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Saturn’s Dynamic Auroras
These images reveal the dynamic nature of Saturn's auroras. Viewing the planet's southern polar region for several days, NASA's Hubble Space Telescope snapped a series of photographs of the aurora dancing in the sky. The snapshots show that Saturn's auroras differ in character from day to day, as they do on Earth, moving around on some days and remaining stationary on others. But compared with Earth, where auroral storms develop in about 10 minutes and may last for a few hours, Saturn's auroral displays always appear bright and may last for several days.
The observations, made by Hubble and the Cassini spacecraft, while enroute to the planet, suggest that Saturn's auroral storms are driven mainly by the pressure of the solar wind - a stream of charged particles from the Sun - rather than by the Sun's magnetic field.
The aurora's strong brightening on Jan. 28, 2004 corresponds with the recent arrival of a large disturbance in the solar wind. The image shows that when Saturn's auroras become brighter (and thus more powerful), the ring of light encircling the pole shrinks in diameter.
Seen from space, an aurora appears as a ring of glowing gases circling a planet's polar region. Auroral displays are initiated when charged particles in space collide with a planet's magnetic field. The charged particles are accelerated to high energies and stream into the upper atmosphere. Collisions with the gases in the planet's atmosphere produce flashes of glowing energy in the form of visible, ultraviolet, and infrared light.
Astronomers combined ultraviolet images of Saturn's southern polar region with visible-light images of the planet and its rings to make this picture. The auroral display appears blue because of the glow of ultraviolet light. In reality, the aurora would appear red to an observer at Saturn because of the presence of glowing hydrogen in the atmosphere. On Earth, charged particles from the Sun collide with nitrogen and oxygen in the upper atmosphere, creating auroral displays colored mostly green and blue.
The ultraviolet images were taken on Jan. 24, 26, and 28, 2004 by Hubble's Space Telescope Imaging Spectrograph. Erich Karkoschka of the University of Arizona used the telescope's Advanced Camera for Surveys on March 22, 2004 to take the visible-light images.
About the Object
- DistanceDistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.The semi-major axis of Saturn's orbit about the sun is 9.5 Astronomical Units (A.U.) or roughly 1.4 billion km.
- DimensionsDimensionsThe physical size of the object or the apparent angle it subtends on the sky.The planet (without rings) has a diameter of roughly 75,000 miles (120,000 km) at the equator.
About the Data
- Data DescriptionData DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.The Hubble image was created from HST ACS data from proposal 9354: E. Karkoschka and M. Tomasko (Univ. of Arizona) and STIS data from proposal 10083: J.T. Clarke (Boston Univ.) and collaborators. The science team includes: J.T. Clarke (Boston Univ.), J.-C. Gerard and D. Grodent (Univ. de Liege), S. Wannawichian (Boston Univ.), J. Gustin (Univ. de Liege), J. Connerney (NASA Goddard Space Flight Center), F. Crary (Southwest Research Institute), M. Dougherty (Imperial College, London), W. Kurth (Univ. of Iowa), S.W.H. Cowley and E.J. Bunce (Univ. of Leicester), T. Hill (Rice Univ.) and J. Kim (Yonsei Univ., Seoul, Korea) - InstrumentInstrumentThe science instrument used to produce the data.HST>ACS/HRC and HST>STIS
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.ACS/HRC: March 22, 2004; STIS: January 24, 2004 (bottom-left), January 26, 2004 (center), and January 28, 2004 (top-right)
- FiltersFiltersThe camera filters that were used in the science observations.ACS/HRC: F439W (B), F502N ([O III]), F550W (V), F658N (H-alpha) STIS: 25MAMA (Near-UV) and F25SRF2 (Far-UV)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.Saturn
- Object DescriptionObject DescriptionThe type of astronomical object.Planet with Aurora
- Release DateFebruary 16, 2005
- Science ReleaseSaturn’s Auroras Defy Scientists’ Expectations
- Credit
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
