Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory

Збережено в:

Бібліографічні деталі
Дата:	2003
Автор:	Jockers, K.
Формат:	Стаття
Мова:	English
Опубліковано:	Головна астрономічна обсерваторія НАН України 2003
Назва видання:	Кинематика и физика небесных тел
Теми:	Plenary Sessions
Онлайн доступ:	http://dspace.nbuv.gov.ua/handle/123456789/78596
Теги:	Додати тег Немає тегів, Будьте першим, хто поставить тег для цього запису!
Назва журналу:	Digital Library of Periodicals of National Academy of Sciences of Ukraine
Цитувати:	Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory / K. Jockers // Кинематика и физика небесных тел. — 2003. — Т. 19, № 4-додаток. — С. 36-42. — Бібліогр.: 4 назв. — англ.

Репозитарії

Digital Library of Periodicals of National Academy of Sciences of Ukraine

id	irk-123456789-78596
record_format	dspace
spelling	irk-123456789-785962015-03-20T03:02:27Z Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory Jockers, K. Plenary Sessions 2003 Article Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory / K. Jockers // Кинематика и физика небесных тел. — 2003. — Т. 19, № 4-додаток. — С. 36-42. — Бібліогр.: 4 назв. — англ. 0233-7665 http://dspace.nbuv.gov.ua/handle/123456789/78596 en Кинематика и физика небесных тел Головна астрономічна обсерваторія НАН України
institution	Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection	DSpace DC
language	English
topic	Plenary Sessions Plenary Sessions
spellingShingle	Plenary Sessions Plenary Sessions Jockers, K. Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory Кинематика и физика небесных тел
format	Article
author	Jockers, K.
author_facet	Jockers, K.
author_sort	Jockers, K.
title	Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory
title_short	Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory
title_full	Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory
title_fullStr	Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory
title_full_unstemmed	Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory
title_sort	six years of observing with the two-channel focal reducer of mpae at the terskol observatory
publisher	Головна астрономічна обсерваторія НАН України
publishDate	2003
topic_facet	Plenary Sessions
url	http://dspace.nbuv.gov.ua/handle/123456789/78596
citation_txt	Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory / K. Jockers // Кинематика и физика небесных тел. — 2003. — Т. 19, № 4-додаток. — С. 36-42. — Бібліогр.: 4 назв. — англ.
series	Кинематика и физика небесных тел
work_keys_str_mv	AT jockersk sixyearsofobservingwiththetwochannelfocalreducerofmpaeattheterskolobservatory
first_indexed	2025-07-06T02:41:55Z
last_indexed	2025-07-06T02:41:55Z
_version_	1836863681875410944
fulltext	Figure 1. Two- olor image of omet C/1995 O1 (Hale-Bopp) obtained with the Two-Channel Fo al Redu eron April 13, 1997. The orange olor represents the dust grains of the ometary atmosphere. Note the dustspirals observed in this huge omet. The blue olor represents the distribution of ometary ions (here the ionOH+) [1℄ 31 -M ar -9 7 Color Polarization Pol. Color Comet C/1995 O1 (Hale-Bopp) max. min. 30000 kmto SunFigure 2. Images of olor, polarization, and polarimetri olor as observed in omet C/1995 O1 (Hale-Bopp)on Mar h 31, 1997. The displayed range of dust olor extends from 0% to 30% reddening per 1000 �A. The po-larization range is from 12% to 20%. The polarimetri olor Pred � Pblue, measured at 642 and 443 nm, rangesfrom 1% to 5% 36 SIX YEARS OF OBSERVING WITH THE TWO-CHANNEL FOCALREDUCER OF MPAE AT THE TERSKOL OBSERVATORYK. Jo kers 2003Max-Plan k-Institut f�ur AeronomieD-37191 Katlenburg-Lindau, Germanye-mail: jo kers�linmpi.mpg.deØÅÑÒÜ ËÅÒ ÍÀÁËÞÄÅÍÈÉ Ñ ÄÂÓÕÊÀÍÀËÜÍÛÌ ÔÎÊÀËÜÍÛÌ �ÅÄÓÊÒÎ�ÎÌÈÍÑÒÈÒÓÒÀ ÀÝ�ÎÍÎÌÈÈÌ. ÏËÀÍÊÀ ÍÀ ÎÁÑÅ�ÂÀÒÎ�ÈÈ ÒÅ�ÑÊÎË, Éîêêåðñ Ê. �Â 1996 ã. íà ïèê Òåðñêîë áûë äîñòàâëåí äâóõêàíàëüíûé �îêàëüíûé ðåäóêòîð Èíñòèòóòààýðîíîìèè Ì. Ïëàíêà äëÿ èñïîëüçîâàíèÿ íà 2-ì òåëåñêîïå ñèñòåìû �è÷è�Êðåòüåíà�Êóäý.Ýòîò ïðèáîð ÿâëÿåòñÿ åäèíñòâåííûì íà ýòîì òåëåñêîïå óñòðîéñòâîì ïîëó÷åíèÿ ýëåêòðîííîãîèçîáðàæåíèÿ. Èñïîëüçóÿ êîìïëåêñ �2-ì òåëåñêîï�2-êàíàëüíûé �îêàëüíûé ðåäóêòîð�, ó÷åíûå�åðìàíèè â ñîòðóäíè÷åñòâå ñ ðóññêèìè, óêðàèíñêèìè è áîëãàðñêèìè àñòðîíîìàìè çàíèìàëèñüèçó÷åíèåì ãàçà è ïûëè â êîìåòàõ, ïðîâîäèëè ïîëÿðèìåòðèþ àñòåðîèäîâ è êîìåòíîãî ãàçà, àòàêæå âûïîëíÿëè ðàáîòû ïî àñòðîìåòðèè è �îòîìåòðèè âíóòðåííèõ ñïóòíèêîâ Þïèòåðà.Êðîìå òîãî, èññëåäîâàëèñü ìîð�îëîãèÿ è ñâåòèìîñòü ïëàçìåííîãî òîðà ñïóòíèêà ÞïèòåðàÈî ñ öåëüþ îïðåäåëåíèÿ åãî �èçè÷åñêèõ õàðàêòåðèñòèê. Â äîêëàäå äàåòñÿ êðàòêîå îïèñà-íèå �îêàëüíîãî ðåäóêòîðà, âîçìîæíîñòè êîìïëåêñà �2-ì òåëåñêîï�2-êàíàëüíûé �îêàëüíûéðåäóêòîð� äåìîíñòðèðóþòñÿ íà ðåçóëüòàòàõ 6-ëåòíåãî ïåðèîäà íàáëþäåíèé.In 1996 the Two-Channel Fo al Redu er of the Max-Plan k-Institut f�ur Aeronomie was brought toTerskol Peak for the use at the 2-m Zeiss Rit hey-Chr�etien-Coud�e teles ope. Sin e then it has beenthe only ele troni imaging devi e available at this teles ope. Using the 2-m teles ope, the Germanside, in ollaboration with Russian, Ukrainian and Bulgarian astronomers, has studied gas and dustin omets, ondu ted polarimetry of ometary dust and asteroids, and astrometry and photometryof the inner Jovian satellites. The morphology and brightness of the plasma torus of the Joviansatellite Io has been investigated in order to derive its physi al properties. The fo al redu er isbriefly des ribed, and the apabilities of the teles ope�fo al redu er ombination are demonstratedwith results obtained during the six years of observing.INTRODUCTIONIn 1996 the Max-Plan k-Institut fur Aeronomie (MPAe) and the International Centre for Astronomi al,Medi al and E ologi al Resear h (ICAMER) have agreed on the joint use of the Two-Channel Fo alRedu er of MPAe at the 2-m RCC Zeiss teles ope of ICAMER. Sin e then six years have passed by.On o asion of the 10th anniversary of the foundation of ICAMER a brief overview of the resultsa hieved by the German side within the framework of the above agreement is presented below.THE TWO-CHANNEL FOCAL REDUCER AT THE 2-m RCC ZEISS TELESCOPEOF THE TERSKOL OBSERVATORYThe primary aim of teles opi astronomi al observations is to get a lose-up view on a elestial obje t.One, therefore, might think that magnifying power, or, if we speak in terms of photography, fo al lengthis the primary �gure of merit for an astronomi al teles ope or, more a urately, for the ombinationof a teles ope with a modern solid state amera employing CCD dete tors. There are two mainreasons why this is not the ase. First, a teles ope represents a \light bu ket", i.e., must olle t asmany photons as possible. The larger the diameter of its primary mirror the more light of a feebleastronomi al obje t is olle ted and, for a given magni� ation, the less time it will take to obtaina de ent image of the obje t. On the other hand, the more light enters the teles ope, if the exposuretime is �xed, the larger an be the magni� ation of the image we want to get. The se ond fa tor limitingthe magni� ation of a large opti al ground-based teles ope is atmospheri turbulen e. Even withthe sometimes ex ellent atmospheri onditions at the Terskol Observatory atmospheri turbulen edoes not allow to get a resolution mu h better than 1/20000 of a degree, i.e., 0.18 ar se . To optimizethe s ar e and expensive observing time available at large teles opes it is, therefore, important to37 adjust the fo al length of a given teles ope to the task of the observations. In its Cassegrain fo usthe 2-m RCC teles ope of the Terskol Observatory has a fo al length optimized to the best onditionsof atmospheri turbulen e. The Two-Channel Fo al Redu er of MPAe [2℄ redu es this fo al lengthby a fa tor of 2.86 to a resolution of about 1 ar se . This allows to obtain sharp images even undernon-optimum onditions of atmospheri turbulen e. At the same time the light gathering powerin reases by the square of the same fa tor (2.862 = 8.2), i.e., less time is needed to get a well-exposedimage. As an additional feature the fo al redu er has two hannels to allow simultaneous images intwo olors. In this respe t the instrument falls short of an ordinary television amera whi h has three olor hannels. But in omparison with a television amera, whi h is restri ted to the natural olorsof the human eye, the fo al redu er allows �lters of wide or narrow bandwidth to be used. In thisway the astronomi al obje ts an be observed in the light of important atoms, mole ules or ions, orin windows free from su h lines ( ontinuum windows), as ne essary for the investigated obje t.GAS AND DUST IN COMETSA omet is a \dirty snowball" of a size of about one kilometer. A ording to present understand-ing omets were formed from the protoplanetary dust loud about 4.6 billion years ago at aboutthe distan e of present-day planet Neptun. During this long time almost all omets remained at largedistan es from the Sun and have always been very old. Therefore, in ontrast to the inner, earthlikeplanets, omets preserved the volatile materials of the early solar system whi h were lost or modi�edin the inner solar system where the earthlike planets formed. Despite of most omets being unobserv-able in the deep voids of the solar system, some are s attered by disturban es of planets or stars intothe inner solar system. When they approa h the Sun their surfa e temperature in reases and theysublimate their volatile materials (i es). The dust grains (the \dirt" of the dirty snowball) are draggedalong with the gases and form the so- alled dust oma and dust tail of a omet. The gas mole ulesof the sublimated i es form the gas oma. They are later ionized, intera t with the solar wind andform the ometary ion tail. Despite of the small ometary nu leus, whi h annot be resolved withground-based teles opes, the oma and in parti ular the dust and ion tails an have a size of manymillion km and be observed not only in teles opes but also with naked eye. Comet Hale-Bopp wasone of these naked-eye obje ts in spring 1997. In Figure 1 (see page 36) two simultaneous images ofthis omet, taken with the Two-Channel Fo al Redu er, have been ombined into a single two- olorimage. The blue, stru tured envelopes in the image are representing the ometary ion tail. The ar sform through intera tion with the solar wind. The yellow oval in the image is ometary dust. A dustspiral is visible. Dust grains with spe ial properties leave a tive areas of the ometary nu leus and aredragged into a spiral by the rotation of the nu leus.We an obtain more information about the dust of omet Hale-Bopp, if besides of investigatingdust images we also determine dust olor ( hange of dust brightness with wavelength) and polarization.Images of dust olor, polarization and \polarimetri olor", i.e., the wavelength dependen e of pola-rization, are shown in Figure 2 (see page 36). The bluer olor and redu ed polarization at the omet's enter as ompared to its surroundings has been interpreted as a slow evaporation of a ompa t organi mantle from a sili ate ore of the dust grains as the parti les leave the ool nu leus surfa e and areheated by solar radiation [3℄.POLARIMETRY OF ASTEROIDSAsteroids are small bodies in the inner solar system. Most of them orbit the Sun between the planetsMars and Jupiter. They are thought to be left-overs from the small body population (\planetesimals")from whi h the planets are built. When giant planet Jupiter formed, its gravity in reased the relativevelo ities of neighbouring planetesimals. As a onsequen e, instead of oales ing and forming anotherplanet, they started to destru t ea h other. There is eviden e for great ollisions between asteroids.Their present-day population is said to be in ollisional equilibrium, i.e., as a result of ollisionssmaller and smaller fragments are onstantly being formed. These fragments orbit not only betweenMars and Jupiter but some of them approa h the earth quite losely. One of these obje ts is asteroid33342 whi h, like most ometary nu lei, has a size of about 1 km and approa hed the earth in Mid-De ember 2001 to 0.0125 AU. A ampaign was organized in order to measure the polarization ofthis obje t over a wide range of phase angles (angle Sun-obje t-Earth). Data were obtained fromthe Crimean Astrophysi al Observatory, the Grakovo station of Kharkov University Observatory and,last not least, from Terskol Peak. The 2-m teles ope was used when the asteroid was still faint.38 Figure 3. Degree of polarization versus phase angle as observed in asteroid 33342 from several ooperatingobservatoriesThe results (see Fig. 3) indi ate that the asteroid is of the rare E type (metalli type) with very lowpolarization. This will help to interpret other data of this asteroid, like, e.g., the �rst radar dataobtained with the help of the Crimean Evpatoria radar.THE INNER JOVIAN SATELLITESThe four large satellites of Jupiter, Io, Europa, Ganymede and Callisto, dis overed by Galileo, werethe �rst obje ts known to revolve around another elestial body di�erent from Earth or Sun. Insidethe innermost of the Galilean satellites, Io, whi h is at a distan e of 5.905 Jovian radii from Jupiter's enter, are the inner satellites Thebe, Amalthea, Adrasthea and Metis with semimajor axes of 3.11,2.54, 1.81 and 1.79 Jovian radii and mean radii of 49.3, 83.5, 8.2 and 21.5 km, respe tively. The largestone, Amalthea, was dis overed by Barnard in 1892. The other three were dete ted only duringthe Voyager mission 1979/80. For ground-based observations they are, like the Jovian ring, normallyhidden in the glare of the bright disk of Jupiter. In the last years we have been able to observethem routinely. This is possible partly be ause of the ex ellent transparen y of the sky at the highaltitude site of Terskol Peak, partly be ause spe ial measures were taken. They are observed mainly inthe methane absorption band at 890 nm, where the disk of Jupiter is omparatively dark. In addition,like in a oronograph, a Lyot-stop suppresses the di�ra tion pattern of Jupiter aused by the teles opeopti s. An elaborate mask at Cassegrain fo us onsisting of bla k glasses of di�erent thi kness andabsorptivity suppresses the light of Jupiter and of the Galilean satellites, but nevertheless allows theirimaging together with the faint inner satellites. This is very important as the images of the innersatellites must be related to alibration obje ts. The remaining halo of s attered light from Jupiter an be determined from the images and is subtra ted during data redu tion. Sample images areshown in Fig. 4. Observation of the positions of the inner satellites relative to those of the Galileanones has allowed to get their a urate astrometri positions, whi h are needed to orre t the orbitpredi tions for these obje ts [4℄. The inner Jovian satellites are under heavy bombardment by energeti parti les of the Jovian magnetosphere. Dust parti les are sputtered from the satellite surfa es andare the sour e for the Jovian ring. To get more information on the nature of the satellite surfa eswe have obtained integral photometry of the satellites. In ontrast to the existing spa e observationsour observations refer to small phase angles. Observations at very small angles provide the mostuseful information about the physi al stru ture and texture of the surfa e layer of the satellite. Dueto adverse weather onditions, the minimum angle so far observed is 1.42Æ. The maximum phaseangle was 8.16Æ. The obtained photometri data allow to measure separately the brightness of bothhemispheres with respe t to the orbital motion of the satellite, i.e., the brightness of the leading andtrailing hemispheres. This investigation may help to understand better the hara ter of the intera tionbetween the satellites and the Jovian magnetosphere. For all satellites the leading hemispheres arebrighter than the trailing ones, despite of the fa t that the orbital periods of Thebe and Amalthea39 Figure 4. The inner Jovian satellites revealed. The satellite Ganymed is behind a weakly absorbing bla k glass,and planet Jupiter itself behind a strongly absorbing glassare larger than Jupiter's rotation period, i.e., the magneti ally bound energeti parti les hit thesesatellites on their trailing side, while for Metis the orbital period is smaller, i.e., the parti les impingeon its leading side. The albedos of Amalthea, Thebe and Metis de rease with their orbital distan efrom Jupiter.THE IO TORUSAnother elusive obje t in Jupiter's satellite system is the Io torus. The innermost Galilean satelliteIo is heated by gravitational intera tion with Jupiter and the other Galilean moons. This ausesits vol ani a tivity. Most of its surfa e is overed by SO2 frost and there is also a very thin SO2atmosphere. The satellite Io orbits in the Jovian magnetosphere, a vast region of orotating ionized40 Figure 5. The Io torus, imaged in the forbidden lines of S+ ([S II℄) and S++ ([S III℄)gas. This magnetospheri plasma disso iates the SO2 mole ules, ionizes them, for es them to rotatearound Jupiter and in this way forms the Io torus. As the magneti dipole of Jupiter is tilted byabout 10Æ with respe t to Jupiter's rotation axis, the Io torus is tilted in a similar way. The sulphurand oxygen ions of the Io torus radiate line emission. The strongest lines are due to S+ and S++.Observations of the torus in the light of these ions allow to determine the torus shape and its densityand temperature. Observations of the Io torus are about as diÆ ult as the observations of the innersatellites, for the same reason of s attered light from the bright Jovian disk. A similar setup is usedas for the inner moons. In addition, a tunable Fabry-Perot interferometer allows only a very narrowrange of wavelengths around the wavelength of the observed ion to be imaged and in this way furthersuppresses the straylight of Jupiter. Imaging of the Io torus allows to \see" part of the otherwiseinvisible Jovian magnetosphere and to determine its ele tron density and temperature. In 1999 and2000 Jupiter's magnetosphere was investigated by the Galileo spa e probe, and the observations ofthe torus ondu ted at Terskol Peak served as a supplement of the spa e probe measurements. Fig. 5shows images of the torus from November 2000 in the light of the S+ and S++ ions. Dawn and duskare the morning and evening sides of the torus, i.e., the sides where, as seen from an observer inthe torus, the sun rises (rotational motion of the torus toward Sun) or sets (rotational motion awayfrom Sun). The ellipsoids represent the lo ation of a ring at Io's distan e from Jupiter in lined asthe Io torus. An open ellipse indi ates that we see part of an open torus. If the ellipse degenerates toa straight line, we see the torus from its side. On the left side of Fig. 5 in the third or fourth panelof the [S II℄ (S+) images we see a narrow inner ring (the old torus) and atta hed to it a verti allyextended feature alled ribbon. In the uppermost and lowermost panel of the S+ images, where wesee the torus edge-on, the ribbon ontinues to be prominently visible. This indi ates that it is nearlyperpendi ular to the plane of the torus. It is aused by warmer ions whi h, be ause of their highertemperature, an move up and down along the magneti �eld lines of Jupiter. We see from this thatthe temperature in the Io torus in reases with distan e from Jupiter. The [S III℄ (S++) emission omesfrom hotter regions in the torus. In the light of this ion the old torus is invisible. In the �rst rowof images bright areas lose to Jupiter indi ate straylight whi h ould not be properly removed fromthe images. This happens when during observations a small loud passed through the �eld of view ofthe teles ope. A remarkable feature is the separation of old torus and ribbon whi h is best visible41 in the third panel of [S II℄ (S+) images. It is not lear what aused this gap. It was not observed in1999, i.e., in 1999 there was a ontinuous transition between old torus and ribbon.OUTLOOKFor many years the Large Azimuthal Teles ope (BTA) of the Spe ial Astronomi al Observatory with its6m mirror has been the largest teles ope of the world. In re ent years, based on the design of the BTAand improving it, a number of larger teles opes have been built and more of these huge teles opesare under onstru tion. In this new era 2m size teles opes are onsidered as survey teles opes to�nd the obje ts whi h then will be investigated more deeply with the huge teles opes. A properway of operation is provided in the framework of a \virtual observatory", where survey data aremade available to all astronomers for use in their di�erent �elds. Another way to ompete withthe huge teles opes has been to spe ialize on obje ts whi h are bright enough to be observable withmedium-sized teles opes but whi h nevertheless have not been studied extensively. As demonstratedin this study small bodies of the solar system are suitable obje ts partly be ause of their temporalvariability and partly be ause they require spe ial observing te hniques not always available at the hugeteles opes. In our ooperative program the 2-m RCC Zeiss teles ope of the Terskol Observatory hasprodu ed internationally ompetitive results, and it an do this not only in the �eld of solar systemastronomy. The present author hopes, however, that sooner or later a huge Russian teles ope will beavailable and give the East-European astronomi al ommunity the resear h tool they deserve.[1℄ Jo kers K., Bonev T., Credner T. Observations of ions in omets: A ontribution towards understandingthe omet-solar wind intera tion // Astrophys. and Spa e S i.{1999.{264.{P. 227{234.[2℄ Jo kers K., Credner T., Bonev T., et al. Exploration of the solar system with the two- hannel fo alredu er at the 2m-RCC teles ope of Pik Terskol Observatory // Kinemati s and Physi s of CelestialBodies. Suppl. Ser, \Astronomy in Ukraine { 2000 and Beyond (Impa t of International Cooperation)" /Ed. Ya. S. Yatskiv.{2000.{3.{P. 13{18.[3℄ Kolokolova L., Jo kers K., Gustafson B. �A. S., Li htenberg G. Color and polarization as indi ators of omet dust properties and evolution in the near-nu leus oma // J. Geophys. Res.{2001.{106.{P. 10113{10127.[4℄ Kulyk I., Jo kers K., Karpov N., Sergeev A. Astrometri CCD observations of the inner Jovian satellitesin 1999{2000 // Astron. and Astrophys.{2002.{383.{P. 724{728. 42

Six years of observing with the Two-Channel Focal Reducer of MPAe at the Terskol Observatory

Репозитарії

Схожі ресурси