Astronomy question (prompted from playing Mass Effect)

[Dr.Demento]

Why do gas giant planets have shorter days than terrestrial planets despite being much larger? That doesn't make much sense to me.

 

[Viperidae]

Gas is mobile, yo.

 

[Dr.Demento]

Yeah, but if you use that logic, then which way is Jupiter even rotating because every single cloud band runs opposite to each other? Google for some footage and you'll see what I mean.

 

[Acepilotf14]

It doesn't rotate in any one direction.

 

[Viperidae]

Um, what?

Surface atmosphere != the whole planet. The whole thing does rotate, quite quickly.

http://www1.nasa.gov/worldbook/jupiter_worldbook.html

 

[Dr.Demento]

Um, what?

Surface atmosphere != the whole planet. The whole thing does rotate, quite quickly.

http://www1.nasa.gov/worldbook/jupiter_worldbook.html

BTW, are there any video's deep within the atmosphere of Jupiter? I've always was interested what it looked like within a gas giant, but any video I've ever seen was orbital shots of Jupiter's cloud bands or Great Red Spot, or Saturn's rings.

I've got Mass Effect2 and am currently still trying to finish the first game so I can transfer data over, but I've heard you can actually visit a colony/helium-3 mining facility that's within the atmosphere of a gas giant. Maybe that could give me an idea what it's like if that's true.

 

[Warped]

a lot of things hit Jupiter, so it spins even faster. durr

 

[Emporius]

BTW, are there any video's deep within the atmosphere of Jupiter? I've always was interested what it looked like within a gas giant, but any video I've ever seen was orbital shots of Jupiter's cloud bands or Great Red Spot, or Saturn's rings.

Cloudy.

 

[Dr.Demento]

Cloudy.

Cloudy as in you wouldn't even be able to see your hand in front of your face cloudy, or are there separate layers of empty space in between layers of clouds? Are the upper layers of clouds too thick for light from the sun to pass though? Probably would be scary as hell for an astronaut granted if they could even survive the violent storms and unbearable pressure for even a few seconds.

 

[Viperidae]

Unless I'm mistaken, once you send something into Jupiter's atmosphere, it ain't coming back.

 

[Dr.Demento]

Unless I'm mistaken, once you send something into Jupiter's atmosphere, it ain't coming back.

According to Mass Effect, that would be true due to the deep gravity well. The more mass, the more gravity if I'm not mistaken.

So then just toss a junker probe down thar and take some picture's/videos before it goes out of range!

 

[pvtbones]

why, why?! are you using a video game as a point of reference, please go read a text book or something then come back and ask.

 

[Dr.Demento]

why, why?! are you using a video game as a point of reference, please go read a text book or something then come back and ask.

I have tonnes of text-book references, but every single one doesn't have any surface atmosphere videos! and they all mostly only talk about planetary data that I've already seen elsewhere. (and it wasn't from just Mass Effect) For example one reference I have is like 10 inches thick and it's actually a copy of the Library of Congress' the, 'Handbook of Basic Knowledge revised edition' Covers everything from basic math to calculus, to English and literature, astronomy and geography, and even politics, but the copyright is 1989 so it's a fairly outdated book.



Can someone guide me to a good astronomy reference on the web besides wikipedia?

 

[15357]

I think the last thing we sent into the atmosphere of a gas giant screamed oh god why at us for 2 whole seconds and went silent, presumably destroyed by all the gas and radiation and atmospheric pressure.


Hence, no videos.

 

[Raziaar]

Cloudy.

With zero chance of meatballs.

Of this, I am entirely certain.





But yes... very cloudy. Not all that hard to visualize. It's not like you're going to get down there and things are suddenly going to clear up.

 

[Dr.Demento]

I think the last thing we sent into the atmosphere of a gas giant screamed oh god why at us for 2 whole seconds and went silent, presumably destroyed by all the gas and radiation and atmospheric pressure.


Hence, no videos.

Drat! :hmph:

Oh well, it wouldn't be the only time our feeble space programmes failed miserably as it seems like I remember reading about our attempts (US and Russia) to map Venus once and even their most advanced probes at the time could only last a maximum of 9 seconds before succumbing to the heat and pressure.

The expedition/arms race to design the best probe lasted until the early 80's IIRC. I found this info on wikipedia once, but I'm not so sure of the quality of the articles on that site these days.

 

[15357]

Drat! :hmph:

Oh well, it wouldn't be the only time our feeble space programmes failed miserably as it seems like I remember reading about our attempts (US and Russia) to map Venus once and even their most advanced probes at the time could only last a maximum of 9 seconds before succumbing to the heat and pressure. The expedition/arms race to design the best probe lasted until the early 80's IIRC. I found this info on wikipedia once, but I'm not so sure of the quality of the articles on that site these days.

IIRC, Venus's surface is made up of acidic jello and volcanoes, and the air is filled with sulfuric acid droplets, so 9 seconds for an 80s probe is kinda outstanding.

But anyway, I've always wondered what it would be like inside a gas giant. I've heard that the atmosphere gets so thick that Hydrogen is turned into a solid.

 

[Dr.Demento]

IIRC, Venus's surface is made up of acidic jello and volcanoes, and the air is filled with sulfuric acid droplets, so 9 seconds for an 80s probe is kinda outstanding.

Ya, but it seems like we haven't gotten very far since then. I only have so long to live if I'm going to see the day when we can actually map these violent worlds in hi-def, much less even have a competent (and affordable) means of space travel.

But anyway, I've always wondered what it would be like inside a gas giant. I've heard that the atmosphere gets so thick that Hydrogen is turned into a solid.

Not that hard to imagine really when you think about the melting point of mercury which is room temperature, or even absolute zero which is the freezing point for oxygen. (turns to a solid)

Holy shit dude, now THAT'S cold! :O

 

[VirusType2]

The thing I find most interesting about Jupiter is the weather. 'The Great Red Spot' on Jupiter is a storm that has raged for well over a hundred years and is absolutely massive

The Great Red Spot (GRS) is a persistent anticyclonic storm, 22° south of Jupiter's equator, which has lasted for at least 180 years and possibly as long as 345 years or more.

The spot is large enough to contain two or three planets the size of Earth.

http://en.wikipedia.org/wiki/Atmosphere_of_Jupiter

 

[Dr.Demento]

The thing I find most interesting about Jupiter is the weather. 'The Great Red Spot' on Jupiter is a storm that has raged for well over a hundred years and is absolutely massive


http://en.wikipedia.org/wiki/Atmosphere_of_Jupiter

Indeed.

If Earth were to be consumed by a storm of equal proportions, we'd be screwed for sure.

The sheer size, and power of celestial bodies like these, gas giants, stars, black holes, etc. is so phenomenal it's scary. Almost makes one feel insignificant.

 

[VirusType2]

Almost? I feel insignificant here on Earth. Also I think the lightning bolts in that storm could destroy Earth or something. They are ****ing sick massive.

I don't know, but it sounds awesome to watch from a safe distance. I would also like to see video of strange and interesting worlds.

 

[The_Freeman]

Yeah, but if you use that logic, then which way is Jupiter even rotating because every single cloud band runs opposite to each other? Google for some footage and you'll see what I mean.

You mean this?

 

[KiplingsCat]

Every planet in the solar system apart from Venus and Uranus rotates counter-clockwise as seen from the north pole, in order to conserve angular momentum.

 

[15357]

Every planet in the solar system apart from Venus and Uranus rotates counter-clockwise as seen from the north pole, in order to conserve angular momentum.

That's because of their orbits, right? (Sorry, my major and education has had unfortunately nothing to do with astrophysics....or physics for that matter )


I'm fascinated with why giant things behave the way they do. Space will always remain fascinating for me.

Ya, but it seems like we haven't gotten very far since then. I only have so long to live if I'm going to see the day when we can actually map these violent worlds in hi-def, much less even have a competent (and affordable) means of space travel.
Not that hard to imagine really when you think about the melting point of mercury which is room temperature, or even absolute zero which is the freezing point for oxygen. (turns to a solid)

Holy shit dude, now THAT'S cold! :O

Yeah.



Man I should have chosen natural sciences back in 11th grade.

 

[Tyguy]

The consensus for how the solar system was formed involves a planetary nebula succumbing to accretion. Under this assumption you can imagine how a rotating disk of debris would tend to rotate in the same direction. It’s assumed Venus and Uranus had some type of interaction with at least one large body which changed their spin, although there are other theories.

 

[Dan]

Why do gas giant planets have shorter days than terrestrial planets despite being much larger? That doesn't make much sense to me.

I am not an astrophysicists, nor have I studied this. But this is my guess:

Planets are not singularities, they have a discrete volume. This volume is tracing out an elliptical orbit in space. The gravitational force pulling it inwards towards the centre of its orbit is applied evenly across the mass of the planet and is effectively constant within the volume occupied by the planet.

For a given inward force and radius of rotation, an object tends to travel at a specific velocity. There is some formula for this, but the general idea is that the greater the force, or smaller the distance the higher the velocity. So the side of a planet nearer to the sun wants to travel faster because it is closer. In other words, the inside of a planet is tracing out a shorter path than the far side of a planet. This difference gives spin to a planet which cause the day/night cycle.

So larger planet equals larger rotational force. Although I imagine that lower density is probably the key factor, although larger radius may also cause a faster rotation. The fluid surface of the planet makes things more complicated. There is probably a lot of shearing going on underneath.

 

[Solaris]

Very interesting Dan... I'd never thought about it like that before

 

[KiplingsCat]

Jupiter, like all the planets, was formed by the collapse of a dust cloud (accretion, like Tyguy said before). Surprisingly, the speed of rotation of a planet depends not on its size, but on how much the dust cloud shrank to form it. Greater shrinking of dust cloud would result in a greater change in energy, which must then be compensated for by the planet's rotational velocity. The dust cloud that formed Jupiter was bigger than the others, giving it a larger rotational velocity as a result.

 

[VirusType2]

Is it in any way similar to a tornado forming? That's what all this reminds me of.

 

[Danimal]

Dan for President of Space '12

 

[kupocake]

Cloudy as in you wouldn't even be able to see your hand in front of your face cloudy, or are there separate layers of empty space in between layers of clouds?

So cloudy, you can't even see Lando's Cloud City.

 

[Avoidist]

A new challenger approaches!

*Read Dan's quite logical post*

Doesn't quite work that way, I am afraid: the most stable configuration two astronomical bodies can possess is essentially what you would call 'tidally locked' - when the two faces of the bodies are constantly facing each other. Our moon does this around us, and a more extreme example is that of Pluto and Charon which are completely tidally locked. That is if you stood on Pluto (or Charon) you would always see the same face of Charon (or Pluto) hovering in the exact same part in the sky. That's pretty awesome if you ask me.

My point being, it becomes rather difficult for the differential gravity of the sun to actually enhance a planet's rotation since the forces will actually try to fight just that, and as been mentioned before the rotation is instead attributed to the environment it formed in.

Avoidist, BSc in Astrophysics.