Astro Bob A look at celestial happenings in the Northland and beyond Bob King View my profile Click here to view previous posts or additional resources

Of tendrils, impacts and asterisms

A halo around the sun yesterday morning came ornamented with cloudy tendrils. Photo: Bob King

I was at a photo assignment yesterday and tried to figure a way to incorporate the halo around the sun in a creative way with my subjects. None of the angles worked, so I just shot it straight which was OK, because there were these crazy cloudy tendrils along one side that made it look like a jellyfish. Halos are very common and form large, narrow rings around the sun and moon when high, icy clouds blow by. We looked at their origin in a blog last week; that time a lunar halo was our focus.

Splat! On April 14th 1970, the Apollo 13 Saturn upper stage impacted the moon north of Mare Cognitum. The impact crater is roughly 30 meters (98 feet) in diameter. Credit: NASA/Goddard/Arizona State University

How about a halo of an altogether different sort? NASA released this photo last week of a manmade lunar crater created by the impact of the Apollo 13 rocket booster. It was taken by the probing eye of the orbiting Lunar Reconnaissance Orbiter (LRO). The Saturn rocket that launched the Apollo craft to the moon consisted of three stages, two of which fell back to Earth. The final stage (at right) propelled the Command and Lunar Modules on their way to the moon. When the booster stage was spent it was jettisoned and directed to hit the moon. Forty years later we have our first clear picture of the impact.

Fresh material exposed by the explosive hit appears like a crown of white rays around the crater. Similar bright ray systems around naturally-made craters indicate relative youth; the moon's soil darkens with time under the influence of sunlight and the solar wind.

The LRO has also been busy lately photographing 1970s-era Soviet lunar landers and rovers on the moon with its narrow angle cameras that can resolve features as small as 1.6 feet across. For latest pictures and information, please click HERE.

The full moon was very bright and cast a joyful light last night around her from its perch in Virgo the Virgin. Around 10 o'clock I could see the terminator (the day-night dividing line) around its northern edge. Lots of foreshortened craters there were partially filled with shadow.

While returning from a night walk a little after 10, I briefly faced west to see the Great Hunter Orion nearly level with Sirius and Aldebaran across the western sky. There weren't many other stars but these still held their own in the moonlight. It was an interesting configuration, one of those asterisms of stars that grabs your attention.

The full or nearly full moon washes out the great majority of the night's stars leaving only a skeletal staff of the brightest to carry on. With a bright moon out tonight we'll once again be star-deprived, but that's not necessarily a bad thing. Moonlight clears away distracting fainter stars letting certain patterns appear even bolder than on dark nights. Perhaps the Sirius-Orion-Aldebaran alignment will catch your eye as it did mine.

If you look west around 10 tonight Orion's Belt is nearly level with the stars Sirius in Canis Major and Aldebaran in Taurus. Created with Stellarium

(Rocket booster photo above by NASA)

Posted by: rking@duluthnews.com on 3/29/2010 at 3:41 PM | Comments (0) | Permalink | Edit

Tags: daily updates, lunar reconnaissance orbiter, apollo 13, full moon, astro bob, life, halo, sun, lro, orion, sirius, aldebaran