Aurora out tonight April 12 in Duluth, Minn.

Active aurora spreads across the lower half of the northern sky about 10 p.m. CDT tonight from Rice Lake Township north of Duluth. Photo: Bob King

Just a heads up from Duluth, Minn. The Kp index hit “5″ at 9 o’clock tonight and the northern lights are putting on a modest show as of 10 p.m. CDT. We have high clouds moving in, but a chunky green arc with a few active rays are sliding around low in the northern sky. The ray tops are reaching about 20 degrees (two fists held at arm’s length); the arc’s about 10 degrees up. There’s a fair amount of movement, but you’ll need to get out of town to a place with a good northern horizon to appreciate it.

The auroral oval is expanding southward tonight. We can see its edge as active auroral arcs low in the north from the northern U.S. The red line is the approximate edge of visibility. Credit: NOAA

Chance for auroras, North Korea’s shining star and Comet Garradd

The green glow of geomagnetic goodness painted the bottom of the northern sky early this morning. Minor auroras are forecast for tonight for northern regions. Photo: Bob King

The aurora crept up in the north very, very late last night. Just a green glow, not too much. I noticed the light around 11:30 p.m. and watched it slowly intensify into a bright arc speared by occasional faint rays just before 1 a.m. A half hour later, a promising display that almost sent me to the computer to post an alert, collapsed into a faint arc at the bottom of the northern sky. Who let the air of the tires?

The northern lights have much in common with the trickster character of many American Indian myths. He’s the prankster and rule breaker. When we think life is predictable, the trickster keeps us on our toes.

Thanks to a big hole in the sun’s corona (outer atmosphere) a stream of high speed particles is buffeting Earth’s protective magnetic bubble, giving us a chance of auroras. No big storms are expected, but you might want to scan the northern sky around midnight the next couple nights. In the photo above, both the green glow, which was visible with the naked eye, and the much fainter pink, were caused by excitation of oxygen atoms high in Earth’s atmosphere.

A North Korean soldier keeps an eye on things at Sohae Satellite Launch Station. The Unha-3 rocket (background) will carry the Bright Shining Star satellite into space. Credit: AP

Satellite watchers are sitting on pins and needles waiting for the imminent launch of North Korea’s  Kwangmyongsong-3 satellite. Billed as an Earth-observation spacecraft, it would be used to gather weather data and photograph the country’s forest and farmland during its two-year lifetime in orbit. You’re probably more familiar with the backstory that the launch is really about testing ballistic missiles.

The satellite’s name means “Bright Shining Star” and it’s the third in a series that began with Kwangmyongsong-1 in 1998. Although North Korea says the first two launches were successful, no independent observer ever saw them in orbit.

Kwangmyongsong-3 will mark the 100th anniversary of founding of the Democratic People’s Republic of Korea by its founder Kim Il Sung. Once in orbit, the satellite will broadcast two patriotic tunes -  ”The Song of General Kim Il Sung” and “The Song of General Kim Jong Il.” If the launch succeeds, I’ll post times when it might be visible from your town. UPDATE 7 p.m. CDT: The satellite was launched at 7:39 a.m. Korean time but failed to reach orbit. Story HERE.

Comet Garradd passes through the toes (Theta, Kappa, Iota stars) of one of the Dipper's paws the next few nights. The comet's path is marked every five days. Stars shown to 6.5 magnitude. Created with Chris Marriott's SkyMap software

If you have a 6-inch or larger telescope, the next couple nights are ideal for finding the comet observers have been going steady with since last summer –  Comet Garradd. It’s passing through ones of the “paws” of the Great Bear a.k.a the Ursa Major a.k.a. the Big Dipper. It’s faded to 7.5-8 magnitude but I still spotted it last night from a dark sky in 10 x 40 binoculars as a faint, fuzzy glow. The map above is drawn for 9:30 p.m. local time as you face north. Through the telescope, the comet is a fuzzy ball with a brighter center or nucleus. A faint dust tail 1/2 degree long pointing northeast is visible in 10-inch and larger scopes.

Kamikaze comets create dusty fireworks around Fomalhaut

The moon rises over Lake Superior and Duluth's Lakeside neighborhood last March. Photo: Bob King

Yesterday night my community education astronomy class and I enjoyed an evening of skywatching along Duluth’s Skyline Parkway, where one can take in the stars above the lights and homes of the city’s Lakeside neighborhood. Standing along the rim, there’s a feeling of being suspended between heaven and Earth like an astronaut in orbit. Which reminds me – Duluth has a great pass of the space station tonight across the southern sky starting at 8:57 p.m.

One student wondered where the moon was. I explained it wouldn’t be up until well after midnight. Not so for the twin GRAIL satellites named “Ebb” and “Flow”. They’ll stare at nothing but the moon 24/7  for the next few months.

The Gravity Recovery and Interior Laboratory (GRAIL) mission measures the moon’s gravitational effects on the two satellites as they orbit around the moon. Small changes in the distance between the two craft will allow scientists to create a detailed map of the moon’s gravity field. They’ll use that information to probe the structure of the moon’s interior from upper crust to inner core. The spacecraft also carry cameras that middle school kids are using to snap photos of the moon.

Using a camera aboard one of the GRAIL spacecraft, middle school students took this picture of planet Earth floating above the lunar farside. Click to enlarge. Credit: NASA/Caltech-JPL/MIT/SRS

Called MoonKAM – Moon Knowledge Acquired by Middle school students – it’s a NASA education and outreach program where participants submit requests to have either Ebb or Flow photograph a favorite moonscape or lunar scene.

Judging by the numbers, it’s wildly popular. 27,000 schools in 52 countries signed up; the first batch of more than 60 photos taken between March 15-17 were recently relayed back to Earth.

What a fantastic way for young people to delve into science. Who knows how many careers in space and astronomy might be inspired. To read more about Moon KAM and see additional images, click HERE.

News also comes today from the European Space Agency’s orbiting Herschel Telescope, which studies the sky in the light of infrared or heat energy, of comet kamikazes around the star Fomalhaut.

Fomalhaut (center) and it disk of fluffy dust imaged by the Herschel Telescope. The dust is being replenished by the comet collisions at the rate of 2000 half-mile-wide comets a day. Fomalhaut is 25 light years from Earth. Credit: ESA

Fomalhaut is a young star just a few hundred million years old (vs. the sun’s 4.6 billion) twice the sun’s size in the constellation of Pisces Austrinus the Southern Fish. Since the 1980s astronomers have known it’s surrounded by a ring of dust and orbited by at least one planet. Recent observations of the dust suggest that the amount we see is far too much to stick around without resupply. Fomalhaut’s light should have blown most it away by now unless it’s being replenished in a big way.

“The only way to overcome this contradiction is to resupply the belt through continuous collisions between larger objects in orbit around Fomalhaut,” according to the agency. The amazing thing is the rate: the equivalent of 2000 1/2-mile wide comets colliding each day into a myriad of fluffy dust particles. Don’t worry – the star won’t run out of comets anytime soon. Scientists think between 260 billion and 83 trillion comets must populate the ring to keep the dust assembly line running. WOW!

Believe it or not the sun probably had a similar belt of comets. Several trillion of them were later tossed through gravitational interactions with giant planets Jupiter and Saturn into a huge spherical cloud or reservoir called the Oort Cloud. Located nearly a light year away, the cloud is believed to be the source for many long period comets, those that take hundreds of thousands or even millions of years to orbit the sun. Watching Fomalhaut’s dusty fireworks is a vision of the early days of our own sun.

The night sky from inside a globular cluster

An imaginary view of a winter night on a planet orbiting a star in the core of a globular cluster. Illustrations created with Stellarium; background image of M4 cluster by the Hubble Space Telescope/NASA/ESA

It’s fun to imagine what the sky would look like if you could plop yourself on a planet around another star. We’ve only scratched the surface, yet in fewer than 20 years, astronomers have discovered more than 750 new planets beyond those in our own solar system.

While I’d love to see a double sunrise and sunset like the fictional Luke Skywalker on the planet Tatooine, one of my favorite places to imagine a radically different sky from Earth’s is inside massive balls of stars called globular clusters. We know of about 150 in the Milky Way galaxy. Most are tens of thousands of light years away in the direction of the center of the galaxy in the constellation Sagittarius. Globulars are tightly bound by the gravity of their many stars into spherical shapes resembling hoards of bees.

The huge Omega Centauri cluster packs 10 million stars into a ball 230 light years across. It’s about 16,000 light years from Earth. Stars are only 1/10 of a light year apart in its core. Click photo to enlarge. Credit: Hubble/NASA/ESA

Most globular clusters contain several hundred thousand stars, but a really big one like Omega Centauri (visible from the southern U.S.) tops out around 10 million. Star densities inside the clusters are much higher than in the sun’s neighborhood. The closest star system to our sun, Alpha Centauri, is 4.3 light years away or some 25 trillion miles. Within the densely packed core of some globulars, star densities are phenomenal – up to 1000 stars stuffed into a cube 3 light years on a side.

Globular clusters form a sphere centered on the Milky Way galaxy’s center. Credit: Science Frontiers online

While so many stars whizzing about make it difficult for planets around stars to remain in stable orbits, we can safely assume planets are still possible. Think of the view on clear night. The sky from Earth contains at best a dozen bright first magnitude stars on a given night, all considerably fainter than Jupiter and Venus. Inside a globular, where stars are only tenths of a light year apart, there would be thousands of stars as bright as Venus and Jupiter. You could easily walk around (or dogsled) at night without the need of a moon to find your way. Some lucky life form must witness bejeweled nights in at least one of the many globulars that dot our skies. My feeble attempt above only hints at what we might imagine.

Because globulars are arrayed in a spherical cloud centered on the core of the Milky Way, they only begin to populate our evening sky as spring turns into summer and Sagittarius makes its appearance in the east. There are several out right now – the vanguard as it were – that you can spot in binoculars. And if you have a telescope, especially from 6-inches and up, you’ll can experience for yourself how fantastically starry-rich these objects are.

M3 is conveniently placed between the bright pink star Arcturus below the Dipper’s Handle and Cor Caroli, the brightest star in the Hunting Dogs, a small constellation near the Dipper.

One of the best in the northern sky is named M3, the 3rd entry in a catalog of deep sky objects compiled by 18th century French astronomer Charles Messier. It’s located in the constellation Canes Venatici the Hunting Dogs below the handle of the Big Dipper. The cluster is 33,900 light years away, spans some 200 light years and contains half a million stars.

To find it, face northeast around 9:30 – 10 p.m. local time and locate brilliant Arcturus by following the arc of the Big Dipper’s Handle. The cluster is located not quite halfway from Arcturus to Cor Caroli, an easy-to-see star to the right of the Handle.

In binoculars look for a fuzzy 6th magnitude blob with a brighter core just to the left or north of a 6th magnitude star. You can use the more detailed map below to pinpoint M3′s location. M3 is easy to see in typical binoculars from suburban and rural areas. Take your imagination for a ride the next clear night.

In this closeup map, start with Arcturus and “star-step” your way upward to M3. The distance between them is about 1 1/2 binocular fields of view.

Venus joins Gang of Four; space station lights up evening sky

No, not the punk rock Gang of Four. From left: Sirius, Orion's Belt, the V-shaped Hyades cluster and Aldebaran and Venus above the Pleiades photographed over the weekend in moonlight. Photo: Bob King

A week ago we looked west at Orion tipping over on his side, his belt nearly parallel to the horizon this month. Off one end was Sirius the brightest star, off the other Aldebaran and the Seven Sisters star cluster. This weekend I noticed a new member in the lineup – Venus. The whole configuration is dropping away to the west quickly; to see it you’ll need to look during early nightfall around 8:30-9:30 p.m. local time.

Facing west, you might see a new star rise in that direction if you time it right. The International Space Station (ISS) returns to easy evening viewing tonight and for the next few weeks. The six-man crew of Expedition 30 recently received some goodies “in the mail” when European Space Agency’s “Edoardo Amaldi” Automated Transfer Vehicle-3 (ATV-3) –  named after an Italian physicist – docked with the space station late last month delivering water, oxygen, food, clothing,  propellant and spare parts.

The ATV-3 (upper left) uses its thrusters to line up to dock with the space station March 28. The automated vehicle resupplied the astronauts aboard with essential items. Credit: NASA

The space station first appears in the western sky and takes several minutes to traverse to the east, appearing like a moving star as bright as Jupiter or sometimes Venus. The times below are for the Duluth, Minn. region. To find when the ISS will pass over your place, log in to Heavens Above or type your zip code into Spaceweather’s Satellite Flyby site.

* Tonight April 9 starting at 9:13 p.m. Brief pass low in the southern sky
* Tuesday April 10 at 9:53 p.m. Brilliant but brief appearance in the west
* Weds. April 11 at 8:57 p.m. A fine, bright pass across the southern sky
* Thurs. April 12 at 9:37 p.m. Great show. Begins in the southwest near Orion’s Belt and crosses almost directly overhead on its way east. Brilliant.
* Fri. April 13 at 8:41 p.m. Your lucky day! A bonus night with two appearances. First is a brilliant pass high in the south. Second pass at 10:18 p.m. in the northern sky, where the station will fade from view as it enters Earth’s shadow directly below the North Star.
* Sat. April 14 at 9:21 p.m. Glides across the northern sky coming very close to the North Star at about 9:25 p.m.

If you still haven’t seen the supernova 2012 aw in the galaxy M95 in Leo, I’m happy to report it’s still hanging in there at 13.3 magnitude, nearly as bright as a few weeks back. Catch it now that dark skies have returned with the moon’s exit from the evening sky. Here’s a chart to find the galaxy and supernova guru Dave Bishop’s page dedicated to the star.

Hunting 4.5 billion year old Easter eggs

A basketful of tiny, rocky eggs is on display in this slice of Northwest Africa 5205, a chondrite meteorite found in the Sahara Desert in 2006. The individual chondrules are from 1-4 mm across. Photo: Bob King

There’s a picture in the newspaper today of a girl placing an Easter egg she found on a hunt in her basket. Astronomers like to go Easter egg hunting too. They slice through meteorites found in Antarctica and the deserts of Africa and Oman to study the little eggs and spheres inside called chondrules (KON-drools). These crystalline grains, which range in size from less than a millimeter to about a half inch, represent the oldest solid material in the solar system. They’re the chief ingredient in chondrites or stony meteorites, the most common type known.

The semi-precious peridot is a gem variety of the common Earth and meteorite mineral olivine.

Chondrules are composed mostly of the silicate minerals olivine and pyroxene, which in turn are constructed of the elements silicon, magnesium, iron and oxygen.

Silicates are very common on Earth too, making up more than 90 percent of the weight of Earth’s crust. Gem-quality olivine is better known as peridot, the birthstone of August. Maybe you’ve seen this beautiful green stone while shopping for jewelry.

Although the photo above shows them as flat ovals and circles, remember you’re looking at a slice of meteorite and seeing a cross section of what are really spherical and egg-shaped beads.

Where did these come from? Scientists trace their origin back to the solar nebula, a rarefied cloud of gas and dust several light years across that collapsed, heated up and eventually formed the sun at its center. Leftover material orbiting the central sun coalesced into the planets, moons, comets and asteroids.

Artist's view of the solar nebula with the sun forming at center. As it collapsed through gravity, the nebula flattened into a disk. Dust and gases in the disk originate in previous generations of stars which either quietly or explosively slough material into space as they age. Credit: NASA

To build the very, very big, nature often starts with the very, very small. Dust in the cloud at some point was flash-heated to 2700-3500 degrees Fahrenheit, melted and then cooled in the low-gravity environment of space into small droplets. These solidified in a matter of hours into chondrules.

No one knows what caused the heating, but there are lots of ideas. Everything from a nearby supernova blast wave to an outburst of energy from the newly-forming sun to titanic lightning discharges within the disk to the shock wave within the nebula itself have been offered as explanations.

A lovely Easter-egg shaped chondrule in the Saharan meteorite Northwest Africa 869. The grain measures almost 1/4 inch across. Photo: Bob King

The path to planet-making began when the millimeter-sized rocky “eggs” and leftover dust stuck together to make clumps. The clumps clumped into larger clumps up to several hundred feet across. Through direct contact and gravitational attraction, these loosely-compacted bodies grew to become planetesimals  - the seeds of the planets – measuring 5-6 miles in diameter. After many collisions, the planets took shape in the next several hundred million years.

Many of the original chondrules were melted and altered by impacts and the heat of radioactive elements within the growing orbs, but some, like those pictured, are nearly as fresh as they day they formed 4.5 billion years ago.

A chondrite is a wonderful souvenir from a time when Earth was only a possibility and Easter farther off yet. Within each chondrule is the liquified dust of long-ago generations of stars.

See the clouds of Mars in your telescope this week

The bright pair of Mars and Regulus are high up in the southeastern sky around 9 p.m. local time. Created with Stellarium

Mars is getting smaller and farther with each passing week, but there’s still much to see if you have a 6-inch or larger telescope and steady air. Also called “good seeing”, calm air is crucial if you want to see detail on planets under high magnification. Jupiter’s big enough for a great view at 70x, but Mars is only one-quarter that size right now, so you’ve got to crank the power up to 150x or higher to see more than just a bright disk.

One of the ultra-coolest things to observe on the planet at the moment is a big white patch that looks like a “third” polar cap.

Summer began in Mars northern hemisphere on March 30, so the north cap is a mere remnant of its winter self – a tiny dollop of white surrounded by a dark ring of polar sand dunes. Keen-eyed observers will spot both features on a good night. The south polar cap is currently tipped out of view and hidden by a shroud of early winter clouds called the south polar hood.

Mars on April 2 (left) and on April 1 at a different time of night. Cloudy Hellas is the bright patch at upper left in the left photo. At right it's front and center above (south of) the dark marking called Syrtis Major. The north polar cap is at bottom. Credit and thanks to Torsten Hansen (L) and Christophe Pellier (R)

What you can see is a prominent white patch coming around the southeast limb or edge of Mars directly south of the dark, funnel-shaped marking called Syrtis Major. It so bright you might think it’s the south polar cap. Nope. It’s Mars’ largest crater Hellas decked over in water-ice clouds and partially covered in frost. They reflect sunlight so well, you can’t miss the sight through a telescope on a good night. Focus the planet sharply, concentrate and look for a white edge or patch contrasting against the overall orange-pink color.

The giant Hellas Basin on Mars spans 1200 miles. From this orbital vantage point, you can see its tell-tale crater shape. The interior, which warms to around 50 degrees F on a summer day, is a site of frequent dust storms during the southern summer. Credit: NASA

Hellas is the ancient Greek word for “Greece”. The Martian Hellas is an ancient impact scar punched out by an asteroid over 4 billion years ago. It spans 1200 miles across with a bottom 5 miles deep. Think of it as Mars version of Death Valley only colder and drier.

During late spring and summer in the northern hemisphere, much of the frozen CO2  and some of the water ice in the north cap sublimes (goes directly from ice to vapor) and migrates toward the southern hemisphere, where it refreezes and replenishes the south polar cap. In the early winter chill, some of that water condenses into ground frost and ice crystal clouds that hover over Hellas.

I’ve looked at Mars the past two nights in my 10-inch scope in fair to good seeing conditions and the top of the planet (south end in a reflecting telescope)  sports a bright Hellas. It thrills me to see something as earthly as seasons progress on another planet, and while I don’t care for clouds in my sky when it comes to nighttime observing, I’m more than happy to spend many minutes enjoying them over Mars.

A simple Mars map to get situated when you're observing the planet this coming week. The north polar cap is extremely small; the clouds of Hellas bigger in comparison. Credit: Meridian software

The next week and a half is ideal for viewing Hellas’ clouds. Now through April 15 you’ll spot the white patch south of Syrtis Major around 8:30-9 p.m. Central Daylight time. Subtract an hour for the East Coast and add two hours for the West.

Since Mars’ rotation period is about 24 1/2 hours, it’s about a half hour out of sync with Earth’s rotation. This causes features on the west side of the planet, where Hellas is now, to slowly shift eastward each night.

By mid to late April, Hellas will have moved over to the far eastern end of the planet. If you want to continue to follow the clouds’ progress after mid-month, you’ll need to look at Mars a couple hours later in the evening to allow the planet’s rotation to carry the feature back into view. To help you keep track of what’s where on Mars, I highly recommend an easy-to-use free software program called Meridian created by Claude Duplessis. Find it HERE.

Mars at the same time of night - 8:30 p.m. CDT - April 10 through 16. Notice how the features move from west to east (left to right) as seen in a typical telescope over time. Credit: Meridian

Hellas is not the only place to watch for cloudy weather on Mars. While it’s the easiest to see, there are lots of hazes across the planet at present especially around its east and west edges called “limbs”. For a weekly Mars weather report with photos, check out the MARCI site. Good luck as you dip into Mars Meteorology 101 this coming week. Let us know if you spot the clouds and frosts of Hellas.

Think pink for tonight’s full moon

Birch trees glow in the light of the setting sun yesterday evening. Sunlight also illuminates the nearly full moon. Photo: Bob King

Like pink? My daughters sure do. Each still has a pair of sweat pants with the word LOVE PINK emblazoned across the rear. Full moons wear pink too thanks to vapor and dust in the atmosphere around the time of moonrise.

The moon is near Spica and Saturn tonight and tomorrow night. Created with Stellarium

Tonight’s full moon is named the Pink Moon – nothing to do with suggestive clothing but a reference instead to moss pink or phlox, one of spring’s early wildflowers. Since full moons are directly opposite the sun, they rise in the east about the same time the sun sets in the west. For Duluth, Minn. the big moment is 8:06 p.m. tonight. Click HERE to find the time of moonrise for your town.

Once the sky darkens, you’ll see the moon has two companions in tow. Virgo’s brightest star Spica sparkles just two degrees to its left (east); five degrees farther to the east you’ll bump into the planet Saturn. Splendid company.

The moon never stops moving as it orbits the Earth, traveling eastward (to the left as you face south) at the rate of about 12 degrees per day or one fist held at arm’s length against the sky. We experience the moon’s orbital motion as hour-later moonrise times with each passing night. Tonight however, you can watch the moon’s motion in a matter of hours with nothing more than your naked eye by noting its position relative to Spica.

Stay up late tonight and watch the moon change position in relation to Spica and Saturn.

Early this evening the moon will form a nearly straight line with Spica and Saturn for sky watchers in the eastern half of the U.S.

By midnight, that line will be bent downward, and if you stay up into the wee hours, the moon’s shift with respect to Spica will be obvious.

When you make your observation, keep in mind that all three objects will change orientation as a group with respect to the horizon as they travel from east to west during the night because of Earth’s rotation.  To notice the moon’s movement, ignore that and compare its position only in relation to Spica and Saturn.

Whether pink, orange, white or blue, I hope your face will reflect a little moonlight tonight.

Aristarchus helps us see the wild and woolly moon of long ago

The bright crater Aristarchus looks like a small but distinct bright patch inside the left or eastern edge of the moon with the naked eye. Photo: Bob King

With the moon turning full tomorrow, let’s take a look at one of its brightest craters, Aristarchus (Aris-TAR-kess). Although only 25 miles in diameter, it’s bright enough to see with the naked eye and positively dazzling in a telescope. The name suits its appearance perfectly. Aristarchus was the Greek philosopher who first proposed the concept of a sun rather than Earth-centered solar system. To this day the crater celebrates this brilliant and ultimately correct idea.

The reason for its radiance has to do with its relative youth. Aristarchus was excavated by a huge meteorite impact “only” 450 million years ago. You’d almost call that recent in lunar years especially considering that most of the moon’s craters are some nine times older, having formed nearly 4 billion years ago. Sunlight and solar radiation darken the lunar surface over time; Aristarchus hasn’t been around long enough for that to happen.

View of the Aristarchus Plateau seen through the window of the Apollo 15 command module. Aristarchus is at left; Herodotus crater and Schroeter's Valley at right. Click for a valley closeup. Credit: NASA

You can see the crater with you unaided eye as a small bright spot in the large dark region that covers much of the eastern half (left side) of the moon called Oceanus Procellarum or Ocean of Storms. It helps that Aristarchus contrasts so well against the dark moonscape. If you have any difficulty seeing it, whip out a pair of binoculars for a second look. Even 5x will bring the shimmering spot into view.

Aristarchus sits on a 125-mile-wide plateau that rises a little more than a mile (at maximum) above the vast “oceanic” plain. The rise is riddles with cracks called rills which long ago carried lava from beneath the moon’s crust into the basin that is now Oceanus Procellarum.

The biggest rill and easiest to see in a small telescope is named Schroeter’s Valley. It begins near the crater Herodotus and winds through the plateau before fading out at the edge of the great “ocean”. If you catch the lighting right, the rill’s as spectacular as the crater. Within its shadowy curves,  it’s not hard to imagine flowing lavas cutting a path through the region and emptying into the vast depression surrounding the plateau. As for the plateau itself, it was lifted to its present height by magmas that welled up from beneath it.

Aristarchus is the bright spot with Schroeter's Valley winding below it. The olive-color of the surrounding region shows up well in this photo. Click to see an overflight of the region by the Japanese Kaguya probe. Credit: Ole Nielsen

While quiet now, the moon once grumbled and roared with vulcanism.

Before we leave Aristarchus, we have to talk about color. Drab grays, whites and the palest of browns tint most of the lunar surface. No so with the plateau. Through a small telescope it has a distinct olive or yellow-brown tinge caused by a 4-12 inch covering of volcanic ash – more evidence of the wild and woolly moon of long ago. See it best around full moon phase.

I like to imagine standing on the Earth 3 billion years ago, watching the flash of crater impacts and glowing lava flows on the lunar nightside through my little telescope. I’d never be able to take my eyes off our companion world. Frankly, I still can’t.

Venus and her sisters; Tell time at night with the Big Dipper sky clock

Venus and the Seven Sisters star cluster last night - what a sight! Details: 200mm at f/5.6, ISO 800 and 20-second guided exposure. Photo: Bob King

It was great to stand in the front yard last night under a clear sky and see Venus and the Pleiades. A casual glance showed a sprinkling of little stars around the brilliant planet. Binoculars gave the best view of the “8 sisters” with Venus the dominant by far. I tried to see how many Pleiads I could count with the naked eye. The five brightest were easy enough but the sixth – Taygeta – was tricky. Pleione was beyond me. It was also fun to recall that 8 years ago to the day I stood in the yard and watched Venus in almost the same position inside the cluster. Apparently I was on time for my next appointment.

A wider view of Venus and the Pleiades along with Jupiter (at bottom). 35mm at f/5.6, ISO 800 and 20 seconds. Photo: Bob King

Tonight Venus glides up and to the left of the star cluster, so if it was cloudy by you last night, you have another shot at seeing them together.

After a good swig of the western sky show, I checked out a new paperless way to tell time using the Big Dipper and North Star. In yesterday’s blog we looked at a simple star clock you can make with paper and scissors. Today we’ll pretend we’re out at night with neither watch nor guide.

The map below shows the North Star as the center of a clock face with the two Pointer Stars in the Bowl of the Big Dipper as the hour hand.  Our example shows the sky at 9 p.m. local time.

To start, face north and look high in the northeastern sky to find the Big Dipper. Draw a line through the two Pointer Stars until you arrive at the first easy-to-see star. That’s the North Star or Polaris. It’s about 5 “Pointer lengths” away. The line connecting the North Star and Pointer Stars now becomes the hour hand on our celestial clock.

To find the time using the Big Dipper and North Star we imagine the northern sky as the face of a clock. Key hours are marked. Illustrations created with Chris Marriott's SkyMap

1. Estimate the time the Pointer hour hand indicates to the nearest quarter hour (15 minutes). In our example, it’s 1 o’clock.

2. This next step is key. We now adjust the clock for the time of year. On March 7, the Pointer Stars stand directly above the North Star at midnight standard time. All you have to do is figure to the nearest quarter month how much time has elapsed since March 7. Since tonight’s April 4th, that rounds off to one (1) month. If it was April 15 instead, the number would be 1 1/4 or 1.25.

3. Add the two figures from above and then multiply by 2 as in: 1 (from 1 o’clock) and 1 (one month) = 2. Then 2 x 2 = 4. Now subtract that sum from 24, so 24-4 = 20. The result will be the time in 24-hour or military style. 20 hours military is the 20th hour of the day or 8 p.m. Add an hour for daylight-saving time and we arrive at 9 p.m. By gosh, that’s correct! Note: If your final number is greater than 24, subtract from 48 instead.

Facing north about 5:15 this morning, the Pointers were now off the left of the North Star in the 9 o'clock position. I figured the time as: 9+1=10. Multiply by 2 = 20. Subtract 24 - 20 = 4 and added one hour for DST to arrive at 5 or 5 a.m. Close enough.

It’s important to remember to add that hour for daylight time when it’s in use and to face north. With practice – and checking against a watch for accuracy – you’ll soon become a master of time at night. Be aware that where you are within your time zone will affect your time estimate. If you try this a few times, you’ll soon be able to factor that in and fine tune your time. I tried this simple method both last night and this morning before dawn and was frankly surprised how well it worked. If you’ve got some time on your hands, let us know how you fare.