The short video above clearly describes how the tilt of the Earth’s axis causes the seasons.

We’ve come to the end of February and tomorrow will tiptoe into March. Traveling at 66,487 miles per hour aboard spaceship Earth, you and I have traveled over 110 million miles around the sun since the first day of winter. That’s far enough to see a new set of constellations surge into the eastern sky as well as to change our hemisphere’s orientation with respect to the sun. No longer is the northern hemisphere pointed directly away from the sun as in December. Spring, the time of equality of light for both hemispheres, is just three weeks away. You’ve probably already noticed that the sun is considerably higher now at noon; it also rises and sets further north. We’ve gained a full hour of daylight in the morning and an hour and a half in the evening. Even with bright moonlight, I could still see the blue tint of twilight in the west yesterday at 7 o’clock.

The star Sirius sparkled in the southeastern sky when I photographed it at 7 p.m. in moonlight last night. Details: 35mm lens at f/2.8. 15-second exposure at ISO 800. Photo: Bob King

Speaking of twilight, two people asked me this week what that bright star is in the south just as the sky gets dark. Although we’ve visited with this star several times over the winter, it doesn’t hurt to return to it again in case you’ve forgotten. It’s Sirius in the constellation Canis Major and the brightest star in the entire night sky. No photo can quite capture its searing, magnesium-white flame. Sirius is 1.75 times the sun’s diameter and about 25 times brighter. Combined with its relative proximity to Earth of just 8.6 light years, it’s no wonder it shines so brightly. Sirius remains prominent in the southern sky throughout March.

Face the moon to find Saturn over the next couple evenings. Created with Stellarium

The moon will be full tonight and conveniently positioned midway between Leo the Lion’s brightest star Regulus and the planet Saturn. Tomorrow night it’s even closer to Saturn. If you’ve been wondering just how to find the ringed planet, let the moon be your guide.

Supernova (SN) 2010Y is an exploding star in the galaxy NGC 3392 not far from the bowl of the Big Dipper. The light from the stellar explosion is so intense it shines as brightly as the galaxy’s entire nucleus which is packed with millions of stars. NGC 3394 is another spiral galaxy in the same field of view.  Credit: William Wiethoff

Champion supernova photographer William Wiethoff of Port Wing, Wisconsin sent me some photos of recent supernovas he photographed with his 14-inch telescope Friday night. At any particular time, there might be a dozen or so supernovas visible in galaxies beyond the Milky Way. Most are very faint and difficult to see visually but show up well in long time exposure photography. 2010Y was the 25th supernova discovered this year and was found by amateur supernova hunter Giancarlo Cortini of Italy on February 8. The host galaxy, NGC 3392 is located about 150 million light years from Earth. This one is bright enough to see at high power through larger amateur telescopes. Supernovas come in two basic varieties:  supergiant stars that run out of nuclear fuel in their cores which leads to collapse, implosion and then explosion or white dwarf stars that "put on" too much weight and explode like titantic thermonuclear bombs.

Early this week spacecraft will make close flybys of three planetary moons. On March 2, Cassini will take closeup photos and "sniff" Saturn’s moon Rhea for unusual particles it might be giving off, while on the 3rd it will photograph the small moon Helene. Also the 3rd, the European Mars Express craft will take the closest pictures ever of Mars’ moon Phobos. We’ll have images to share as they arrive. 

I was a just a boy of 10 or 11 when I first got interested in astronomy. I still can’t recall exactly what spurred my interest — was it the space program, a total lunar eclipse or did I just decide to look up for the first time and wonder? From suburban Chicago I followed the motions of the planets and still have meticulous notes of lunar conjunctions, ice halos and interesting clouds. At age 13 I decided it was time to start an astronomy club. It went by the somewhat overblown name "The Organization of Amateur Astronomers" and garnered a few of my grade school friends. We hung out talking about astronomy … and girls.

Two of my favorite inspirational books from that time were Eleanor Cameron’s The Wonderful Flight to the Mushroom Planet and The Stars by Herbert Zim and Robert Baker. The first was a science fiction story about two boys who saw an ad in the paper looking for someone to build a rocket ship for a very special mission:

"WANTED: A small space ship about eight feet long, built by a boy or two boys. The ship should be sturdy and well made, and should be of materials found at hand. Nothing need be bought. No adult should be consulted as to its plan or method of construction. An adventure and a chance to do a good deed await the boys who build the best space ship. Please bring your ship as soon as possible to Mr. Tyco M. Bass, 5 Thallo Street, Pacific Grove, California."

They go on to meet the curious and kind Tyco Bass, build the space ship and travel to a little, inhabited moon called Basidium that can only be seen with a special filter from Earth. On Basidium the boys use real science to discover why the Basidiumites are sick and how to make them better. I loved the idea of flying off into space in my own rocket without adult supervision. What 10-year-old boy or girl wouldn’t? The story’s mix of science, adventure and friendship absorbed every proton of me. I went on to read the remaining four books in the series but the first remains my favorite.

The other book, titled Stars: A Guide to the Constellations, Sun, Moon, Planets and other Features of the Heavens, was one of the Golden Nature Guide series. It cost all of a dollar and contained seasonal star maps, short chapters on the planets and stars and the best illustrations ever. With no steady income I only had a few astronomy books at the time and this was my favorite. I learned my constellations and all the basics about the sky, the seasons and celestial motions. The illustrations, which were done with warmth and a feel for the seasons, appealed to my developing romantic nature.

Not surprisingly both books are still in print. That’s how good they still are. As I got older, I went on to read every astronomy book and magazine I could get my hands on, but those two volumes remain close to my heart. If you have a favorite inspirational book about the sky, we’d love to hear about it. Just click on the comments link below.

This illustration comes from the Constellations of Spring chapter in the Stars. Credit and copyright: James Gordon Irving, Golden Press.

I leave you with a recent photo of a little moon about the size of Tyco’s Basidium. This one’s called Calyspo and it’s far away in orbit around the planet Saturn. Measuring only 12 miles across and as white as snow, Calypso has an unusually smooth surface that scientists think might be covered in fresh ice particles falling from Saturn’s E ring. Much of the E ring ice likely originates from the plumes of icy vapor spewed by yet another Saturnian moon, Enceladus. Thanks to space probes like Cassini we can all go along for a vicarious ride to places only imagined when the mushroom planet books were written.

The Cassini probe made its closest approach ever about two weeks ago to Saturn’s small moon Calypso. It shows an unusually smooth surface. Scientists hypothesize that ice filled in many of the moon’s craters, evening out the rough spots. Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

This photo was taken by an astronaut on February 19 of Endeavour mission commander George Zamka who was visiting the new cupola while the shuttle was still docked to the space station. You don’t see any stars in the background because the exposure was made for sunlight, too brief to capture faint starlight. Credit: NASA

What a view! Astronauts on the Endeavour space shuttle delivered the Tranquility node to the space station during the most recent mission. The new module included a cupola, a dome-shaped viewing port with seven windows. The cupola will give astronauts a better visual take on docking operations, spacewalks and future robotic work on the station’s exterior. Typically these operations have been performed "remotely" using video monitors. Very awkward. The dome will also give astronauts incredible panoramic views of outer space and better opportunities and angles for shooting pictures of the Earth.

A coronagraph aboard SOHO uses a metal mask (center) to cover the sun so it can photograph its outer atmosphere. SOHO also recorded the planet Jupiter (bright with a glare streak) in this photo taken yesterday. The center white circle is the outline of the sun behind the mask. More SOHO photos HERE. Credit: NASA/ESA

Jupiter has disappeared from the night sky but not from the cameras aboard the orbiting Solar and Heliospheric Observatory (SOHO).With no atmosphere in the way to scatter light and brighten the sky, SOHO can simply block the sun from view and see stars and planets in the middle of the day the same way you’d block the moon with your hand to see a star near it. Jupiter will be in conjunction this Sunday when it passes very close due south of the sun. From our perspective, the planet will lie exactly on the opposite side of its orbit from Earth and farthest from us for the year. After conjunction, Jupiter will gradually reappear in the morning sky in the constellation Aquarius. In the photo above, try to imagine Jupiter far behind the sun to the tune of almost half a billion miles.

That nearly pure white crater is Aristarchus, a spot so bright on the moon that you can see it in earthshine when the moon’s a thin crescent. If you succeed in finding the crater, see if you can also spot its neighbors, Copernicus and Kepler. Details: Small telescope at f/14, ISO 100 at 1/60" exposure. Photo: Bob King

The moon is nudging toward full phase (Sunday the 28th) as it moves from Cancer toward Leo. Tomorrow night it’ll be just five degrees or "three fingers" below Leo’s brightest star Regulus. Last night was what I like to call "Aristarchus night" when the moon’s most brilliant crater makes its first appearance on the sunny side of the terminator.

The crater is named after the ancient Greek astronomer Aristarchus of Samos, who first proposed the idea that the sun — not the Earth –  was the center of the solar system. He even got the planets in the correct order, but his ideas were rejected in favor of an Earth-centered cosmos. It just made more sense at the time. Back then people believed that if the Earth rotated, a ball thrown straight up into the air wouldn’t land back in the same place as it was seen to do. We know now that both the ball and the thrower share the same speed because Earth carries us and everything else along with it. A similar situation thing happens in an airplane which is traveling at over 500 mph — the passengers don’t crash into each other because we’re all traveling at the same speed and at rest relative to one another.

Aristarchus brilliant idea lives on with his namesake crater. It measures 28 miles across, modest by moon standards, and is located in a vast, relatively smooth lunar "sea" called the Ocean of Storms. This is the moon’s largest sea, and it stretches across some 1500 miles. Most lunar craters are more than three billion years old but Aristarchus’ age is estimated to be only 450 million, a teenager in comparison. That’s why it’s so bright. When the asteroid hit that excavated the crater, it exposed fresh lunar soil from beneath the surface. Over time the soil, or regolith as it’s called, weathers to darker greys under the influence of the sun’s radiation. The crater’s relative youth gives it that fresh-faced look and also makes it an easy target for binoculars.

Give it a try with your binoculars during the next few nights. Look for a small, bright spot well off to the east or left side of the moon. If your vision is keen, you can even see Aristarchus with your naked eye. The diagram at right simulates a binocular view and will help you to pinpoint the brilliant spot that still recalls the man with ideas far ahead of his time.

A closeup of Aristarchus as photographed by the Hubble Space Telescope. The bright streaks in the crater’s walls as well as the central mountain peak are visible in modest-sized telescopes. Through any telescope Aristarchus is so bright it looks "white-hot". Credit: NASA/ESA

One regular-sized flake and one tiny one dress up my deck this morning after a light snowfall last night. Photo: Bob King

I know, I know. I should have taken a picture instead of describing to you know how incredible it was to see hundreds of snowflakes silhouetted against the gibbous moon last night. When I went to walk the dog, I was struck by the unusual combination of snow and moonlight. The clouds were thin enough to reveal individual flakes flying past the moon like runners in front of a spotlight. The best I could do was photograph the the pillowy piles of snowflakes on my deck this morning. A flake is composed of ordinary water molecules but who isn’t amazed by how much beauty is wrought by so minute and simple an ingredient?

Not only will the moon and Mars be close tonight (Thurs.) but there are other bright stars in their vicinity to spark up the scene. This may shows the sky around 7 o’clock. Created with Stellarium

Tonight the moon will return but according to our local forecast without snowy accompaniment. Not that the moon will be lonesome. Far from it. It’s in conjunction with the brilliant planet Mars, and the two will certainly catch your attention if you’re out and about. Look high in the eastern sky. Mars will sit atop the waxing gibbous moon.

Yesterday one of our readers, Andrew Kirk, wondered if there was a time-exposure photo available of the Magellanic Clouds circling around Sigma Octantis, the southern pole star. After some digging and contacting, I’m pleased to share with you several very nice images of star trail photos of both northern and southern skies. Enjoy!

This award-winning photo was taken by Australian Ted Dobosz while camping in the Blue Mountains near Sydney. It’s a half-hour long time exposure aimed at the south celestial pole and shows the Large and Small Magellanic Clouds (right of center). The stars and Clouds trailed during the exposure because of Earth’s rotation. No trailing is seen at the pole because it lies in the direction of our planet’s south polar axis. The orange glow is light pollution. For the full-sized version, please click HERE. Details: 17mm lens at f/4.5, 30-minute exposure at ISO 400. Credit and copyright: Ted Dobosz

Another amazing view of the southern sky and dim southern pole star Sigma Octantis from the shore of Lake Titicaca in Bolivia. The bright band at upper right is the Milky Way. This very long exposure shows well the apparent motion of the stars due to Earth’s rotation. Details: 16mm lens at f/4, 2-hour exposure at ISO 800. See more nice star trail photos HERE. Credit and copyright: Fred Espenek

Let’s return now to the northern hemisphere and take a look at how stars circle about Polaris. While you may have had a hard time finding the southern pole star in the photos above, you can’t miss the tiny, bright arc of the North Star near the center of this picture. For more photos by the photographer, please click HERE. Credit and copyright: Kirk Rogers

This time exposure was taken in the forest north of Duluth a few years back. Can you find the outline of the Big Dipper in the seven bright trails at top? Photo: Bob King

If you’d like to make your own star trail photos of the stars near the north or south celestial pole, you’ll need a camera that can take a long time exposure and a tripod to put it on. Go out to a dark sky site on a moonless night and use a wide angle lens — something in the range of 24mm or wider. Frame your picture with an interesting foreground, set your f-stop on the lens to f/4 or 4.5, and lock your camera shutter open with a cable release. Try an exposure of at least 15 minutes. If your sky is really dark, you can go for an hour or longer. You’ll love the results.

Last night in my community education class a student asked about a southern polestar. "Do they have one like we do?" Yes they do, but it’s one not likely to catch the eye for most casual sky watchers living in the southern hemisphere.

If you extend the Earth’s imaginary axis into space it points at Polaris for northern hemisphere viewers and at Sigma Octantis for those living in the southern hemisphere. Illustration: Bob King

Our polestar Polaris is relatively bright and easy to find. You use the convenient "Pointer Stars" of the Big Dipper to point the way. Polaris is the same brightness as the brighter Dipper stars and sits at the sky’s north celestial pole, a point in the sky directly above Earth’s north polar axis. From the diagram above you can see that our inclined axis points straight out into space and by good fortune is aimed right at Polaris. As our planet rotates, all the other stars in the northern sky appear to describe circles around the polestar which remains nearly stationary atop the north celestial pole.

With the help of the Big Dipper, Polaris is easy to find. This map shows the sky around 8:30 p.m. Maps created with Stellarium

The Earth’s south polar axis also points into space in the direction of the faint constellation Octans the Octant, named after a navigational aid similar to the sextant. The brightest stars in Octans are only fourth magnitude and only dimly visible from a suburban location. Worse yet is the southern polestar. It’s barely above the naked eye limit and too faint to even garner a proper name like Polaris. Called Sigma Octantis, it’s located just as close to the south celestial pole as Polaris is to the north and shines at magnitude 5.5.

This map shows the sky from Sydney, Australia looking due south around 1:30-2 a.m. in late February. Southern observers can use the axis of the Southern Cross (Crux) to point them to the southern polestar. LMC and SMC stand for the Large and Small Magellanic Clouds, small satellite galaxies of the Milky Way.

When I flew down to Peru with my buddy Glenn back in 1986 to view Halley’s Comet I was able to see Sigma Octantis low in the southern sky from our desert observing site. Like the Big Dipper in the north, the Southern Cross, formally called Crux, points the way to Sigma. Draw a line through the north-south axis of the cross and it will take you to right to it. OK, so it’s not much to look at, but it does serve the same purpose as our polestar. From the perspective of those living down-under, all the stars in the southern sky appear to describe circles around Sigma Octans during the night. Despite its obscurity, Sigma rules!

Even if Octans doesn’t grab your attention, there’s much to see in the neighborhood. The second brightest star in the sky, Canopus, lies off to the west. Several outstretched fists above the octant you’ll find Alpha Centauri, probably the most famous star in the sky after the sun. Alpha is a triple star system and the closest star to Earth beyond our own. Then there’s the bright and compact Southern Cross — you can easily cover it with four fingers — which shines both in the sky and on Australia’s flag.

The Small (left) and Large Magellanic Clouds. Each galaxy contains many stars as well as star clusters and gas clouds like the Milky Way but packaged in a smaller volume. Each looks like a fuzzy chunk of the Milky Way set adrift in the night sky. Credit: ESO/S.Brunier

The two fuzzy objects on our map are the Large and Small Magellanic Clouds, the two brightest companion galaxies of the Milky Way galaxy. Named after Ferdinand Magellan, who with his crew were the first Europeans to sail around the globe, they belong to a group of about a dozen galaxies gravitationally bound to our own. The peoples of the southern hemisphere were long familiar with the clouds, but Magellan "discovered" them for European civilization in 1519. Unlike the grand spiral design of our Milky Way, the Magellanic Clouds are classified as irregular dwarf galaxies and only about a tenth its size. The LMC lies 179,000 light years away while the SMC is 210,000.

While driving back from an archaelogical site in the Peruvian desert our car broke down one afternoon, and we were forced to wait hours until help arrived. Glenn and I nursed the vehicle to a truck stop and had dinner by lantern. My most vivid memory of the place was an enormous painting of a topless mermaid on the interior restaurant wall. We invited the staff outside later when the sky got dark and showed them Halley’s Comet. That was the first time I got to see the Large Magellanic Cloud, and it was a thrill to see the real thing after years of studying pictures in textbooks. Me and Magellan, yeah, we were gellin’.

A map showing the satellite or companion galaxies of the Milky Way. We’re the Big Kahuna in the neighborhood. The other galaxies revolve around ours with periods of millions of years. Credit: Richard Powell

To find Arcturus, face northeast around 10 o’clock from a location with a good view of the eastern sky. Start with the Big Dipper and follow the bend in the Dipper’s handle straight down to Arcturus. Saturn is three outstretched fists to the right and above Arcturus and a magnitude fainter. Created with Stellarium

We touched on winter and summer stars in yesterday’s blog but between these extremes lies the transition season of mud and grass fires we call spring in Duluth. Just as winter has Orion, spring has brilliant Arcturus in Bootes the Herdsman. No need to set the alarm to see this one. If you’re out around 10-10:30 p.m. and look to the northeast, Arcturus is that flashing red ruby well below the Big Dipper. Just follow the arc of the Dipper’s handle down toward the east and you can’t miss it. Arcturus is the third brightest star in the sky and "waiting in the wings" low in the northeast. Catch sight of it now and you’ll be able to follow its gradual ascent to dominance in the southern sky come May.

Arcturus is an orange giant star 26 times larger than the sun and shines 110 times more brightly. When you find it, consider that the light you see left the star in 1973 which is another way of saying it’s 37 light years away. The name Arcturus derives from "arktos" the Greek word for bear (also the root of the word arctic), and indeed Arcturus means the Bear Guard. He keeps watch on Ursa Major the Great Bear (Big Dipper) as the bear paws his way up in the northeastern sky during February and March.

Arcturus is 22.5 million miles in diameter compared to the sun’s 864,000 miles. Illustration: Bob King

Once you’ve found Arcturus, look three fists to the right and above it and you’ll bump into the planet Saturn. It’s in Virgo and a little higher up in the southeastern sky. Saturn, while bright at first magnitude, is no match for brilliant Arcturus. If you compare the two, you’ll notice a key naked eye difference between a planet and a bright star. Stars twinkle and planets generally do not since planets have measurable disks compared to the pointlike stars. Air turbulence affects tiny point sources much more than celestial objects that have distinct dimensions.

Highlights this week include nice pairings of Mars and Saturn with the moon plus the improving visibility of Venus after sunset. Illustration: Bob King

This map shows the sky for tonight with the waxing moon at upper right. The Winter Triangle is easy to find in the south through mid-March during the early evening. The cloudy band is the Milky Way. Maps created with Stellarium

For most of us one slice of pie is plenty but for the astronomically inclined, we may help ourselves to two this month and next. I’m referring to the two large triangles of stars — one in the evening, the other in the morning — that call our attention in the night sky.

While the constellations have their individual patterns and associated stars, many of us love to go to the next level of pattern-making by constructing superconstellations using stars from multiple sources. Case in point is the Winter Triangle, now prominent in the evening at the convenient hour of 8 o’clock. It’s formed from Procyon of the Lesser Dog, Sirius from the Greater Dog and Betelgeuse from Orion the Hunter. With three nearly equal sides and angles, the triangle formed is close to being equilateral. I don’t know when this figure originated or by whom, but it’s bright and crisp and a big help in finding other constellations in Orion’s neighborhood.

The Summer Triangle is highest in the eastern sky at the start of dawn. Vega, the topmost  and brightest star in the figure, is Lyra the Harp’s brightest star; Deneb heads up the Northern Cross, also known as Cygnus the Swan, and Altair is the brightest star in Aquila (AK-will-uh) the Eagle.

Our second triangle is the familiar Summer Triangle visible in the eastern sky at dawn’s first blush. It’s more of an acute triangle, where none of the angles is greater than 90 degrees. This triangle is larger than the winter version with the two long sides about three outstretched fists in length. Two fists separate Deneb and Vega. Coincidentally, the Milky Way crosses through the center of both winter and summer triangles though the summer version is considerably brighter and easier to see.

The changing starscape of the morning sky reminds us that warmer weather and longer days are on the way. My friend Greg, who arises before dawn to drive to work each day, is cheered by the trio of Deneb, Vega and Altair in the east. It’s balm for his summer-starved soul. Perhaps you need some cheering, too? It’s waiting for you the next clear morning.

This time exposure photo taken this weekend shows the Milky Way and the Summer Triangle. Details: 16mm lens at f/2.8, ISO 1600 and 25-second exposure. Photo: Bob King

Last night’s moon photographed through a small telescope.
Sunlight comes in a at low angle along the day-night boundary
(terminator) casting long shadows that enhance the outlines of craters
and other landscape features. Photo: Bob King

I stopped during a walk in the woods yesterday and looked around at the small balsam firs standing in snow littered with bits of bark, pine cone scales and broken evergreen needles. This is where I belong, I thought. Somehow a kid from Chicago found his favorite place on Earth, and it turned out to be in the middle of a scrubby forest atop volcanic bedrock. I’m not sure how we become more comfortable in one landscape over another but I’m glad for it. Perhaps you have a special corner of Earth you call home. If so, I hope you’re living there now.

What a nice surprise the clear sky was last night. I spent at least an hour looking at the moon in the scope. All sorts of delicacies were on the table from thread-like faults to ancient, colorful lava flows to watching the first rays of sunlight touch the pinnacle of a mountain peak inside a shadow-filled crater. If northern Minnesota is my primary home, the moon is my second. Because it’s so close to Earth, a vast amount of detail is visible even in a small telescope. If I had no need for sleep, I’d spend the whole night looking at the moon. Soft, moist eye meets dry, sunbeaten rock. What wonders we’re permitted to enjoy in a lifetime.

Three mountain ranges come into view tonight near the terminator in moon’s northern hemisphere (top half). Photo: Bob King

Tonight the moon’s terminator scootches further to the east; what was in shadow last night emerges now into sunlight. Highlights this evening include a great profusion of craters large and small in the vicinity of the terminator. Some of these as well as three of the moon’s 18 mountain ranges — the Apennines, Alps and Caucasus — are visible in binoculars. The Apennines are a gently curving range about 400 miles long with peaks as high as three miles. Their tops will be lit in the early morning lunar sun. Can you also see the other two ranges in binoculars? Give it a try tonight.

Mountains on Earth generally form as a result of moving tectonic plates that "bump" into one another. On the moon, many of the most prominent mountain chains like the Apennines were formed from rock uplifted during enormous impacts long ago. One of the largest dark spots that forms part of the "man in the moon’s" face is Mare Imbrium or the Sea of Rains. This 700-mile diameter basin was formed formed by a colossal asteroid impact about 3.7 billion years ago which later filled up with lava. Several mountain ranges define its perimeter including the Apennines.

Were you out this morning to see the shuttle Endeavour and space station cross through the sky? I went out not knowing how far apart in time they’d be. Endeavour came first and passed right next to Saturn as it traveled from the southwest to the southeast. But where was the space station? Ah! Two minutes later the considerably brighter station followed virtually the same path.

We might have another chance to see them tomorrow morning if the weather is bad at the landing sites. For Duluth and region, take a look in the southeastern sky at 5:06 a.m. for the shuttle followed by the space station at 5:10 a.m.

 
Both Endeavour and the ISS flew right past Saturn during dawn this morning. Since their paths are not identical they must have been in slightly different orbits, one higher and the other lower. Details: 35mm lens at f/2.8, 25-second exposure at ISO 200. Photo: Bob King

The flag next to the Duluth Public Library flaps in the wind toward the crescent moon earlier this week. The ghostly glow of earthshine is visible above the crescent. Details: 180mm telephoto at f/2.8, ISO 1600 and 1/50" exposure. Photo: Bob King

The lunar crescent was a big banana last night and bright enough to set the landscape softly aglow. Tonight the moon will pull up alongside the Pleiades or Seven Sisters star cluster in Taurus. Matter of fact, the moon, Pleiades, Hyades and Orion all parade together high across the southwestern sky around 8 o’clock.

The moon will be near the Seven Sisters cluster tonight and tomorrow night as it transitions from a thick crescent to half. This map shows the sky as you look toward the southwest around 8 p.m. Maps created with Stellarium

Because the moon is less than half-lit tonight (40 percent), the boundary separating the bright, daylit part from the part still not in sunlight will be slightly curved. This boundary is called the terminator. Sunday night the moon will be seven days old, exactly half-lit and the terminator will run straight up and down. Try to visualize the terminator as the advancing edge of sunrise on the moon’s surface. The moon never sits still but is always moving apace in its orbit around Earth. Before full moon, the terminator advances toward the east (left) and reveals a new slice of lunar landscape each night. After full moon, the moon’s phase lessens or "wanes" and the terminator becomes the advancing line of lunar sunset. When the sun has set over most of the moon, we see it as a thin crescent in the morning sky at dawn. The moon disappears for a day or two around new moon phase because it’s lost in the glare of the daytime sun. When it reappears as an evening crescent, the terminator once again becomes the advancing line of lunar sunrise. The changing phases and shifting terminator of the moon are ultimately caused by the ever-changing angle between Earth, sun and moon during the moon’s monthly orbital cycle. Use the illustration below to help guide you through the phases.

A full cycle of lunar phases as seen from the northern hemisphere. Sunlight shines from the right. Starting from left, the moon begins its cycle in new moon phase and waxes toward full. After full moon, it wanes to a thin crescent and returns to new to repeat the cycle. Credit: Wiki commons

I didn’t get up this morning to see the shuttle-space station combo but others who did say the sight was very cool. Here’s Lyle Anderson’s report from Duluth: "I decided to step out and glance at the sky, and the sky was nice and clear. I did not think I would have had time to get the camera and tripod set up, and I did not want to miss the flyover. What a spectacular sight, and there they were cruising across the sky northwest to southeast and so bright. Endeavour leading ISS by a few degrees and getting up to around 68 degrees at the highest. Endeavour was not quite as bright as the station but still quite bright. What a spectacular site cruising across the sky."

We’ll have one more opportunity to see the two ships tomorrow morning before the shuttle lands tomorrow night at Kennedy Space Center in Florida.

The International Space Station and shuttle Endeavour made an eye-catching pair this morning in this photo taken by Marco Langbroek of Leiden, the Netherlands. At the time they were separated by just a couple degrees and crossed the sky in tandem. Credit and copyright: Marco Langbroek

I got a press release yesterday from NASA about the launch of the Solar Dynamics Observatory (SDO) last week. As the rocket carrying the observatory was launched, it passed through high cirrus clouds and a colorful sundog created by floating ice crystals. The rocket’s great speed sent a shock wave through the hovering crystals disrupting their orientations and causing the sundog to suddenly vanish. In the video above you can actually see the shock wave ripple through the clouds as the sundog goes poof! Sundogs are formed by millions of tiny, plate-shaped ice crystals with their broad, flat faces oriented parallel to the ground. The shock sent them scurrying. It really gives you a new appreciation for how evanescent and delicate sundogs truly are.

An artist’s view of NASA’s new Solar Dynamics Observatory (SDO) launched last Thursday. The satellite contains a variety of instruments that will study everything from the sun’s interior to its outer atmosphere called the corona. It can take a photo of solar activity every 1/10 of a second. Credit: NASA/Goddard Space Flight Center

The new solar observatory will help us learn more about the sun’s effects on Earth and near-Earth space by studying the sun in multiple wavelengths (colors) of light over very short timescales. Scientists hope to learn what drives the 11-year sunspot cycle, how the sun’s magnetic field is generated and how the energy from that field is released into space by flares and other eruptions on the sun’s surface. SDO’s pictures will also have better resolution than those taken any other current space observatory.

Yesterday I mentioned how Mars’ retrograde movement to the west is slowly coming to a halt. In three weeks the planet will appear stationery in the sky, anchored just to the left and below the two bright stars Castor and Pollux in Gemini the Twins. Mars resumes its normal eastward motion on March 12 when it begins to track back toward Leo the Lion.

 
This map shows a big chunk of the south-southwestern sky from now into early spring and positions for Mars through the end of April.  Mars spends several more weeks in nearly the same spot before changing direction and moving east (left). Created with Stellarium

 In a blog last month we learned this apparent loop-de-loop Mars makes is a perspective effect that happens whenever our faster planet pulls up alongside and then passes slower Mars. Like one car passing another on a freeway, the car being passed appears to slow down and drop backwards as you pass.

Mars has been "going backwards" since late December. Now that we’ve passed it, the Red Planet will once again start heading east. The NASA diagram (right) helps us visualize Mars’ retrograde loop in step-by-step fashion.

We were at the "c" spot in mid-December and have traveled from d toward e since then. During March and April, we’ll start at e and move toward f. As we pull away from Mars toward g, the planet will quickly shrink in size and fade.

Tomorrow and Sunday morning you can watch the International Space Station (ISS) and Endeavour space shuttle flying near one another in the morning sky.  Yes, two satellites for the price of one! Endeavour has undocked from the ISS in preparation for its return to Earth. Here are Central times for viewing the ISS across northern Minn. / NW Wisc. When I get them, I’ll post separate times for Endeavour. (UPDATE 8 p.m.: No special times for Endeavour. It should be flying very near the ISS.) For pass times for your town, please click HERE and enter your zipcode.

* Saturday morning beginning at 5:53 a.m. A brilliant pass across the north-northeastern sky. 
* Sunday at 6:14 a.m. Another brilliant pass high across the south-southeastern sky.
* Monday at  5:05 a.m. (Bright and low across the south) and again in the southeast only at 6:38 a.m.