Sep 1, 2017
by Tre Gibbs, Los Angeles Astronomical Society
Welcome Fall! On September 22nd at 12:53 pm, the Northern Hemisphere welcomes the return of Autumn.By now, you probably have noticed the days getting shorter as summer slips away. If you are particularly observant, you may have also noticed the sunrise and/or sunset moving farther and farther southward, which, by the way, is what’s causing the amount of daylight to wane while the nights gradually get longer. As the sunrise and sunset continue their journey southward on their respective horizons, the Equinoxes signal the time when the sun rises due east and sets due west, causing both the Northern and Southern Hemispheres to receive an equal amount of daylight and night. In fact, the word Equinox is a latin word meaning “Equal Night”. After the 22nd though, the sun will continue its southward journey until late December, when it stops, turns around and heads north again.
This is what’s known as The Winter Solstice.
Saturn is the prominent planet in the night sky, although by now, the quintessential ringed gas giant has slipped further west as it ultimately will head into the glare of the sun, rendering it invisible to sky watchers until it slips into our eastern pre-dawn skies. Saturn is huge – almost as big as Jupiter. But remember that it’s practically twice as far away from Earth as Jupiter, and therefore appears not nearly as bright, making it slightly harder to find. This is where the moon comes in as a useful tool. Since the moon, sun and planets all travel the same path in the sky, and since the moon completes one full orbit around Earth every month (or “moonth”), there are times when the moon travels the night sky with each individual planet. The evening of the 26th is the night that the moon, orbiting Earth every 28 days, pairs up with mighty Saturn. Look for faint but steady glowing Saturn just below the almost half moon.
Speaking of Saturn, an amazing 20-year expedition is coming to an end. In 1997, NASA launched the Cassini Spacecraft. Its mission, to travel to Saturn and explore its spectacular system of rings and moons. Saturn is so far away that it took the spacecraft seven years to reach the gas giant. Reaching Saturn in 2004, Cassini has been sending home amazing photos, information leading to incredible scientific achievements and fascinating discoveries for more than a decade. The spacecraft though is running out of fuel, and, in order to protect the moons of Saturn which could harbor potential signs of life, the spacecraft has one last daring mission – The Grand Finale. 22 dives between Saturn and its rings, gathering new data about Saturn, closer than ever before until on its last dive, on September 15th, Cassini will plunge into Saturn’s atmosphere, burn up and become part of the planet itself. Here is a link to a great animated video, which I encourage everyone to see and share: vimeo.com/210782375 So this month, when you look up at Saturn, know that in many ways, there is more to what you are seeing than what meets your Earthly eye.