Serious about Ceres? Vested in Vesta? A last-minute conjunction guide

Last night July 2, 2014 Ceres and Vesta were about a quarter degree apart in Virgo above Mars and Spica in the southwestern sky around 11 p.m. You can clearly see that Vesta is the brighter asteroid. 70mm lens at f/2.8, ISO 2500, 15-second exposure. Credit: Bob King

And yes the twain shall meet! Tonight I have a couple new photos to share with you showing the asteroids Ceres and Vesta just before their face-to-face meeting on July 5. That night they’ll be 10 arc minutes or just a third of a full moon diameter apart. Don’t fret if the weather’s supposed to be cloudy then – they’ll be nearly close tonight through the 6th.

Ceres and Vesta on the move! Pictures taken last night July 2, 2014 and tonight July 3 around 11 p.m. CDT show both asteroids zipping along near Zeta Virginis. The small triangle of stars serves as a reference to help you judge their movement. Photos taken with a 70mm lens, enlarged and cropped. Credit: Bob King

Besides, tonight the moon’s still a crescent and neither as bright nor as close to our asteroidal celebrities as it will be on the 5th. Glare that night will make seeing fainter Ceres difficult. If you have a telescope, both can be viewed right on through the full moon.

Map showing the motion of Ceres and Vesta at 1-day intervals near Zeta Virginis, a 3rd magnitude star located above the bright pair of Mars and Spica in the southwestern sky at nightfall. They’ll be closest on July 5. Stars plotted to magnitude 8.5. I also drew in the same triangle as in the photos. Source: Chris Marriott’s SkyMap

Vesta shines at magnitude 7, one magnitude fainter than the naked eye limit. I had no problem seeing either asteroid in 8×40 binoculars last night (July 2). They also showed up in my camera with a 15-second exposure at ISO 2500 with the lens wide open at f/2.8. The next few nights present a great opportunity for anyone with a medium to higher end digital camera and tripod to create a series of photos showing their convergence and divergence over time. A animated gif of the motion would be sweet!

Ceres and Vesta through a 14-inch telescope on July 3, 2014 when they were 13 arc minutes (a bit less than a 1/4 of a full moon diameter) apart. Both asteroids are too small and far away to appear as real disks in most telescopes. Credit: Gianluca Masi

Italian astronomer Gianluca Masi plans to feature live telescope images of Ceres and Vesta at closest approach on his Virtual Telescope site beginning at 3 p.m. CDT (4 p.m. EDT, 2 p.m. MDT and 1 p.m. PDT) Saturday July 5.

Hope you get to see the pair. Their last conjunction was in 1996 when they were much farther apart (2 degrees). And don’t forget the nearby conjunction of the moon and Mars with Spica nearby the same night.

Two asteroids approach in the night / See Saturn’s elusive moon Iapetus

Map showing Ceres and Vesta as they approach each other closely this coming week. Both asteroids are near the easy-to-find star Zeta in Virgo not far from bright Mars (see map below). Although the asteroids appear very close together in the sky, they’re really about 51 million miles apart with Vesta in the foreground. Click to enlarge. Source: Chris Marriott’s SkyMap

This coming week there will be something for everyone in the night sky whatever instrument you choose: telescope, binoculars or naked eyeballs.

The biggest asteroid, Ceres, and brightest, Vesta, have been on converging paths since early spring. Right now they’re about a moon diameter (1/2 degree) apart and closing with each passing night. Saturday night July 5 – one week from today –  they’ll be three times closer yet, separated by just 10 arc minutes. To see this double asteroid treat a pair of 35 or 50mm binoculars should do the trick.

Use this wider view to help get oriented. Our two featured asteroids are near the 3rd magnitude star Zeta Virginis just above the bright pair of Mars and Spica. The map shows the sky around 10 p.m. local time tonight June 28, 2014 for the central U.S. Stellarium

Just as moon routinely has conjunctions with bright planets and stars during its monthly round through the zodiac, Vesta and Ceres will be in conjunction one directly atop the other on July 5. Vesta will shine at 7th magnitude and be easy to spot in binoculars; fainter Ceres at magnitude 8.3 will take a little more effort. Since asteroids are too small and far away to show as disks in most telescopes, the pair will look like a temporary ‘double star’ in all instruments.

Double your conjunction fun on Saturday night July 5. The same night Ceres and Vesta are closest, the moon and Mars form a tight duo nearby. From parts of South America, the moon will cover or occult the Red Planet. Stellarium

Another celestial duo debuts on the very same night the asteroids are closest. For observers in the U.S. and Canada, the moon, some 7 degrees south of Vesta-Ceres, passes only a half degree from Mars. Two conjunctions in the same small pocket of sky on the same night!

For U.S. observers, this all happens the night after the July 4 Independence Day fireworks. Could July start with more of a bang?

Another telescopic delight is happening a stone’s throw from Mars around the planet Saturn. Of the 62 known moons of the ringed planet, one of the most peculiar is 907-mile-wide Iapetus, which orbits well beyond the more familiar telescopic moons Titan, Rhea, Tethys and Dione.

Ever seen Saturn’s peculiar moon Iapetus? Right now it’s west of the planet and bright — second only to the moon Titan. Click to enlarge. Source: Starry Night

Iapetus has two faces really. One is shiny white and bright as snow, the other dark as the sky above Gotham City. The moon takes 79 days to complete one orbit around Saturn and like our own moon, keeps one face locked toward the planet. When it orbits east of Saturn, Iapetus shines dimly at magnitude +12 because its dark side faces us. But when it’s off to the west of the planet, the brilliant side turns our way and we see it shine two magnitudes brighter.

Saturn’s moon Iapetus, 907 miles (1,460 km) in diameter, has a dual personality. One hemisphere is covered with bright ice, the other with darker material possibly ejected by impacts on the more distant moon Phoebe. Credit: NASA / JPL / Space Science Institute

Greatest brightness occurs at the time of greatest distance west of the planet which happens on July 3. You can use the map above to help you follow the moon through its cycle of bright to dim. For more information, please see this recent article in Sky and Telescope.

Drum roll please … Curiosity takes first-ever pix of asteroids from Mars!

The Curiosity rover captured the first image of asteroids from the surface of Mars. Also included in the image are separate photos of Mars’ moon Deimos in a circular, exposure-adjusted inset and square insets at left from other images the same night of its second moon Phobos as well as Jupiter and Saturn. Credit: NASA/JPL-Caltech/MSSS/Texas A&M

Dang! NASA’s Curiosity rover beat me to it by just one day, spotting the asteroids Ceres and Vesta from the surface of Mars on Sunday April 20. Me? I caught them later that night from a comfortable location on Earth with a pair of 8×40 binoculars.

The rover aimed its high-resolution mast camera skyward to take the first-ever photos of the largest (Ceres) and brightest (Vesta) asteroids. Both objects are destinations of NASA’s Dawn Mission as we learned in this recent blog. The photo shows trailed images of both – it was a 12-second time exposure – and Mars’ smaller moon Deimos. The others were added to make a composite. While it looks like it was taken with a mobile phone, it’s one of very few photos taken of the night sky from another planet.

Original mastcam photo of Ceres, Vesta and much brighter Deimos, the smaller of Mars’ two moons. Credit: NASA

The two asteroids and three stars would be visible to someone of normal eyesight standing on Mars. Specks are effects of cosmic rays striking the camera’s light detector. Given that Mars is located closer to the asteroid belt than Earth, I checked the brightness of Ceres and Vesta. Interestingly, both are located in the constellation Virgo just as they are from our own planet right now, but their brightnesses differ. Vesta shines at magnitude +4 (+5.8 from Earth), making it a relatively easy naked eye object from the Martian ‘countryside’. Ceres is currently magnitude +7 from home but magnitude +5.8 and dimly visible with the naked eye from Mars.

Thinking about it a minute, it shouldn’t surprise us that both asteroids are traveling together in the same constellation as seen from both planets. Can you guess why? Remember that Mars was at opposition earlier this month and lined up with Earth on the same side of the sun. That alignment means that we both look out at virtually the same “springtime” constellations in our respective night skies AND look in nearly the same direction when viewing Ceres and Vesta. If Mars was on the opposite side of the sun, Martians would have to look in the opposite direction of the sky to see them.

Curiousity took this fisheye photo with its front hazcam on April 24, 2014 from the Kimberley showing one of the three hills, likely Mt. Remarkable. Credit: NASA/JPL-Caltech

“This imaging was part of an experiment checking the opacity of the atmosphere at night in Curiosity’s location on Mars, where water-ice clouds and hazes develop during this season,” said camera team member Mark Lemmon of Texas A&M University, College Station. “The two Martian moons were the main targets that night, but we chose a time when one of the moons was near Ceres and Vesta in the sky.”

We love it and wouldn’t complain if you guys shot more nighttime stuff. How about a sequence of images of the rising Earth or a longer time exposure showing star trails with the landscape faintly illuminated by the light of Phobos and Deimos?

If you can find Mars, you can spot Ceres and Vesta too – try it!

Ceres, the largest asteroid, and Vesta, the brightest, lurk near the bright planet Mars this spring. They’re easy to see in binoculars and showed up clearly in this 30-second time exposure made April 20, 2014. Credit: Bob King

Who hasn’t been dazzled by the Red Planet these April nights? Come 10 o’clock, Mars shines brilliantly in the south accompanied by the the blue-white star Spica. But did you know that just a short distance away, asteroids Ceres and Vesta are making their rounds in the night sky too?

Use this map to get started. The star to find is labeled Zeta Virginis, located a little less than one outstretched fist to the left of Mars. Point your binoculars there and then use the more detailed map below to navigate to Ceres and Vesta. Stellarium

Ordinary binoculars will easily show both. Last night I stood in my driveway with a pair of 8x40s and hopped from Mars to Zeta Virginis and then to the “Vesta Triangle” and saw them in the same field of view. Vesta shines at magnitude 5.8, bright enough to be dimly visible with the naked eye from a dark sky. Talk about easy. I hardly had to try with binoculars.

Ceres and Vesta hang out this month  near the “Vesta Triangle”, a small group of stars located about 3 degrees north of Zeta. Positions for both asteroids are shown for 10 p.m. CDT every five days with stars to magnitude ~8.5. The stars will remain in their places, but you’ll see Ceres and Vesta move slowly among them as the nights pass. Click to enlarge, then print to use outside. Created with Chris Marriott’s SkyMap software

Ceres, at magnitude 7, is fainter but well within easy reach from suburban skies. Now the cool part – both asteroids will be no more than a few degrees apart through July. That means they fit in the same binocular field of view, so if you find brighter Vesta, Ceres will always be nearby. Matter of fact, they’ll really get close come late June and early July. As we approach that time, I’ll provide additional maps.

Vesta (left) and Ceres. Vesta was photographed up close by the Dawn spacecraft from July 2011-Sept. 2012, while the best views we have to date of Ceres come from the Hubble Space Telescope. The bright white spot is still a mystery. Credit: NASA

If you’ve never seen an asteroid before except in close up photos taken by spacecraft, lower your expectations right now. They look exactly like stars. Even Ceres, the largest at 590 miles in diameter, is too small to appear more than stellar in even a large telescope. Vesta’s smaller yet – 330 miles wide – but brighter because it’s somewhat closer and also more reflective.

That’s OK. Getting to see the real thing is what skywatching’s about. I love the photos but honestly get more of a kick out of seeing the asteroids with my own eyes. When life gets tedious, I like to think of them silently cycling over my little patch of earth, Vesta 114 million miles away, Ceres 153 million.


Dawn’s Greatest Hits at Vesta – A Look at What We Learned (spiced up with guitar)

Coincidentally, both Vesta and Ceres, which orbit in the main asteroid belt, are the targets of NASA’s Dawn Mission. Dawn visited and studied Vesta from July 2011 to Sept. 2012 and revealed that the tiny world had something much in common with its big brothers, the planets. Vesta was once hot enough to melt and differentiate into an iron core, rocky mantle and crust like the terrestrial planets. Heat from the decay of radioactive elements like aluminum-26 caused heavier iron to trickle down to the core while lighter minerals floated to the top to form Vesta’s crust.

Ceres rotates once on its axis every 9 hours (Vesta takes 5.3 hours). These four photos span 2 hours 20 minutes. Photos taken with the Hubble Space Telescope. Credit: NASA/ESA

While Ceres can still be considered an asteroid it’s also a member of a select group of dwarf planets, bodies large enough to have crunched themselves into spheres through their own gravity but not big enough to clear the region they orbit of smaller asteroids. Dawn’s on its way to its final target, a rendezvous with Ceres next February. Unlike dry and rocky Vesta, Ceres shows signs of water and clay.

While you’re waiting for the next close up photos, why not go out on the next clear night and see them for yourself?

Load up the car, we’re going to Vesta

A section of Vesta’s southern hemisphere imaged by NASA’s Dawn spacecraft from low orbit in 2011-12. Click for large version with a resolution of 75 feet per pixel. All photos credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Before voice navigation and cellphones we all kept our car glovebox stuffed with maps of favorite states traveled. Some of us still do. When you needed directions to a city, you unfolded the map or atlas on your lap and followed the vein-like red and blue lines to the your destination.

Vesta’s equatorial regions are scarred by a series of deep, parallel grooves or geologic faults, likely created when a smaller asteroid blasted out the huge Rheasilvia basin at the asteroid’s south pole. One of the bigger ones is named Divalia Fossa. Click to enlarge.

Now there’s an out-of-this-world virtual atlas that let’s you do the same. If you’re ever in a mood to drive around the asteroid Vesta, you can have at it. NASA has released 29 maps created from 10,000 images shot by Dawn spacecraft’s framing camera from 130 miles (210 kilometers) high. The maps are at a level similar to the state maps you’d pick up at a roadside rest; one inch covers a little more than 3 miles of asteroid (1cm = 2km).

Antonia Crater in Vesta’s southern hemisphere is about 9 miles (15 km) across and appears partly filled with debris possibly deposited by another impact. This picture is a tight crop from one of the 29 maps. Click to enlarge.

The level of detail is astonishing. Just click on one of the photos, allow a couple minutes to download and then go for a ride with your mouse. Each of the maps was pieced together as a mosaic using 400 images. Three different projections were applied depending on latitude: Mercator for equatorial regions, Lambert conical projections for mid-latitudes and a stereographic projection for the Rheasilvia Basin at Vesta’s south pole.

Vesta was the fourth asteroid discovered. It’s 326 miles (525 km) across, large and bright enough to occasionally be visible with the naked eye. Credit: NASA

Because Vesta’s north pole was still in mid-winter darkness during part of the mapping, a small patch there escaped coverage. Otherwise the map is complete.

Vesta, first seen by German astronomer Heinrich Olbers in 1807, was only the 4th object to be discovered in the asteroid belt between Mars and Jupiter, hence its formal designation of 4 Vesta.  It was named after the goddess of the hearth, home and family in ancient Rome. All the names of geological features on Vesta relate to Roman Vestals (priestesses of Vesta), famous Roman women and cities in which the cult of Vesta is known or festivals in which the Vestals participated.

Vast aprons of rock and soil fallen from the walls of Matronalia Cliff on Vesta are highlighted in this image. Click for large version.

To see all the maps as well as a helpful series of pdf files identifying features and locations, click HERE. I’ve been enjoying my ramble across Vesta and hope you’ll do the same. The only thing missing are the roads.

A comet tale plus pummeling asteroids leave carbon stains on Vesta

Comet C/2012K5 passes near the bright star cluster M36 in the constellation Auriga the Charioteer last night. The comet is fading now but still visible in binoculars from a dark sky. Details: 200mm lens at f/2.8, ISO 800 and 2-minute exp. Photo: Bob King

Last night I attached my camera to a battery-operated mount designed to track the stars. What a comedy. Polar alignment kept slipping, the camera-lens weight was too much for the mount and focusing the telephoto lens proved tedious. All I wanted was a single picture of comet C/2012 K5. In the end, I got a lot of exercise hopping back and forth making adjustments …  and a somewhat serviceable image.

Up around 6 a.m. this weekend? Look south and you’ll see the last quarter moon pass the bright star Spica in Virgo Saturday and then Saturn on Sunday. Created with Stellarium

The comet had faded a bit but was still a fuzzy blotch in binoculars and showed an obvious northeastward-pointing tail at low magnification through the telescope. Although the tail color was too subtle to be seen with the eye, a time exposure reveals the yellow tint caused by sunlight reflecting off dust particles. Heat from the sun vaporizes comet ice, releasing embedded rocks and dust into the tail behind the comet’s head.

Scene from Yellowknife Bay on Mars photographed today Jan. 4, 2013. Credit: NASA/JPL-Caltech with color added by Bob King

Not much news has been reported from the Curiosity rover of late. NASA mission specialists are probably happy they can work in peace out of the media spotlight. Pictures keep pouring in just the same. You can view the most recent set of raw images HERE.

The rover’s been exploring a shallow basin called Yellowknife Bay. It’s one bleak-looking landscape that begs for the introduction of a few saguaro cacti. After finishing up exploration of the bay, scientist plans to spend most of 2013 piloting the rover toward the mission’s primary science destination – the 3-mile-high layered mound at center of Gale Crater center named Mt. Sharp. There the robot will study and sample water-rich clays deposited long ago when Mars was a wetter world.

Most of the dark, carbonaceous material on Vesta can be found on the rims of smaller craters (left) or scattered in their surroundings (right). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

A recent paper published in the November-December issue of the journal
Icarus describes the dark splotches of carbon-containing materials exposed along the rims of small craters as well as along the edges of the huge impact craters Rheasilvia and Venenaeia on the asteroid Vesta.

NASA’s Dawn mission to Vesta last year took thousands of photos, some of which show dark patches of carbonaceous (car-bon-NAY-shuss) material that matches the dark, carbon-rich mineral fragments found in Vesta meteorites here on Earth.

Dark materials streak Vesta’s Cornelia crater in this three-dimensional image from Dawn. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

“The dark material was most probably delivered during the formation of the older Veneneia basin (large impact crater in Vesta’s southern hemisphere) when a slow impacting asteroid collided with Vesta. Dark material from this two to three billion year old basin was covered up by the impact that Dark material from this two to three billion year old basin was covered up by the impact that subsequently created the Rheasilvia basin,” according to Lucille Le Corre and Vishnu Reddy, lead authors of the study.

In this slice of a Howardite meteorite found in the Sahara Desert, some of the small, dark chips are carbon-rich rocks from an asteroid that collided with Vesta long ago. Howardites and eucrites were blasted from the crust of Vesta by later impacts and arrived on Earth as meteorites. Photo: Bob King

The scientists measured the light from the dark patches on Vesta and discovered they were made of the same material as the dark carbon-rich fragments inside a group of fallen space rocks called eucrites and Howardites.

Asteroids, many of which orbit in the main belt between Mars and Jupiter, come in all flavors. Some are made of bone-dry, rocky materials, others contain clays and water and still others are nearly pure metal. Bashing and smashing into one another they left their marks not only on each other but in the pieces that came (and still come) to Earth.

Read more about the new study HERE.

Happy New Baktun and a joyous solstice to all

Circumscribed halo around last night’s half moon. Photo: Bob King

Today the Mayan calendar rolls over to a new Baktun or 144,000 day cycle as it has for centuries. Coincidentally, it’s also the first day of winter in the northern hemisphere and summer for folks down under. Winter tiptoed in at 5:12 a.m. (CST) this morning while many of us were snug in our beds. Looking out my window, the world looks much the same as it did yesterday – with a difference. It’s sunny!

Come join Duluth’s celebration of the solstice at the University of Minnesota-Duluth’s planetarium.

That means a clear sky tonight and a chance to celebrate the new season. If you live in the Duluth, Minn. region, the Marshall Alworth Planetarium will feature a special “End of the World – Winter Solstice” party with shows on the half-hour in the dome, telescope viewing, pizza, cider, a raffle and a free 2013 calendar. Cost is $8 per person or $15 per family. The event starts at 6 p.m. and runs until 9. More information HERE.

Only 8 hours and 32 minutes separate sunrise and sunset in Duluth, Minn. today. The rest belongs to the night. Solstice is combination of two Latin words – sol for sun and sistere to stand still. That’s what it feels like for a week or two at the time of the summer and winter solstices, when the sun reaches its highest and lowest points in the sky.

The seasons are caused by the 23.5 degree tilt of our axis. In summer, Earth’s north polar axis is tipped toward the sun, causing it to appear higher in the sky and making for longer days. Half an orbit later in winter, the north polar axis is tilted away from the sun, making for a low sun and short days. In spring and fall, the axis is tilted neither toward nor away and day and night are equal. Credit: Tau’olunga with additions by Bob King

On Dec. 21 the sun reaches its lowest altitude above the southern horizon at noon for the year. Here in Duluth, that’s about 20 degrees or two fists held at arm’s length. For Chicagoans, it’s 25 degrees, a bit higher. But if you live in Anchorage, the yellow orb of day climbs to just under 6 degrees before slinking back toward the west. My dear brother Mike who lives there must wait until 10:14 a.m. for the sun to rise today. With sunset at 3:42 p.m., he’ll need to be vigilant to catch sight of it. Buildings and trees could easily block the sun from view. .


Excellent, short video on how the seasons happen

These extremes of daylight and night are brought on by Earth’s tipped axis. If it ran straight up and down, much as Jupiter’s axis does, sunrise and sunset times would barely vary for your location. The sun would rise in the east and set in the west 12 hours later every day of the year. No variation and no seasons. Who wants that?

Thanks to the Earth’s tipped axis we experience the joys winter and the ice it brings. These are air bubbles trapped in pond ice near my home yesterday. Photo: Bob King

The tip ensures that the northern hemisphere of the planet tilts toward the sun in the summer and away in the winter. As a consequence, the sun appears very high in the sky in summer. Its longer, steeper path naturally means longer days and more intense heat. In the winter, we’re tipped away from the sun. Slanted, less intense solar rays and short days follow.

Vesta shown at 9:30 p.m. (CST) every 5 days now through Jan. 10, 2013 as it glides near the Hyades cluster. 97 Tauri is mag. 5.  Stars shown to 7.5 magnitude. Created with Chris Marriott’s SkyMap software

If you’re looking for an interesting astronomical treat in the night sky this solstice, face east anytime during the evening hours and find the brightest “star” you can see. That’s the planet Jupiter. Just below Jupiter is the bright star Aldebaran and a V-shaped pattern of stars called the Hyades star cluster. Not far from the cluster is the famous asteroid Vesta. You’ll recall it was was orbited and studied by NASA’s Dawn spacecraft this past year.

Vesta shines at magnitude 6.5 (just under the naked eye limit), as bright as it gets this year. The star-like asteroid is super easy to see right now in binoculars, especially with Jupiter to help point you there. Take a look the next clear night.

Be your own spaceship, visit Vesta and Ceres this month

Both the asteroid Vesta (left) and dwarf planet / asteroid Ceres are easily visible in binoculars this month and next as they travel through the early winter constellations Taurus and Gemini. Ceres is 590 miles in diameter; Vesta 326 miles. Credit: NASA, ESA

Would you like to pretend you’re riding piggyback on NASA’s Dawn mission hopping from the asteroid Vesta to its next target Ceres? All you need is a pair of 7×35 binoculars, a reasonably dark sky and a bit of imagination. November may not be the most pleasant month for skywatching in the northern hemisphere, but Ceres and Vesta, two of the brightest, biggest asteroids, are making their closest approach to the Earth in 2012 at nearly the same time. Surely this fortunate coincidence will inspire you to bundle up and brave the chill.

Vesta comes to opposition (closest to Earth) on December 9 when it will shine just below the naked eye limit at magnitude 6.4; Ceres reaches opposition only nine days later at magnitude 6.7. While the two almost-planets will be brightest then, they’re already nearly as bright and an easy catch now that the moon has retired from the evening sky.

Ceres is close to Eta Geminorum the next few nights. Later it passes under the open cluster M35. Positions are shown for 11 p.m. (CST) every five days. Stars are plotted to magnitude 9. North is up and west to the right. Maps created with Chris Marriott’s SkyMap software

Ceres is especially easy to spot over the next few nights since it keeps close company with the naked eye star Eta Geminorum in the toes of Gemini the Twins. Watch for it to buzz just south of M35 – one of the prettiest star clusters in the sky for both telescopes and binoculars – around Thanksgiving time. Consider their juxtaposition another reason to be thankful.

Ceres begins November at magnitude 8.0 but brightens to 7.3 by month’s end. Vesta meanwhile sidles up the south side of Taurus the Bull, home to the V-shaped Hyades star cluster and brilliant Jupiter. At magnitude 7.2 this week, you’ll find it a tad brighter and easier to see than Ceres. On the map, notice that Vesta glides through the northern edge of the bright, loose star cluster Collinder 65. Another bonus.

Vesta spends the next week crossing through the edge of the open cluster Collinder 65 as it works it way in Jupiter’s direction in the constellation Taurus. Stars plotted to magnitude 8. West is up and north to the left.

Both asteroids are presently traveling west – opposite their normal orbital motion – in what astronomers call a retrograde loop. The outer planets perform the same crazy backwards move around the time of their oppositions, too. Ceres and Vesta aren’t defying orbital mechanics. They only appear to move backwards because the faster Earth is passing them by, much like a car in the right lane appears to move backward as you pass it on the left. Soon enough, they’ll resume their routine eastern motion through the constellations as the viewing geometries of Earth and asteroids change.

A wide view of the sky facing east around 11 p.m. (CST) will help you get oriented when you look for the asteroids. The boxes show the general area covered in the more detailed charts above. Created with Stellarium

Dawn spent about a year in orbit around Vesta and finally departed late this summer with its sights set on a February 2015 encounter with Ceres. We learned lots at Vesta including that it differentiated into core and crust much like planets do. Rocks in its crust studied from orbit are a match for a suite of meteorites found on Earth called eucrites, diogenites and Howardites. No need for a sample return mission – pieces of Vesta have been falling from the sky for centuries.

Ceres is the largest asteroid – a dwarf planet actually – and another place altogether. By examining sunlight reflected from its surface, Ceres appears more carbon and water-rich than Vesta and a closer match to carbonaceous chondrite meteorites.

You can share in these discoveries and the road ahead by stepping outside the next clear night with binoculars and chart in hand. There’s nothing like seeing the real thing.

Let me know how you like the maps. I reversed the stars, going with black-on-white for greater clarity. Hopefully, they’re easier to read. To use a map, right-click and save to your desktop and then print out a copy. I’ll update them later this month, so you can continue to “mission along”.

Lifestyles of the hydrogen-rich and erratically famous

A huge glacial erratic versus a small human on the Superior Hiking Trail this week. Photo: Bob King

Wait a minute. What is this thing? Asteroid, alien spacecraft, rock of doom? No, it’s only a 20-foot-high glacial erratic astride the Superior Hiking Trail 5 miles east of Finland, Minn. The guidebook indicated its location but I wasn’t prepared for the sight of this behemoth. Erratics are boulders plucked by glaciers and deposited miles from their source. This one , composed of the mineral anorthosite, appeared to have been dropped in the middle of nowhere, hence it’s otherworldly appearance.

A very tight closeup of lichens (center) and crystal structure (right) on a small patch of the erratic. Photo: Bob King

When seen up close up, the bland, gray exterior of the rock proved to be composed of coarse crystals. Tiny patches of tough lichens hid parts of the weathered surface.

The boulder probably parted company with the glacier 10,000 years ago. Anything around that long in one place becomes a time machine into the past. Through its dark crystal panes, we glimpse a long-gone world of mile-thick ice and numbing cold. Given enough time, life’s tiny fungal tentacles, working in tandem with nature’s freeze-thaw cycle, will reduce this titan to shards and finally soil.

The Dawn spacecraft used its gamma ray and neutron detectors to discover hydrogen hot spots on the asteroid Vesta this past year. Red indicates the greatest amount of hydrogen; gray the lowest. Credit: NASA/JPL-Caltech

Another big rock – this one in the asteroid belt – shares an even more ancient past than my erratic. Rather than rocks dropped by ice, Dawn was hit with hunks of water-rich asteroids from the asteroid belt called carbonaceous chondrites. The probe found Vesta’s equatorial zone laced with hydrogen from water chemically bound to the rocks as -OH, also called hydroxyl. Free water’s formula is OHH, described more simply as H2O.

“The source of the hydrogen within Vesta’s surface appears to be hydrated minerals delivered by carbon-rich space rocks that collided with Vesta at speeds slow enough to preserve their volatile content,” said Thomas Prettyman, the lead scientist for Dawn’s gamma ray and neutron detector (GRaND) at the Planetary Science Institute in Tucson, Ariz.

Hundreds of small pits inside Vesta’s crater Marcia may have formed when late bombardment heated earlier materials deposited by water-rich asteroids. Heated by impact, water bound in rocks escaped to create the pits. Credit: NASA/JPL-Caltech/University of Arizona/MPS/DLR/IDA/JHUAPL

If any ice itself were to survive, you’d think Vesta’s polar regions would be the best places for preservation just as on the moon. The moon’s rugged terrain and an axis tipped just 1.5 degrees to the plane of Earth’s orbit create permanently shadowed havens for ice in craters at its north and south poles. Unlike the moon, Vesta’s axis has a considerable 29-degree tilt. As it rotates and orbits the sun, both north and south polar regions are repeatedly exposed to sunlight just as they are on Earth. If ice once languished there, it’s long gone.

The Sutter’s Mill carbonaceous chondrite, which fell on April 22, 2012 in California, is dark colored like most of its class. Photo: Bob King

In fact, most of the hydrogen was found in darker-colored rocks encircling the equator. Since carbonaceous chondrites are themselves dark and water-rich compared to other meteorites, they’re a good match for what Dawn found on Vesta.

More evidence for ancient water comes from strange clusters of pits measuring about 100-800 feet across discovered in the 40-mile diameter crater Marcia. They resemble similar features on Mars that likely formed when water within the rocks vaporized explosively during an impact leaving behind pothole-shaped depressions.

Similar pits on Mars from water boiling from the surface by the heat of impact. Credit: NASA/JPL-Caltech

It’s thought that a second round of high-speed impacts accomplished the same on Vesta. Marcia’s center is pocked with pits and has very low levels of hydrogen, consistent with water boiling off into space when the crater was formed.

Water. It’s always at the center of the story when it comes to space exploration. Earth’s water is believed to have arrived the same way as Vesta’s through comet and “wet” asteroid bombardment. Much later, water would build the glacier that plucked the boulder that now reposes alongside a woodland trail. You never know what adventures may lie ahead when you go with the flow.

Dawn probe departs Vesta, shoves off for Ceres

NASA’s Dawn spacecraft, which has been in orbit around the asteroid Vesta since mid-July 2011, left Vesta this week to fly to its next target, the dwarf planet Ceres.  Photo: Bob King / Vesta image: NASA

NASA’s Dawn spacecraft departed the asteroid Vesta early yesterday morning en route to a rendezvous with the carbon-rich dwarf planet Ceres in early 2015. The probe quietly entered into orbit around Vesta last July and began mapping its surface in great detail. Before the mission, the best photos we had resolved only the largest feature on the little world, the 310-mile-wide impact crater named Rheasilvia Basin. Now we have 31,000 photos of cliffs, basins and the tiniest of craters just meters across. Other instruments measured the elements in the rocks below, the composition of minerals in the crust and looked for signs of water. Scientists used Dawn’s radio antenna in combination with antennas on Earth to probe the protoplanet’s interior.

Artist’s view of Vesta showing its 136-mile-wide iron core in brown, the mantle in green and crust in gray. Vesta is “differentiated” or layered in composition just like the inner planets. Credit: NASA/JPL-Caltech

As the craft slowly spiraled away from Vesta, it took a final set of pictures showing its north polar region, which has been in shadow until recently. So what did we learn during our sojourn around this distant world?

* That Vesta is very much like a planet with a crust, mantle and iron core. Scientists estimate Vesta’s core at 136 miles in diameter. Vesta melted billions of years ago just like the Earth, Mars and other rocky planets. Iron trickled down to make the core while the lighter elements floated to the top to form a crust.

Vesta’s two biggest hits – the Rheasilvia and Veneneia impact basins. The map is color-coded by elevation with red highest and blue lowest. Rheasilvia is about a billion years old; Veneneia happened 2 billion years ago. Credit: NASA

* Dawn revealed Vesta’s giant Rheasilvia impact basin at its south pole in detail, showing that the asteroid impact that created it was powerful enough to launch chunks of Vesta’s crust into space. Scientists called the debris “vestoids”.

Some of the material was nudged by Jupiter’s powerful gravity into orbits that eventually sent pieces to Earth as meteorites millions of years later.

* The clan of meteorites from Vesta are called HED (Howardite-eucrite-diogenite) meteorites and have the same composition as the asteroid’s surface, confirming that they originated there. Vesta joins Mars and the moon as the only other solar system body we know we have samples or right here on Earth. (Bits of Vesta are available through a variety of meteorite dealers’ websites. E-mail me for recommendations if interested.)

Three slices of meteorites that fell to Earth that Dawn has confirmed as originating from the giant asteroid Vesta. The meteorites, known as howardite, eucrite and diogenite meteorites, are seen through a polarizing microscope, where different minerals appear in different colors. Credit: University of Tennessee

* Devoid of smooth plains and lava flows, Vesta shows no signs of the volcanic activity that must have been present in its early history when the asteroid was still molten. Scientists suspect activity must have shut down early in its history – perhaps within the first 100 million years. Since then, meteorites have pulverized the surface and obliterated any evidence. Craters pock the crust everywhere you look.

* The blows that created the two largest impact scars, Rheasilvia and the newly discovered Veneneia Basin (250 miles across), reverberated through the asteroid to create a sprawling network of nearly parallel troughs hundreds of miles long stripping Vesta’s equator. Any more force and the asteroid would have been blown apart.

* Vesta has the tallest mountain discovered to date in the solar system – a 14-mile-high peak formed by rebound after the impact that blasted out the giant Rheasilvia basin. That’s more than twice the height of Mt. Everest.

Craters, craters, everywhere, including a dark splat that may have been from a carbon-rich meteorite strike. Either that or the impact excavated darker material from beneath the surface. Credit: NASA/ JPL-Caltech

Both Vesta and Ceres are currently visible in the constellation Taurus in the pre-dawn sky. Later this fall, when they’ll both be bright enough to be easily viewable in binoculars at a more convenient hour, I’ll prepare maps for you to find them. In the meantime, you can browse a gallery of Vesta photos and learn a lot about this almost-planet by reading the accompanying captions.