Jupiter's Great Dark Spot

Edball writes "For more than a century astronomers thought that the Great Red Spot was the biggest thing on Jupiter. Not anymore. Images from NASA's Cassini spacecraft have revealed something at least as large, The Great Dark Spot." In related solar system news, pajamacore writes "Space.com reports that the first extrasolar planet to have its atmosphere detected is having its gas envelope boiled off by heat and blown away by tidal forces. At present, the planet is 70% the size of Jupiter but its orbit is closer to its parent star than Mercury's is to our own Sun. It should be a treat to eventually see the planet's core and maybe it'll clue us in a bit to gas giant formation."

Comments

Faster better cheaper?

[Tailhook]

Chalk one up for slow, lame(?) and expensive. Cassini is firmly among the old-school "big budget" NASA projects. The probe cost over 3 billion dollars. Read about that here.

Cassini. Remember that name. You're going to hear a lot about Cassini over the next few years. The knowledge brought to us by that probe will make science headlines for the rest of this decade. Not bad for something that cost 15% of the Federal Foodstamp budget in FY2001.

Re:Faster better cheaper?

[EvilTwinSkippy]

You're going to hear a lot about Cassini over the next few years.

That is assuming the folks at Lockhead and Boeing can stick to metric.

Man, if I screw up a client's computer, I don't get hired back. Hell, they will usually go so far as to tell their friends and peers not to use me.

If you are a miliary^H^H^H^H^H^Haerospace contractor and you screw something up you get bonuses and additional contracts.

Re:Faster better cheaper?

[kilonad]

You get additional contracts because who else are you going to hire? The number of large, experienced aerospace companies is tiny and for a while was shrinking every year with all the mergers. Imagine you bought a car from Ford, and you were unhappy with it. Now imagine your only other choices were GM/Chevy (the same company) or Chrysler/Dodge, and you had problems with both of those companies in the past. Who are you going to buy your next car from? You surely won't buy it from some shady guy who made it in his garage down the street. This is why the big aerospace companies keep getting contracts. On the whole, they've done a pretty good job with their contracts (or else they wouldn't be getting them), and if they haven't, they offer such a compelling product that the government is willing to take that risk.

Somewhat unrelated...

[1fitz2many]

Today's APOD has a pic of Jupiter in IR (can't see the pole though).

Losing mass, changing orbit?

[gnovos]

Wouldn't the loss of mass for that planet eventually cause it's orbit to get bigger and bigger? Eventually it would reach some kind of break even point where it's no bigger than the head of small dog, no?

Re:Losing mass, changing orbit?

[doughmein_dot_net]

Yes, but when the planet "loses mass", where does that mass go?

When it gets stripped away, either the solar wind will carry it away from the star, or it will remain in orbit around the star at roughly the same place. From the observations so far, it looks like the mass is staying in roughly the same place - in the orbital path of the planet, which causes it to behave like the "comet's tail" that it essentially is. Therefore, the star, its planet, AND its gas trail will be orbiting one common center of mass, and barring any effects by the solar wind, this should not change appreciably.

Remember that this planet is maybe 7 million miles from its star, by which point it is so close that there would need to be a very major force from a 3rd party in order to remove any of its mass from that vicinity. The star exerts a very strong grip on that planet at that distance.

However, the remainder of the mass of the planet remains gravitationally bound to the star. Remember that the star's gravitational field affects all mass according to the inverse-square law. Even though there will be less of a planet in one roughly spherical ball, and the dwindling planet will exert less total gravitational force on the star, the star will still exert the same gravitational force on the remaining planet and it will stay in orbit pretty much where it is.

Actually, now that I think about it, the drag and tidal effects would probably take away the planet's orbital speed over time, which means that it would lose kinetic energy and drop even closer to its star as it dissipates.

Your argument about "less force acting" is fallacious - it's the same force and it applies to all mass. According to your logic, blowing the dust off a dirty tabletop would mean the table starts to float away from the ground. Sorry, but gravity just doesn't work that way. Remember the classical "thought experiment" where a bowling ball and a feather are both dropped in a vacuum? Remember how they both ended up landing at the same time? Just because the bowling ball is shedding dust doesn't prevent it (or rather, its common center of mass) from hitting the ground at the same time as the feather. Gravity works equally across all mass according to the inverse square law. The fact that the bowling ball has more mass to start merely means that it exerts more force on the ground in return.

A moon hit the planet

[termilitor]

It could be a moon that hit Jupiter a long time ago, or some giant crater under the layers of clouds. I bet that there must be a surface structure under those spots.

Re:A moon hit the planet

[Oddly_Drac]

"Learn some basic astronomy."

You mean planetography.

"Underneath the outer atmosphere is liquid metallic hydrogen. What does that mean?"

You're putting forward theory as fact and missing a several thousand kilometre thick wodge of increasingly dense gas that can stay partially stable for months or centuries in the case of the Great Red Spot.

OD

Re:I don't know how to take this...

[Wyatt Earp]

There is enough food for everyone to eat.

There isn't enough infrastructure to move it around efficently.

And in some cases the leadership of a nation will do things that cause starvation - Robert Mugabe

Or sometimes it's a mix of the two, like in the DPRK, where food shipments wait on the docks until the Army can rebag the food so the people don't know it's from the US, RoK or Japan.