|
|
The Question
(Submitted August 21, 1996)
I understand Jupiter is not dense enough to walk around on, and that
it has a deadly radioactivity about it. That doesn't seem reasonable
to me, because it's too far from the Sun. How do you account for this?
Is the radioactivity stable, or does it fluctuate? And what is its
Source? Just curious. Thanks a lot. I NEVER heretofore have had any
interest in Astronomy--that is, until I had a couple of sons to talk
with. Now Mom has fun also.
The Answer
It is true that you cannot walk on Jupiter. This is because the atmosphere
is very deep, perhaps comprising the whole planet (which would mean there
is no solid surface to walk on!). It is composed mainly of hydrogen and
helium, with small amounts of methane, ammonia, water vapor and other
compounds. At great depths within Jupiter, the pressure is so great that
the hydrogen becomes metallic.
This metallic hydrogen core generates a huge magnetic field around Jupiter.
It's like the magnetic field of Earth, but Jupiter's field is 10 times
stronger. This magnetic field traps high energy particles --- the particles
come from the Sun, from outside the Solar system, and from the volcanoes on
Io, one of Jupiter's many moons. The trapped particles then creates the
radiation belt. This is similar to the Van Allen belts around Earth, but can
be up to 10,000 times more intense. These levels of radiation near Io are so
high that a human would absorb a lethal dose in just minutes.
It's not quite correct to call this "radioactivity", which
is different from radiation. Radiation can refer to a lot of things:
sunlight, broadcast signal from a
radio station,
microwaves in
your microwave oven, ... Some are dangerous, some are not. Radioactivity
refers to the properties of certain atoms and subatomic particles that
spontaneously decay and emit particular types of radiation (gamma-rays,
alpha particles etc.) that are often dangerous and sometimes deadly.
We hope you and your sons will continue to enjoy
astronomy!
Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html
for help on other astronomy Q&A services.
|
