Rosetta’s comet from 17.8 miles – forbidding yet inviting

Four image mosaic of comet 67P/Churyumov-Gerasimenko, using images taken on September 19th by Rosetta. Faint jets of vaporizing ice carrying dust and gas shoot upward from the comet’s ‘neck’.  Click for a jumbo version. Credit: ESA/Rosetta/NAVCAM

2.5 miles of rugged, icy, airless desert. Is there a more forbidding looking place in the solar system than Comet 67P/Churyumov-Gerasimenko? In this new close-up, composed of four separate images taken with Rosetta’s navigation camera on September 19, we take in the comet from a distance of only 17.8 miles (28.6 km).

Crop of the original photo mosaic showing a big boulder tilted on its side and casting a shadow.  Relatively smooth and rugged terrain are found side by side all over the comet. Credit: ESA/Rosetta/NAVCAM

Click to pull up the giant version on your screen and spend some time scrolling around the landscape. Layering and striations abound, especially in the center of the larger lobe (left). The top of the larger lobe and ‘neck’ between lobes display smoother terrain that looks as though softened either through below-surface melting and refreezing. Or maybe it’s just covered in dust.

A possible fissure across the comet’s neck. Credit: ESA/Rosetta/NAVCAM

Boulders are everywhere like sprinkles on a cupcake, but the most interesting feature to my eye is the apparent crack or fissure in 67P/C-G’s neck. No telling how deep it might be. Given that comets are easily breakable objects – sometimes crumbling to bits in the solar heat – we would expect to see cracks in its surface.

Toned up version of the Comet 67P/C-G showing active jets and spots and specks of possible dust in the vicinity. Click to enlarge. Credit: ESA/Rosetta/NAVCAM

A hint of the geyser-like jets are seen in the original photo, but I’ve lightened it further to make the near-comet environment easier to see. Recent measurements by Rosetta’s MIRO instrument reveals the comet losing water at a much faster rate than three months ago. Although the amount varies as the nucleus rotates, the maximum measured recently was 1.3 gallons (5 liters) per second with an average of a quarter-gallon (1 liter) per second.

The toned photo also shows lots of small flecks that might be noise in the camera detector, cosmic ray hits or sunlight reflecting off dust and ice lifting off the comet –  I can’t say.

Reconstructed color view of 67P/Churyumov-Gerasimenko showing how truly dark and coal-colored the comet is. Credit: ESA/Rosetta/MPS for OSIRIS team; MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA. Additional processing and copyright: Elisabetta Bonora and Marco Faccin (Alive Universe Images - flickr.com/photos/lunexit)

Finally, if you haven’t already seen it, I wanted to share a recent Astronomy Picture of the Day (APOD) photo of the comet taken in early September with Rosetta’s high resolution OSIRIS camera and reconstructed as a color image by Elisabetta Bonora and Marco Faccin. I’m not sure how they determined color shadings but the darkness of the comet is accurate.

Harvest Moon glow show / Rosetta captures pieces of a comet

The Full Harvest Moon rises from Lake Superior in Duluth, Minn. as the HR Maria heads down the lake last night September 8, 2014. Credit: Bob King

We luckily avoided the clouds last night to see a big pink moon rise from Lake Superior. The moon languished near the horizon for a long time as if reluctant to meet the deck of clouds waiting for it higher up.

The full moon prepares to enter the cloud deck shortly after moonrise last night. Credit: Bob King

Watch for it to rise tonight about a half hour later. Will you be able to tell it’s no longer a perfect circle? A shadow has crept up along its western edge transforming it from a full to a waning gibbous moon.

Because the moon orbits Earth, we see it from a slightly different angle in relation to the sun each night, causing different parts of the globe to be in sunlight and shadow.

COSIMA catches bits of the comet. Left: an image of the target plate (measuring about 1/2-inch on the side) on which the grains were collected; right: a section of the plate showing it on August 17 when no dust grains were visible and August 24 (bottom) when some large dust grains were detected. The plate is illuminated from the right by LEDs and the length of the shadows is proportional to the height of the dust grains. Credit:  ESA/Rosetta/MPS for COSIMA Team et. all

While you and I may prefer our dust swept away, planetary astronomers feel otherwise. Scientists at the European Planetary Science Conference (EPSC) in Lisbon, Portugal, recently got a look at photos of the first dust grains collected by Rosetta’s COSIMA instrument. The specks were gathered between August 11th and 24th  from a distance of around 62 miles (100 km) from the nucleus of comet 67P/Churyumov-Gerasimenko

Many tiny grains showed up on the plate; the two largest, each about the width of a human hair, stand out in the photo above. Some of the samples will be selected for further analysis on board the probe. Here’s how it works.

Jagged cliffs and prominent boulders are visible in this image taken by the OSIRIS camera on September 5, 2014 from a distance of 39 miles (62 km) from comet. The left part of the image shows a side view of the comet’s ‘body’, while the right is the back of its ‘head’. One pixel corresponds to 3.6 feet (1.1-m). Click for a huge picture! Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The target plate will be moved to place each selected grain under an ion gun, a device that blasts the particle with a beam of ions. Ions are atoms which have gained or lost an electron and become either positively or negatively charged. The ion beam will ablate or vaporize the grain layer by layer. The material is then analyzed in a secondary ion mass spectrometer to determine its composition.

Several different regions are indicated in this preliminary map, which is oriented with the comet’s ‘body’ in the foreground and the ‘head’ in the background. The brown smooth terrain contrasts with the rugged blue region.
Credits: ESA/Rosetta/MPS for OSIRISTeam/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Astronomers are quite excited about getting these early dust grains studied as they’re the first to be retrieved from the solar system’s “snow line”, the distance from the sun at which stable ice grains can form.

A new color-coded terrain map of 67P/C-G has also been created based depicting regional variations in the comet’s landscape. Some terrains are smooth, others dominated by cliffs and still others by craters and depressions. The maps will play a key role this weekend (Sept. 13-14) as Rosetta’s Lander Team and the Rosetta orbiter scientists determine primary and backup landing sites for the Philae lander.

Sharing stars and making comets at Northwoods Starfest

7-year-old Madeline Chopp of Green Bay, Wis. laughs as she peeks into her dad Brian’s scope Friday evening. Credit: Bob King

Every August, the Chippewa Valley Astronomical Society (CVAS) holds a two-night star party at Hobbs Observatory near Fall Creek, Wisconsin. Tucked in a patch of forest between cornfields, Hobbs’ dark skies entice amateur astronomers across the Midwest to get their fill of nebulae, galaxies and comets otherwise lost in the glow of city lights.

Guest speakers, good food and great conversation liven up the mix and always make for an immensely satisfying weekend. Whenever you spend time with those who share your passion, you can’t help but come away energized.

Mike Brown, CVAS president, assembles his self-built, computer controlled 24-inch Dobsonian reflector Friday afternoon. He uses an iPad and tracking software to slew quickly to any object in the sky with a tap on the keypad. The club’s radio dish is seen in the background. Credit: Bob King

I attended Friday and set up my 15-inch (37-cm) reflector on the sandy flats among dozens of other telescopes. All types were represented – small to medium refractors, binoculars on homemade mounts and reflecting telescopes with mirrors up to 24-inches (61-cm) across. The club even operates a radio telescope.

Friday night I spoke on comets and the European Space Agency’s Rosetta Mission. Judging from the audience reaction, the ESA needs to fire up that high-resolution OSIRIS camera and shoot a lot more close-up, 3-D views of comet 67P C-G. Everyone loved the in-your-face realism of seeing the comet’s alien landscape in three dimensions.

Comet Hobbs is born during a comet-making demonstration at Northwoods Starfest Friday night. Notice the little ‘geysers’ of outgassing. Credit: Greg Furtman

After the talk, we gathered round a table to make a much smaller version of Rosetta’s comet in a bucket. I added water (comets are mostly water), molasses (sugar as organic molecules), dirt (dust embedded in cometary ices), ammonia, alcohol (methanol has been found in comets) and powdered charcoal (more carbon and to create a realistic black-coated ice ball) in a plastic bag and mixed it all together with a wooden spoon.

A real comet! 30-second time exposure of Comet Jacques at ISO 6400 with a 400 mm f/5.6 lens. Credit: Bob King

Then it was time for the crucial ingredient: dry ice. Three gloved handfuls of smoky white pellets went into the cosmic ‘stone soup’, the bag was closed and the mix crushed together into a well-packed snowball. Peeling back the plastic, a delightful mini-comet emerged replete with jets of vaporizing gas geysering from small cracks in the carbon-coated surface.

All new comets have names and this would be no exception, so we settled on Comet Hobbs, or more formally, C/2014 Q1 Hobbs. Sadly, this comet exists no more. A final observation revealed the fist-sized object had morphed into a petite puddle.

Mike Brown’s 24-inch reflector had a steady stream of customers at Northwoods Starfest this weekend. Mike treated folks to views of the globular cluster M13, Comet Jacques, the planetary nebula NGC 6210 and many others. Credit: Bob King

The night began overcast but soon turned partly cloudy. We had fun observing a real comet – C/2014 E2 Jacques – as it inched its way across Cassiopeia. The bright coma was very easy to see in 50mm binoculars. Mike Brown, CVAS president, generously shared time with anyone who wanted to see anything in his 24-inch reflector. In a big scope like that, even tiny objects like the planetary nebula NGC 6210 in Hercules invite many minutes of exploration.

Jon Dannehy of Arcadia, Wis. and Eric Norland of Duluth, Minn. have fun while standing around Eric’s homemade telescope Friday. Credit: Bob King

Another CVAS member, Greg Furtman, treated us to wide-field views of the comet and Veil Nebula in Cygnus with his homemade short-focus 6-inch (15-cm) reflector. At midnight, we welcomed the opportunity to rest our legs and recharge with the traditional ‘midnight snack’ in the campground’s dining cabin. Besides fruits, juices and chips, someone broke out a box of ice cream sandwiches. Deluxe!

Although I had to leave Saturday for work, Day 2 featured additional speakers, a swap meet, a dinner BBQ and l’m sure lots more great laughs and discussion. Nothing like hanging out with a bunch of crazy astronomers.

Comet Jacques zips through Cassiopeia – catch it this week!

Wow! Comet Jacques cuts between the Heart (right) and Soul Nebulae in Cassiopeia on August 19th. These clouds of fluorescing hydrogen gas are also known as IC 1845 and IC 1848. Click to enlarge. Credit: Michael Jaeger

Not many clear nights in my town lately – we had exactly one this week. I’m grateful because we finally got a peek at Comet Jacques, which recently climbed out of the morning sky into the familiar ‘W’ of Cassiopeia. That’s good news because it means you can spot Jacques now at nightfall instead of dawn.

Comet C/2014 E2 Jacques cruises through the W of Cassiopeia the next few nights. The view shows the sky facing northeast at nightfall in late August around 9:30 p.m. Click for a detailed map showing the comet’s position nightly through early September. Stellarium

Through a pair of 8x40s two nights ago, the comet was a faint, fuzzy patch next to the lower left star of the ‘W’. Jacques is currently making its closest approach to Earth; on August 28 it will pass us at 52.4 million miles (84 million km). While that’s a fair distance, its relative proximity causes it to move relatively quickly across the sky. Currently the comet’s puffing along at a couple degrees a day. Those with telescopes can easily see it shift position against the background stars within an hour.

Small telescopes will reveal Jacques’ largish diffuse coma and bright core. The core is where the icy nucleus hides behind a shroud of dust and gas vaporized by the heat of the sun. No one knows its exact size – thanks to all that dust – but it’s probably a mile or two across, typical of many comets.

36 pictures of Comet Jacques taken on August 17th combined into a movie show its motion and changes in its gas tail caused by interaction with the solar wind, a stream of subatomic particles blowing from the sun. Click to enlarge. Credit: Gianluca Masi

Larger scopes 8-inches and up will show varying amounts of the comet’s long, faint ion or gas tail that points to the southwest and a hint of green color in the coma from fluorescing gases.

Even though Jacques has been traveling away from the sun since closest approach on July 2, its brightness will remain nearly constant at magnitude +7 through early September because it’s ‘in the neighborhood’.

Try to spot it the next clear night. From a dark sky, the comet’s easy in binoculars and any telescope will show it. Moonlight won’t get in the way until early next month.

Comet 67P/C-G comes alive in 3D – Must see!

Beg, borrow or steal a pair of those cheap 3D red-blue anaglyph glasses and take a look at this photo. It’s made of two different images taken by Rosetta 17 minutes apart from a distance of 65 miles (103 km) on August 7, 2014. For the full effect, click to view the hi-res version. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

I was awestruck looking at this photo with just a pair of cardboard red-blue 3D glasses. Grab your pair and let your eyes climb over the foreground crags and onto the ‘neck’ joining the top and bottom lobes of the comet. A thick blanket of dust appears to cover the area. Did some spill from the spectacular range of cliffs above? And how about the boulders? Did they roll down the same cliffs?

One of the two images used to make the stereo image above. Click to enlarge. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Some of the crater-like depressions in the bulbous foreground lobe are filled with similar but smaller boulders while others liberally pepper the landscape. At front left, check out that huge jagged gash in the comet.

We’ve grown accustomed to detailed, close-up photos of planets and asteroids from our spacecraft and landers, but there’s something about seeing this comet in three dimensions that brings an alien landscape alive. It looks familiar in some respects, but strange and incomprehensible too.

Here are a couple more full-screen variations on the original stereo perspective: 1, 2

I’ve also selectively cropped several areas from the original image:

Boulders protrude from a smoother surface, while at left there appears to be a rockfall at the bottom of a cliff. Could ice flows have been active beneath the dust? Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Eroded crater with a craggy rim. Speculation only, but everything appears to be covered in dust. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Boulders collect on a smooth area of finer debris. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Rugged landscape of possible craters that have morphed in shape from erosion due to vaporizing ice. Rocks/boulders are everywhere! Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Rosetta comet update Aug. 10 – See it in cross-eyed stereo

Two pictures of comet 67P/Churyumov-Gerasimenko taken two days apart. Sit back about a foot (0.3-meter) from the screen and slowly cross your eyes until you see the third stereo image appear between the two. Careful not to fall in any holes! Click to enlarge. Credit: ESA/Rosetta/NAVCAM

Here are a few new photos for your supermoon-drenched eyes today showing comet 67P/C-G in stereo as well as in fresh views from different angles made on August 8th and 9th.

The comet from 50 miles (81 km) on August 8, 2014. Assuming a length of about 2.5 miles for the comet nucleus, I estimated the largest boulder in the boulder field (center-left) at roughly 115 feet (~35-m) across. That’s about 3 school buses parked end to end. Credit: ESA/Rosetta/NAVCAM

What I call the Star Trek Enterprise angle on comet 67P/C-G from August 9, 2014 from 61 miles (99 km). Credit: ESA/Rosetta/NAVCAM

The Rosetta Triangle / Comet 67P/C-G shoots cool jets!


Rosetta’s wild 3-legged orbit around comet 67P/C-G

Now that the Rosetta spacecraft has arrived at the comet, it’s busy following a three-legged triangular orbit. At each apex of the triangle, the probe fires its thruster to turn to follow the next leg of the triangle. Each triangle not only brings Rosetta closer to 67P/Churyumov-Gerasimenko but also serves to measure the comet’s mass. Until we know the comet’s precise mass and center of gravity, the spacecraft can’t enter a direct orbit around it.

Navigation camera image taken on August 7 from a distance of about 52 miles (83 km) from comet 67P/Churyumov-Gerasimenko. Credits: ESA/Rosetta/NAVCAM

While that’s happening, Rosetta has been taking more detailed measurements of 67P’s temperature and found variations across the surface. The warmest spot recorded so far is -63° F (-53° C), very close to the lowest temperature (-60°F) ever recorded in my home state of Minnesota. Still, this is a relatively high temperature especially considering the comet’s great distance from the sun, suggesting that 67P/C-G’s surface is devoid of icy materials, because these compounds are not capable of removing heat.

Two jets shoot vaporized ice and dust from the nucleus of the comet. The bright nucleus had to be overexposed to capture the much fainter jets. Credit: ESA/Rosetta/NAVCAM

MIRO or Microwave Instrument for Rosetta Orbiter has been measuring the amount of ice vaporizing off the comet’s nucleus. If you could somehow gather it up and convert it to liquid, 67P/C-G is releasing the equivalent of two glasses of water a second. Some or much of that water departs in geyser-like fashion as jets seen in the photo above.

Sam Gulkis, principal investigator of MIRO, holds a glass of water to demonstrate that the comet’s now releasing about two glasses of water per second. Credit: ESA/S.Bierwald

Meanwhile, Rosetta is now close enough to its target to study the dust in the coma or comet atmosphere using COSIMA (Cosmic Secondary Mass Analyzer). This Sunday August 10, it will expose the first of 24 target-holders that will collect single dust particles. The instrument will analyze their composition and determine if the material is organic (carbon-containing) or inorganic.

Once collected, the dust will be bombarded with beams of indium ions, kicking ions out of the comet dust. Another instrument called a mass spectrometer will fingerprint and determine the amount of atoms and molecules that make up the dust by analyzing the escaping ions.

An ion, by the way, is an atom that has gained or lost an electron and no longer in its neutral state.

Landing sites are being studied for the November touchdown of the mini-probe Philae, and more detailed images are on their way. Exciting stuff!

Take a close look at this photo of 67P/C-G taken on August 6, 2014. If you look along the left side you’ll see a pattern of interesting striations or layers. Click photo for more information and updates. Credit: Rosetta/Osiris camera

Rosetta in orbit, shoots incredible close-up views of comet

Boulders, cliffs, craters and smooth plains stand out in striking detail in this photo taken from only 81 miles (137 km) away. All photos credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

I know I’ve said this before, but WOW! I’ll step out of the way so you can enjoy these spectacular photos taken today when the Rosetta spacecraft arrived at comet 67P/Churyumov-Gerasimenko. Congratulations to all those at the European Space Agency (ESA) for a fantastic job!

Full view of the comet’s nucleus shows amazing details. Come November, ESA will land the small probe Philae on the comet.

Another full view of 67P/Churyumov-Gerasimenko.

Here the comet is overexposed to capture vaporizing ice and gases jetting away from the nucleus.

An ‘in your face’ close-up taken from 75 miles (120 km) away. Click photo to watch a 101-image animation of the comet during Rosetta’s approach.

Rosetta Mission main control room this morning August 6. Credit: S. Bierwald

For updates and more photos, click HERE. For live streaming reports, click HERE.

Don’t wait – go out now to see the Perseid meteor shower

The annual Perseid meteor shower radiates from a point in the constellation Perseus just below the W of Cassiopeia. Rates are usually around 100-120 meteors per hour from a dark, moonless sky at peak. This map shows the sky facing east around midnight Aug. 12-13. Stellarium

The beloved Perseid meteor shower peaks next Tuesday night August 12-13, but it wouldn’t be a bad idea to go out right now for a look. Why? Two good reasons.

First, Earth has already entered the meteor stream formed by dust and grit left in the wake of comet 109P/Swift-Tuttle. I can attest to this. While hardly trying, I spotted a half dozen Perseids after moonset this morning. Second, the nearly full moon will compromise the shower when it’s at its best.

Composite of bright Perseid meteors recorded by NASA all-sky cameras in 2011. Each is a grain rock shed from the tail of comet 109P/Swift-Tuttle. Every year in mid-August, Earth passes through the comet’s debris trail as it orbits around the sun. Any particles we smack into burn up as meteors some 60-70 miles overhead. Credit: NASA

Between now and Friday morning, the moon will set before the start of dawn, leaving skywatchers a dark, moonless window of meteor watching. You might be surprised and see more than you expected. I did.

Come August 12, when the number of meteors peak, a nearly full moon will be up all night compromising the fainter meteors. That doesn’t mean you should abandon viewing that night. Just be aware that you’ll probably see closer to 30 per hour instead of the higher number.

The moon, two days past full, will brighten the sky during the Perseid peak. This view shows the sky facing east around midnight Aug. 12-13. Stellarium

If you’re OK with losing a little sleep sometime in the next few nights, set the alarm for 2-3 a.m., face east or south and relax for an hour under the sky as the Perseids fly by.

Rosetta comet update Aug. 5 – Countdown to orbit

Comet 67P/C-G from 145 miles photographed by Rosetta’s navigation camera on August 4. The comet is about 2.5 miles (4 km) across. Credit: ESA/Rosetta/NAVCAM

Today’s photo, taken Monday at a distance of only 145 miles (234 km), gives us a fresh perspective on comet 67P/Churyumov-Gerasimenko. From this angle, the larger lobe faces us, partially hiding the smaller lobe that’s been sticking up like a thumb in recent images. Beside craters, there are about a dozen small ‘dots’ with shadows that may be boulders and interesting variations in tones and textures in and around the smooth regions.

Rosetta is still slowly approaching the comet. Tomorrow, after additional rocket firings to slow it further, the spacecraft will be traveling in tandem with 67P C-G at the same 34,000 mph speed and enter orbit. The final thruster burn will slow the probe relative to the comet to just 3 feet per second – about the same as human walking speed. We’ll also start receiving full-frame pictures of 67P/C-G instead of cropped wide-field views. Can’t wait!

Sketch I made of Comet 67P/C-G (here abbreviated ‘Churyumov’) on Dec. 12, 1982 showing the comet’s starlike nucleus, bright coma and faint tail extending to the west. Tracking it across the winter sky in 1982 inspired my interest in comets. Credit: Bob King

Comet 67P/C-G got its mouthful of a name back in 1969 when astronomers Klim Churyumov and Svetland Gerasimenko of Kiev (now part of Ukraine) discovered it on a photographic plate. The letter ‘P’ refers to ‘periodic’ comets or those that cycle around the sun with periods of fewer than 200 years. The number ’67′ tells us that the comet was the 67th periodic comet to have its orbit determined; the first was famed 1P/Halley.

I’ve seen the 67P on three returns – 1982, 1995 and 2002 – and can honestly say that watching it change in size, brightness and appearance inspired a lifelong interest in comets. “Chury”, as I once called it, led to chasing one fascinating fuzzball after another. Some people make life lists of birds. I keep just one list – comets – and it’s waiting for entry #304.

For more about the Rosetta mission, check out this excellent FAQ.