger — can watch as the star leisurely fades in and out of view behind the various rings, gaps, and the open space between the rings and the ball of Saturn itself.

Skywatchers with the best view of this rare event are those living in western North America. They’ll be able to see the star enter the ring system Friday evening and finally leave it 7 hours later.

For eastern North America and most of South America, Saturn is higher in the sky during the initial stages; the star should reach the Cassini Division in the rings shortly before 1 a.m. Eastern Standard Time. These viewers can see the star coast right up to the planet’s limb around 2 a.m. EST, but dawn will prevent them from seeing it come out the other side.

European observers are limited to watching the star just enter the ring system as morning twilight interferes.

Sky & Telescope contributing editor Thomas A. Dobbins notes that two British amateurs witnessed a similar occultation of a 7th-magnitude star in 1917. Using 5-inch and 9-inch telescopes, they could dimly see the star behind the outer ring (ring A), making that ring seem translucent. But they failed to see the star when it was behind the brighter B ring.

Titan Too!

Just one day before it encounters Saturn this week, the same 8.4-magnitude star will be occulted by Titan, Saturn’s largest moon. Bruno Sicardy (Paris Observatory) describes this event on his Web site and points out that it may produce a “central flash” around 0:13 Universal Time on November 14th. Most likely to be seen from parts of South Africa, and lasting up to 10 seconds, the flash is a visible focusing of the star’s light by Titan’s atmosphere.

An Occultation Primer
An Observing Guide to Saturn

Although this is not my photo, it is a good representation of what I was able to view from my home in Minnesota on 28 October 2003. I did take some images, but my CCD camera does not have a long exposure option and they all turned out black.

Watching an aurora directly over your head and seeing the lines radiate out in all 360 degrees, is difficult to express. Not only did it invoke a feeling of absolute wonder, I have to admit, a certain amount of fear also.

This is the best image that represents what it looked like that evening.

Perhaps in the next two weeks, we may see such a wonderful sight once again.

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