... The Moon (1) . ... At any time, only half of the Moon's surface is visible from Earth, but librations allow us to "peek around the edges." ... Just as the rotation axis of the Earth is inclined by (90њ?23.5њ) to the Earth-Sun direction ( drawing above , from section #3 "Seasons of the year"), so the rotation axis of the Moon is inclined by about (90њ?6.5њ) to the mean Moon-Earth line. ... When it speeds up, the rotation of the Moon-Earth line around the Earth (measured in degrees per hour) is faster...

The Sun is our nearest star and the source of energy for life on Earth. ... For centuries astronomers wondered whether they were clouds floating in the Sun's atmosphere, but we now know that they really are huge regions of magnetic field, about as intense as the field at the poles of an iron magnet. ... Such abrupt events were named solar flares , and what made them especially interesting was that occasionally, after a prominent flare, a magnetic storm would erupt on Earth. ...

Titan . ... Hubble Space Telescope Images of Titan's surface . ... Later that year, it will release the European-built Huygens probe for a descent through Titan's atmosphere. ... This artist's rendering shows the European Space Agency's Huygens probe descending into the atmosphere of Saturn's moon Titan after being released by NASA's Cassini spacecraft. ... This artist's rendering shows the Huygens probe on the surface of Saturn's moon Titan after being released by NASA's Cassini spacecraft. ...