Cosmos

At first glance, one might mistake this for an image of our familiar lunar neighbor, but it's not. It is, in fact, one of the first close-up images of Mercury taken since Mariner visited the planet over 30 years ago - and it's of a region not seen before. This week, NASA's Messenger spacecraft slipped within 125 miles of Mercury to begin what will be a multi-year exploration of this most unusual planet. The heavy cratering certainly reminds us of the Moon, but looking deeper reveals vast differences between these two solar system bodies. In particular, Mercury is extremely dense - nearly 50% of it's volume is iron - making it denser, even, than the Earth. How did this planet come to be so dense? The Messenger mission has been designed to help scientists answer this intriguing question and a host of others.

The sudden dramatic brightening of comet Holmes 14P last month sent many amateur astronomers, myself included, scurrying to their telescopes. On October 23th, Holmes 14P was a very faint object (magnitude 17) in the constellation Perseus. A day later, it had brightened nearly 1 million-fold to approximately magnitude 2.5. Even in light-polluted skies, such as those over Los Angeles, it had become a naked-eye object overnight. Perseus had sprouted a new "star"!

On Saturday night, May 19th 2007, amateur astronomers from all over the world will bring their passion to the public. The goal of the 1st Annual International Astronomy Night is to setup over 1000 telescopes across the globe in public places in order to provide all comers with a view of the night sky's magic. I, for one, plan to participate by setting up at least one (perhaps two) scopes on or near the pier in Hermosa Beach, CA. Cloud cover permitting, we will glimpse a beautiful crescent moon, a bright venus, Saturn and perhaps even Jupiter, if people stay around long enough. I'm looking forward to opening more eyes to the wonders over our heads. Please come join us!

Saturday evening, March 17th-18th, I made the trek with fellow South Bay Astronomical Society (SBAS) members to our observing site near Red Rock Canyon State Park for a night of dark-sky observing. As the "new moon" weekend in March, this would be the best time to attempt a Messier Marathon - an annual adventure in which astronomers attempt to view all 110 Messier objects in a single night. Having completed a marathon in 2004, I was more interested in another event which, coincidentally, was anticipated that same evening - an occultation of Pluto.

Happy Solstice Day! Once again, it's December 21st and this year at 4:22 PM PST, the North Pole will be tipped further away from the sun than at any other moment this year (approximately 23.5 degrees). Today, the northern hemisphere will experience its shortest period of daylight and it's longest period of night - it's the middle of winter. Simultaneously, it's the middle of summer in the southern hemisphere and people there are enjoying the longest day and shortest night of the year today.

Last week, I spent some class time with the 6th Graders at Rolling Hills Country Day School (RHCDS). This time, I was asking the question, "Why does the moon change shape from night to night?" And from there, we launched into an exploration for an answer - into the motion of the Moon around the Earth, the effect of sunlight on both and an understanding that how the moons looks to us is really just about point of view. Judging by the questions and comments I received, I felt the lessons had been a success, that the students left the room with an understanding somewhat deeper than when they had arrived. In short, I was satisfied, but didn't think much more about it.

Today, however, I received an unexpected package when I came home from work - a manila envelope labelled Mr. Newton!!! - that could mean only one thing. I had to smile, for I knew instantly it contained notes from a host of 6th graders. I knew this because I've been blessed with similar packages in the past. The entire grade had written me thank-you notes for my lunar lesson. Some were simple words, some included elaborate drawings. Some made me laugh out loud, all thanked me for my time and effort, all warmed my heart.

Resources

• Celestia - A Cosmic Simulation!
• Scale Model of Common Stars [Powerpoint slides (PPT) - 1.0MB]
• When's a Planet Not A Planet? [Powerpoint slides (PPT) - 1.6MB]
• Recent Photos From Saturn [Powerpoint slides (PPT) - 10.8MB]
• Saturn Through Cassini's Eyes [low resolution video (MPEG1) - 60MB]
• Saturn Through Cassini's Eyes [high resolution video (MPEG2) - 130MB]
  

Perhaps you heard about the asteroid that passed close by the Earth recently? On the morning of July 3rd, the asteroid designated 2004 XP14 zoomed by at a distance only slightly further away than the Moon's orbit - approximately 270,000 miles. In astronomical terms, that's very close, indeed. As chance would have it, North America was about the best place to be to view the fly-by, so many amateur astronomers had an excellent chance at a first-hand look. Since the asteroid is only 800 meters (1/2 mile) across, even at it's closest approach it was expected to brighten to only 11th magnitude - quite faint for amateur observers. I certainly couldn't see such a faint object from the city. But luckily I was to be in Mammoth Lakes, high in the Sierra Nevada mountains on that evening. Could I find it myself? I took it as my next observing challenge!

On June 21st, I hosted the first-ever summer-time Astronomy Night at Rolling Hills Country Day School (RHCDS). At the previous gathering in May, a number of parents had suggested the summer hiatus was no reason not to get interested school families together to enjoy the night sky. I certainly wasn't going to argue. Since Jupiter is the dominant night-sky object right now, I decided to focus attention there. The monthly almanac in Sky & Telescope magazine indicated that the Jovian moon Io would transit Jupiter on the evening of 6/21, its shadow beginning a match across the giant planet at approximately 9:45PM PDT. This is a fascinating sight, even for regular Jupiter observers, so I decided to time our activities around it.