|
Posted by baalke on March 30, 2007, 1:49 pm
Please log in for more thread options
http://science.nasa.gov/headlines/y2007/29mar_bigauroras.htm
Big Auroras on Jupiter
NASA Science News
March 29, 2007
March 29, 2007: So you thought Northern Lights were big in Alaska?
"That's nothing," says Randy Gladstone of the Southwest Research
Institute in San Antonio, Texas. "Jupiter has auroras bigger than our
entire planet."
Last month, Gladstone and colleagues used NASA's Chandra X-ray
Observatory to capture this picture:
<http://chandra.harvard.edu/photo/2007/jupiter/>
Above: X-ray auroras observed by the Chandra X-ray Observatory
overlaid
on a simultaneous optical image from the Hubble Space Telescope.
The purple ring traces Jupiter's X-ray auroras. Gladstone calls them
"Northern Lights on steroids. They're hundreds of times more energetic
than auroras on Earth."
Chandra has observed Jupiter's auroras many times before, but this
recent dataset is exceptional both in length and quality. Gladstone
hopes it will help him solve some mysteries lingering for almost 30
years.
Jupiter's auroras were discovered by the Voyager 1 spacecraft in 1979.
A
thin ring of light on Jupiter's nightside looked like a stretched-out
version of our own auroras on Earth. But those early photos merely
hinted at the power involved. The real action, astronomers soon
learned,
was taking place at high-energy wavelengths invisible to the human
eye.
In the 1990s, ultraviolet cameras on the Hubble Space Telescope
photographed raging lights thousands of times more intense than
anything
ever seen on Earth, while X-ray observatories saw auroral bands and
curtains bigger than Earth itself.
Jupiter's hyper-auroras never stop. "We see them every time we look,"
says Gladstone. You don't see auroras in Alaska every time you look,
yet
on Jupiter the Northern Lights always seem to be "on."
Gladstone explains the difference: On Earth, the most intense auroras
are caused by solar storms. An explosion on the sun hurls a billion-
ton
cloud of gas in our direction, and a few days later, it hits. Charged
particles rain down on the upper atmosphere, causing the air to glow
red, green and purple. On Jupiter, however, the sun is not required.
"Jupiter is able to generate its own lights," says Gladstone.
The process begins with Jupiter's spin: The giant planet turns on it
axis once every 10 hours and drags its planetary magnetic field around
with it. As any science hobbyist knows, spinning a magnet is a great
way
to generate a few volts?it's the basic principle of DC motors.
Jupiter's
spin produces 10 million volts around its poles.
"Jupiter's polar regions are crackling with electricity," says
Gladstone, "and this sets the stage for non-stop auroras."
The polar electric fields grab any charged particles they can find and
slam
them into the atmosphere. Particles for slamming can come from the
sun,
but Jupiter has another, more abundant source nearby: the volcanic
moon
Io, which spews oxygen and sulfur ions (O+ and S+) into Jupiter's
spinning magnetic field.
Somehow, these ions make their way to Jupiter's poles where electric
fields send them hurtling toward the planet below. Upon entering the
atmosphere, "their electrons are first stripped away by molecules they
run into, but as they slow down they start grabbing electrons back.
The
'charge exchange reaction' produces intense X-ray auroras," he
explains.
So Jupiter's Northern Lights are, in a sense, volcano powered. Mystery
solved? Not quite.
No one knows exactly how volcanic exhaust meanders from Io out through
Jupiter's magnetosphere and back to Jupiter's poles. "We're still
trying
to figure it out," says Gladstone.
But that is a minor detail compared to another, even bigger puzzle:
There is an X-ray "pulsar" inside Jupiter's northern auroras.
Sometimes
Chandra sees it, sometimes not. When it's on, the pulsar emits
gigawatt
bursts of X-rays with a regular beat of 45 minutes.
Gladstone suspects the pulsar has nothing to do with Io's volcanoes,
but
instead is caused by the sun. "Maybe Jupiter's magnetic field, when it
gets hit by a solar wind gust, rings like a bell with a 45-minute
period," he speculates. "There are many other possibilities as well."
The February 2007 dataset may hold important clues. "Chandra observed
the auroras for 15 hours, and we weren't the only ones watching," he
says. The Hubble Space Telescope, the FUSE satellite, XMM-Newton (a
European X-ray observatory), the New Horizons spacecraft and many
ground-based observatories were all taking data at the same time. The
campaign was timed to coincide with New Horizons flyby of Jupiter - a
slingshot maneuver designed to increase its velocity en route to
Pluto.
"Jupiter's auroras have never been observed by so many telescopes at
once," says Gladstone. "I'm really excited by these data, and the
analysis is just beginning."
NASA's Marshall Space Flight Center, Huntsville, Ala., manages the
Chandra program for the agency's Science Mission Directorate. The
Smithsonian Astrophysical Observatory controls science and flight
operations from the Chandra X-ray Center, Cambridge, Mass.
|
| Similar Threads | Posted | | Any Auroras on Titan? | June 21, 2005, 2:59 am |
| Any Auroras on Titan? | June 21, 2005, 3:15 pm |
| Hundreds of Auroras Detected on Mars | December 12, 2005, 2:24 pm |
| The moons of Jupiter | September 13, 2005, 3:53 pm |
| The moons of Jupiter | September 14, 2005, 10:33 am |
| Re: The moons of Jupiter | September 16, 2005, 3:24 pm |
| Re: The moons of Jupiter | September 19, 2005, 9:58 am |
| Re: The moons of Jupiter | September 20, 2005, 10:06 am |
| Re: The moons of Jupiter | September 20, 2005, 10:10 am |
| Re: The moons of Jupiter | September 22, 2005, 9:09 am |
|
XML Sitemap