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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

Weird auroras / Mercury meets a dainty moon / See 5 evening planets!

An oval patch of glowing green aurora appeared in the northern sky in Cassiopeia last night (April 17). Credit: Bob King

An oval patch of glowing green aurora pulses in Cassiopeia last night (April 17). Credit: Bob King

It’s been a fantastic 4 nights of northern lights. For now, Earth’s magnetic environment has returned to quiet conditions. Similar to the run of auroras that began on St. Patrick’s Day, this one finished with the same peculiar, sausage-shaped patches.

Last night I noticed a single elongated glow about two fists across in the northern sky in late twilight that slowly pulsed in brightness, often disappearing for 10-15 seconds and then reappearing in the same spot. Like breath on a mirror.

Another view of the diffuse aurora seen last night across the northern sky. Credit: Bob King

Another view of the diffuse aurora seen last night across the northern sky. Credit: Bob King

During the night, the patch slinked slowly westward into Cassiopeia and then disappeared altogether around 11 o’clock. At midnight it reappeared in the northeastern sky below the Northern Cross.  The strange apparition added quiet intrigue to the evening’s boisterous calls from the frogs.

Use bright Venus to help point you in the right direction. This map shows the sky facing west-northwest around 40 minutes after sunset. Created with Stellarium

Use bright Venus to help point you in the right direction. This map shows the sky facing west-northwest around 40 minutes after sunset. Mercury is 7° to the lower right of the moon. Created with Stellarium

Tomorrow night (April 19), look to the northwest about 40 minutes after sunset for a rare alignment of a day-old moon and two planets. One of them, Mars, has been around since last spring. Back then it was much closer to Earth and brilliant. Since then the two planets have separated with Mars now far away and rather faint. You wouldn’t ordinary seek it out so low in a bright sky, but the youthful crescent moon will certainly lure you there.

Mercury's approximate path and altitude during its dusk appearance this spring. Notice how its phase changes from the current gibbous to half to crescent. Source: Stellarium, Bob King

Mercury’s approximate path and altitude during its dusk appearance this spring. Notice how its phase changes from the current gibbous to half to crescent. Source: Stellarium, Bob King

The moon will be just a bit more than one day old and appear as a razor-thin sliver about 5-7° high (three to four fingers held at arm’s length). It should be easily visible from anywhere with a wide open view to the west-northwest. Because of its relative faintness, Mars will probably require binoculars to see. Focus on the moon first and then slide to the right to find the star-like planet.

As an inner planet, Mercury goes through phases just like Venus and the Moon. We see it morph from crescent to “full moon” as its angle to the Sun changes during its revolution of the Sun. Credit: ESO

As an inner planet, Mercury goes through phases just like Venus and the Moon. We see it vary from crescent to “full moon” as its angle to the Sun changes during its revolution of the Sun. Credit: ESO

Mercury shines at magnitude -0.5, even brighter than Vega or Arcturus, but it’s only a few degrees high, so you might need binoculars to see it, too. Once again, the moon comes to the rescue. Look either with your eyes or binos 7° (four fingers) to its lower right.

Mercury quickly moves up from the horizon in the next two weeks for its best evening appearance of the year for northern hemisphere skywatchers. As it comes into better view, the planet will slowly fade and change phase just like the moon. You can see the phases through a small telescope magnifying about 75x. Be sure to look for Mercury early when it’s highest or the blurring effect of the atmosphere will turn it into a ball of quivering mush.

Saturn pops up in the head of the Scorpion in late April around 11-11:30 p.m. This photo was taken early this morning just after midnight. Credit: Bob King

Saturn pops up in the head of the Scorpion in late April around 11-11:30 p.m. This photo was taken early this morning just after midnight. Credit: Bob King

With Mercury joining the scene, we now have five — count ‘em — five planets visible in the evening sky. Throw in the Earth and that makes six out of a total of eight! Mercury and Mars hang low in the west; Venus can’t be missed, shining like a lighthouse high in the west at dusk; Jupiter dominates the southern sky in Cancer and if you stay up till 11:30, you’ll see Saturn rise in Scorpius low in the southeastern sky.

Such riches for planetary enthusiasts. Go out and meet your solar system at the next opportunity.

Rosetta bumps into some flaky characters

Meet more COSIMA dust grains! Credits: ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S

Meet some of the more personable COSIMA dust grains. To get an idea of their size, the plate is 100 millimeters (~1/2 inch) across. Credits: ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S

Here’s a family portrait only a scientist could love. 12,000 grains of Comet 67P/C-G were collected between last August and mid-March of this year on nine target plates measuring a little less than 1/2-inch square (1 cm). This photo shows one of these targets with grains collected up to December 12.

Imagine my thrill seeing that one of the motes was named “Bob”. Rosetta employed its COSIMA instrument to capture the grains wafting from the comet onto the sticky target surfaces. After taking close-up photos of the particles, COSIMA then analyzed the composition of selected grains using a secondary ion mass spectrometer, a device that shoots a beam of ions (atoms that have lost or gained an electron) at a grain and collects the ions that are bounced back for analysis. By identifying the sputtered ions, scientists can determine the individual elements that compose the grain.

Montage of photos of Comet 67P/Churyumov-Gerasimenko taken by Rosetta. Obvious in all the images are the active plumes of gas and dust grains leaving the comet, some of which have been captured by COSIMA. Credit: ESA/Rosetta/Navcam

Montage of photos of Comet 67P/Churyumov-Gerasimenko taken by Rosetta. Obvious in all the images are the active plumes of gas and dust grains leaving the comet, some of which have been captured by COSIMA. Credit: ESA/Rosetta/Navcam

Last October, COSIMA found magnesium and sodium this way in a dust grain named Boris. 95% of known minerals observed in comets resemble olivine and pyroxenes, common in meteorites and in the upper mantle of the Earth. Sodium has also been seen in comet comas and tails, and originates in dust grains, but its mineral source remains uncertain.

A false color/color enhanced view showing the smooth Hapi region connecting the head and body of Comet 67P/C-G. Color filters have been used in a way to enhance slight color differences in the comet's nucleus. The bluish coloring in the smooth area might indicate the presence of ice at or just below the dusty surface. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

A false color/color enhanced view showing the smooth Hapi region connecting the head and body of Comet 67P/C-G. Photos taken through separate color filters have been combined to enhance slight color differences in the comet’s nucleus. The bluish tint in the smooth area might indicate the presence of ice at or just below the dusty surface. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Many of the particle names are given for COSIMA team members, along with other Rosetta mission team colleagues. But by the time they had reached 2,000 particles, names were getting in short supply, so Sihane Merouane, who’s responsible for cataloguing the grains, decided they’d only name dust particles larger than 40 microns (about 1/3 the width of a human hair) with some exceptions made for special, smaller particles.

There’s nothing like a name to make even the most obscure objects approachable. Touché team!

Farewell Orion / See a Dragon / Aurora update

Orion's Belt (left) is reflected in calm waters in  a lake north of Duluth as the constellation tilts toward the western horizon last night. Credit: Bob King

Orion the Hunter and his three belt stars (left) are reflected in a lake north of Duluth last night. Venus, along with the Hyades and Pleiades star clusters, shine at right. Credit: Bob King

Last night while watching the northern lights, we saw the Great Hunter head for the hills. Orion has been the center of attention since December, as recognizable in the southern sky as the Big Dipper is in the north. Now he’s trotting off toward the western horizon, replaced by Jupiter, Leo and the constellations of spring.

Like a furniture clearance commercial that airs during the nightly news, ALL WINTER CONSTELLATIONS MUST GO! With new inventory coming in, the sky’s gotta make room.

Like it or not, Orion will toddle out of the picture soon. The rising and setting of the stars is a reflection of our planet’s rotation; the Earth spins toward the east, pushing up new stars from the eastern horizon and leaving those in the west behind. We see this grand parade every clear night.

View of Earth's orbit around the sun seen from above the northern hemisphere. As our planet moves to the left, the background constellations appear to drift to the right or westward. Credit: Bob King

View of Earth’s orbit around the sun seen from above the northern hemisphere. As our planet moves to the left during its yearly swing around the Sun, the background constellations appear to drift to the right or westward. Credit: Bob King

But there’s a more subtle shift happening at the same time. As Earth travels in its orbit around the sun, we peer out into different sectors of the sky at night as the weeks and months pass. Like a runner facing a different set of fan-packed bleachers while circling the track in a 1000-meter race, Earth faces Orion in winter, Leo in spring, Scorpius in summer and Pegasus in the fall.

They constellations appear to drift westward very gradually at the rate of about 1° per day. That’s small enough we don’t notice night to night. But the degrees add up. In two weeks, a constellation will drift about 14° to the west — more than the length of your fist held at arm’s length against the sky.

To see this for yourself, find a bright star like Betelgeuse in Orion or Arcturus in Bootes (located below the Big Dipper’s Handle) and note its position in relation to a nearby landmark like a church steeple, mountaintop or Pizza Hut at a particular time. Wait a few nights and then return to the exact same spot at the same time, and you’ll see that the star has slid westward.

Just the way the rising and setting of the stars is an illusion caused by Earth’s rotation, the seasonal drift of the stars and constellation is a sleight of hand caused by Earth’s revolution around the Sun. Now you know why the stars can sit still — it’s YOU who’s doing the moving.

Earth zips around the Sun at a speed of 18.5 miles per second (30 km/sec), covering 26,640 miles each day. In the time it takes for you to notice your reference star has moved – we’ll say 3 nights – you and the home planet have traveled nearly 80,000 miles!

Falcon 9 was carrying the Dragon spacecraft, which is loaded with about 4,300 pounds of supplies and payloads bound for the International Space Station (ISS). Credit: SpaceX

Falcon 9 lifts off April 14 carrying the 9,300-pound Dragon spacecraft, which was loaded with about 4,300 pounds of supplies and payloads for the International Space Station (ISS). Credit: SpaceX

Being outside at night can be a wonderful thing because you inevitably see something unexpected. Two nights ago, I was out with my astro class and we saw the weirdest pair of satellites in the northeastern sky – a bright one and a faint companion just a few degrees apart. Both moved quickly and faded out in less than a minute.

I later discovered we saw the Dragon cargo ship en route to deliver supplies to the International Space Station and the upper stage of the Falcon 9 rocket that lofted the ship into orbit.

You can see either or both in the next few nights by going to Heavens Above and selecting your city and then clicking on the Dragon CRS-6 link just below the ISS link under the Satellites heading. Passes are only a minute or two long and occur in evening twilight. The brighter object will be the rocket stage.

The Falcon rocket's second stage engine burns for about 7 minutes to deliver the Dragon ship to its initial orbit. Credit: SpaceX

The Falcon rocket’s second stage engine burns for about 7 minutes to deliver the Dragon ship to its initial orbit. Credit: SpaceX

Bring binoculars and you might still be able to see the solar panel covers that were ejected from the Dragon as separate fainter objects nearby. Dragon will arrive at the space station around 6 a.m. CDT tomorrow (April 17), when astronauts will use the robotic arm to secure it. I expect that tonight, Dragon will follow the ISS by only a couple minutes.

Last night’s aurora glowed until the wee hours. I hope you were able to see at least some of the show. Tonight, forecasters predict another chance for more northern lights though they’re expected to be a little “quieter” than yesterday.

Nature cooks up a fine aurora tonight – don’t miss it

A tall red beam of aurora stands up from the lower green rayed arc in the northern sky around 10:30 p.m. tonight. Even to the eye, this one was obviously pink. Credit: Bob King

A tall red beam of aurora stands up from the lower green rayed arc in the northern sky around 10:30 p.m. tonight. Even to the eye, this clearly looked pink. Credit: Bob King

I can’t believe it. The northern lights are back … again! Sure, they were in the forecast, but that doesn’t always mean they’ll show up.

It’s been quite a wonderful pageant tonight. Lots of rayed arcs with occasional Star Wars “lightsaber” beams. The delicate pink coloration in the ray pictured above was one of the most beautiful I’ve seen in several years of aurora watching.

Around 10:15 p.m. tall, faint red rays stretched toward the North Star from an active green arc. Venus is reflected in the lake at left. Credit: Bob King

Around 10:15 p.m. tall, faint red rays stretched toward the North Star from an active green arc. Venus is reflected in the lake at left. Credit: Bob King

There was a lot of action, but nothing too fast. Rays and rayed arcs slowly materialized, hung back and then reformed over and over in a way that reminded me of a symphonic theme and variations.

Multiple rayed arcs are reflected in still waters in a lake north of Duluth, Minn. Wednesday night. Credit: Bob King

Multiple rayed arcs are reflected in still waters in a lake north of Duluth, Minn. Wednesday night. Credit: Bob King

The Kp-index sits at “5” or minor storm, and the northern lights are still out there as I write. If you can find a dark sky with a good view to the north, I encourage you to lose a little sleep to see what natures’s offering tonight.

* Update 1 a.m. Thursday April 16 – The aurora is now in the flaming phase, where pulses or waves ripple through the lights from bottom to top across the entire northern sky. Although the rays are now fainter, they reach all the way to the zenith compared to earlier in the evening. What are you seeing? Let us know by clicking on and adding a comment.

Red and green all over! Credit: Bob King

Red and green all over! Credit: Bob King

Aurora alert tonight April 15-16

What a display! The aurora on the morning of April 11, 2015 reflected in St. Croix River near Gordon, Wis. Credit: Kathleen Wolleat

What a display! The aurora on the morning of April 11, 2015 reflected in the St. Croix River near Gordon, Wis. Credit: Kathleen Wolleat

Good news on the northern lights front. Earth’s expected to get a bath from subatomic particles streaming from the Sun’s southern hemisphere tonight. They originate from a gap in its magnetic canopy called a coronal hole.

A big, extended coronal hole in the Sun's atmosphere or corona is sending a high-speed package of solar wind our way tonight. This photo was taken on April 13 by NASA's Solar Dynamics Observatory. Credit: NASA

A big, extended coronal hole in the Sun’s atmosphere or corona is sending a high-speed package of solar wind our way tonight. This photo was taken on April 13 by NASA’s Solar Dynamics Observatory. Credit: NASA

Not a big storm. The space weather office at NOAA is calling for a G1 or minor geomagnetic storm, the type that brings arcs and occasional rays of aurora across the northern U.S. and southern Canada.

The last G1 storm we experienced on April 11 produced a fat, quiet arc that broke up into a modest but attractive display visible as far south as Colorado.

The best time to watch for tonight’s possible show will be from nightfall – around 8:30 p.m. – until midnight. In other words, on the early end. There’s no moon in the sky and April brings some of the most pleasant, mosquito-free evenings of the year.

Aurora over Boulder Lake north of Duluth, Minn. on April 11, 2015. Credit: Deb Carroll

Aurora over Boulder Lake north of Duluth, Minn. on April 11, 2015. Credit: Deb Carroll

The northern lights often begin as an arc or rainbow-shaped glow low in the northern sky. When night has begun, the light lingers in the north as if twilight isn’t over yet. Don’t be fooled. That’s the aurora gearing up.

Dwarf planet Ceres – a more colorful view

The map is an enhanced color view that offers an expanded range of the colors visible to human eyes. Pictures were taken using blue, green and infrared filters and combined. Scientists use this technique to highlight subtle color differences across Ceres, which can provide insights into the physical properties and composition of the surface.  Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

A new color map of Ceres based on photos taken by the Dawn spacecraft suggest a little planet that continues to evolve.

“This dwarf planet was not just an inert rock throughout its history. It was active, with processes that resulted in different materials in different regions. We are beginning to capture that diversity in our color images,” said Chris Russell, principal investigator for the Dawn mission.

Many thanks to graphics wizard Tom Ruen who created this simulated rotation using the color map

While the first thing you might notice about Ceres are the many craters, scientists doing the counting note that the miniature planet has fewer large craters than expected. That pair of bright spots that has everyone scratching their chins also hint at more recent activity.

Dawn's visible and infrared mapping spectrometer (VIR), highlight two regions on Ceres containing bright spots. The top images show a region scientists have labeled "1" and the bottom images show the region labeled "5." Region 5 contains the brightest spots on Ceres. VIR has been examining the relative temperatures of features on Ceres' surface. Preliminary examination suggests that region 1 is cooler than the rest of Ceres' surface, but region 5 appears to be located in a region that is similar in temperature to its surroundings. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF

Pictures from Dawn’s VIR instrument highlight two regions on Ceres containing bright spots. The top images show a region scientists labeled “1” and the bottom images show the region labeled “5,” which show the Ceres’ brightest pair of spots. Region 1 is cooler than the rest of Ceres’ surface, but region 5 appears to be located in a region that is similar in temperature to its surroundings. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF

More details will come to light after the spacecraft begins its first intensive science phase on April 23 from a distance of 8,400 miles (13,500 km) from the surface. Dawn’s tool belt totes a visible and infrared mapping spectrometer or VIR, that examines Ceres in visible and infrared or thermal light. Already, data from VIR indicate that light and darker regions on the dwarf planet have different properties.

A topographic map of Ceres with provisional names given to each quadrangle. Ceres' craters are named for agricultural gods; other features after world agricultural festivals. Credit: NASA / JPL / UCLA / MPS / DLR / IDA / JohnVV / Emily Lakdawalla

A topographic map of Ceres with provisional names given to each quadrangle. Ceres’ craters are named for agricultural gods; other features after world agricultural festivals. Credit: NASA / JPL / UCLA / MPS / DLR / IDA / JohnVV / Emily Lakdawalla

The Hubble Space Telescope has even gotten into the act. With it, astronomers have identified 10 bright regions on Ceres’ surface. The dual pair of bright spots inside a 57-mile-wide crater is located in a region with a similar temperature to its surroundings. But a a different bright feature appears in a region that’s cooler than the neighboring surface.

“The bright spots continue to fascinate the science team, but we will have to wait until we get closer and are able to resolve them before we can determine their source,” Russell said. That said, one of the more interesting possibilities is that they’re caused by outgassing or a release of vapor and dust, a dirty geyser as it were. During the day it brightens, while at dusk it fades, much like a jet from a comet. Still, no one can say just yet what it is, but given that Ceres is composed of about 25% water, it seems a possibility.

Fast-spinning asteroid tears itself to pieces

Top panel shows a wide-angle view of the main nucleus and smaller fragments embedded in a long dust trail.

Top panel shows a wide-angle view of the main nucleus of the crumbling asteroid P/2012 F5 and smaller fragments embedded in a long dust trail. Bottom panel shows a close-up view with the trail removed for a clearer view of the individual fragments. Credit: M. Drahus, W. Waniak (OAUJ) / W. M. Keck Observatory

A team of astronomers led by team led by Michal Drahus of the Jagiellonian University (Krakow, Poland) used one of the twin 10-meter (394-inch) telescopes of the W.M. Keck Observatory in Hawaii to study the strange behavior of four comet-like asteroids.

Most of the hundreds of thousands of known asteroids are made of rock and don’t develop fuzzy comas and tails the way similar-sized icy comets do. But since 2010, astronomers have uncovered a small number of oddball, “active asteroids” that mimic comets by releasing clouds of dust as they spin.

Artist illustration of the active asteroid P/2012 F5 trailing a tail of dust spun off due to its fast rotation. Credit: SINC

Artist illustration of the active asteroid P/2012 F5 trailing a tail of dust spun off due to its fast rotation. Credit: SINC

One of them, P/2012 F5 (Gibbs), located in the outer zone of the main asteroid belt, spins so fast, it’s literally falling apart. Using the Keck II telescope, Drahus and team discovered at least four fragments flung from the object.

We knew the asteroid was an active one because it had previously released a cloud of dust in a single, quick impulse back around July 1, 2011. Like a comet, the object looked slightly fuzzy and left a left a dust trail; this time around, P/2012 F5 took it to the next level and deposited a string of tiny asteroid satellites.

There are two theories on how otherwise quiet asteroids can suddenly explode to life — through a collision with another smaller asteroid or by “rotational disruption”, which is exactly what it sounds like.

Yorping the day away. Illustration showing how sunlight absorbed unevenly by an asteroid’s surface creates torque that can increase its spin rate. Illustration: Bob King

Yorping the day away. Illustration showing how sunlight absorbed unevenly by an asteroid’s surface and re-released as heat creates torque that can increase its spin rate. Illustration: Bob King

An asteroid can spin so fast that its weak gravity is overwhelmed by centrifugal force, the tendency of material to pull away from a rapidly spinning object. Centrifugal force can cause small objects like P/2012 F5 and its ilk to break apart. No surprisingly, the team measured F5’s rotation rate at just 3.24 hours, fast enough for it to theoretically explode.

So how do you spin up an asteroid until it shoots pieces of itself into space like some hell-bent disk golfer? Just add a little YORP. An acronym for Yarkovsky–O’Keefe–Radzievskii–Paddack effect, heating from the Sun can cause an asteroid’s tilt and rotation rate to change over time.

Sunlight shining on an asteroid warms the rock which releases the energy as heat, giving the object a tiny push. Assuming the asteroid is irregular in shape – and most are because they’re so small – some areas get hotter and give off more heat than others. The imbalance causes a torque on the asteroid, increasing its spin rate. Depending on the shape of the asteroid and variations in the reflectivity of its surface (some areas may be darker or lighter than others), those smidgeons of thrust can add up to twirl an asteroid to the breaking point.

And because many asteroids are little more than rubble piles, breaking up is easy to do.

This illustration shows one possible explanation for the disintegration of asteroid P/2013 R3. Sunlight absorbed unequally across the asteroid’s surface can spin up its rotation and cause it to fall apart. More details on how this happens below. Credit: NASA, ESA, D. Jewitt (UCLA), and A. Feild (STScI)

Sunlight absorbed unequally across the asteroid’s surface can spin up its rotation rate and cause it to fall apart. While it’s possible P/2012 F5 was struck by another object, this explanation best fits the observations. Credit: NASA, ESA, D. Jewitt (UCLA), and A. Feild (STScI)

“This is really cool because fast rotation has been suspected of catapulting dust and triggering fragmentation of some active asteroids and comets. But up until now we couldn’t fully test this hypothesis as we didn’t know how fast fragmented objects rotate,” Drahus said.

Astronomer Alex Gibbs discovered P/2012 F5 on March 22, 2012 with the Mount Lemmon 1.5 meter reflector in Arizona. It was initially classified as a comet, based on its fuzzy look, but two independent teams quickly showed that the dust was blasted out in a single pulse about a year before the discovery – something that doesn’t happen to comets, which continuously emit dust and other materials as the Sun vaporizes ice from their nuclei.

Gibb’s find and the other known active asteroids are all under 0.6 miles or one kilometer across. So tiny they’re incredibly faint. That’s why the biggest telescope on Earth was needed to dig down into the details and uncover the tale of an asteroids torn asunder by nothing more than sunlight.

A moon rock lands in Duluth

Chelsea Paulson, 5, of Saginaw, holds her grandfather Randy Paulson's hand as she studies the Apollo moon rock inside a lucite pyramid at NASA's Journey to Tomorrow traveling exhibit at the Home Show at the DECC Thursday evening. The rock (seen in the inset at upper left) was collected by Apollo 17 astronauts Gene Cernan and Harrison Schmitt in December 1972. It's about 3 inches across, weighs 152 grams (1/3 lb.) and is 3.9 billion years old. Credit: Bob King

Chelsea Paulson, 5, of Saginaw, holds her grandfather Randy Paulson’s hand while looking at the Apollo moon rock inside a lucite pyramid at NASA’s Journey to Tomorrow traveling exhibit at the Home Show in Duluth, Minn. Thursday. The rock was collected by Apollo 17 astronaut Gene Cernan in December 1972. Credit: Bob King

A priceless moon rock lies locked in a glowing pyramid of lucite a few blocks from Lake Superior in Duluth today. NASA’s “Journey to Tomorrow” traveling exhibit pulled into town a few days ago, and among the displays is a palm-sized lunar rock collected by Apollo 17 astronaut Gene Cernan sometime on December 13,1972.

Closer view of the 152 gram polycrystalline moon rock returned from the moon during the Apollo 17 mission to the Taurus-Littrow highlands. Credit: Bob King

Closer view of the 152 gram polycrystalline moon rock returned from the moon during the Apollo 17 mission to the Taurus-Littrow highlands. Credit: Bob King

The 152 gram (1/3 lb.) concrete-gray rock measures about 3 inches (7.6 cm) across. It was part of a larger rock picked up by Cernan on his third moonwalk with fellow astronaut Harrison Schmitt. Moon-drive might be a better description. The two boarded the Lunar Rover that Wednesday evening and drove 2.5 miles (4 km) northeast of their landing site in Taurus-Littrow Valley, a relatively smooth area snaking between the rugged peaks of the Taurus Mountains just beyond the lava plains of the Sea of Serenity.

Astronauts often used tongs to pick up lunar samples. It was a lot easier than bending over in bulky space suits to pick up a rock. The rock in the NASA exhibit was likely collected this way. Credit: NASA

Astronauts often used tongs to pick up lunar samples. It was a lot easier than bending over in bulky space suits to pick up a rock. The rock in the NASA exhibit was likely collected this way. Credit: NASA

During one of their stops to collect samples, Cernan’s curiosity must have been peaked by the rock’s appearance. Using a set of tongs (or possibly a hammer to bust a chip off a larger formation), he retrieved the sample and dropped it in a bag. Schmitt and Cernan later placed the bags into specially sealed storage boxes and loaded them — along with our featured rock — into the lunar module ascent stage for the trip back to lunar orbit and Earth.

After Apollo 17 safely landed, the boxes were taken to the Lunar Receiving Laboratory at the Johnson Space Center near Houston, Texas and opened in a vacuum chamber to avoid contamination by the atmosphere. Before our 152 gram “rock star” began its 50-state tour, it was sliced (hence the smooth face on one side), classified and its age determined by radioactive dating methods.

This is as close as I could get to the moon rock. Not only was it contained in lucite, it was also in a glass case. You can easily see cracks formed by impact bombardment as well as tiny holes or vesicles where gases escaped when the rock was melted and or re-heated during an impact. Credit: Bob King

This is as close as I could get. Not only was the rock contained in lucite, it was behind glass. You can easily see cracks and melt veins formed by impact bombardment as well as tiny holes or vesicles where gases escaped when the rock partially melted an impact. Credit: Bob King

It looks so ordinary to the eye. Like I said, a gray rock. I’ve seen better tossed up by the waves of Lake Superior. But before you lies a 3.9 billion-year-old stone far older than most Earth rocks.

The outside of the moon rock is darker than the inside. This is probably caused by "space weathering" or radiation and high-speed particles from the Sun that slowly darken the moon's surface over time.  Credit: Bob King

The outside of the moon rock is darker than the inside. This is probably caused by “space weathering” – radiation and high-speed particles from the Sun that slowly darken the moon’s surface over time. Younger craters on the moon are much brighter than older because the impacts plow up dust and debris from under the surface that haven’t be exposed to the Sun for millions or billions of years. Credit: Bob King

Here in Duluth, we admire the tough 1.1 billion-year-old lava formations that tower above the waves of Lake Superior and underlie the region for miles. Ancient for sure, but the traveling moon rock provides a fresh perspective on exactly how old is old. It solidified just 400 million years after the moon itself took shape from the debris released during the cataclysmic impact of a Mars-sized planet with Earth.

This is the traveling moon rock's home base - the Apollo 17 landing site,  photographed  by the Lunar Reconnaissance Orbiter. Click for a larger view. Credit: NASA

This is the traveling moon rock’s home base – the Apollo 17 landing site, photographed by the Lunar Reconnaissance Orbiter. Click for a larger view. Credit: NASA

The display next to the sample describes it as a “polycrystalline breccia” or rock composed of many older crystalline rocks melded together. The vast majority of rocks gathered by the Apollo astronauts are rock fragments or breccias cemented together through impact. Is it any surprise? The early moon was a devil’s playground of non-stop bombardment by meteoroids and asteroids. Each impact crushed and re-mixed the crustal rocks, creating oodles of fragments. Breccia within breccia.

Check out the melt veins, cracks and vesicles (little holes) in the cut face — all indications of the violence that visited not only the moon but all the planets and moons during the solar system’s formative years.

Apollo 17 astronaut Eugene Cernan checks out the Lunar Rover before he and Harrison Schmitt head out for another moonwalk. On the day our featured rock was found, the astronauts collected 146 pounds of lunar samples. Credit: NASA

Apollo 17 astronaut Eugene Cernan checks out the Lunar Rover before he and Harrison Schmitt head out for another moonwalk. On the day our featured rock was found, the astronauts collected 146 pounds of lunar samples. These were the last rocks to date brought back from the moon by the United States. Credit: NASA

You can see all this history wrapped up in a single rock with your own eyes still today. The big NASA truck with the moon rock and other space-themed exhibits will be open through 5 p.m. today (April 12) at the annual Home and Builder Show at the Duluth Entertainment Convention Center (DECC). If you can’t make it, the traveling exhibit may be coming to a town near you, although they don’t have a set schedule. For more information, click HERE.

Apollo landing sites. Apollo 17's location is highlighted in red. Credit: Soerfm

Apollo landing sites. Apollo 17’s location is highlighted in red. Credit: Soerfm

Pleiades passage / Aurora night 3?

Venus nearly overwhelms the Seven Sisters or Pleiades star cluster yesterday evening around 9 p.m. in the western sky. Watch for the two to be nearly as close together tonight. Credit: Bob King

Venus nearly overwhelms the Seven Sisters or Pleiades star cluster yesterday evening around 9 p.m. in the western sky. Watch for the two to be nearly as close together tonight. Credit: Bob King

You couldn’t help noticing Venus and the Pleiades last night glimmering in the west at dusk. Tonight they’ll be nearly as close. If you have a small telescope, take a closer look and see if you can discern the planet’s small, not-quite-round disk.

Venus passes through phases just like the moon and has surprised more than a few first time viewers who thought that’s what they were looking at. A moon in miniature but shiny white and without a bump or crater to mare its smooth and perfect “skin”. Unlike the moon, Venus is 100% cloaked in clouds. From its surface you wouldn’t see a single star not just for a week or two but for as long as you’d live. If there were ever a nightmare planet for amateur astronomy, this is it.

As Venus revolves around the Sun interior to Earth's orbit, we see it go through phases depending on its position in relation to the Sun.  Credit: Wikipedia

As Venus revolves around the Sun interior to Earth’s orbit, we see it go through phases depending on its position in relation to the Sun. Credit: Wikipedia

Venus orbits the Sun inside of Earth’s orbit — the reason we see lunar-like phases — with a period of 225 days. That makes a Venusian year only 0.6 times as long as an Earth year. For those who love birthdays then, Venus offers nearly twice as many as our plodding planet.

Through April, Venus appears as small waxing gibbous moon through a telescope, but as it catches up to Earth, it will gradually slim down to a half-moon and finally a crescent. Because it’s approaching our planet, its apparent size will also increase. By crescent phase, Venus’ shape is easily visible in little more than 10x binoculars.

While Venus is 106 million miles (170 million km) from us today, that’s peanuts compared to its neighbor, the Pleiades, which beckons from a distance of 444 light years or 2.66 quadrillion miles.

The aurora at 3:27 a.m. this morning April 10 from Midway Township near Duluth, Minn. Moonlight lit the foreground. Credit: Matthew Moses

The aurora at 3:27 a.m. this morning April 11 from Midway Township near Duluth, Minn. Moonlight lit the foreground. Credit: Matthew Moses

I can vouch that the northern lights remained active all the way into twilight this morning. Even with the last quarter moon shining, a rayless hump of aurora glowed brightly in the lower half of the northern sky until finally quenched by dawn. Chances for seeing northern lights drop off this evening, but there may still be some action. Once again, watch for a glow in the north as soon as the sky gets dark.

Last night, a low auroral arc minded its own business for a very long time before surging into activity. I stood out on a dirt road somewhere north and watched the slow, slow process unfold to the sound of a single saw-whet owl’s relentless peeping.

Northern lights on cue tonight – Go out for a look!

Nice active rays and curtains around 11 p.m. CDT this evening April 9-10. Credit: Bob King

Nice active rays and curtains around 11 p.m. CDT this evening April 9-10. Credit: Bob King

A very good forecast this evening for the aurora. If you’ve been outside the past hour or so, you know what I mean. At nightfall, a double-arc of pale green light slung 10° high across the northern sky and quietly glowed until around 10 p.m. (CDT). Around 10:30, rays appeared within the slushy glow as if by magic, but they were subtle. A half hour later, the display went full tilt when a large northern arc broke up into tall rays splayed across the northern sky.

The western end of the aurora extended just about to Venus and the Pleiades (far left) around 10:45 this evening. Credit: Bob King

The western end of the aurora extended just about to Venus and the Pleiades (far left) around 10:45 this evening. Credit: Bob King

Not an explosive display but very nice. They’re still out now at midnight with a big glow visible from my home. If you can find a spot with a view way down low in the north, there’s still plenty to see.

For much of the early evening, a large, rainbow-like arc dominated the lower half of the northern sky. It broke into rays only later. Credit: Bob King

For much of the early evening, a large, rainbow-like arc dominated the lower half of the northern sky. It splintered into rays around 10:30-11 p.m. Credit: Bob King