In this Hubble Space Telescope picture, a curtain of glowing gas is wrapped
around Jupiter's north pole like a lasso. This curtain of light, called an
aurora, is produced when high-energy electrons race along the planet's magnetic
field and into the upper atmosphere where they excite atmospheric gases, causing
them to glow. The aurora resembles the same phenomenon that crowns Earth's polar
regions. But this Hubble image, taken in ultraviolet light, also shows the
glowing "footprints" of three of Jupiter's largest moons: Io,
Ganymede, and Europa.
Courtesy of NASA/ESA, John Clarke (University of Michigan)
Jupiter's
Magnetosphere
This image taken by the ion and neutral mass spectrometer instrument on NASA's
Cassini spacecraft makes the huge magnetosphere surrounding Jupiter visible in a
way no instrument on any previous spacecraft has been able to do. The
magnetosphere is a bubble of charged particles trapped within the magnetic
environment of the planet. A magnetic field is sketched over the image to place
the energetic neutral atom emissions in perspective. This sketch extends in the
horizontal plane to a width 30 times the radius of Jupiter. Also shown for scale
and location are the disk of Jupiter (black circle) and the approximate position
(yellow circles) of the doughnut-shaped torus created from material spewed out
by volcanoes on Io.
Some of the fast-moving ions within the magnetosphere pick up electrons to
become neutral atoms, and once they become neutral, they can escape Jupiter's
magnetic field, flying out from the magnetosphere at speeds of thousands of
kilometers, or miles, per second.
Jupiter's
Auroras
These HST images, reveal changes in Jupiter's auroral emissions and how small
auroral spots just outside the emission rings are linked to the planet's
volcanic moon, Io. The top
panel pinpoints the effects of emissions from Io. The image on the left, shows
how Io and Jupiter are linked by an invisible electrical current of charged
particles called a flux tube. The particles, ejected from Io by volcanic
eruptions, flow along Jupiter's magnetic field lines, which thread through Io,
to the planet's north and south magnetic poles.
