14 January 2008

Moon in Action / Being on KFOG

This week the waxing moon journeys across Taurus and Gemini. As it does, it encounters the Pleiades, the small but distinctive cluster of stars in Taurus also known as "the Seven Sisters." On the evening of January 17th, the moon will graze through this region of the sky in what is called an "occultation" of the Pleiades. Occultations are special times when a celestial object is "blocked" from our point of view by another object. The most common are occultations of stars and planets by the moon. When this is being caused by the moon, it affords anyone with binoculars or a telescope to easily observe the motion of the moon against the background stars as the moon makes its monthly journey around the earth. On the evening of January 17th as the moon variously covers and uncovers stars in the Pleiades, you will be able to sense that motion. Over the course of approximately three hours the moon will move across the Pleiades.

Two days later, the nearly full moon will pass very close to Mars but will not occult the planet from our vantage point in San Francisco. Observers much further north (in Canada) will in fact see the moon completely cover Mars. Because Mars is bright and fairly close to earth right now, the sight of it so close to the full moon will be quite beautiful. Take a few moments on the evening of January 19th to enjoy this spectacle. I observed a similar lineup of moon and Mars in December during the previous full moon two days before Christmas.

Earlier this month I was a guest on the KFOG radio morning show (104.5 FM in San Francisco). KFOG features the best morning show program in the San Francisco Bay Area (in my humble opinion) because the DJ and his crew talk about relevant subjects and current news items in an intelligent way. I thought it would be interesting for the KFOG listeners, affectionately known as Fogheads, to hear about astronomy and I asked to be a guest on the program. Morning show producer Greg McQuaid welcomed me to join and on January 8th I was a guest. The program went well and the Fogheads asked interesting questions. I am invited to return to the morning show in March and will post an update to the blog when the date is confirmed.

There were many more questions from Fogheads that we did not get to answer during the show, so I will post them to this blog from time to time.


Anonymous said...


We heard you on KFOG last week. Very cool! Perhaps you can answer an astronomy question for us? Sunday evening we got a call from a friend who lives on a houseboat in the San Rafael harbor (we live in the east bay). He said there was something strange on the horizon & to go outside & look east. Just below orion's belt was a bright "object", sort of Southeast of us & just above the horizon. None of us could identify it... Can you tell us what it was? Planet? (vegetable? mineral..?) I'm pretty sure mars was above us (it was steady & red). I thought you'd said something about an upcoming planet alignment on KFOG, which is why I came looking for your blog.

Looking forward to reading your blog & hearing you on KFOG in the future.

Thanks :)

~your (New) adoring fans in Dublin

The Urban Astronomer said...

Hello dudemomdude - based on the description, you saw Sirius which is the brightest star in the sky. Sirius is also known as the "Dog Star" because it is the eye on Orion's hunting dog, Canis Major. It is a very brilliant star which is going to be visible throughout the Winter and into early Spring.

The exciting planetary alignment will be with Venus and Jupiter at the end of the month. Closest approach of the two is on Jan 31st and Feb 1st in the early morning just before sunrise. I'll post some additional notes on that in the blog later this month.