Rosetta update Aug. 1: Comet 67P/C-G’s pitted surface

July 31 photo of Comet 67P/Churyumov-Gerasimenko shows lots of shallow depressions and two curious bright spots. The comet is 2.5 miles (4 km) across. Credits: ESA/Rosetta/NAVCAM

In case you couldn’t tell, I’m kind of excited about the Rosetta mission to Comet 67P/Churyumov-Gerasimenko. Today, the European Space Agency published a fresh, more detailed photo taken on July 31. Notice how rugged the comet’s surface looks. Right away I thought of another comet with a similar appearance, 81P/Wild.

Comet 81P/Wild 2 photographed during the Stardust mission in 2004. Wild 2 measures 1.03 x 1.24 x 1.71 miles and goes around the sun once every 6.4 years. Its surfaced is riddled with flat-bottomed craters, some of which may also be gas vents from vaporized ice. Credit: NASA

NASA flew the Stardust spacecraft past the comet in January 2004, took photos and measurements and collected particles from 81P’s coma that were later returned to Earth for study. If you compare the photos, both show lots of shallow depressions.

It’s speculation only, but there appear to be two small hills, large boulders or even spires near the top of 67P’s smaller lobe. Studying the photo closely, the direction of sunlight is from the bottom up . Whatever the two bright dots are, they rise above the general landscape because they cast clear shadows. The lower rims of several of the comet’s ‘craters’ are rimmed with shadow as well.

Just a caution – I could be wrong about this interpretation. The little hills or whatever they are may be little more than image artifacts.

Either way, looking at the photo makes me feel like I need a new glasses prescription. So much detail is tantalizingly close to coming into clear focus. We’re not quite there yet.

New Rosetta pix show comet craters – only 6 days to go!

The nucleus of comet 67P/Churyumov-Gerasimernko as seen from a distance of 1,200 miles (1,950 km) on July 29th, 2014. One pixel corresponds to approximately 121 feet (37 m). The bright neck region between the comet’s head and body is becoming more and more distinct. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Closer, closer, closer. Rosetta sent back more detailed images taken on July 30 that confirm the comet’s bright neck collar and show much more surface texture than earlier photos – including two craters! The collar’s light tone hints of fresh ice vaporizing in sunlight but could also be caused by different materials on that part of the comet’s surface. Maybe the next round of photos will offer a clue.

Two distinct craters stand out in this lower resolution navigation camera photo. What started out looking like a rubber ducky now reminds me of a primitive bird. The bright collar is also seen from this point of view. In 6 days, Rosetta will enter orbit around the comet. Credit: ESA/Rosetta/Navcam

The wider-view navigational camera sent back an even more fascinating image showing dual craters, one on each lobe, with hints of other crater or depressions in the ice. Comets, including 67P C-G, are made of mostly water ice and dry ice or frozen carbon dioxide. The ices act as glue to hold the dust, sand-sized grains and pebbly pieces of the comet together.

The inner coma of comet 67P/Churyumov-Gerasimenko is about 93 miles (150 km) across.  This image was taken on July 25th, 2014. The hazy circular structure on the right and the center of the coma are artifacts due to overexposure of the nucleus. Credit: ESA

When a comet’s orbit takes it into the inner solar system, some of the ice vaporizes, releasing dust and grit, along with a variety of gases like carbon monoxide, methanol, ethane and ammonia. The melange forms the comet’s coma or temporary atmosphere.

Next, the pressure of sunlight pushes back coma gases and dust to form tails – one of dust and the other of gas.

As Rosetta’s camera tried to record the coma, which is much fainter than the nucleus, the brighter nucleus was overexposed, creating an artifact. Taking pictures of comets is challenging enough, but evidently even more so when you’re standing right next to one!

* UPDATE 8/1: The ‘craters’ are more likely artifacts in processing of the image according to other sources.

Crescent moon joins a planet parade / Opportunity ready for marathon run

The moon scoots by two bright stars and two bright evening planets in the next few nights. This map shows the sky facing southwest in late evening twilight. Stellarium

The moon joins a lineup of planets and bright stars hung like tiki lamps across the southwestern sky at dusk. Watch for it to pass near fading Mars Saturday evening and Saturn on Monday.

The Martian landscape photographed by on July 30, 2014. The rover is exploring south along the west rim of Endeavour Crater heading toward a notch called ‘Marathon Valley’ about 1.2 miles (2 kilometers) away. Credit: NASA/JPL

While you’re gazing at the Red Planet, know that the Opportunity rover made news this week when it set a record for the most miles ever driven off-planet, tallying a satisfying 25 miles (40 km) of Martian travels. The previous record was held by the Soviet Union’s Lunokhod 2 rover when it ambled across 24.2 miles of the moon’s surface in 1973.

Out of this world distance records compared. Credit: NASA

Opportunity surpassed that record on Monday July 28 when it registered 25.01 miles en route to a notch called Marathon Valley along the west rim of Endeavour Crater. Mission controllers would like to get a look at clay minerals there that have been spotted from orbit.

Lunokhod 2 crater photographed by Opportunity last spring. The crater’s 20 feet (6 meters) in diameter. Credit: NASA/JPL

When it reaches the Valley it will have completed 26.2 miles (42 km), the official distance of a marathon. When you consider that Opportunity and its sister probe Spirit were only intended to function for 90 days, the current record-breaking feat and upcoming marathon completion are that more remarkable.

How to watch the space station and cargo ship play hide-and-seek

ATV-5 (George Lemaitre) will dock with the ISS using a sophisticated laser system on August 12. Between now and then you can watch it track along with the space station in both the morning and evening sky. Credit: European Space Agency (ESA)

The Georges Lemaitre cargo ship successfully launched on a 14-day journey to the International Space Station (ISS) yesterday. Starting tomorrow morning you can watch it chase the space station around the sky for the next two weeks.

The ship is Europe’s fifth and final automated transfer vehicle (ATV-5) for hauling materials to the station. It’s also the heaviest craft ever launched by the European Space Agency and has the biggest cargo space.

ATV-3 docking animation created from 70 hi res ATV-3 images. NASA/ESA

The ship will transport 1,257 pounds (570 kg) of water, 220 pounds (100 kg) of gas (air and oxygen), 4,916 pounds (2,230 kg) of propellants to use for ISS reboosts, additional propellant for the Russian portion of the space station, science equipment and food.

After the astronauts unload all the goodies, the ship will be filled with trash and sent back to burn up in Earth’s atmosphere. A special infrared camera inside the craft will take pictures of the burning hull during the fiery reentry and send them to a waiting satellite for re-transmission to Earth.

While the agency will wrap up its supply trips to the ISS, it’s will re-purpose the ATV service module to participate in NASA’s Orion mission, which will ultimately send astronaut crews to the moon, Mars and asteroids.

The International Space Station is currently making passes over the U.S. and Canada during early morning twilight. This map, taken from Heavens Above, shows its path across the sky tomorrow morning July 31 from the Duluth, Minn. region. Starting August 2, the ISS will also appear in the evening sky. Source: Chris Peat/Heavens Above

Because ATV-5 will take its time arriving at the space station, we’ll have lots of chances to see it ‘chasing’ the ISS around the sky. For my region (Duluth, Minn.) for instance, the station glides from west to east across the sky between 4:18 – 4:25 a.m. tomorrow following a nearly identical path.

ATV-5 shows up in the sky about 5 minutes after the space station bows out tomorrow morning. It will shine at magnitude 0.7, the same as a bright star but not nearly the brilliance of the much larger ISS. Source: Chris Peat/Heavens-Above

Five minutes later, Georges Lemaitre’s namesake zips by at 4:30 a.m. Although the ISS and ATV-5 lie at opposite sides of the sky right now, as docking time draws near on August 12, they’ll be neck in neck – a very cool sight!

ATV-4 passes over the W of Cassiopeia in this time exposure taken on June 8, 2013. The ATVs range in brightness from magnitude 0 (brightest) to 3. Credit: Bob King

Good news too for those who don’t like getting up at dawn. Both ships will begin making convenient evening passes starting this Saturday August 2 and continuing through late August.

To find out where and when to look to track both the ISS and ATV-5, go to Heavens-Above, sign in and select the ISS and ATV-5 links under Satellites. You’ll next be shown a table with times, brightness, directions, etc. for a series of dates. Click on the date of your choice to get a map of the sky showing the object’s path. What could be easier?

Georges Lemaitre was a Belgium Catholic priest, physicist and astronomer. In 1927 he discovered that Einstein’s equations implied an expanding universe. Credit: Wiki

I like that ESA has named the ATV series after famous scientists and a science fiction writer. It gives the machines a little personality. It started with ‘Jules Verne’ (ATV-1), then Johannes Kepler (ATV-2), Edoardo Amaldi (ATV-3), Albert Einstein (ATV-4) and finally Georges Lemaitre (ATV-5).

Lemaitre originated the whole idea of the Big Bang. He argued that if the galaxies were receding into the distance in an expanding universe, they must once have been scrunched together in one unimaginably tiny space he called the ‘primeval atom’ or ‘cosmic egg’.

Fire haze turns sun into big red ball

A towering cumulus cloud partially eclipses the setting sun Monday evening seen from Duluth. Haze from Canadian forest fires has returned to the region making for deep red suns around sunrise and sunset. Credit: Bob King

Smoke from fires in the Canada’s Northwest Territories continues to funnel down across Manitoba and into the U.S. Upper Midwest creating an artificial overcast of smoky haze. We’ve lost the blue clarity of our daytime sky; at night stars look much dimmer seem more distant.

If you’re a skywatcher, everything in the nighttime sky looks noticeably fainter, especially objects within 20° of the horizon. I feel as if I’m looking through gauze. The unusually pallid appearance of the sky from dinnertime onward might make you think the sun has already set until you realize it’s still out there in the west looking little brighter than the full moon.

Funny. Yesterday, when I took this picture, someone pulled up alongside my car and remarked at how amazing the moon looked. The strangely faint sun had thrown him off!

The full sun shortly before setting yesterday July 28, 2014. You might see three small sunspot groups – two to the right of center and a third a short distance within the sun’s left limb. Credit: Bob King

Fire smoke generally scatters away nearly all light from the setting sun except deep oranges and reds.

The haze is both good and bad when it comes to observing. We like a big red sun, but it’s tough sacrificing otherwise clear nights.

I shouldn’t complain. People farther north, where the smoke is heavier, have to breath it.

Keep watch on the moon the next few nights as it waxes from crescent to half. If you live where there’s forest fire smoke, chances are you’re in for some red moons too.

101 geysers erupt from Enceladus’ salty deeps

At least 20 geysers blast icy particles and water vapor from cracks in the icy crust of Saturn’s moon Enceladus. Scientists recently confirmed the geyser material derives from a salty ocean beneath the moon’s surface. Credit: NASA/JPL

Future astronauts better watch where their step when exploring the south polar terrain of Saturn’s icy moon Enceladus. A geyser could pop up anywhere.

This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus’ south polar terrain by the method of triangulation. Credit: NASA/JPL-Caltech/Space Science Institute

NASA’s Cassini spacecraft have identified 101 distinct geysers erupting on Saturn’s icy moon Enceladus. Cassini has studied and photographed the moon’s intriguing ‘tiger stripe’ fractures for over 7 years and discovered that each of them coincides with a particular hot spot within a fracture.

Three competing hypotheses were put forward to explain how geysers might happen on an ice-covered moon nearly a billion miles from the warmth of the sun.

#1 – Tidal flexing: As Enceladus revolves around Saturn, the planet’s enormous gravity flexes the little moon, heating up its interior and melting ice into water which escapes as vapor through openings in the icy crust.
#2 – Frictional heating: Back-and-forth rubbing of opposing walls of the fractures generate frictional heat that turns ice into geyser-forming vapor and liquid. Same principle as rubbing your hands together to create heat.
#3 – Jaws of ice: The opening and closing of the fractures caused by Saturn’s gravitational might exposes water from below when then quickly vaporizes in the moon’s vacuum.

This artist’s rendering shows a cross-section of the ice shell immediately beneath one of Enceladus’ geyser-active fractures, illustrating how water works its way to the moon’s surface. Credit: NASA/JPL-Caltech/Space Science Institute

But a detailed study by Cassini in 2010 appears finally to have netted the correct explanation. The probe’s heat-sensing instruments matched the geysers’ locations with small-scale hot spots only a few dozen feet across - too small to be produced by frictional heating, but the right size to be the result of condensation of vapor on the near-surface walls of the fractures.

“Once we had these results in hand, we knew right away heat was not causing the geysers, but vice versa,” said Carolyn Porco, leader of the Cassini imaging team and lead author of the first scientific paper on the discovery. “It also told us the geysers are not a near-surface phenomenon, but have much deeper roots.”

Researchers concluded the only logical source of the material forming the geysers is the sea now known to exist beneath the ice shell. They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water. This implies, at least in my mind, that liquid water might exist as pools in hot spots encircled by thick rims of ice (condensed water vapor) on the moon’s chill -330° F (-201° C) surface.

Imagine standing nearby watching fountains of vapor turn to ice crystals before your eyes and sparkling like diamond dust against the black starry sky.

Source: JPL

Seeing meteors? Delta Aquarids peak this week!

Meteors from Delta Aquarid meteor shower radiate from near the star Delta Aquarii not far from the bright star Fomalhaut in the Southern Fish low in the south before dawn. Stellarium

With the Southern Delta Aquarid meteor shower peaking tomorrow morning, the summer meteor season’s officially underway. While not a spectacular shower from mid-northern latitudes, why not chance  a look anyway. With a rate of 10-15 per meteors an hour from a dark sky you’re bound to catch at least a few.

The farther south you live, the better it gets. Observers in the southern hemisphere can expect double that number because the shower’s radiant will be much higher in the sky. Any meteors flashing south of the radiant won’t get cut off by the southern horizon like they do further north.

The annual shower gets its name from Delta Aquarii, a dim star in the dim zodiac constellation Aquarius. You don’t need to know the constellations to enjoy a meteor shower but it doesn’t hurt to know the general location of the radiant, the point in the sky from which the meteors appear to radiate. If you can trace the path of a meteor backward toward Aquarius, chances are it’s an Aquarid.

A Southern Delta Aquarid meteor captured on July 30, 2013. Credit: John Chumack

There are actually two meteor showers in Aquarius active this time of year – the northern and southern Delta Aquarids. The northern version sports fewer meteors and peaks in mid-August.

The Southern Deltas peak over the next two mornings – July 29 and 30. Both serve as warm-ups for the upcoming Perseid meteor shower that climaxes on August 12.

Tonight’s shower will suffer no interference from moonlight, making this an ideal time for meteor watching. Unfortunately, Perseid rates will be reduced by a bright waning gibbous moon. Don’t be surprised though if you see a few Perseids while you’re out. The shower’s just become active. If you can draw a meteor’s trail back to the northeastern sky, it just might be one. Perseids are also known for leaving bright streaks in their wake called trains.

Nearly all meteor showers originate from clouds of sand to seed-sized bits of debris spewed by vaporizing comet ice as they swing near the sun. The Delta Aquarids may trace its origin to dust boiled off Comet 96P/Machholz.

The best time to watch the shower is in the early morning hours before dawn when the radiant rises in the south-southeastern sky above the bright star Fomalhaut. Try to get away from city lights. Point your lawn chair south and spend some time in heavenly contemplation as you wait for Aquarius to toss a few javelins of light your way.

Sunrise and sunset – nature’s most beautiful illusions

Earth turns on its axis to greet the sun at sunrise each morning of the year. Credit: Bob King

Every day the sun rises, crosses the sky and sets. And it does it again and again and again like the perpetually repeating cycle of events in the movie Groundhog Day.

Except perhaps for a few remaining Flat-Earthers, we know what’s going on here. The sun’s not doing the moving. Instead, the Earth’s rotation causes the apparent motion of the sun across the sky. Yet the sense of the sun’s movement is so powerfully ingrained in our experience you might balk if I told you it’s essentially sitting still in the sky.

Every day the turning Earth causes the nearly static sun to rise in the east at sunrise and set in the west at sunset. Credit: Canadian Space Agency

For you to see a sunrise, Earth must rotate on its axis until your location faces the sun as it crests above the planet’s curvature. The following morning, when Earth rolls around after another 24 hours, the sun is very nearly in the same place in the celestial sphere as the previous morning. Once again, we see the sun ‘rise’. Ditto for the next morning and the next. It’s like turning over in your bed each and every morning and seeing your spouse in the same spot. Or very nearly.

If the Earth spun but stood in one spot never circling the sun, we would meet the rising sun at precisely the same time and place every day ad infinitum – a true Groundhog Day scenario. But the Earth orbits or revolves around the sun as surely as it rotates. Just like our daily spin, our planet’s revolution is reflected in the sun, which appears to slowly crawl across the sky, inching its way from one background zodiac constellation to the next, during the course of a year.

The orbiting and titled Earth cause slow but continuous changes in the times of sunrise and sunset during the course of a year. Credit: Thomas G. Andrews, NOAA Paleoclimatology

The ever-changing times of sunrise and sunset stem from the Earth’s orbital travels combined with the shifting seasonal tilt of the planet. From December 21 until June 21, as the amount of daylight increases in the northern hemisphere, the sun appears to travel slowly northward in the sky and we meet its welcome rays a couple minutes earlier each morning.

The sun’s yearly motion across the sky during the year traces out a path called the ecliptic. The top of the curve, at right, is the sun’s position during the summer. The low part of the curve is the sun’s location during winter. The up-and-down path is a reflection of the 23 1/2-degree tilt of the Earth’s axis. Illustration and animation by Dr. John Lucey, Durham University

Then from June 22 to December 20, Earth’s orbital motion causes the north polar axis to slowly point away from the sun. The sun appears to slide south as the hours of daylight wane, and we meet the sunrise a minute or two later each morning.

The sun, located some 26,000 light years from the center of the Milky Way galaxy, takes about 220 million years to make one revolution around its core moving at 483,000 mph. Credit: ESO

Earth moves along its orbit at an average speed of 67,000 mph (108,000 km/hr).

How about the sun? If I left the impression that it’s totally static I apologize. Yesiree, it’s moving too – at the astonishing speed of 483,000 miles per hour (792,000 km/hr) around the center of the galaxy.

Don’t look now, but you and I are going on the ride of our lives.The only reason stars remain static in the sky over the span of many generations despite the sun’s hurry is because nearly all of them are too far away to show a shift in position with the human eye. Telescopes, which magnify everything including motion, do show very subtle changes in the positions of nearby stars over much shorter time intervals.

Rising each morning to the same old sun, I try to remind myself that with every rotation comes a new opportunity to spin some joy into the day.

A comely cometary coincidence / New camera to record cargo ship’s fiery reentry

In this happy alignment, perfectly composed and exposed by Italian amateur astronomer Rolando Ligustri, Comet Jacques pairs up with IC 405, the Flaming Star Nebula on July 26. The comet will be visible in binoculars now until the moon returns to brighten the sky around August 8. Credit: Rolando Ligustri

A stunning photo! It’s comet C/2014 E2 Jacques, tail as straight as a Q-tip, forming a cosmic question mark with the glowing cloud of hydrogen gas called the Flaming Star Nebula. Two tails stand out. The one reaching beyond the frame is made of carbon monoxide gas fluorescing in the sun’s ultraviolet light. To the left of the bright head a meeker dust tail shines by reflected sunlight.

This close-up photo taken July 25 reveals that the glowing gas tail (right) is made of multiple streamers. Heat from the sun vaporizes ices which stream back to form a comet’s tails. Credit: Damian Peach

The nebula’s 1,500 light years away in the direction of the constellation Auriga the Charioteer, while Jacques plies the solar system just 112 million miles from Earth. Discovered by a group of Brazilian amateur astronomers last March, a study of its orbit hinted it might wax bright enough to see with binoculars after making its closest approach to the sun in late May.

That’s exactly what happened, and you can see it right now – assuming you’re willing to rise at 4 a.m. – low in the northeastern sky just before the start of morning twilight. I caught it in 8×40 and 10×50 binoculars Saturday from home. No tail stood out but the comet’s head looked like a small, fuzzy spot compared to the sharp points of nearby stars. Through a telescope I saw a dense, bright cotton ball and hint of a tail.

Follow Jacques in a small telescope or binoculars in its travels across Auriga into Perseus during the next two weeks. Comet positions are shown for 4 a.m. CDT every 5 days. Stars to magnitude +8.0. Click to enlarge. Source: Chris Marriott’s SkyMap

Comet Jacques glows at magnitude 6.5 and will remain about that bright through early August. Because the comet’s moving up and away from the sun, it’s getting higher in the east and easier to see with each passing morning.

If you need another reason to arise so early, the International Space Station will light your path all this week and next. Head over to Heavens-Above and click on the ISS link to get times for passes over your city. Simultaneous evening passes begin on or around August 2.

The last of the European Space Agency’s five automated space freighters, ATV-5, is being prepared for launch to the ISS on Tuesday, July 29. Named “Georges Lemaître” in honor of the Belgian astronomer who first proposed the idea of the Big Bang, the ship will ferry six tons of supplies including lots of drinking water and food to the astronauts. If there’s an opportunity to see it ‘chase’ the space station, I’ll provide an update.

Artist’s view of ATV-5’s destructive reentry into Earth’s atmosphere over the Pacific Ocean. A special camera will record the scene from inside. Copyright: ESA–D. Ducros

ATV-5 is the last of the European cargo ships and will burn up like the others during atmospheric reentry once its mission is complete. But this one ends with a twist. The fiery burn-up and disintegration will be recorded from the inside by a unique infrared camera. Before the camera becomes toast, it will transmit the images to a ‘black box’ called the Reentry SatCom, a spherical capsule protected by a heatshield. The SatCom will relay the data to a nearby Iridium satellite and from there back to mission control. Can’t wait to see that video!

Tomorrow’s new moon foretells October’s solar eclipse

Tomorrow July 26, 2014, the invisible new moon will pass a few degrees south of the sun in the daytime sky. Stellarium

New moons aren’t much to look at. You can’t even see them most months of the year. That’s true for tomorrow’s new moon which will invisibly accompany the sun in its journey across the sky.

New moons occur about once a month when the moon passes between the sun and Earth. We can’t see them for two reasons: first, no sunshine touches the Earth-facing side when the moon lies in the same direction as the sun. It’s completely dark. From our perspective, the out-of-view lunar farside gets all the sunlight. Second, since the moon is nearly in line with the sun, it’s utterly lost in the glare of daylight.

The moon seesaws 5 degrees north and south of Earth’s orbit during its monthly cycle because its orbit is tilted with respect to Earth’s. Only when the moon crosses the plane of Earth’s orbit at the same time as a new moon do we see a solar eclipse. Illustration: Bob King

We normally have to wait two days after new moon – when the moon’s orbital motion carries it to the left (east) of the sun – to see it as a thin crescent at dusk.

Most of the time the moon passes north or south of the sun at new phase because its orbit is tilted 5 degrees with respect to Earth’s. But 2.4 times a year on average, new moon coincides with the time the moon’s seesawing path slices through the plane of Earth’s orbit. For a brief time during that crossing, all three bodies are aligned and happy earthlings witness a solar eclipse.

If the alignment is imprecise, the moon blocks only a part of the sun, giving us a partial solar eclipse.  If dead-on, we see a rarer total solar eclipse.

View of the partial solar eclipse across the Upper Midwest a half hour before sunset on October 23. By coincidence, Venus will be near conjunction at the same time and only a couple moon diameters north of the pair. Seeing the planet in a telescope will still be challenging because of daylight glare.  Stellarium

On October 23 this year, the lineup at new moon will be a good if imperfect one with a maximum of 81% of the sun covered. The partial eclipse will be visible across much of North America; from the eastern half of the U.S. and Canada the event will occur near sunset, adding a touch of drama to the scene.

I wrote earlier that we can’t see a new moon. That’s only partly true. We mostly pay attention to the sun’s changing shape during solar eclipses, but the dark, curving bite working its way slowly across the sun’s disk is none other than the new moon seen in silhouette.