Moonshine, Sunshine, Treeshine


The last quarter moon Wednesday morning. Notice that the
sunlight falls on the same side of the moon as
it does on the trees. Photo: Bob King

Went to get the morning paper just after sunrise today and was greeted by the last quarter moon hanging low in the southern sky. Did you see it too? By the time I fed the dog, the first sunlight touched the trees. That’s when it happened. Suddenly I saw the light … literally. The moon was lit on the same side as the trees. I suppose I shouldn’t have been surprised, but in that moment, a routine bit of cosmic geometry connected the distant moon to the sunlit branches in my front yard. The layout of the our neck of the solar system was thrust into clarity.


The view from space today of the moon, Earth and sun as seen from above. Sunlight illuminates the left half of the moon from our perspective. Our observer (in red) stands on the sunrise line separating day and night on our planet. Illustration: Bob King

Two weeks from today on April 2, these circumstances will repeat but with a twist. Then the moon will be in the evening sky in its first quarter phase, and we’ll see the trees and the moon lit on the other side at sunset. What about full moon? Since the full moon is opposite the sun and rises at sunset, we’ll see both moon and trees lit face on — no sidelighting — on April 8-9.


A gorgeous image of the quadruple transit on Saturn taken last month. From left, you can see the moons Enceladus and Dione and their shadows. Titan’s the big one at top, while tiny Mimas is the white pinprick at far right. Click here to enjoy the high-resolution version. Credit: NASA/ESA/Hubble Heritage Team

You might recall the quadruple transit of Saturn’s moons on February 24. The Hubble Space Telescope’s camera was busy snapping away as the moons and their shadows dotted the planet’s cloud belts. Because we can only view transits when Saturn’s rings are nearly edgewise to us, a circumstance that happens every 14-15 years, any transits are rare. This one was particularly special because so many moons took part. View more images at this website.


As Saturn travels around its orbit, Hubble sees a different view of the tilted rings from a position near Earth. The rings nearly disappear twice during Saturn’s approximately 30-year orbit, because we see them edge on and they’re extremely thin relative to their diameter. Illustration Credit: NASA, ESA, and Z. Levay (STScI)

Were you doing anything particular at 7:17 Central time this morning? Frying some eggs or combing your hair? At that moment, an approximately 60-foot long asteroid flew only 49,000 miles over your head. That’s just twice the distance of the main belt of communications satellites in orbit around the Earth. Called 2009 FH, the asteroid posed no danger to our planet now or in the future, but it’s a great example of the potential for an impact when you least expect it. Smaller versions of 2009 FH fall all the time as meteors, some of which land on Earth as meteorites. The recent West, Texas fall comes to mind.

Tonight the International Space Station-Discovery space shuttle will make a high, bright pass over the region beginning at 8:40 p.m. Watch for it to rise in the west and pass an outstretched fist above the North Star before fading out in Earth’s shadow at the end of the Big Dipper’s Handle.

Dig out your binoculars because tomorrow we’ll talk about how to find one of spring’s brightest galaxies.

2 Responses

  1. Jordan

    Caught your page out in CA while just doing a little astronomical reading for fun. Originally from Duluth myself, it’s nice to see someone from back home taking advantage of the incredible beauty the Great North has to offer. Sure enjoyed your posts!

  2. astrobob

    Thanks for writing Jordan, and I’m glad you enjoy the posts. How are the night skies where you live in CA?

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