APOD and General Astronomy Discussion Forum
https://asterisk.apod.com/
MargaritaMc wrote:
This week’s images of comet 67P/Churyumov-Gerasimenko reveal an extraordinarily irregular shape. We had hints of that in last week’s images and in the unscheduled previews that were seen a few days ago, and in that short time it has become clear that this is no ordinary comet. Like its name, it seems that comet 67P/C-G is in two parts.
... ...A second image and a movie show the comet after the image has been processed. The technique used, called “sub-sampling by interpolation”, only acts to remove the pixelisation and make a smoother image, and it is important to note that the comet’s surface features won’t be as smooth as the processing implies. The surface texture has yet to be resolved simply because we are still too far away; any apparent brighter or darker regions may turn out to be false interpretations at this early stage.
But the movie, which uses a sequence of 36 interpolated images each separated by 20 minutes, certainly provides a truly stunning 360-degree preview of the overall complex shape of the comet. Regardless of surface texture, we can certainly see an irregular shaped world shining through. Indeed, some people have already likened the shape to a duck, with a distinct body and head. ...
The Rosetta blog post mentioned ITOKAWA as well, and gave a link to this paper and image:geckzilla wrote:That's a very funny comet nucleus. Someone else called it a rubber ducky. Reminds me of Itokawa.
Itokawa was new to me, so I found this very informative.The internal structure of asteroid (25143) Itokawa as revealed by detection of YORP spin-up
The internal structure of asteroids can tell us a lot about how they were formed and thus about collision processes in our solar system and the processes that are responsible for planet formation. Asteroid (25143) Itokawa is interesting in this respect because of its distinctive bean shape filled with boulders, as revealed by spacecraft Hayabusa in 2005....
geckzilla wrote:
That's a very funny comet nucleus. Someone else called it a rubber ducky.
http://www.planetary.org/blogs/emily-lakdawalla/2014/07150633-quick-rosetta-update.html wrote:
Churyumov-Gerasimenko is a contact binary!
Posted by Emily Lakdawalla, 2014/07/15 13:42 UTC
<<Philae navigator Eric Jurado as saying that “navigation around such a body should not be much more complex than around a nucleus of irregular spherical type, but landing the Philae probe however, could be more difficult, as this form restricts potential landing zones.>>\
More at: http://www.planetary.org/blogs/emily-la ... pdate.html
geckzilla wrote:
I bet they wish they sent two Philae (is that noun already plural?) so that they could have plopped one down on the big rock and another one down on the small rock.
http://en.wikipedia.org/wiki/Philae wrote: <<Philae (Greek: Φιλαί Philai) was, as the plural name indicates, the appellation of two small islands situated in latitude 24° north, just above the First Cataract of the Nile River near Aswan. Philae proper, although the smaller island, is, from the numerous and picturesque ruins formerly there, the more interesting of the two. Prior to its inundation from Lake Nassar, it was not more than 380 metres long and about 120 metres broad. It is composed of Syenite stone: its sides are steep and on their summits a lofty wall was built encompassing the island. Philae is mentioned by numerous ancient writers, including Strabo, Diodorus, Ptolemy, Seneca, Pliny the Elder. Philae, being accounted one of the burying-places of Osiris, was held in high reverence both by the Egyptians to the north and the Nubians (often referred to as Ethiopians in Greek) to the south. It was deemed profane for any but priests to dwell there and was accordingly sequestered and denominated "the Unapproachable". It was reported too that neither birds flew over it nor fish approached its shores. These indeed were the traditions of a remote period; since in the time of the Ptolemies of Egypt, Philae was so much resorted to, partly by pilgrims to the tomb of Osiris, partly by persons on secular errands, that the priests petitioned Ptolemy Physcon (170-117 BC) to prohibit public functionaries at least from coming there and living at their expense. In the 19th century AD, William John Bankes took the Philae obelisk on which this petition was engraved to England. When its Egyptian hieroglyphs were compared with those of the Rosetta stone, it threw great light upon the Egyptian consonantal alphabet.>>
geckzilla wrote:
That's a very funny comet nucleus. Someone else called it a rubber ducky.
http://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasimenko wrote: On 6 June 2014 water vapor was detected coming from 67P at a rate of roughly 1 liter/sec when Rosetta was 360,000km from the comet and the comet was 3.9AU from the Sun.
3D illustration of the nucleus of Churyumov–Gerasimenko from Hubble telescope observations. This is a low-order spherical-harmonics fit to the nucleus's shape, smoothing over small features that the Hubble data are not sensitive to.
There is lively and informed discussion amongst the commentators on the Rosetta blog http://blogs.esa.int/rosetta/geckzilla wrote:Rubber Duckie Gate intensifies... (Ok, I didn't realize there was a kerfuffle at all, so this is news to me!)
http://www.planetary.org/blogs/guest-bl ... uffle.html
Less than a week before Rosetta’s rendezvous with comet 67P/Churyumov-Gerasimenko, images obtained by OSIRIS, the spacecraft’s onboard scientific imaging system, show clear signs of a coma surrounding the comet’s nucleus. While OSIRIS’ view of the coma covers an area of 150 kilometers across, its outskirts might reach much farther.
“Even though it sounds like a contradiction, imaging the comet’s coma from nearby is more difficult than from far away”, says OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany. At the end of April, for example, OSIRIS had witnessed a distinct rise of cometary dust production from a distance of more than two million kilometers. At that time, one pixel in OSIRIS’ images corresponded to a region in space covering 2500 square kilometers at the nucleus. The reflected light from all dust particles seen in this column worked together to create a signal. Now, as the resolution of OSIRIS images increases, a much smaller region — and thus far less dust particles — contributes to one pixel.
Nevertheless, a new image dating from July 25th clearly reveals an extended coma shrouding 67P’s nucleus. “Our coma images cover an area of 150 by 150 square kilometers”, says Luisa Lara from the Instituto de Astrofísica de Andalucía. However, most likely these images show only the inner part of the coma, where particle densities are highest. Scientists expect 67P’s full coma to actually reach much farther.
Another challenge for OSIRIS is the bright nucleus that outshines the surrounding coma. While OSIRIS is designed to deal with a controlled overexposure in the region of the nucleus, the stray light from this strong source causes artifacts by the optical system. In the current image, the hazy bright circular structure to the right of the comet’s nucleus is such an artifact. The center of the image located around the position of the nucleus is obscured by overexposure. ...
ESA’s Rosetta spacecraft has made its first temperature measurements of its target comet, finding that it is too hot to be covered in ice and must instead have a dark, dusty crust.
The observations of comet 67P/Churyumov–Gerasimenko were made by Rosetta’s visible, infrared and thermal imaging spectrometer, VIRTIS, between 13 and 21 July, when Rosetta closed in from 14 000 km to the comet to just over 5000 km.
At these distances, the comet covered only a few pixels in the field of view and so it was not possible to determine the temperatures of individual features. But, using the sensor to collect infrared light emitted by the whole comet, scientists determined that its average surface temperature is about –70ºC. ...
"When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck."http://en.wikipedia.org/wiki/Sphinx wrote:
<<It was said that Hera sent the Sphinx from her Ethiopian homeland to Thebes in Greece where she asks all passersby the most famous riddle in history: "Which creature has one voice and yet becomes four-footed and two-footed and three-footed?" She strangled and devoured anyone unable to answer. Oedipus solved the riddle by answering: Man—who crawls on all fours as a baby, then walks on two feet as an adult, and then uses a walking stick in old age. Bested at last, the tale continues, the Sphinx then threw herself from her high rock and died. >>
http://en.wikipedia.org/wiki/Philae wrote:
<<Philae (Greek: Φιλαί Philai) was, as the plural name indicates, the appellation of two small islands situated in latitude 24° north, just above the First Cataract of the Nile River near Aswan. Philae is mentioned by numerous ancient writers, including Strabo, Diodorus, Ptolemy, Seneca, Pliny the Elder. Philae, being accounted one of the burying-places of Osiris, was held in high reverence both by the Egyptians to the north and the Nubians (often referred to as Ethiopians in Greek) to the south. It was deemed profane for any but priests to dwell there and was accordingly sequestered and denominated "the Unapproachable". It was reported too that neither birds flew over it nor fish approached its shores. These indeed were the traditions of a remote period; since in the time of the Ptolemies of Egypt, Philae was so much resorted to, partly by pilgrims to the tomb of Osiris, partly by persons on secular errands, that the priests petitioned Ptolemy Physcon (170-117 BC) to prohibit public functionaries at least from coming there and living at their expense.>>
Watch as ESA's Rosetta spacecraft makes its historic rendezvous with a comet after a decade-long journey through space. Livestream from ESA's operations centre starts at 08:00 GMT (10:00 CEST) on 6 August
Beyond wrote:Gee, it really does look like mud that's hardened.neufer wrote:
http://www.esa.int/Our_Activities/Space ... om_Rosetta
http://www.bbc.com/news/science-environment-28659783 wrote:
<<In a first for space history, the spacecraft was manoeuvred alongside a speeding body to begin mapping its surface in detail.>>
http://en.wikipedia.org/wiki/Dorodango wrote: <<Dorodango [ 泥 (doro どろ) "mud" + だんご (dango) a type of round dumpling created from pressed rice flour] is a Japanese Art form in which earth & water are molded to create a delicate shiny sphere, resembling a billiard ball. Making the basic dorodango is a traditional pastime for school children in Japan. Several different techniques can be used. Across all methods, a core of the ball is made of basic mud, which has been carefully shaped by hand to be as round as possible. This core is left to dry, and then methodically and carefully dusted with finely sifted soil to create a crust several millimeters thick around the core. This step may be repeated several times, with finer and finer grains of dirt in order create a smooth and shiny surface. A cloth then may be used to gently polish the surface. The dorodango, once completed, may look like a polished stone sphere, but it is still very fragile. The process requires several hours and careful focus so as not to break the ball.
In the episode "End with a Bang" (Episode 113) of the Discovery series "MythBusters", hosts Adam Savage & Jamie Hyneman investigated the truth behind the everyday saying that one "can't polish a turd". They used the dorodango technique to create dung spheres in order to bust the myth. Using a glossmeter, they measured gloss levels substantially higher than the value of 70 gloss units which is considered "high gloss". Savage's 106 gloss unit dorodango used an ostrich's feces, while Hyneman's 183 gloss unit specimen used a lion's feces. They therefore deemed the myth "busted".>>
.Rosetta spacecraft becomes the first to orbit a cometClick to play embedded YouTube video.
CNN
Uploaded on 6 Aug 2014The Rosetta spacecraft, launched 10 years ago, became the first to orbit a comet. CNN's Chad Myers explains
Rosetta arrival highlightsClick to play embedded YouTube video.
European Space Agency, ESA
Uploaded on 7 Aug 2014
Highlights from ESA's mission control centre during Rosetta's arrival at comet 67P/C-G on 6 August 2014. Includes live updates from the Rosetta flight control team, confirmation of orbit entry and presentation of latest images and science results.
Rosetta Blog, 8th August 2015
COSIMA REACHES FOR DUST
Now that comet 67P/Churyumov-Gerasimernko is within our reach, Rosetta’s mass spectrometer COSIMA, managed by the Max Planck Institute for Solar System Research in Germany, is beginning to reach for cometary dust. Literally.
On Sunday 10 August 2014, COSIMA will expose its first of 24 targetholders aiming to collect single dust particles. This might take a while. After all, from dust particle modeling, 67P/C-G’s coma is still comparable to a high-quality cleanroom. But, as 67P/C-G travels closer to the Sun along its orbit, the comet’s activity will increase and more dust will be within reach. For now, we are planning to keep the target exposed for one month, but checking on a weekly basis if the model predictions are not too low and if we are lucky.
hereI mentioned in an earlier post that ESA appears to be better at public relations now - they now seem to be releasing photos from Rosetta's navcam every day now.ESA Euronews: Comet Hunters: Rosetta's race to map 67PClick to play embedded YouTube video.
European Space Agency, ESA
Uploaded on 11 Aug 2014
The Rosetta mission is now on a race against time to prepare maps and collect data before the Philae lander is due to be sent down to the surface of comet 67P in November. In this edition of Euronews Space, the 'Comet Hunters' show us how to orbit a comet, how Rosetta 'sees' its target, and what the mission means to the world of science, and to this team in particular.
This video is available in the following languages:
Spanish: http://youtu.be/YBsk_qWuC8M
Portuguese: http://youtu.be/gVXQTYVjhkQ
Greek: http://youtu.be/PEbdC0FB1n8
Italian: http://youtu.be/D7RoCVKSYjg
German: http://youtu.be/AOdQc_vapF0
French: http://youtu.be/HF3Y6eKciLk
Hungarian soon!
