365DaysDate:  January 27, 2009


Title:  Jupiter’s Great Red Spot

Podcaster:  Kevin Graham

Description: The Great Red Spot has been circling the planet Jupiter for over 300 years. What is it? And what makes it so great?

Bio:  I have a passion for Astronomy, Space travel and all things Star Trek, that started on a July night in 1969, when, as an 11 year old boy I watched the 1st Apollo moon landing.  I have been happily married to my wife Kathy for 26 years. I have a daughter Jessica, who never fails to remind me of how much of a geek I am. And a son Adam who never fails to remind me of how much of the 11 year old boy is still inside me.

Today’s Sponsor:  Matt Young of Virginia Peninsula Astronomy/Stargazer to fellow stargazers


Hi, My name is Kevin Graham and welcome to another of the 365 Days of astronomy Podcasts. I’m not a scientist, nor do I write for a science magazine, or have a science blog. But what I do have is a love for astronomy and a serious man crush on both Phil Plait and George Hrab.

But who doesn’t? I hope you enjoy my small contribution to this amazing endeavor.

For 10’s of thousands of years mankind has gazed up at the night sky with constant wonder at the majesty and mystery of the Universe.

When Galileo turned his telescope to the night sky in the early 17th century things only got more majestic and more mysterious.

While gazing at the planet Jupiter in 1610, Galileo discovered 4 of its moons(Io, Europa, Callisto, and Ganymede) and began the 1st true astronomical studies of our solar systems largest planet.

In 1665 Italian Astronomer Giovanni Domenico Cassini (yes the very same guy whose namesake is currently orbiting the planet Saturn) Cassini became one of the 1st astronomers to observe and document one of our Solar systems biggest (literally biggest) mysteries. The Great Red Spot of Jupiter.

Just what is this Red Spot and what makes it so great?

Jupiter, as we all know,is Named after the Roman king of the gods and is the largest planet in our Solar system. It is a gas giant   2.5 x more massive than all the other planets combined, with a diameter 11x larger than the Earth. A true King of planets. It has 63 moons, so many moons that we haven’t even gotten around to naming all of them. So Jupiter is big, and it does things big, it makes Great things.

Of course everybody has seen the time lapse movie taken during the Voyager flyby in 1979.

And you can’t help but notice the GRS, and the fact that Jupiter rotates pretty fast. Jupiter doesn’t do anything small. The rotational period of this planet is approx. 10 hours, Faster than any other planet, Imagine a planet that big, spinning that fast.   A definite hare to our tortoise of 24 hrs.

And while watching the movie you’ll also notice the planet divided into numerous atmospheric bands, caused by the fact that it has 12 jet streams, compared to Earths 2. Yes Jupiter doesn’t do anything small.

The Great Red Spot is an anticyclonic vortex(or a hurricane)that is jammed between 2 of these jet streams, one moving east to west and the other west to east.  that has been continuously observed for almost 350 years. It’s anticyclonic because its located in Jupiter’s southern hemisphere and is rotating in a counter clockwise motion. A cyclone is just the opposite, with cyclones rotating in a clock wise motion.

It takes about 6 Earth days, or 14 Jovian days to complete 1 rotational cycle. The reason it takes so long is because this storm is huge. It’s approx. 24-40,000 KM from west to east, and 12-14,000 km from north to south. That’s 15-25,000 miles wide and 7.5 to 9,000 miles high to those of us who are metrically impaired. This eye shaped storm is large enough to comfortably fit the Earth and Mars inside of it with room enough for dessert. That is one Great Spot.

The winds generated by this storm around its edge approach 265 MPH. Compare that with Earth’s largest Category 5 Hurricanes that reach a measly 160 MPH and have a life span of a couple of weeks. While its spinning around It actually is also slowly putting laps around Jupiter making approximately 10 round trips over the last 200 years. 20 years to put in 1 lap. Did I mention Jupiter was big?

Imagine the devastation to life and property if a Category 5 Hurricane had been circling the Earth for the last 350 years.

How has the GRS been able to hang around so long and maintain its, size?

Scientists don’t really know. They have put together some computer models based on what is known about the conditions on Jupiter that allows for the GRS. But when they plug in the numbers to recreate it it becomes very unstable and just rips itself apart.

What we do know is that it is colder than the surrounding atmosphere which indicates that it is higher than the surrounding clouds, maybe even 8km, or 5 miles higher than the surrounding atmosphere.

It does change color fluctuating from a bright brick red to a pale salmon color.

The color is probably do to the material that the storm is drawing up from the lower atmosphere, possible organic molecules, red phosphorous, or some kind of sulphur compound. Exposing these particles to ultraviolet radiation from the sun giving it its lovely red color.

And of course since Jupiter never does anything small there is also another red spot on the planet. Lovingly called Red Spot jr. It was 1st seen in 2000 as a white anticyclonic storm and as it got larger it to started to turn red and now has the same lustrous red hue as it’s big brother after reaching its current earth like size in 2006

The 2 brother storms periodically pass by each other, and there has been some speculation that Great red would swallow up Red jr. But so far red jr. has held its own and as GRS has gotten smaller over the last 100 years, There is some conjecture that Junior may eventually meet and surpass his elder sibling in size.

Just recently in May of 2008 3 small storms converged forming the adorably named Baby red spot. But The GRS and RSJ would have nothing to do with this interloper and promptly gobbled him up in July of 2008.

Jupiter may be big but the Red spot club is entirely exclusive.

Neptune the 8th planet in our solar system was found to have a similar atmospheric storm in its southern hemisphere when voyager 2 flew by in 1989. Unimaginatively called the Great Dark spot. It was approx. 13,000km by 6,600 km in size. Big but not Jupiter big. Unfortunately when we pointed Hubble at Neptune in 1994 The GDS was no longer there and had been replaced by a different GDS now formed in the Northern Hemisphere. And once again Jupiter does it bigger and Jupiter does it better.

There have been some noticeable climactic changes occurring on Jupiter recently where the surrounding atmosphere in the southern Hemisphere has actually calmed down. Leaving the GRS RSJ isolated from many of the other smaller storms that periodically pop up in the turbulent atmosphere of Jupiter. So the majesty, mystery and beauty the GRS and his little brother Red Spot Jr. may be around for a long long time.

I thought I’d end this podcast with a few words from Walt Whitman.

Walt Whitman loved baseball, he loved himself, and if he were alive today he too would have a man crush on Phil Plait and George Hrab. But he also loved the beauty of the Universe, and I hope my reading of his words can do him justice.

Walt Whitman wrote in SONG OF MYSELF

This day before dawn I ascended a hill, and look’d at the crowded
And I said to my Spirit, When we become the enfolders of those
orbs, and the pleasure and knowledge of everything in them,
shall we be fill’d and satisfied then?
And my Spirit said, No, we but level that lift to pass and continue
. . . . . . . . . . . .
And I say to any man or woman, Let your soul stand cool and
composed before a million universes.

Thank You for listening and Have a great Astronomical year.

365 Days of Astronomy

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