quote:Rosetta finds magnetic field-free bubble at comet
11 March 2016
ESA’s Rosetta spacecraft has revealed a surprisingly large region around its host comet devoid of any magnetic field.
When ESA’s Giotto flew past Comet Halley three decades ago, it found a vast magnetic-free region extending more than 4000 km from the nucleus. This was the first observation of something that scientists had until then only thought about but had never seen.
Interplanetary space is pervaded by the solar wind, a flow of electrically charged particles streaming from the Sun and carrying its magnetic field across the Solar System. But a comet pouring lots of gas into space obstructs the solar wind.
At the interface between the solar wind and the coma of gas around the active comet, particle collisions as well as sunlight can knock out electrons from the molecules in the coma, which are ionised and picked up by the solar wind. This process slows the solar wind, diverting its flow around the comet and preventing it from directly impacting the nucleus.
Along with the solar wind, its magnetic field is unable to penetrate the environment around the comet, creating a region devoid of magnetic field called a diamagnetic cavity.
Prior to Rosetta arriving at Comet 67P/Churyumov-Gerasimenko, scientists had hoped to observe such a magnetic field-free region in the environment of this comet. The spacecraft carries a magnetometer as part of the Rosetta Plasma Consortium suite of sensors (RPC-MAG), whose measurements were already used to demonstrate that the comet nucleus is not magnetised.
However, since Rosetta’s comet is much less active than Comet Halley, the scientists predicted that a diamagnetic cavity could form only in the months around perihelion – the closest point to the Sun on the comet’s orbit – but that it would extend only 50–100 km from the nucleus.
During 2015, the increased amounts of dust dragged into space by the outflowing gas became a significant problem for navigation close to the comet. To keep Rosetta safe, trajectories were chosen such that by the end of July 2015, a few weeks before perihelion, it was some 170 km away from the nucleus. As a result, scientists considered that detecting signs of the magnetic field-free bubble would be impossible.
“We had almost given up on Rosetta finding the diamagnetic cavity, so we were astonished when we eventually found it,” says Charlotte Götz of the Institute for Geophysics and extraterrestrial Physics in Braunschweig, Germany.
Charlotte is the lead author of a new study, published in the journal Astronomy and Astrophysics, presenting the detection of a diamagnetic cavity obtained by RPC-MAG on 26 July. The paper describes one of the most spectacular measurements from almost 700 detections of regions with no magnetic field made by Rosetta at the comet since June 2015.
“We were able to detect the cavity, and on many occasions, because it is much bigger and dynamic than we had expected,” adds Charlotte.
To investigate why the magnetic field-free cavity is so much bigger than predicted, Charlotte and her colleagues looked at measurements performed around the same time by other instruments, such as Rosetta's scientific camera, OSIRIS, and the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument, ROSINA, to verify whether any anomalous changes in the comet's activity could be pushing the cavity away from the nucleus.
While one of the cavity detections, on 29 July, occurred in conjunction with a strong outburst of gas and dust recorded by other instruments on Rosetta, this seems to be an isolated case. Almost all of the other observations of magnetic field-free regions, including the one recorded on 26 July, were not accompanied by any appreciable increase of outgassing.
The most likely explanation seems to lie, instead, in the dynamical nature of the cavity boundary.
Boundaries between plasma regions with different properties are often unstable, and small oscillations can arise in the pile-up region of the solar wind, where it encounters the magnetic field-free region, on the Sun-facing side of the comet. If these oscillations propagate and get amplified along the boundary, in the direction opposite the Sun, they could easily cause the cavity to grow in size.
Such a moving instability would also explain why the measurements of magnetic field-free regions are sporadic and mainly span several minutes, with the 26 July one lasting 25 minutes and the longest one, recorded in November, about 40 minutes. The short duration of the detections is not a result of Rosetta crossing the cavity – the spacecraft moves much too slowly with respect to the comet – but of the magnetic field-free regions repeatedly passing through the spacecraft.
“What we are seeing is not the main part of the cavity but the smaller pockets at the cavity boundary, which are occasionally pushed farther away from the nucleus by the waves propagating along the boundary,” adds Charlotte.
Scientists are now busy analysing all the magnetic field-free events recorded by Rosetta, to learn more about the properties of the plasma in the comet environment and its interaction with the solar wind. After perihelion, as the comet moved away from the Sun and its outgassing and dust production rate declined, the spacecraft was able to move closer to the nucleus, and the magnetometer continued detecting magnetic field-free regions for several months, until the latest detection in February 2016.
Three decades ago, Giotto’s detection at Comet Halley was a great success, because it was the first confirmation of the existence of a diamagnetic cavity at a comet,” says Matt Taylor, Rosetta Project Scientist at ESA.
“But that was only one measurement, while now we have seen the cavity at Rosetta’s comet come and go hundreds of times over many months. This is why Rosetta is there, living with the comet and studying it up close.”
UHM.... Rosetta werdt op 2 maart 2004 gelanceerd...quote:Op vrijdag 8 april 2016 08:43 schreef ExperimentalFrentalMental het volgende:
07-04-2016
Rosetta’s komeet werd helderder en blauwer
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‘Aangedikte’ kleurenopname van de ‘nek’ van komeet 67P/Churyumov-Gerasimenko. De blauwachtige tint van het gebied wijst op aanwezigheid van oppervlakte-ijs. (ESA/Rosetta/MPS for OSIRIS Team)
De komeet waar de Europese ruimtesonde Rosetta omheen cirkelt, is sinds de aankomst van de sonde van kleur veranderd. Dat blijkt uit waarnemingen die Rosetta in de periode augustus-november 2004 heeft gedaan. In die vier maanden nam de afstand van de komeet tot de zon af van 542 miljoen kilometer tot 438 miljoen kilometer, waardoor het ijsachtige object begon op te warmen.
Bij aankomst trof Rosetta een extreem donker hemellichaam aan, dat ongeveer 6 procent van het ontvangen zonlicht weerkaatste. Deze donkere tint wordt veroorzaakt doordat een groot deel van het oppervlak is bedekt met een laag van donker, droog stof dat uit een mengsel van mineralen en organische stoffen bestaat.
Door sublimatie (‘verdamping’) van het onderliggende ijs is steeds meer van dat oude stof de ruimte in geblazen, waardoor vers onderliggend materiaal bloot kwam te liggen. Dat nieuwe materiaal bevatte meer ijs, waardoor de komeet tegelijkertijd blauwer en helderder werd. Gemiddeld nam de helderheid van zijn oppervlak met ongeveer 34% toe.
De gegevens van na november 2004 zijn nog niet volledig geanalyseerd, maar het lijkt erop dat de waargenomen trend zich heeft voortgezet. (EE)
(allesoversterrenkunde)
Dat vind ik toch een enorme blunder van allesoversterrenkunde.quote:
quote:Op zaterdag 9 april 2016 08:57 schreef qajariaq het volgende:
Dit is gewoon een test of het topic nog wel gelezen wordt. (Ja dus).
quote:
quote:Op vrijdag 29 juli 2016 19:22 schreef -CRASH- het volgende:
New Vangelis album inspired by ESA’s Rosetta mission
Legendary composer and pioneer of electronic music Vangelis has produced a brand new album, ‘Rosetta’, inspired by ESA’s Rosetta mission
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The release of the album by Decca Records on 23 September coincides with the culmination of Rosetta’s 12-year mission to orbit and land its Philae probe on Comet 67P/Churyumov-Gerasimenko. Rosetta is set to complete its journey in a controlled descent to the surface of the comet on 30 September.
The story of this mission fuelled Vangelis’ long-held passion for space and inspired him to create his first new studio album in 18 years.
Vangelis’ music is often linked to themes of science, history and exploration. Alongside his Academy Award-winning score for ‘Chariots of Fire’, he has written for the films including ‘Antarctica’, ‘1492: Conquest of Paradise’, ‘The Bounty’ and ‘Alexander’.
“Mythology, science and space exploration are subjects that have fascinated me since my early childhood. And they were always connected somehow with the music I write,” said Vangelis.
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ESA’s connection with Vangelis goes back several years to when ESA astronaut André Kuipers was on the International Space Station. André is a big fan and he had a lot of Vangelis’ music with him in space.
After sharing stories and experiences with André via video call from the ISS, Vangelis was inspired to write some music for ESA to mark the landing of Philae on the comet in 2014.
To Vangelis, music is a sacred, basic force of the Universe, its purpose to elevate, inspire and to heal humankind. Never has this been more obvious than on ‘Rosetta’, an album that perfectly blends his fascination with the Universe and his ability to compose stirring music.
“With music, you can enhance emotions and create memories: I believe that what Vangelis wanted to do was share a lasting memory of our Rosetta mission through his music,” said Carl Walker, from ESA’s Communication Department.
Vangelis has dedicated this new album to everyone who made the ESA’s ongoing Rosetta mission possible, in particular extending the track called ‘Rosetta’s Waltz’ as an expression of his appreciation to the mission team.
“Rosetta has been an amazing journey for everybody involved, both scientifically and technically, but it has also connected emotionally with so many people around the world,” said ESA’s Prof. Mark McCaughrean, Senior Science Advisor in the Directorate of Science.
“So you can imagine how proud we were when one of the world’s great composers Vangelis made some music for us at the time of landing, and how excited we are that he’s put together a whole album of original music about this astonishing adventure.”
quote:
Kan iemand mij uitleggen waarom de energievoorziening wordt uitgezet en waarom de rosetta gecontroleerd moet neerstorten? Kunnen ze de rosetta niet gewoon zijn werk laten doen en afwachten totdat ze zelf uit elkaar valt/neerstort.quote:Op vrijdag 5 augustus 2016 14:11 schreef rubbereend het volgende:
bijzonder om de vluchroute rond de komeet zo te zien
de afstand tussen de komeet en de zon wordt steeds groter. Tegen het einde van september zal Rosetta nog maar heel weinig zonlicht ontvangen (Rosetta draait op zonne-energie), bij de afdaling naar de komeet zal er evengoed nog onderzoek gedaan worden, als de sonde eenmaal op het oppervlak staat zal die daar niet meer toe in staat zijn en komt logischerwijs een einde aan de missie.quote:Op vrijdag 5 augustus 2016 14:26 schreef Rick_Van_Acht het volgende:
[..]
Kan iemand mij uitleggen waarom de energievoorziening wordt uitgezet en waarom de rosetta gecontroleerd moet neerstorten? Kunnen ze de rosetta niet gewoon zijn werk laten doen en afwachten totdat ze zelf uit elkaar valt/neerstort.
quote:Op donderdag 1 september 2016 08:35 schreef ExperimentalFrentalMental het volgende:
31-08-2016
Maagdelijk stof van komeet 67P onder de microscoop
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Komeet 67P/Churyumov-Gerasimenko, op 22 november 2014 gefotografeerd door Rosetta. De kern is opzettelijk overbelicht om de ‘jets’ van gas en stof die de komeet uitstoot beter te laten zien. (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
Een internationaal team van wetenschappers met daarbij Pascale Ehrenfreund van de Universiteit Leiden heeft ontdekt dat de stofdeeltjes van komeet 67P/Churyumov–Gerasimenko zijn opgebouwd uit nog kleinere stofdeeltjes. Deze ontdekking bevestigt de heersende theorie dat klonten stof de basis vormen waaruit kometen en planeten ontstaan. De onderzoekers publiceren hun bevinding donderdag in het wetenschappelijk tijdschrift Nature.
De wetenschappers gebruikten voor hun onderzoek een atoomkrachtmicroscoop in de ruimte. De microscoop bevindt zich aan boord van het onbemande ruimtevaartuig Rosetta dat twee jaar geleden na een reis van tien jaar aankwam bij de komeet 67P. Dankzij het onderzoek aan de stofdeeltjes van de komeet kunnen wetenschappers meer te weten komen over hoe ons zonnestelsel is gevormd. Kometen zijn namelijk een soort tijdcapsule. Ze bevatten materiaal in een bijna ongerepte staat, dat wil zeggen, zoals het eruit zag 4,7 miljard jaar geleden toen ons zonnestelsel werd gevormd.
Het is voor het eerst dat deze ongerepte stofdeeltjes van een komeet in zulk detail en van zo dichtbij zijn bekeken. Een eerdere expeditie naar komeet Wild 2 in 2004 ging op grote afstand langs een komeet. En bij onderzoek naar ruimtestof in de aardatmosfeer kan dat stof veranderd zijn door langdurige inwerking van zonnestraling en door botsingen met andere deeltjes.
Het instrument dat de onderzoekers gebruikten heet MIDAS: Micro-Imaging Dust Analysis System. Het instrument toont de grootte, de vorm en de structuur van het komeetstof. Het blijkt dat het stof bestaat uit klonten van kleinere korrels. De stofdeeltjes verschillen in grootte: van tientallen micrometers tot enkele honderden nanometers. En ze variëren van vorm: van losse korrels tot grotere, poreuze, langwerpige klonten. Ook vonden de onderzoekers een klont die bestaat uit 114 kleinere stofdeeltjes.
Eerder al bekeken onderzoekers met een ander instrument de grotere brokken stof van 67P. Die bleken op hun beurt weer uit kleinere brokjes te bestaan. Met MIDAS konden de kleinste deeltjes worden bestudeerd.
De waarnemingen die nu door Ehrenfreund en haar collega’s worden gepubliceerd, bevestigen de theorieën die voorspellen dat kometen en planeten zijn opgebouwd uit kleine stofdeeltjes die samensmelten tot grotere en waaruit uiteindelijk planeten en kometen vormen.
(allesoversterrenkunde)
Dan lijkt mijn vermoeden dat ie ergens in gevallen wasquote:Op maandag 5 september 2016 15:59 schreef ExperimentalFrentalMental het volgende:
PHILAE IS GEVONDEN!!!!![]()
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05-089-2016
PHILAE FOUND!
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Less than a month before the end of the mission, Rosetta’s high-resolution camera has revealed the Philae lander wedged into a dark crack on Comet 67P/Churyumov–Gerasimenko.
The images were taken on 2 September by the OSIRIS narrow-angle camera as the orbiter came within 2.7 km of the surface and clearly show the main body of the lander, along with two of its three legs.
The images also provide proof of Philae’s orientation, making it clear why establishing communications was so difficult following its landing on 12 November 2014.
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Philae close-up
“With only a month left of the Rosetta mission, we are so happy to have finally imaged Philae, and to see it in such amazing detail,” says Cecilia Tubiana of the OSIRIS camera team, the first person to see the images when they were downlinked from Rosetta yesterday.
“After months of work, with the focus and the evidence pointing more and more to this lander candidate, I’m very excited and thrilled that we finally have this all-important picture of Philae sitting in Abydos,” says ESA’s Laurence O’Rourke, who has been coordinating the search efforts over the last months at ESA, with the OSIRIS and SONC/CNES teams.
Philae was last seen when it first touched down at Agilkia, bounced and then flew for another two hours before ending up at a location later named Abydos, on the comet’s smaller lobe.
After three days, Philae's primary battery was exhausted and the lander went into hibernation, only to wake up again and communicate briefly with Rosetta in June and July 2015 as the comet came closer to the Sun and more power was available.
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OSIRIS narrow-angle camera image with Philae, 2 September
However, until today, the precise location was not known. Radio ranging data tied its location down to an area spanning a few tens of metres, but a number of potential candidate objects identified in relatively low-resolution images taken from larger distances could not be analysed in detail until recently.
While most candidates could be discarded from analysis of the imagery and other techniques, evidence continued to build towards one particular target, which is now confirmed in images taken unprecedentedly close to the surface of the comet.
At 2.7 km, the resolution of the OSIRIS narrow-angle camera is about 5 cm/pixel, sufficient to reveal characteristic features of Philae’s 1 m-sized body and its legs, as seen in these definitive pictures.
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Philae close-up, labelled
“This remarkable discovery comes at the end of a long, painstaking search,” says Patrick Martin, ESA’s Rosetta Mission Manager. “We were beginning to think that Philae would remain lost forever. It is incredible we have captured this at the final hour.”
“This wonderful news means that we now have the missing ‘ground-truth’ information needed to put Philae’s three days of science into proper context, now that we know where that ground actually is!” says Matt Taylor, ESA’s Rosetta project scientist.
"Now that the lander search is finished we feel ready for Rosetta's landing, and look forward to capturing even closer images of Rosetta's touchdown site,” adds Holger Sierks, principal investigator of the OSIRIS camera.
The discovery comes less than a month before Rosetta descends to the comet’s surface. On 30 September, the orbiter will be sent on a final one-way mission to investigate the comet from close up, including the open pits in the Ma’at region, where it is hoped that critical observations will help to reveal secrets of the body’s interior structure.
Further information on the search that led to the discovery of Philae, along with additional images, will be made available soon.
(ESA.int)
twitter:ESA_Rosetta twitterde op woensdag 07-09-2016 om 19:09:23Meet Kenneth & Juliette, #67P dust particles that contain solid organics! #New #Discovery https://t.co/7G06ErvxFf https://t.co/0R4m3B4TEk reageer retweet
Misschien is het een rendering van een simulatie die ze zelf ook gebruiken?quote:Op donderdag 22 september 2016 16:45 schreef qajariaq het volgende:
Zou het budget voor de leuke en duidelijke animatiefilms op zijn? :-(
Het eindigt met "To be continued", dus er zal nog wel zo'n fantastische video komen.quote:Op dinsdag 27 september 2016 18:11 schreef ExperimentalFrentalMental het volgende:
Het einde is nabij
En dit is de laatste video van Once Upon a Time
Maar wat was het toch een fantastische missie en we gaan nog door tot de allerlaatste snik
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