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Skies Over Louisville: Fall 2009

Click here for a free starmap to download and print.

Click here for September's What's Up Video from NASA.

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Download Stellarium, a free open source planetarium program for your computer!

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Skies Over Louisville Fall Schedule at the Planetarium

Interested in seeing the fall sky in action, complete with guides and constellation tales? Join us for Skies Over Louisville, our monthly, live star program at the planetarium. Always on Saturday night at 9 PM, the dates for the fall 2009 edition are Sep 5, Oct 3 and Nov 7. After the show, enjoy a telescope viewing party on the planetarium terrace with Louisville's own Astronomical Society (the telescopes are weather permitting, but the Skies Over Louisville show happens rain or shine!)

Fall Skies

As we move into the fall months, we have the longer nights and lower temperatures of autumn to look forward to, perfect for observing the night sky. The full moons during the fall have names which seems to predict the change in weather; the Harvest Moon, on September 4th, was used by early farmers to signal the time to harvest crops; the Hunter’s Moon, on October 4th, is named for the hunters out gathering meat before winter; and the Frost Moon, on November 2nd, foretells the frigid temperatures of the oncoming winter.

On the planetary front, Jupiter is clearly visible during the fall in the southern sky, looking like a very bright star. As the largest planet in the Solar System, Jupiter's gaseous cloud tops act like a giant mirror, reflecting much of the sunlight that falls on them. Some of reflected light makes it back to Earth to be collected and observed by our eyes and telescopes, making Jupiter the brightest object in the southern sky this season. Through a good pair of binoculars it is possible to see the four largest moons of Jupiter, Io, Europa, Ganymede, and Callisto. In July 2009, Jupiter was struck by a comet, which burned up in the atmosphere and left a hole in the clouds the size of the Pacific Ocean.

The Summer Triangle remains visible throughout the fall, sinking lower towards the western horizon as we move through the fall. The Summer Triangle contains three bright stars, each one belonging to a different constellation: Lyra, the Harp; Cygnus, the Swan; Aquila, the Eagle. If in a dark area a person may even see the faint glow of the Milky Way as it passes across the sky through the center of the triangle of bright stars. For this reason the Summer Triangle is also known as the Gateway to the Milky Way.

The Fall constellations all share the same story in Greek mythology, that of the hero Perseus. The first group of five bright stars can be seen high in the northern sky and looks very much like the letter W. This is Cassiopeia. Her husband Cepheus is located to the west and is shaped like a house; a triangle resting atop a square. Perseus is to the east of Cassiopeia and is marked by a bright star, Algol. This star is said to represent the head of the gorgon, Medusa.

The southern sky is home to two prominent constellations. To see them one only need look straight overhead. The constellation Pegasus is marked by a large square of four stars, sometimes called the Great Square. The northeastern star in this square is shared with the constellation Andromeda . Andromeda is very tall and narrow, resembling the letter A.

Next to the constellation Andromeda, there is a very dim splotch of light. This dim light is the farthest object visible to the naked eye, the Andromeda Galaxy. It is a spiral galaxy much like our own Milky Way and sits about 2.5 million light years away. That means the light coming to us from Andromeda started out before modern humans evolved on Earth.

Celebrate Saturn's Ring Plane Crossing 2009!

On Friday, Sept 4, Saturn's rings will appear to disappear from view on Earth. It's called the ring plane crossing- and it only happens once every 14 to 15 years. Interested in seeing it in the sky? Since Saturn is located behind the Sun right now, it is not possible to get out your telescope and look at it. But, don't worry, there are other options! We have collected some great views and information for you to satisfy your curiosity:
Watch an animation of a ring plane crossing as seen by the Cassini spacecraft.
See a photo montage of Saturn's rings at different angles.
See what the Hubble space telescope saw during the 1995 ring plane crossing.
And finally, visit a great FAQ on Saturn’s rings.

Messenger mission to Mercury! New images from latest fly-by:

On September 29, 2009, the MESSENGER spacecraft passed by Mercury for the third time, flying 141.7 miles above the planet’s rocky surface for a final gravity assist that will enable it to enter orbit about Mercury in 2011. During the encounter, the MESSENGER cameras imaged a portion of Mercury's never-before-seen surface. See the new images and learn more about the mission at the Messenger mission website.

Send Your Name to Mars!

NASA invites you to submit your name to be included on a microchip that will be sent to Mars as part of NASA's Mars Science Laboratory mission, scheduled to launch in 2011. The "Send Your Name to Mars" web page enables anyone to take part in the mission by sending his or her name to the Red Planet. Participants can print a certificate of participation and view a map showing where other contributors are from.

Storms on Titan

Saturn's moon Titan is the only other planetary surface in our Solar System besides Earth that is wet, with active erosion from rain runoff and monsoons happening right now. Titan's monsoons are surprising us because they can disappear for years at a time. By studying Titan, we are gaining a greater understanding of how to predict rainstorms, and how they connect with surface erosion and climate.
More on this developing story here.

To Ask the Astronomer a question, send your email to planet @ louisville.edu.
To listen to the Sky hotline, call 502-852-6664 and press 4 for the Sky this Month.