26 October 2010

KFOG Podcast - October 26, 2010

Today's Urban Astronomer talk with Irish Greg of the KFOG Morning Show features the North Star, Meteor Showers in November and December, some early shopping tips for the holidays, cool iPhone Apps, Jupiter and more. It's always a treat to talk with KFOG and share some astronomy tips with the listeners. Click here to listen.

24 October 2010

Waning Moon, Morning Darkness

Each month the Moon makes a 29 1/2 day journey around the Earth, bringing different faces of the Moon to light, making beautiful patterns with the surrounding stars and planets, and shining light into the evening, midnight or morning skies. Right now, the Moon is waning, getting smaller each night as it passes through gibbous phases while moving from Full Moon to Last Quarter, lining up with bright celestial objects such as the Pleiades and Taurus. During the gibbous phases, the orientation of the Moon is quite different from what we normally expect in the evening skies.

The illustration shows the changing orientation of the Moon just after sunset in the waxing phases, as the Moon grows from New to Full. This view is for Northern Hemisphere viewers. But after the Full Moon, the orientation reverses and is best measured in the sunrise sky. So the view you can see right now is of a Moon curved not toward the east as normally seen in the evening sky, but rather curved toward the west in the morning sky. It's refreshing to see this time of year while it is so dark in the morning, and it provides a chance to see things in a different light. Eye-opening.

Image courtesy of University of Virginia.

12 October 2010

An Elusive Comet in Urban Skies: Hunting for Hartley 2

Comets can be bold and brash, streaking across the sky like Hale-Bopp in 1997 (see image on right), a comet that was visible even in light-polluted urban areas. Comets can be more humble but then unexpectedly brighten, as did Comet Holmes in 2007. This year marks the return of periodic Comet Hartley 2, a small but frequent visitor to the inner Solar System that is making a fairly close pass to the Earth (11 million miles) on October 20th. Because of the bright Moon on October 20th, this and last week mark the best chances to see the comet because the Moon is young and not brightening the sky. So I took a look last week and again this week to see if I could spot this elusive comet from a city location (last week in a suburb of Frankfurt, Germany and this week from my home in San Francisco).

I hunted quite a while on both occasions, using this very helpful map from Sky and Telescope Magazine. In fact, S&T has been running updates as viewers report seeing Comet Hartley 2 with binoculars. However, it seems that to see Comet Hartley 2 you need a location with very dark skies. I can attest to this, having twice tried and failed to discern the comet from the surrounding stars.

However, all is not lost. Searching for Hartley 2 requires you to find Cassiopeia, Perseus and Auriga, three very nice constellations that grace the Fall and Winter skies. While searching the path of the comet, you encounter a range of deep space objects near and between Cassiopeia and Perseus, and tonight the view was quite good. So even though city lights may have drowned out the faint comet, I enjoyed my first good look at the Double Cluster in Perseus and other celestial gems in the spiral arm of the Milky Way that is beyond Cassiopeia.

I recommend a good jacket, a comfortable chair or blanket, a few minutes patience, the S&T sky map, and binoculars. No matter whether your hunt for Comet Hartley 2 is a success or not, you will be glad you made the effort.