Just as anticipated, scientists have confirmed that Saturn’s elaborate aurora displays are caused by the fluctuations of its magnetosphere. The findings are not necessarily surprising; in fact, they reiterate what was already expected to be the case. Nonetheless, a recent collaboration between the Hubble Telescope and the Cassini–Huygens spacecraft has increased our knowledge of planetary light shows.
Saturn’s core produces a magnetosphere that helps protect it from the Sun’s assailing high-energy particles. Fortunately, this field stops its atmosphere from being blown away by solar winds; perhaps even more fortunate for us, it also allows for the spectacular sight of aurorae!
The Earth and Saturn are both planets that produce magnetic field lines; collectively, these lines are called a magnetosphere. Think of it as a bubble surrounding the planet; though instead of it being spherical, the bubble is compressed on the side closest to the sun and an elongated tail is produced at the opposite end, this is called the magnetotail. The Sun's wind is comprised of plasma- ionized particles that are affected by magnetism. Large amounts of solar energy cause the field lines to stretch and twist; like pulling on one end of a rubber band, eventually the magnetotail becomes so extended that it must snap back and reconnect to the planet. This causes the solar energy trapped within the field lines to discharge into the atmosphere at the poles. On Earth, we see the majority of aurorae as green, but this doesn’t mean that solar energy itself is green in any way. In fact, what it means is that energized particles (electrons and protons) are colliding with gases in the atmosphere and this interaction produces the release of light. It is the atmospheric gases involved that determine which colors are visible; we mostly see green aurorae on Earth because oxygen atoms are being excited.
Saturn's Light Shows:
But what about Saturn? What colors are produced by its aurorae? By examining the planet in April and May of 2013, scientists were able to capture the twirling images of the light from all angles of the planet, and indeed, they were impressive! Saturn’s intense winds helped amplify the effect; clocking in at an impressive 1,120 mph. Some would even travel three times faster than the rotation of planet.
Cassini, which has been orbiting Saturn since 2004, took photographs of the aurorae, but because the atmosphere is primarily made of hydrogen and helium, the light emitted is bluish-red and violet. Perhaps most alluring are the images taken by Hubble using its "Advanced Camera for Surveys." This instrument allow us to see what is normally not visible to the human eye, a majestic display of ultraviolet light. These findings have recently been accepted for publication in the Geophysical Research Letters. Bibliography:
- American Geophysical Union
- European Space Agency
- MIT Physics
- National Geographic, Beyond Our Galaxy, (April, 2014) p.42.