Photo of Jupiter's south pole, Grodent/Hubble Space Telescope Team; HST program GO-10862, May 2007
From Denny: Ganymede is Jupiter's largest moon, also the only one with serious gravitational pull. Scientists have analyzed and studied thousands of images from the Hubble Telescope to figure out that it's partly the magnetic field from the moon Ganymede creating the spectacular auroras seen at Jupiter’s poles. You can imagine just how long it has taken scientists to analyze all this data to gain this new information.
These bright spots seen at the poles are known as "auroral footprints." Don't you just love the names these guys come up with? Io is another moon of Jupiter's and is volcanically active. Along with Ganymede, Io too also interacts with Jupiter's plasma as they both orbit around the planet, generating those auroral footprints. Up until Hubble returned the latest images scientist were unable to determine just why those spectacular light shows were created or how big was Ganymede's footprint.
Today researchers have measured the exact size of the Ganymede footprint to realize it is not being projected by Jupiter because it's just too big. What its size does correspond with is the diameter of Ganymede's protective magnetic field.
What about the moon Io's footprint? Researchers measured that too because its footprint is created by its active volcanoes ejecting charged particles.
Photo of auroral footprint - Grodent/Hubble Space Telescope Team; HST Program GO-10140, PI: Denis Grodent (ESA Univeristy of Liege), filter F125LP, exposure time 110 sec, April 2005
"Each of these auroral structures is telling an ongoing story about vast transfers of energy taking place far away from the planet,” astrophysicist Denis Grodent of the University of Liege in Belgium said in a press release. “By analyzing the exact locations of these features and how their shape and brightness changes as Io and Gaynmede move in their orbit around Jupiter, we have created the most detailed picture to date of how Jupiter and these moons are electromagnetically interconnected.” Grodent presented his research today in Germany at the European Planetary Science Congress.
Grodent's and his team's accomplishments:
They linked the footprint of Ganymede to its magnetic field.
They discovered something unexpected about the moon's aurora: there were periodic variations in its brightness. They measured this occurence on three different timescales.
They are speculating that each variation may be reflecting a specific interaction between Jupiter's plasma and Ganymede's magnetic field. They admit they still don't know exactly what is causing the interactions.
Well, that was fun to learn the why and how of Jupiter's light show! Thanks for visiting!
