Monkey's been staring at the Sun too long

[Badly Shaved Monkey]

and his little brain has come up with these questions.

1. When the Sun first ignited into fusion, did it go BANG all at once, did it creep up to a high temperature, did the centre undergo fusion first but then the photons took their famous million years to make the outer layers look hot? Basically, what did it look like?

2. In a nearly-Sun like Jupiter, what are the processes that make it generate heat even though nuclear fusion is not occurring?

3. Why is there so much radiation around Jupiter that it would be hazardous for people to get too close?

[Diamond]

Originally posted by Badly Shaved Monkey
and his little brain has come up with these questions.

1. When the Sun first ignited into fusion, did it go BANG all at once, did it creep up to a high temperature, did the centre undergo fusion first but then the photons took their famous million years to make the outer layers look hot? Basically, what did it look like?

Stars like the sun form via gravitational collapse of material. The ignition of the star's core would be sudden, but the outflow of light would take a lot longer. Basically the star would glow brighter and brighter.

The time? Difficult to say, but probably in the region of thousands of years at least.

2. In a nearly-Sun like Jupiter, what are the processes that make it generate heat even though nuclear fusion is not occurring?

As with stars, heat generation can be caused by continuing gravitational compression. Bear in mind that material infalling into a massive body is losing potential energy, and this energy gets transformed into heat. There is another source of heat that for the moment escapes my memory.

3. Why is there so much radiation around Jupiter that it would be hazardous for people to get too close? [/B]

Because Jupiter is large enough to have a largish core of highly compressed hydrogen where the protons and electrons behave a liquid metal, Jupiter produces a very large magnetic field which attracts and focuses charged particles both from the Sun and from the rest of the Universe.

Since Io, the innermost Galilean satellite, has a metal core and is therefore moving in Jupiter's magnetic field by orbiting, this induces an enormous current of tens of thousands of amps between Jupiter and Io that disturbs the upper layers of clouds in the Jovian atmosphere.

[Badly Shaved Monkey]

Originally posted by Diamond
Because Jupiter is large enough to have a largish core of highly compressed hydrogen where the protons and electrons behave a liquid metal, Jupiter produces a very large magnetic field which attracts and focuses charged particles both from the Sun and from the rest of the Universe.

Since Io, the innermost Galilean satellite, has a metal core and is therefore moving in Jupiter's magnetic field by orbiting, this induces an enormous current of tens of thousands of amps between Jupiter and Io that disturbs the upper layers of clouds in the Jovian atmosphere.

Thanks for that.

Just to rephrase that last bit to clarify it, you are saying that the radiation is not itself created in the Jovian system, but is funnelled and focused from solar and cosmic ray sources?

[neutrino_cannon]

Depends on what you mean by radiation. Jupiter's magnetic fields are quite impressive indeed, as noted by Diamond, because of metallic hydrogen in its core. Charged particles (electrons, ions, muons etc.) do get swirled around a bit, and a vaguely recall some trouble with a mission there when the satellite began to orbit what was essentially a huge cyclotron track.

That said, anything above absolute zero will emit electromagnetic radiation at a maximum wavelength of (2.9*10^-3)/(object's temperature in Kelvin).

[geni]

Originally posted by Badly Shaved Monkey

2. In a nearly-Sun like Jupiter, what are the processes that make it generate heat even though nuclear fusion is not occurring?


Jubiter is not a near star by any means. Most of the energy jubiter thorws out comes from it formation rather than gravitational compression.

[Matabiri]

Originally posted by Diamond
As with stars, heat generation can be caused by continuing gravitational compression. Bear in mind that material infalling into a massive body is losing potential energy, and this energy gets transformed into heat. There is another source of heat that for the moment escapes my memory.

Compression of the gases/material falling in? Although that's technically the same source (conversion of gravitational potential energy), I suppose.

[Badly Shaved Monkey]

But to summarise with respect to Jupiter, the real nastiness in its environment in large part arises from its intense magnetic field which is a consequence of its being, to a first approximation, a vast lump of metallic hydrogen.

So, never mind the BBC's Space Odyssey programme, is human exploration of the Jovian system just a stupdily hazardous thing to do for squishy watery humans, or are parts of the system relatively safer?

[Hamish]

Originally posted by Diamond

There is another source of heat that for the moment escapes my memory.


Do you mean the "Helium Drip"? Although that is not so much a source of heat on Jupiter. It is a source of Saturn's heat though. Helium slowly condenses and falls as rain, a sort of slow gravitational collapse.

See here (http://burro.astr.cwru.edu/Academics/Astr201/Jovian/jovians1.html) for some basic information on Jupiter's composition and heating. It has a bit about the Jovian magnetosphere too.

[neutrino_cannon]

Originally posted by Badly Shaved Monkey
But to summarise with respect to Jupiter, the real nastiness in its environment in large part arises from its intense magnetic field which is a consequence of its being, to a first approximation, a vast lump of metallic hydrogen.

So, never mind the BBC's Space Odyssey programme, is human exploration of the Jovian system just a stupdily hazardous thing to do for squishy watery humans, or are parts of the system relatively safer?

My guess (and this is just a guess) is that the trapped radiation would be in discreet "belts", which the correct orbit might be able to avoid. I think a little shielding could go a long way too.

[wollery]

Originally posted by Diamond
Stars like the sun form via gravitational collapse of material. The ignition of the star's core would be sudden, but the outflow of light would take a lot longer. Basically the star would glow brighter and brighter.

The time? Difficult to say, but probably in the region of thousands of years at least.Before stable hydrogen fusion begins there are other fusion reactions that take place at lower temperatures, first deuterium, and then lithium. These reactions help to push the temperature high enough for the hydrogen fusion to start.

As with stars, heat generation can be caused by continuing gravitational compression. Bear in mind that material infalling into a massive body is losing potential energy, and this energy gets transformed into heat. There is another source of heat that for the moment escapes my memory.Jupiter's core gained large amounts of heat during its formation, and the only source of energy is the slow release of that core heat by convection and radiation. The atmosphere above the core acts as an insulator preventing the heat from escaping quickly. Also the Sun's radiant energy heat the atmosphere, reducing the temperature gradient from the core to the upper atmosphere.

Edit to add - the rotation of the metallic hydrogen core produces a dynamo effect (and the massive magnetic field), and that may produce some heating.

Were you thinking of degeneracy pressure as a source of heat?