CosmosPlasma

Animations of Saturn’s aurorae

Earth isn’t the only planet in the solar system with spectacular light shows. Both Jupiter and Saturn have magnetic fields much stronger than Earth’s. Auroras also have been observed on the surfaces of Venus, Mars and even on moons (e.g. Io, Europa, and Ganymede). The auroras on Saturn are created when solar wind particles are channeled into the planet’s magnetic field toward its poles, where they interact with electrically charged gas (plasma) in the upper atmosphere and emit light. Aurora features on Saturn can also be caused by electromagnetic waves generated when its moons move through the plasma that fills the planet’s magnetosphere.  The main source is the small moon Enceladus, which ejects water vapor from the geysers on its south pole, a portion of which is ionized. The interaction between Saturn’s magnetosphere and the solar wind generates bright oval aurorae around the planet’s poles observed in visible, infrared and ultraviolet light. The aurorae of Saturn are highly variable. Their location and brightness strongly depends on the Solar wind pressure: the aurorae become brighter and move closer to the poles when the Solar wind pressure increases.

Spacecraft History: Vostok 1

A 15-times magnified image of a dinosaur bone from the Jurassic period.

Control room. Text on the left side monitor: NASA Lewis Research Center 9X15 LOW SPEED WIND TUNNEL. 11:19:28 3/6/1989

Wandering Stars

To ancient astronomers, the stars seemed fixed, moving across the sky during the night but always in fixed constellations—except for five bright points that appeared to wander among the stars. In the geocentric model of the solar system, where everything orbits the Earth, the paths of these five seemed strange, with several even backtracking and looping around in a retrograde motion. Today, we know that our solar system is heliocentric and all planets orbit the sun, so the retrograde motions are only perspective issues, but the ancient names for the planets remain. The Greeks called them ‘planets’, meaning wanderers, and the five were originally named after Roman deities: Mercury, messenger of the gods, Venus, the goddess of love and beauty, Mars, the god of war, Jupiter, king of the gods, and Saturn, father of Jupiter and god of agriculture.