* Astronomy

Astronomers using the ESA's XMM-Newton telescope has discovered that observing Jupiter's atmosphere may actually give them an insight in to solar activity on the far side of the Sun.

It was discovered that Jupiter's x-ray glow is due to x-ray photons from the Sun being reflected back off the planet's atmosphere, with typically about one in a few thousand x-ray photons reflected back.


"We found that Jupiter's day-to-day disk x-rays were synchronised with the Sun's emissions."
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Now the Chandra x-ray telescope finds Saturn reflects X-Rays from the Sun too.

When it comes to mysterious X-rays from Saturn, the ringed planet may act as a mirror, reflecting explosive activity from the sun, according to scientists using NASA's Chandra X-ray Observatory.
The findings stem from the first observation of an X-ray flare reflected from Saturn's low-latitudes, the region that correlates to Earth's equator and tropics.

Dr. Anil Bhardwaj, a planetary scientist at NASA's Marshall Space Flight Centre (MSFC), Huntsville, Ala., led the study team.
The study revealed Saturn acts as a diffuse mirror for solar X-rays.

Counting photons, particles that carry electromagnetic energy including X-rays, was critical to this discovery. Previous studies revealed Jupiter, with a diameter 11 times that of Earth, behaves in a similar fashion. Saturn is about 9.5 times larger than Earth. It is twice as far from Earth as Jupiter.


Expand to see `before and after` images...

"The bigger the planet and nearer to the sun, the more solar photons it will intercept; resulting in more reflected X-rays. These results imply we could use giant planets like Jupiter and Saturn as remote-sensing tools. By reflecting solar activity back to us, they could help us monitor X-ray flaring on portions of the sun facing away from Earth's space satellites." - Dr. Anil Bhardwaj.

Massive solar explosions called flares often accompany coronal mass ejections, which emit solar material and a magnetic field. When directed toward Earth, these ejections can wreak havoc on communications' systems from cell phones to satellites.

Even as the research appeared to solve one mystery, the source of Saturn's X-rays, it fuelled long standing questions about magnetic fields. Of the three magnetic planets in our solar system, Jupiter and Earth emit two general types of X rays, auroral emissions from polar regions and disk emissions from low latitudes. No research has observed unambiguous signatures of auroral X-ray emissions on Saturn.

"We were surprised to find no clear evidence of auroral X-ray emissions during our observations. It is interesting to note that even as research solves some mysteries, it confirms there is much more we have to learn." - Dr. Anil Bhardwaj.

The research appeared in the May 10, 2005 issue of Astrophysical J. Letters. the research team also included Ron Elsner of MSFC; Hunter Waite of the University of Michigan, Ann Arbor; Randy Gladstone of the Southwest Research Institute, San Antonio, Texas; Thomas Cravens of the University of Kansas, Lawrence; and Peter Ford from the Massachusetts Institute of Technology, Cambridge.

Bhardwaj is working at MSFC as a National Research Council scholar. MSFC manages the Chandra program for NASA's Science Mission Directorate in Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Centre in Cambridge, Mass.


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-- Edited by Blobrana at 23:04, 2005-05-25