KFOG Broadcast - September 8, 2009

Get involved: AANC astronomy lectures and star party on September 12

Here's a chance to dive into astronomy and hear from the scientists that are making news right now. The Astronomical Association of Northern California (AANC) is opening the first day of its annual meeting to the public on Saturday September 12th at the Westin Hotel at SFO in Millbrae. The day features a broad range of talks about astronomy, from imaging of the heavens through the Hubble Space Telescope, to the Search for Extraterrestrial Intelligence (SETI), to the upcoming NASA Lunar Impactor mission (LCROSS mission), and the history of the telescope. Also there will be telescopes for solar observing during the day and a star party in the evening (lead by yours truly). Register online - high-school age students are Free. Visit aancstars2009.org for details.

Saturn has no rings!

If you could get a good telescopic view of Saturn today, you would find that it has no rings. At least that would appear to be the case for several days as another rare phenomenon takes place in the Solar System. Of all of the beautiful objects in the sky, Saturn is one of those wonderful heavenly targets that can be seen from cities and country, from spacecraft and flying telescopes, and always impresses the viewer. The second largest planet in the Solar System, Saturn has the largest and most distinctive ring system (Jupiter, Uranus and Neptune also have ring systems). The detailed photographs sent back to Earth from the Voyager and Cassini spacecraft and the Hubble Space Telescope have given us stunning perspectives into the depth and intricacies of the Saturnian ring system.

Saturn's ring system is very thin (less than 50 feet thick), and when viewed 'edge-on' from Earth it is virtually invisible. Saturn, like Earth, has a tilt in its rotation such that it has seasons as it moves around the Sun in its 30-year orbit. Consequently, every 15 years we see the ring system from the side and for a short while it disappears from view altogether. Although the ring system is very thin, it is extremely wide -- about 170,000 miles across, making the system even bigger than Jupiter!

Saturn is currently moving its way westward across the constellation Leo the Lion and is not visible due to its proximity to the Sun in the morning sky. It will gradually emerge from the glare of the dawn and be visible before sunrise. By the end of the year it will be rising in the east just before midnight and by next spring will be a gorgeous evening object with its ring system back in view. Until then, enjoy Jupiter and its fascinating moon system -- except when they aren't there!

Jupiter has no moons!

Tonight Jupiter will have no moons. At least that will appear to be the case for a short while, as a rare phenomenon takes place in which all of the four bright moons of Jupiter will not be visible for viewers on Earth.

Any night of the year that Jupiter is visible, you can usually spot several of the four Galilean moons. Io, Europa, Ganymede and Callisto are big enough that they are easy to find in a telescope or even binoculars. The inner three moons, Io, Europa and Ganymede orbit Jupiter very rapidly, in 2, 4 and 8 days respectively. So on any given night the relative position of the four moons changes and the pattern of the four moons around Jupiter - from our point of view - is always in flux. The above image from Sky and Telescope Magazine helps to illustrate this.

To make things more interesting, as a moon passes directly in front of Jupiter or behind it (or in the shadow of Jupiter) it becomes invisible for a few hours. This evening from 7:00 to 12:00 pacific time, the moons will be invisible for some period of time, with all four moons being out of view from 9:43 until 11:29 pacific. If you have a telescope or binoculars, use them to catch the changing pattern of the moons and witness this unusual alignment.

Jupiter, by the way, can be easily spotted tonight as the bright "star" in the east near the full Moon.

The Milky Way and the Galactic Center

At the SFAA star party a couple nights ago on Mt Tam, the conditions were very clear and dark and we had a nice view of the Milky Way. With an excellent southern horizon, we could see all of Scorpius and Sagittarius and as my daughter and I were giving star tours to guests at the star party, I was happy to point out these two constellations and note that the center of the Milky Way was in the vicinity of the tail of Scorpius and the "teapot" of Sagittarius. This is called the "Galactic Center" and is the central bulge of the Milky Way Galaxy.

Looking toward the galactic center, however, you don't see a huge ball of light. That is because there is a massive dust cloud that lies between the Sun and the galactic center. Too bad for us, because it would be quite amazing to see the center of our own galaxy. Nonetheless, there is much richness in the sky near the galactic center and even in city lights you can begin to see some of that beauty if you use a pair of binoculars. Standard 7x35 or 10x50 binoculars can substantially increase the amount of light you can see, and that means you can begin to discern the stars and shapes of deep space objects such as the Lagoon Nebula or the Swan Nebula. Take out binoculars and point yourself south and see if you can start to see some of the wonders that are at the heart of the Milky Way.

Get involved: Astronomy events in August

San Francisco Amateur Astronomers (SFAA) are hosting two events in the coming days, both open to the public at no charge.

The monthly meeting of the SFAA takes place on Wednesday evening August 19th at 7:30 pm at the Randall Museum in San Francisco. From the SFAA: "Jack Welch of the Robert Ferguson Observatory in Sonoma gives a presentation on how we measure time and how time measurement is handled in various astronomy and space situations. Welch will explain how our understanding of time measurement has changed as technology and theory have developed, and will explore some of the special challenges satellites and spacecraft have when it comes to timekeeping."

The monthly SFAA event on Mount Tamalpais in Marin features a speaker and a public Star Party. It takes place at the Mountain Theater on Mt. Tam on Saturday August 22nd at 8:30 pm (lecture) with the star party immediately following the lecture. From the SFAA: "Dr. Anthony Coloprete of NASA-Ames will fill us in on all the details of the LCROSS mission. Two spacecrafts are on their way to the moon, and the impending impact on October 9 will be visible even with small scopes from Earth. Why crash into the moon? Dr. Coloprete’s talk 'Prospecting for Water on the Moon' reveals all."

The SFAA welcomes all to their events each month. I hope to see you at one of these events.

Perseid Meteor Shower 2009

It's August and that means its time for the annual Perseid Meteor Shower, this year reaching its peak on the evening and through the morning of August 11-12. Meteors are visible just about any night of the year, but throughout the year there are periods of intense activity in the sky ("meteor showers") because the Earth travels through a point in its orbit where there is a higher amount of space dust, rocks and other particles that enter the atmosphere at tens of thousands of miles per hour and burn up, creating bright streaks across the sky.

The Perseid Meteor Shower is going to be harder to see in 2009 because of the bright Moon that rises at 10:40 pm in San Francisco. For the city dweller, however, the shower is not much worse because of the bright Moon, as our city lights obscure many meteors anyhow. So the best you can do is simply enjoy the shower the evening of August 11th from wherever you are in the city. Pick a darkened comfortable spot. Lay back on a blanket and point your feet to toward the north-east and look around the sky. As the evening wears on, the origination point ("radiant") of the meteor shower rises in the north-east. This area is near the constellations Perseus and Cassiopeia as shown in the illustration to the right.

This year there will be a possible jump in the number of meteors as the Earth passes through a denser-than-usual filament of dust from the remnants of comet Swift-Tuttle. That will happen around 1:00 am pacific time on the 12th, so if you are up late you might just see a more intense period of meteor activity. Throughout the entire evening, the Moon will remain the one bright light everyone cannot escape, so when it rises just point your gaze in another direction and keep your eyes on the sky. And stay warm!

If you want to see a good meteor shower this year that won't have moonlight in the way, look ahead to December 14th when the Geminids will peak at an even higher rate than the Perseids. However it will be considerably cooler and the weather is less predictable at that time.

Get involved: AANC astronomy lectures and star party in September

Save the date: September 12th in Millbrae (just south of San Francisco near SFO). The Astronomical Association of Northern California (AANC), along with the Astronomical Society of the Pacific (ASP), are sponsoring the AANC annual meeting and has designated Saturday September 12th as a day open to the public. The day will include lectures by expert astronomers and astrophysicists, solar viewing through telescopes during the day, brown bag workshops, exhibits by local astronomy clubs and dealers, and an evening star party. Families are welcome and children are admitted free. Check out the details on the AANC Annual Meeting 2009 website and register now. I'll be taking part throughout the day and I'll be supporting the evening Star Party as well. More on these topics soon.