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Bu çalışma, XV. yüzyıla ait bir metinde, dönemin insanlarının günlük işlerine gezegenlerin etki ettiğine dair inanışları ele almaktadır. İncelenen metin ŞEYH VEFÂ adlı astronomi bilginine ait olan 4 yapraklık küçük bir risaledir. Metin Eski Anadolu Türkçesine aittir, müellifin vefatından bir asır sonra kopya edilmiştir. Müellif bu eserinde, gezegenlerin günün hangi saatine nasıl etki ettiği, bu saatlerde hangi işlerin yapılmasının iyi, hangilerinin kötü olacağı; ayın hangi günlerinde hangi işlere kalkışılmasının iyi, hangi işlerin yapılmasının da kötü sonuçlanacağı üzerine düşüncelerini aktarmaktadır.

The predicted primordial lithium abundance differs from observations of unevolved halo stars on the Spite plateau by a factor two to three. Surface depletion due to atomic diffusion has been suggested as a cause of this so-called cosmological lithium problem. Evolutionary abundance trends indicative of atomic diffusion have previously been identified in the metal-poor globular cluster NGC 6397 ([Fe/H] = -2), with stellar parameters deduced spectroscopically in a self-consistent manner. Abundances of five elements (Li, Mg, Ca, Ti, and Fe) were found to be in agreement with stellar structure models including the effects of atomic diffusion and a free-parameter description of turbulent mixing at the lowest efficiency compatible with the flatness of the Spite plateau. It is our aim to evaluate the interplay of modelling assumptions and theoretical predictions under various priors, e.g. the independent age determination using the white dwarf cooling sequence, and the high efficiency of turbulent mixing recently found compatible with halo field stars. We perform self-consistent spectroscopic abundance analyses at an expanded effective temperature scale inspired by results of new photometric calibrations from the infrared flux method. The resulting abundances are compared to predictions in a grid of theoretical isochrones, chosen in light of the priors for age and efficiency of turbulent mixing. We find that the observed abundance trends are not artefacts of the effective temperature scale, as it cannot be arbitrarily modified to flatten all trends. The inferred abundance trends seem to be in agreement with predictions for an age compatible with the white dwarf cooling sequence, and a limited range of weak turbulent mixing. The inferred initial lithium abundance of these stars is merely 30 % lower than the primordial abundance, discrepant at 1.5 standard deviations. Hence, a stellar solution to the cosmological lithium problem is still within reach.

Syftet med denna kvalitativa undersökning var att ta reda på hur barn förklarar att det blir natt. En intervjustudie gjordes med 21 skolbarn i år tre. Barnens svar kategoriserades enligt två olika svarsmodeller, tidigare utarbetade av Baxter och Brewer. Analysen av resultaten visade att barnens svar kunde tolkas olika beroende på vilken modell som användes. Även undersökningsmetoden visade sig vara avgörande för de svar vi fick. Vår undersökning gjordes ur ett sociokulturellt perspektiv där språkets nyanser och användandet av artefakter som tankeredskap legat till grund för resultaten och vår tolkning. Det visade sig att flera barn hade en vetenskaplig bild av fenomenet men saknade begrepp för att synliggöra detta. Dessa barn kunde med hjälp av papper, pennor och sitt kroppsspråk förtydliga sina tankar.

Küçüközer, Hüseyin (Balikesir Author), Bu çalışmanın amacı, astronominin bazı temel kavramlarına yönelik İlköğretim Matematik Öğretmenliği 2. sınıf öğrencilerinin öğretim öncesi ve sonrası fikirlerinin ne olduğu ve yapılan öğretimin kavramsal değişime etkisini belirlemektir. Astronomi eğitimine verilen önemin artması ile bu alanda yapılan çalışma sayısında artış olmuştur. Hem yurt içinde hem de yurt dışında öğretmen adaylarının astronomi kavramlarını ortaya çıkarmaya yönelik çok sayıda çalışma yapılmıştır. Verileri elde etmek için, literatür destekli olarak hazırlanan 31 soruluk çoktan seçmeli bir test geliştirilmiştir. Anket 3 fizik eğitimcisi tarafından gözden geçirildikten sonra 55 Fen Bilgisi öğretmen adayı ile yapılan güvenirlik çalışmasında $\alpha$=0.61 elde edilmiştir. Öğretim öncesi 78 İlköğretim Matematik öğretmen adayına bu anket uygulanmıştır. 10 haftalık öğretimin ardından aynı örnekleme anket tekrar uygulanmıştır. Ön-test ve son-test sonuçları arasında son-test lehine anlamlı bir fark bulunmuştur. Kavramsal değişim açısından yapılan öğretimin etkili olduğu sonucuna ulaşılmıştır., The purpose of this study is to reveal the ratio of misconceptions pre-service mathematics teachers have about astronomy before and after instruction and to determine the conceptual change rate. With the increased importance given to astronomy education, the number of studies in this field has increased. In Turkey and abroad, a large number of studies have aimed at revealing the astronomy concepts pre-service teachers have. In this study, a literature-aided multiple-choice test of 31 questions has been developed. After the revision of the survey by 3 physics experts, reliability studies have been done with 55 pre-service science teachers, and $\alpha$=0.61 has been obtained. This questionnaire was applied to 78 pre-service mathematics teachers before the instruction. After a 10- week instruction, the questionnaire was carried out again with the same subjects. A significant difference has been found between the results of pre and post-tests of four sections and the general questionnaire. It can be said that instruction has lead to a conceptual change.

Optical lucky imaging polarimetry of HL Tau and XZ Tau in the Taurus-Auriga molecular cloud was carried out with the instrument PolCor at the Nordic Optical Telescope (NOT). The results show that in both the V- and R-band HL Tau show centrosymmetric structures of the polarization angle in its northeastern outflow lobe (degree of polarization ~30%). A C-shaped structure is detected which is also present at near-IR wavelengths (Murakawa, 2008), and higher resolution optical images (Stapelfeldt, 1995). The position angle of the outflow is 47.5+-7.5 degrees, which coincides with previous measurements and the core polarization is observed to decrease with wavelength and a few scenarios are reviewed. Measuring the outflow witdh versus distance and wavelength shows that the longer wavelengths scatter deeper within the cavity wall of the outflow. In XZ Tau the binary is partially resolved, it is indicated by an elongated intensity distribution. The polarization of the parental cloud is detected in XZ Tau through the dichroic extinction of starlight. Lucky imaging at the NOT is a great way of increasing the resolution, shifting increases the sharpness by 0.1 asec and selection the sharpest frames can increase the seeing with 0.4 asec, perhaps more during better conditions.

Menneskets syn på universet blev ændret for bestandigt, da Galilei for 400 år sidenrettede en kikkert mod himlen. Siden da har udviklingen af kikkerten og andre astronomiske instrumenter til stadighed flyttet grænsen for vores erkendelse.

Jag har tillverkat ett undervisningsmaterial, i form av en serietidning, som riktar sig mot elever i grundskolans tidigare år och i detta arbete utvärderas undervisningsmaterialet. Med syfte att utvärdera undervisningsmaterialet kartlades elevernas förkunskaper med hjälp av ett frågeformulär innan de fick tillgång till serietidningen. Då eleverna haft tillgång till serietidningen i 12 skoldagar gjordes en eftermätning, med samma frågeformulär som använts vid förmätningen, för att se om eleverna tagit till sig det budskap som materialet vill förmedla. Resultatet visade att alla elever utom 2 presterade bättre på eftermätningen än på förmätningen. På alla frågor utom 3 var det fler elever som svarade korrekt vid eftermätningen än det var vid förmätningen. Att alla elever utom två förbättrade sitt resultat efter att ha haft tillgång till serietidningen tyder på att eleverna har tagit till sig undervisningsmaterialets budskap och att utvärderingen av elevernas kunskaper visar det.

There are over 300 exoplanets detected through radial velocity surveys and photometric studies showing a tremendous variety of masses, compositions and orbital parameters. Understanding the way these planets formed and evolved within the circumstellar disks they were initially embedded in is a crucial issue. In the first part of this thesis we study the physical interaction between a gaseous protoplanetary disk and an embedded planet using numerical simulations. In order to trust the results from simulations it is important to compare different methods. However, the standard test problems for hydrodynamic codes differ considerably from the case of a protoplanetary disk interacting with an embedded planet. We have carried out a code comparison in which the problem of a massive planet in a protoplanetary disk was studied with various numerical schemes. We compare the surface density, potential vorticity and azimuthally averaged density profiles at several times. There is overall good agreement between our codes for Neptune and Jupiter-sized planets. We performed simulations for each planet in an inviscid disk and including physical viscosity. The surface density profiles agree within about 5% for the grid-based schemes while the particle codes have less resolution in the low density regions and weaker spiral wakes. In Paper II, we study hydrodynamical instabilities in disks with planets. Vortices are generated close to the gap in our numerical models in agreement with the linear modal analysis. The vortices exert strong perturbations on the planet as they move along the gap and can change its migration rate. In addition, disk viscosity can be modified by the presence of vortices. The last part of this thesis studies the mass transfer in symbiotic binaries and close T Tauri binary systems. Our simulations of gravitationally focused wind accretion in binary systems show the formation of stream flows and enhanced accretion rates onto the compact component.

Barns föreställningar kring naturens olika fenomen är många. Ett fenomen som alla barn upplever varje dag är övergången från dag till natt och tvärtom. För att kunna ge barn förklaringar om hur saker och ting sker och hänger samman, är det viktigt att lyssna på deras föreställningar för att sedan bygga vidare på dessa. För att ta reda på barns föreställningar kring fenomenet dag och natt, har enskilda semistrukturerade intervjuer genomförts med elever i årskurs tre. Resultaten visar att eleverna hade förståelse för att solen, månen, jorden och andra planeter är i ständig rotation. Hur dessa objekt roterar ute i rymden varierade i svaren hos eleverna. Slutsatsen av detta arbete blir att elevernas föreställningar kring fenomenet dag och natt kan kopplas samman med de vetenskapliga förklaringarna samt att de hade förståelse för att olika objekt i rymden ständigt roterar på olika sätt. Children's conceptions are several about different natural phenomenon. One phenomenon that every child comes in contact with every day is the transition from day to night and vice versa. To be able to give children explanations about thing that happens and how they are connected to each other, it is important to listen to what conceptions they have and then explain on the basis from their conceptions. Individual semi constructed interviews have been made with pupils in 3rd grade to find out what conceptions they have. The results show that the pupils were certain that the sun, the moon, the earth and other planets are rotating out in space varied. The conclusion of this work is that the pupils conceptions about the phenomenon day and night can be connected with the scientific explanations and that they also had understanding about how different objects are rotating in space.

In this work, the long-term evolution of globulettes, low-mass globules found in H II regions, is studied through numerical hydrodynamic simulations. It has been proposed by Gahm et al. (2007) that these clouds may form free-floating planetary mass objects due to shock compression, caused by heating from the intense UV radiation of the central OB star cluster. To address this possibility, lifetimes are calculated for three different 3D simulated cases, similar to globulettes found in the Rosette Nebula. A plane-parallel approximation of the radiation field is used, as well as an inhomogeneous initial density distribution. The ionizing radiation will cause the globulettes to photo-evaporate, creating a rocket acceleration effect from the mass ejected on the heated side of the cloud. For a typical globulette with an initial mass of 29.5 Jupiter masses a lifetime of 50 000 yrs is estimated. This estimate is compared to the analytical models of Mellema et al. (1998) and Bertoldi and McKee (1990) which suggest longer lifetimes; the discrepancy is attributed to fragmentation of the clouds in the numerical simulation, which is not adequately described by the models. Synthesized H-alpha images and lightcurves are presented, indicating that the bright rims of small clouds are only likely to be visible in dim parts of the Rosette Nebula. The morphology of simulated clouds generally agrees with observations. While the code does not include self-gravity, the gravitational stability of the clouds is studied indirectly. It is concluded that clouds in the planetary mass range are stable against gravitational collapse, from supporting thermal pressure alone, when in pressure equilibrium with the heated ionization front. However, gravity may play a significant role during the initial shock compression.

This thesis presents a brief review of gravitation and cosmology, and then gives an overview of the theory of cosmological perturbations; subsequently some applications are discussed, such as large-scale structure formation. Cosmological perturbations are here presented both in the Newtonian paradigm and in two di¤erent relativistic approaches. The relativistic approaches are (i) the metric approach, where small variations of the metric tensor are considered, and (ii) the covariant approach, which focusses on small variations of the curvature. Dealing with these two approaches also involves addressing the gauge problem –how to map an idealized world model into a more accurate world model.

The information about the chemical compositions of stars is encoded in their spectra. Accurate determinations of these compositions are crucial for our understanding of stellar nucleosynthesis and Galactic chemical evolution. The determination of elemental abundances in stars requires models for the stellar atmospheres and the processes of line formation. Nearly all spectroscopic analyses of late-type stars carried out today are based on one-dimensional (1D), hydrostatic model atmospheres and on the assumption of local thermodynamic equilibrium (LTE). This approach can lead to large systematic errors in the predicted stellar atmospheric structures and line-strengths, and, hence, in the derived stellar abundances. In this thesis, examples of departures from LTE and from hydrostatic equilibrium are explored. The effects of background line opacities (line-blocking) due to atomic lines on the statistical equilibrium of Fe are investigated in late-type stars. Accounting for this line opacity is important at solar metallicity, where line-blocking significantly reduces the rates of radiatively induced ionizations of Fe. On the contrary, the effects of line-blocking in metal-poor stars are insignificant. In metal-poor stars, the dominant uncertainty in the statistical equilibrium of Fe is the treatment of inelastic H+Fe collisions. Substantial departures of Fe abundances from LTE are found at low metallicities: about 0.3 dex with efficient H+Fe collisions and about 0.5 dex without. The impact of three-dimensional (3D) hydrodynamical model atmospheres on line formation in red giant stars is also investigated. Inhomogeneities and correlated velocity fields in 3D models and differences between the mean 3D stratifications and corresponding 1D model atmospheres can significantly affect the predicted line strengths and derived abundances, in particular at very low metallicities. In LTE, the differences between 3D and 1D abundances of C, N, and O derived from CH, NH, and OH weak low-excitation lines are in the range -0.5 dex to -1.0 dex at [Fe/H]=-3. Large negative corrections (about -0.8 dex) are also found in LTE for weak low-excitation neutral Fe lines. We also investigate the impact of 3D hydrodynamical model stellar atmospheres on the determination of elemental abundances in the carbon-rich, hyper iron-poor stars HE 0107-5240 and HE 1327-2326. The lower temperatures of the line-forming regions of the 3D models compared with 1D models cause changes in the predicted spectral line strengths. In particular we find the 3D abundances of C, N, and O to be lower by about -0.8 dex (or more) than estimated from a 1D analysis. The 3D abundance of Fe is decreased but only by -0.2 dex. Departures from LTE for Fe might actually be very large for these stars and dominate over the effects due to granulation.

More than 200 exoplanets have been found to this day, and the quest continues. The work behind this master thesis in Space Engineering at Luleå University of Technology was conducted at the Uppsala Astronomical Observatory. The purpose was to inspect if the Westerlund Telescope could be used for extra-solar planetary transit searches by photometry. Observations were made during two nights in the fall of 2005 with the 90-cm cassegrain telescope. The centre point of the observed field had coordinates RA 20h 51min 20s, Dec 36º 52’ 32’’. No exoplanets were found, but detection of a 1% dimming in the light intensity was confirmed. Six variable stars were mapped and periods were calculated for four of these. A total of 32 interesting light-curves were kept for further investigation, tentatively by another Master of Science student. Validerat; 20101217 (root)

Syftet med detta examensarbete är att ta reda på hur elevers uppfattningar om de rörelser som sker i vårt solsystem stämmer överens med de vetenskapliga fakta som finns. I våra vardagliga situationer refererar vi till det vi med ögats hjälp kan uppfatta i fråga om vad som rör sig eller ej. Hur påverkas eleverna av de dagliga uttryck som de får höra sedan de är mycket små, och har de en möjlighet att med skolans hjälp förändra dessa tankesätt? Undersökningen genomfördes med hjälp av kvalitativa intervjuer av elever i skolår 1 respektive 5. Detta för att se hur stor skillnaden är mellan de elever som inte har erhållit någon undervisning om solsystemet och de elever som ska ha uppnått de mål för fysik som skolverket har ställt upp. Eleverna som deltog i studien valdes slumpmässigt ur respektive klasser. De fick besvara 14 frågor, var och en för sig. De besvarade frågorna olika utförligt, vissa var mycket fåordiga. Ibland var jag tvungen att ställa följdfrågor, eftersom jag ville förstå eleverna på ett bra sätt. Resultatet av undersökningen visar att elevernas kunskaper inom området har en stor variation, även inom samma åldrar. Detta kan härledas till elevernas eget intresse av vårt solsystem. Den slutsats som jag har dragit av undersökningen är att det är viktigt att ta reda på vilka föreställningar som eleverna har inför arbetet med arbetsområdet. The purpose of this degree project is to find pupils´ understanding about the movements which occur in our solar system and compare them with the scientific facts we know about. In our daily life we refer to what we can see with the help from our eyes whether something moves or not. How do the pupils´ get affected by these daily expressions they hear from early ages, and do they have an opportunity with the help from the school to change these ways of thinking? The survey was carried out with help of qualitative interviews of pupils´ in class 1 and 5. This because to see how large the difference is between pupils´ who hasn’t received any education about the solar system and the pupils´ who are supposed to have reached the goals compiled by The National Agency for Education. The pupils´ who took part in this study were chosen by random from both classes. They answered to 14 questions, each and everyone on their own. They answered the questions with various details, some were very taciturn. Sometimes I had to ask resulting questions, since I wanted to understand the pupils´ properly. The result of the survey shows that the pupils´ knowledge within the area have a large variation, even within the same ages. This can be deduced to the interest of the pupils´ in our solar system. The conclusion I have maid from this survey are that it is important to find out which understandings the pupils´ have before the work with the subject area.

Amatör astronomi, mühendislik ve temel bilimler ve sosyal bilimler gibi çok farklı alanlarla ile doğrudan ilişkili olduğundan her yaştan, her meslekten insanların hayat boyu zevkle uğraşabilecekleri bir hobidir. Genelde amatör astronomi ile ilgilenmeye başlayan insanlar bilgi açıklarını çok hızlı bir şekilde kapatma ihtiyacı duyarlar. Bu noktada, doğru bir başlangıç yapmak, hayal kırıklığına uğramaları en aza indirmek açısından çok önemlidir. Bu bildiride, kurulu amaçlanan biri amatör astronomiyi halka sevdirmek ve yaymak olan Ali Kuşçu Amatör Astronomi Topluluğunun yaptığı aktivitelerden edindiği deneyimler anlatacaktır. Ayrıca topluluğun, astronominin önemli bir kolu olan astronomi fotoğrafçılığı konusunda yaptığı çalışmalar verilecektir. Bu bildirinin amaçlarından biri de, ister gözlem isterse astronomi fotoğrafçılığı konusunda olsun astronomiden beklentilerin fazla masraflara girilmeden de karşılanabileceğini ve bundan da zevk alınabileceğini göstermektir. Amateur Astronomy is a nice hobby for everyone. It is related to many branches of science such as engineering, social and fundamental sciences. Generally, first of all the person who is interested in Amateur Astronomy needs many useful information about it. The most important thing is to start in a right way. Ali Kuşçu Amateur Astronomy club was built for this requirement. The aim of our club is to help someone to love astronomy and start astronomy rightly. This paper consists of a guide for beginners and describes how to use a camera in astronomy. It is called astrophotography. This paper tells our experiences about astrophotography and shows you our photos. You can take some ideas from them. One of the aims of this paper is to show people right way to start astronomy and whatever their finance condition are, they can meet their requirements and learn Astronomy and be happy. First of all, look to the sky, see Milky Way, be happy, be curious to learn more information about astronomy.

Adım Yenal Öğmen. Matematik ve Bilgisayar öğretmeniyim. Central Lancashire Üniversitesinden (Preston /İngiltere) Astronomi alanında üniversite sertifikası sahibiyim. Astronomical League topluluğu üyesiyim. Dört yıldır Meade ETX125 teleskobuyla gözlem yapmaktayım. Bugüne kadar yaptığım Ay ve çift yıldız gözlemleriyle Astronomical Legue Lunar Clup ve Double Star Clup ve Double Star Clup sertifikalarını aldım. Şu an Messier Clup sertifikası için Messier çizimlerini gözlemlemekteyim. Aynı zamanda ALPO için Ayda ’ki parlak ışın gözlemleri AAVSO için ise değişen yıldız gözlemleri yapmaktayım. Haftada genellikle üç gece gözleme çıkmaktayım. Gözlem yerim evimin bahçesine yaptırdığım GREEN ISLAND gözlem evidir. Gözlemevi yapma düşüncesi esas olarak teleskop ve gerekli malzemelerin her gözlem için yeniden gözlem yerine taşınması zorunluluğunun yarattığı sorunlardan ortaya çıkmıştır. Yapımına Temmuz 2004’te başlanan ve Şubat 2005’te biten gözlem evi Kuzey Kıbrıs’ın Geçit kale köyünde bulunmaktadır. Gözlemevi beton bloktan yapılmış silindirik duvar üzerine oturtulmuş ahşap kubbeden oluşmaktadır. U-kirişinden yapılmış ray üzerine oturmakta olan kubbe el yardımı ile hareket etmektedir. İleride daha büyük çaplı bir teleskop ve CCD kamerayla sahip olmayı planlıyorum. Sabit ayak üzerine oturtmayı düşündüğüm bu teleskopun hareketlerimden kaynaklanacak ufak titreşimlerden etkilenmemesi için zeminin ortasında zeminden izole edilmiş beton kısıma dört parça cıvata gömülmüştür. Astronomi alanında daha ileri üniversite sertifikaları için eğitim almak ve gözlem tecrübemi artırarak astronomiye katkıda bulunacak gözlemler yapmak gelecekle ilgili planlarım arsındadır. My name is Yenal Ögmen. I'm a teacher of Mathematics and Computer. I own a University Certificate in Astronomy in the University of Central Lancashire, Preston, UK. I'm a member of Astronomical League. I've been doing observations for four years with Meade ETX125 telescope. Up to now, I've taken Astronomical League Lunar Club and Double Star Club certificates by doing Moon and Double Star observations. Currently I'm observing Messier objects for the Messier Club certificate. At the same time, I'm observing Bright Lunar Rays for ALPO and Variable stars for AAVSO. I do observations about three nights a week. My observation site is the observatory I've built in my house's backyard, Green Island Observatory. The need for building the observatory has risen due to the difficulties faced with when carrying all the stuff each time needed for the observation. The observatory, which was built between the July 2004 and February 2005, is situated in Geçitkale, Northern Cyprus. The observatory is formed from cylindrical concrete walls and a wooden dome situated on its top. The dome, which is mounted on a U-joist ray, is moved manually. I'm planning to have a bigger aperture telescope and a CCD camera. In order to prevent the small vibrations caused by my movements while observing, j-bolts are fixed in an isolated concrete part in the centre of the floor. The telescope will be mounted on a pier, which will be set on j-bolts. My future plans are, to get more educated by having the advanced university certificates in Astronomy and to develop observational experiences and to do observations to contribute the Astronomy.

NASA'nın Goddard Uzay Uçuş Merkezi'nce, her gün astronomiyle ilgili yeni bir fotoğrafın ve bilimsel açıklamasının yayımlandığı popüler bir internet sitesi bulunmaktadır. Bu sitede 16 Haziran 1995'ten beri 3600’den fazla görüntü yayımlandı ve giderek daha çok dilde yayımlanan internet aynaları ile astronomi meraklarına sunulmaya devam ediyor. Bu sunuşta, sitede ne konularda fotoğraf yayımlandığı, aday fotoğrafları göndermek için ne tür bir başvuru yapılması gerektiği ile bilgiler ve çoğunluğu yazanın yayımlanan fotoğraflanandan oluşan bazı örnekler veriliyor. Fotoğraf göndermek isteyenler için bu görüntülerin sitede yayınlanma durumları ile ilgili bilgi veriliyor. Sitenin, yayınlanan fotoğrafları yazarlarına olan manevi ve maddi katkılarının yanı sıra Türkiye'nin tanıtımına yaptığı katkılar da unutulmamalı. Son olarak, yakın gelecekte NASA Günün Astronomi Resmi sitesinde yayımlanmaya aday ilginç gök olaylarının bir listesi de meraklılar için çıkarıldı. APOD is a popular internet site that features a different astronomic image along with a brief explanation. The site is run by NASA's Goddard Space Flight Center since 16'h June 1995. These pictures make the largest collection of annotated astronomical images on the internet. More than 3600 pictures can be viewed in different languages with the help of a number of mirror sites. In this presentation, information such as what sorts of pictures the site features, how should one submit pictures for the site. Some example images are shown, many of which are taken by the author. The contribution of Turkish photographers and pictures taken in Turkey are mentioned, for the sake of photographers' and Turkey's recognition alike. Finally, a list of some interesting celestial evens that can be featured in NASA APOD site is given.

Biz bu çalışmada, bir Türkçe sözlükteki astronomi ve uzay ile ilgili kelime ve terimleri söz konusu edeceğiz. Çalışmamızda örneklem olarak alınan Türkçe sözlükteki Türkçe kökenli astronomi sözcükleri, analitik bir incelemeye tabi tutulmuştur. Bu incelemede tespit edilen kelimeler tasnif edilmiştir. Tasnif evrenle ilgili, gök cisimleri ile ilgili, astronomik olaylarla ilgili Türklere özgü duyuş, yaklaşım ve algılamaları ortaya çıkarmayı amaçlamıştır. At this study, we will evaluate the word of the astronomy and space in a Turkish dictionary. This study, it was evaluated Turkish originated word in a Turkish dictionary as a sample. Firstly this Turkish words was classfied. Hence it was pointed out that to exist about Turkish approaching and thinking on universe.

Ünlü Stonehenge veya Camac'dan, tapestrilere (Bayeux), arma sembollerine, güneş saatlerine, eski gözlemevleri ve elyazmalarına kadar tüm dünyada astronomik kültürün kanıtları vardır. Hepsi, evren ve gökyüzü hakkında yüzyıllar boyu birikmiş bilgiyi; ta, tahta, seramik, metal veya kag1t eklinde korumuştur. Bütün dünyaya yayılmışlardır. Bazen iyi kataloglamış, araştırılmış ve korunmuşlardır. Yine de nadiren çok az bilinirler ve çok kötü korunmuş hatta yok olmak üzeredirler. Belli bir epoktan bir güne saatinin nerede olduğunu bulmak isteyebilirsiniz ancak nasıl bilmezsiniz. Bazı olayların ilk kez ne zaman kaydedildiğini bilmek isteyebilirsiniz ve bu çaba için araştırmalar zordur. Astronomik amaçlar için de kullanılmış bir tapınağın restorasyonuna destek vermek isteyebilirsiniz ve böyle bir operasyonun gerektirdiği bazen çok yüksek masraflar karşılayacak yeterli kanıtımız yoktur. Tüm bu bilginin içerisinde toplanacağı bir veri bankası, uluslararası boyutta bir elektronik kütüphane; araştırmayı kolaylaştırmak ve bu gezegendeki uygarlığın hazinelerini oluşturan sanat, bilim ve tarih anıtlarının korunmasına destek vermek için en doğru ey olacaktır. İşte bunlar kısaca, "Arkeoastronomik Miras" adında yeni bir çalıma grubunun oluşturulmasının sebebi. (http://www.archeoastronomy.org/) Bu zengin mirası tanımlamak ve korumak isteyen herkes bu etkinliğe katılmaya davetlidir. In the entire world there are proofs of astronomical culture, from the famous Stonehenge or Camac, up to tapestries (Bayeux), heraldic symbols, sundials, old observatories or manuscripts. All of them preserve in stone, wood, ceramics, metal or paper the knowledge gathered throughout the centuries concerning the sky, the cosmos. They are spread all over the world. Sometimes they are well catalogued, researched or preserved. Nevertheless, very often they are very little known and very badly preserved, sometimes about to disappear. You want to find out where there is a sundial from a certain epoch and you do not know how. You want to know when some phenomena were recorded for the first time and researches to this effect are difficult. You want to support the restoration of a sanctuary, also used for astronomical purposes, and you do not have enough proofs to motivate the sometimes very high expenses required by such an operation. A data bank in which all this information should be gathered, an electronic library of international size, would be the exact thing to facilitate research, to support the conservation of the art, science and history monuments, which together make up the thesaurus of civilization on this planet. This is shortly the reason why a new working group "The Archaeoastronomical Heritage" (http://www.archeoastronomy.org/) was set up. Everyone interested in identifying and preserving this rich heritage is invited to contribute to its activity.

Tübitak Ulusal Gözlemevi (TUG), TÜBİTAK bünyesinde yer alan, Enstitü statüsünde bir AR-GE kolaylık birimidir. Ana görevi, Üniversitelerimizde yürütülen gözleme dayalı bilimsel araştırmalar için teleskop desteği sağlamaktadır. Bugün, bu destek gözlemevindeki dört teleskop ile verilmektedir. Gözlemsel destek için gerekli donanımların çalışır olmasını sağlamak, bakım ve onarımları yapmak, geliştirmek ve güncel kalmasını sağlamak ana görevin gerekliliklerindendir. Ulusal ve uluslararası araştırma merkezleri ile işbirliği yapan TUG, öğrencilere ve halka yönelik gözlemsel astronomide eğitim programları ve etkinlikler düzenlemek gibi önemli görevler de üstlenmiştir. Konferanslar, seminerler, Astronomi ve gözlem enlikleri, eğitim programları, ışık kirliliği konusunda çalışmalar yapmakta, ulusal düzeyde toplantılar düzenlemekte, bilgi ve donanım desteği vermektedir. TUG' un kısıtlı kadrosu, yoğun idari, teknik ve sosyal ileri arasında bu konulara da özellikle zaman ayırmaktadır. TüBiTAK National Observatory is an institute of the Scientific and Technical Research Counsil of Turkey. Its main mission is to provide telescope time for observational projects from he universities. Today, this support is given with four telescopes. TUG is also charged to run and maintain all the facilities at the observatory. TUG, in cooperation with national and international institutes and research centers, undertakes to organize edFA0150 ucational and observational activities for the students, the public and the amateurs. The other duities of TUG are to arrange conferences, seminars and star parties and to organize various meetings or workshops, together with technical equipments and knowhow.

Astronomi insanlar tarafından bilinen en eski bilim dallarından biridir. Astroarkeoloji ise, antik yapılar üzerinde çalışır ve bunları Güneş'e, Ay'a ve yıldızlara göre nasıl konumlandırılmış olduklarını yorumlar. Ancak bunu yaparken de jeodezi ve mitolojiden de faydalanır. Çünkü eski uygarlıklar doğayı tanrılarla özdeştirmiştir ve doğa olaylarını, bunlar üzerine kurarak kanıtlamışlardır. Dünya' da bilinen önemli astroarkeolojik alanlar ise şöyledir: Piramit ve kuleler: Caracol, Chitchen Itza, Meksika Yer izleri: Nazca, Peru Megalitik alanlar: Stonehenge, Carnac, Newgrange Astroarkeoloji'nin en büyük özelliği, eski uygarlıkların yaptıkları gözlemler sayesinde geçmişte uzayda meydana gelen değişimlerden haberdar olunmasıdır. Bu sebepledir ki, 1960 yılından beri bu alan hızla geliştirilmektedir. Ülkemizde de pek çok Astroarkeolojik alan vardır. Ancak bunların çoğu gerekli önemi görmemektedir. Bazıları ise yok olmanın eşiğine gelmiştir. Ülkemizdeki alanlardan bazıları ise Şöyledir: Van-Kalecik’teki Urartu kalıntıları Nemrut Dağı’ndaki Kommagene Krallığı'nın kalıntıları Astronomy was one of the ancient part of the science known by humanbeing. On the otherhand Astroarcheology is working on the ancient construction & structure and explain the their situations & locations against to the Sun and the Moon. Besides, it benefits from the guidance of the geodesy and mythology while doing this. Because the Ancient Civilizations have equated the Nature with the God and have explained the nature events by considering on that acceptance. The most important astroarcheology areas on the earth are listed below: Pyramids and Towers: Caracol, Chitchen Itza, Mexico Ground Trace: Nazca, Peru Megalytic Area: Stonehenge, Carnac, Newgrange The Major Characteristic of Astroarcheology is that becuase of the Ancient Civilization's Valuable Observations, easly able to be informed about the occured changes in the Space. Therefore, Astroarcheology has rapidly been develop since 1960. There are too many Astroarcheological area in Turkey but most of them has been kept with extreme carelessness. Some of the astroarcheological areas on our land: Urartu Heritage in Van-Kalecik The Heritage of the Kommage Kingdom in Nemrut Dağı

Kullanıcısının yazılımı çalıştırma, yazılımın yapısını anlama ve ihtiyaçlarına uydurma, kopyalarını dağıtma, geliştirme ve geliştirdiği bölümlerini diğer kullanıcıların kullanılımına sunma haklarına sahip olduğu yazılımlar olan özgür yazılımlar herhangi bir işletim sistemi üzerine çalışmak üzere yazılabilir. Bir yazılımın özgür yazılım olabilmesi için sağlaması gereken bu koşullar, yazılımın kaynak kodlarının kullanıcısına açık olmasını gerektirir. Bu çalışma, özellikle son yıllarda sayıları artan astronomi ile ilgili açık kaynak kodlu, özgür yazılımlardan Linux ve Unix işletim sistemleri üzerinde çalışanları sınıflandırmak, yazılımları objektif olarak değerlendirmek üzere kriterler koymak, amatör astronomiye yönelik olarak hazırlanmış popüler özgür yazılımlar seçerek bu yazılımları koyulan değerlendirme kriterleri çerçevesinde değerlendirmek ve sonuçlarını paylaşmak amacmındadır. Sınıflandırılan ve incelemesi yapılan yazılımların seçimi için ayrı kriterler saptanmış ve tartışılmıştır. Free sofware is that whose users have freedom to run it, to study how it Works and adapt it to his/her needs, to redistribute its copies, to improve it and share the improvements with public. Hence, the source code of such a software have to be open to public by definition. This study aims to classify the free astronomy softwares programmed to be run on computers with Linux or Unix operating systems, to define quantitatve rating criteria for such software, to analyze them according to the rating criteia defined and share the results of cuch an analysis. The criteia for classification and selection of the softwares were defined and discussed seperately.

Hayatının son yılına kadar Janet ile tanışmamış olsam da, hemen iyi arkadaş olduk; astronomi aşkı kadar çok olmasa da nerdeyse ona eşit çiçek tutkusu. David ona bizim gözlemevimizi gösterdiği zaman, çöl evimizdeki doğal çiçeklerin çeşitliliği takdir etmek için her duruşunda hayretini paylaştım. Birgün çiçekler ve evren aşkını ilişkilendiren bir proje yapma istediğini anlattı. Janet’in onuruna, atomların ve doğanın karşımıza çıkardığı ilginç tesadüflere bir bakmayı öneriyorum: Yer’deki bir karahindiba ve gökyüzündeki Akrep takım yıldızı; bize Messier 80 deki bir uzun süreli novayı hatırlatan ve sadece bir günlüğüne açan bir çiçek; uzak galaksilerin bazı geniş yapılarını taklit eden diğer küçük çiçek tasarımları. Although I didn’t meet Janet until the last year of her life, we immediately became good friends-not so much for her love of astronomy but for her almost equal passion for flowers. As David showed her our observatory complex, I shared her amazement as she stoped over and over again to admire the diversity of natural flowers in our desert home, and she told me of her interest in doing a Project-some day-relating her two loves of flowers and the universe. In her honor, I offer a look at the amazing coincidences that atoms and Nature can come up with- a dandelion on Earth and Scorpius in the sky, a flower blooming for only a day to remind us of long-gone nova in Messier 80, and other tiny flower designs that mimic some of the vast structures of distant galaxies.

A number of dwarf irregular galaxies have been selected in the three most nearby groups of galaxies: the M81, Centaurus A, and Sculptor groups. The final objective is to establish whether there is a relationship between the luminosity and the fraction of oxygen contained in dwarf irregular galaxies and for that homogeneous oxygen abundances and near-IR luminosities are being collected. By comparison of observations from different groups at considerably different interaction rates we are hoping to clear up the debated luminosity-metallicity assumption for the case of dwarf irregular galaxies. We have reduced, measured and analysed optical spectra of HII regions of five dwarf irregular galaxies in the Sculptor group. Fluxes are measured and corrected from reddening and electron temperatures and homogeneous chemical abundances are obtained. The oxygen abundances normalised to hydrogen are estimated with calculations that ranges between 2×10-5 and 33×10-5. The empirical method based on R23 is also applied. We are now presenting the results for the Sculptor group. Validerat; 20101217 (root)

We are made of stardust in the sense that most atomic nuclei around us have been formed by stars. Stars synthesise new elements and expel them to the interstellar medium, from which later new generations of stars are born. We can map this chemical evolution by analysing the atmospheric contents of old Galactic halo stars. I have done two such investigations. A vigourous debate is going on whether the oxygen-to-iron ratio varies strongly with the general metal-content of halo stars. In my first study, I made an abundance analysis of 43 halo stars, and found no support for such a variation. I have also found that there probably is a cosmic spread in the abundances of oxygen, magnesium, silicon, and calcium relative to iron for halo stars. This may be an indication that the halo was built up by subsystems with differences in the star formation rate. In my second study, I performed a thorough abundance analysis of the star HE0338-3945, which is strangely overabundant in both r- and s-elements. Several other stars have been found with abundance patterns curiously similar to this star, and I define new criteria for the class r+s stars. The abundance similarities among the r+s stars suggest a common formation scenario. However, as the s-elements usually are considered to be produced in binary systems of low mass, and r-elements in supernovae of Type II, this scenario is not obvious. In the article I discuss seven hypotheses, and several of them are dismissed.

Stellar atmospheres constitute excellent environments to study the chemical evolution of our Galaxy. The chemical composition of these atmospheres reflects the composition of the gas from where these stars were born. As the Galaxy evolves, the composition of the gas changes from being primordial (Big-Bang nucleosynthesis) to being enriched in heavy elements (stellar and interstellar nucleosynthesis). The abundances of fragile chemical elements can be affected by stellar mixing processes. Precise lithium, beryllium and oxygen abundance determinations in old stars are presented in this thesis. These determinations are based on the analysis of the observed spectra of a sample of thirteen metal-poor subgiant stars. According to stellar mixing theories, these stars are in a stellar evolutionary stage in which mixing by convection is expected. Abundances of fragile elements like lithium and beryllium are thus expected to be affected by such mixing processes. As a consequence of this, the abundances of these elements are discussed in a dilution context. Lithium and beryllium abundances are compared with the abundances of stars with similar characteristics but in a less evolved stellar phase so that mixing processes have not acted yet. As expected, our abundances seem to be depleted following reasonably well the standard predictions. Stellar abundances of oxygen should give an estimate of the oxygen contribution of core-collapse supernovae to the interstellar medium. However, there is poor agreement among the abundances determined from different atomic or molecular indicators in general. Abundances coming from three different indicators are compared in this thesis. The abundances determined from the O I infrared triplet lines at 777.1-5 nm give the poorest agreement among the three indicators. The abundances based on OH ultraviolet lines around 310 nm are lower for the subgiants in comparison with previous studies of main-sequence stars, becoming even lower than values based on the O I forbidden line at 630.03 nm. Still the most reliable indicator appears to be the O I forbidden line which suggests a plateau-like or only slowly increasing [O/Fe] towards lower [Fe/H]. In addition, the line formation of the Be II ultraviolet resonance lines at 313.0-1 nm, commonly used for abundance determinations purposes, is investigated under non-local thermodynamic equilibrium. We find that the common assumption of local thermodynamic equilibrium typically gives systematic errors of about 0.1 dex.

Most of the matter in the Universe appears to be in some form which does not emit or absorb light. While evidence for the existence of this dark matter has accumulated over the last seventy years, its nature remains elusive. In this thesis, quasars and low surface brightness galaxies (LSBGs) are used to investigate the properties of the dark matter. Quasars are extremely bright light sources which can be seen over vast distances. These cosmic beacons may be used to constrain dark matter in the form of low-mass, compact objects along the line of sight, as such objects are expected to induce brightness fluctuations in quasars through gravitational microlensing effects. Using a numerical microlensing model, we demonstrate that the uncertainty in the typical size of the optical continuum-emitting region in quasars represents the main obstacle in this procedure. We also show that, contrary to claims in the literature, microlensing fails to explain the observed long-term optical variability of quasars. Here, quasar distances are inferred from their redshifts, which are assumed to stem from the expansion of the Universe. Some astronomers do however defend the view that quasar redshifts could have a different origin. A number of potential methods for falsifying claims of such non-cosmological redshifts are proposed. As the ratio of dark to luminous matter is known to be unusually high in LSBGs, these objects have become the prime targets for probing dark matter halos around galaxies. Here, we use spectral evolutionary models to constrain the properties of the stellar populations in a class of unusually blue LSBGs. Using rotation curve data obtained at the ESO Very Large Telescope, we also investigate the density profiles of their dark halos. We find our measurements to be inconsistent with the predictions of the currently favoured cold dark matter scenario.

Chemical evolution addresses the problem of the formation of the chemical elements and their evolution throughout the history of the universe. This thesis discusses in particular the chemical evolution in the young universe and what we may learn from the observations of the oldest stars. The present day production of carbon in the Galaxy is also discussed. Interstellar media of young, metal-poor, star-forming systems are expected to show large chemical abundance inhomogeneities due to local supernova explosions. These inhomogeneities are reflected in the surface abundances of the population of longlived, low-mass stars. A stochastic model of the chemical evolution in such systems is presented and used to study the metallicity distribution and the scatter in chemical abundance ratios. The model takes into account mixing of the enriched material by turbulent motions and cloud collisions in the interstellar medium as well as infall of pristine matter. The predicted metallicity distribution shows, in accordance with observations of extreme Pop II strars in the Galactic halo, a distinct cut-off at [Fe/H]~-4. However, the fraction of stars below [Fe/H]=-4 agrees with observatrion only if a population of metal-free stars (Pop III) was never able to form. The predicted scatter in abundance ratios is demonstrated to be crucially dependent on the as yet uncertain supernova yields and the relatively small star-to-star scatter is tentatively explained by the averaging of a large number of contributing supernovae and by the selection effects favouring contributions from supernovae in a certain mass range for the most metal-poor stars. Furthermore, stars enriched by one single supernova are predicted to be found in very narrow sequences in the abundance ratio diagrams (so called A/A diagrams). Verification of the existence of such features, called single supernova sequences, is observationally challenging. Abundance analysis of carbon was performed in a large sample of solar-type stars in the Galactic disk using the forbidden [C I] line at 8727 Å. A comparison between the relation of [C/O] with metallicity for the Galactic stars and that of dwarf irregular galaxies suggests that large amounts of carbon are produced today by massive, so called Wolf-Rayet stars. Low-mass stars are less important. This was also demonstrated by modelling the chemical evolution of carbon.

When modelling the collapse of massive stars leading to supernova explosions and the cooling of neutron stars, understanding the microphysical processes, such as the interaction of neutrinos within a dense medium are of vital importance. The interaction of neutrinos with nucleons (neutrons and protons) is altered by the presence of the medium, compared to the same process with free nucleons. Neutrino scattering and production processes may be characterized in terms of the excitations that are created or destroyed in the nuclear medium. One way to analyse the effects of the medium is by using Landau's theory of normal Fermi liquids. This theory gives simple relationships between physical quantities such as the spin susceptibility or the response to a weak interaction probe in terms of Landau parameters, that are measures of the interaction between quasiparticles. One problem when using Landau Fermi liquid theory for nucleon matter is that the interaction has a tensor component. The tensor interaction does not conserve the total spin and, as a consequence, there are generally contributions to long-wavelength response functions from states that have more than one quasiparticle-quasihole pair in the intermediate state. Such contributions cannot be calculated in terms of Landau parameters alone, since in the usual formulation of Landau theory, only singlepair excitations are considered. In this thesis three problems are addressed. First, we obtain bounds on the contributions from more than one quasiparticle-quasihole pair by using sum-rule arguments. Second, we derive expressions for static response functions allowing for the tensor components of the interaction. We analyse which the most important effects are on the static response of nucleon matter, and find that the major contributions comes from renormalization of coupling constants and transitions to states with more than one quasiparticle-quasihole pair. Third, we show how contributions to the dynamical response coming from states containing two quasiparticle-quasihole pairs may be evaluated in terms of Landau theory if one allows for the effect of collisions in the Landau kinetic equation. We consider the case of asymmetric nuclear matter, and our work goes beyond earlier works in that they contain the effects of collisions in addition to those of the mean field.

The origin and evolution of the thin and thick disks in the Galaxy have been studied by means of detailed stellar abundances. High-resolution spectra of 102 F and G dwarf stars have been obtained with the spectrographs on the ESO 3.6-m and ESO 1.5-m telescopes on La Silla (Chile), the Very Large Telescope (VLT) on Paranal (Chile), and the Nordic Optical Telescope (NOT) on La Palma (Canary Islands, Spain). Abundances for 14 elements (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, Ba, and Eu) have been determined. The following results were found: 1) Both the thin and the thick disks show distinct and well-defined abundance trends at sub-solar metallicities; 2) The thick disk shows signatures of chemical enrichment from Type Ia Supernovae; 3) [O/Fe] in the thin disk continues to decrease linearly at super-solar metallicities; 4) The abundance trends we see in the thick disk are invariant with distance from the Galactic plane ($Z_{ m max}$) and galactocentric radius ($R_{ m m}$); 4) The thick disk sample is in the mean older than the thin disk sample. The thesis also includes an investigation of ages and metallicities in the thick disk. The results from this study are; 5) There is a possible age-metallicity relation present in the thick disk, 6) Star formation has been ongoing for several billion years in the thick disk. Based on these findings, together with other constraints from the literature, we discuss different formation scenarios for the thick disk. We suggest that the currently most likely formation scenario is a violent merger event or a close encounter between the Galaxy and a companion galaxy. Vår galax, Vintergatan, är en spiralgalax som innehåller bortåt 200 miljarder stjärnor. En mörk natt kan man urskilja ca 3000 av dessa på himlavalvet. Tittar man noggrant så kan man också se ett diffust ljusband som sträcker sig genom, bland andra, stjärnbilderna Skytten och Cassiopeia. Detta diffusa band är det samlade ljuset från alla de miljarder stjärnor i Vintergatans skiva som antingen är för ljussvaga eller för avlägsna för att kunna ses som individuella objekt med blotta ögat. Man kan dela upp Vintergatan i olika komponent: den tunna skivan (thin disk), den tjocka skivan (thick disk), den centrala ansvällningen (bulge), och halon. Egenskaperna hos stjärnorna i dessa olika populationer skiljer sig åt. De äldsta stjärnorna finns i halon och har i många fall daterats till en bra bit över 12 miljarder år. Det som är karaktäristiskt för halostjärnor är att de rör sig med höga hastigheter relativt lokala vilostandarden (local standard of rest, LSR). Deras banor runt Vintergatans centrum är mer eller mindre slumpvisa, vilket också medför att halon som helhet i stort sett inte deltar i den allmänna galaktiska rotationen (som är ca 220 km/s). Halostjärnorna innehåller också mycket lite av tyngre grundämnen såsom järn - man säger att de är metallfattiga (Astronomer använder av hävd ofta beteckningen ``metaller" för alla grundämnen förutom väte och helium). Generellt sett har halostjärnorna järnhalter (relativt vätehalten i stjärnan) som är mindre än 1/10 av vad som finns i solen. Den mest metallfattiga halostjärnan som observerats har en järnhalt som endast är 1/200000 av solens. Den tjocka skivan innehåller också mestadels äldre stjärnor. Det finns dock en betydligt större spridning i åldersfördelningen hos dessa stjärnor och man kan relativt lätt hitta stjärnor vars åldrar inte är mer än 7--8 miljarder år. Andelen av tyngre grundämnen är också högre hos stjärnorna i den tjocka skivan än för halostjärnorna. Metallhaltsfördelningen sträcker sig från ungefär 1/10 av solens järnhalt och upp till solhalten. Stjärnorna i den tjocka skivan rör sig också med relativt höga hastigheter relativt LSR. Detta gör att ``formen" på den tjocka skivan är en ellipsoid med en exponentiell skalhöjd på ungefär 1000--1500 pc. Till skillnad från halostjärnorna deltar den tjocka skivans stjärnor i den galaktiska rotationen. Dock så ``släpar" de efter den allmänna rotationshastigheten i Vintergatsplanet med ungefär 40--50 km/s. Den tunna skivan innehåller mestadels stjärnor som är unga och har betydligt mer tyngre grundämnen än stjärnorna i halon och den tjocka skivan. Deras metallhalter spänner från ungefär 1/10 och upp till ungefär 3 gånger solens metallhalt. Syftet med denna avhandling är att studera hur den tjocka skivan har utvecklats i jämförelse med den tunna skivan och på så sätt söka förklaringar till deras respektive uppkomster. Eftersom den kemiska sammansättningen i atmosfärerna hos sollika stjärnor (s.k. huvudseriestjärnor av F- och G-typ) i stort sett inte har påverkats under de miljarder år som gått sedan de bildades, kan man genom att spektroskopiskt analysera sådana stjärnor bestämma vad deras atmosfärer består av och således vad de gas- och stoftmoln som stjärnan bildades ur bestod av. Detta leder i sin tur till att man kan spåra den kemiska utvecklingen i Vintergatan och dess olika komponenter. Skillnader och likheter i ymnigheterna, av speciellt utvalda grundämnen, mellan de båda stjärnpopulationerna kan då användas för att få en bättre uppfattning om deras respektive uppkomst. Speciellt uppkomsten av den tjocka skivan har många tänkbara förklaringar. Noggranna undersökningar av sollika stjärnor kräver stjärnspektrum med hög upplösning och högt signal/brus-förhållande. För att få observationstid för en sådan undersökning av ett stort antal stjärnor så är det nödvändigt att observationerna kan utföras under en rimlig tidsperiod. Det bästa sättet är då att observera stjärnor som är befinner sig i solens närhet och är relativt ljusstarka. Att de är närbelägna medför vissa problem i urskiljandet av stjärnor tillhörande de två olika skivkomponenterna. Stjärnorna i solens närhet består nämligen av en blandning av stjärnor från den tunna skivan (ungefär 90%), den tjocka skivan (ca 10%), och halon (ca 0.1--0.2%) och det finns ingen definitiv metod för att särskilja dem. Den metod som anammats i denna avhandling är att använda stjärnornas kinematik (hastigheter) då denna torde vara det mest fundamentala som skiljer komponenterna åt. Ytterligare egeneskaper såsom metallhalt och åldrar skulle också kunna användas men eftersom syftet är att studera de kemiska egenskaperna i de två skivorna så skulle sådana urvalskriterier underminera syftet med undersökningen. Utifrån de kinematiska kriterier som beskrivs i kapitel~2 så har vi valt ut och observerat drygt hundra stjärnor vars hastigheter gör att de med stor sannolikhet tillhör antingen den tunna eller den tjocka skivan. Observationerna har utförts vid det Europeiska Sydobservatoriets (European Southern Observatory, ESO) anläggningar på La Silla och Paranal i Chile och vid det Nordiska teleskopet (Nordic Optical Telescope, NOT) på La Palma. Resultaten som presenteras i denna avhandling (artiklar I--VI) angående halttrender av olika grundämnen visar på att det finns tydliga skillnader mellan stjärnor tillhörande den tjocka och den tunna skivan. De skillnader vi ser tyder på att bildandet av stjärnorna i dessa komponenter har skett under skilda epoker. Formen på de halttrender vi ser ger också information om bildandet av de olika komponenterna gått fort eller långsamt. Tecken på en intensiv och snabb stjärnbildning finns i den tjocka skivan, medan stjärnbildningen i den tunna skivan skett i långsammare takt. Våra resultat i artikel~V tyder också på att själva bildandet av stjärnorna i den tjocka skivan fortgick under flera miljarder år, uppskattningsvis 2--3 miljarder. Frågan om varför Vintergatan har två skivkomponenter kan dock inte entydigt förklaras. Våra resultat pekar på att den mest troliga förklaringen till den tjocka skivans uppkomst är en kollision mellan Vintergatan och en annan (antagligen mindre) galax. Som ett resultat av denna kollision så blev det en kinematisk ``upphettning" av en redan existerande stjärnpopulation (antagligen i form av en tunn skiva). Vid kollisionen är det möjligt att Vintergatan även berikades med stjärnor och gas från den andra galaxen. Den kvarvarande gasen kom med tiden att koncentreras mot Vintergatans plan. Ur denna gas började sedan stjärnor åter bildas, och det är dessa som vi idag ser som den tunna skivan.

This thesis is a detailed observational study of the accretion processes in T Tauri stars (TTS). The interaction between the central star, the circumstellar disk and the magnetic field gives rise to a wide range of features in the spectra of TTS. The current picture of TTS is based on rather simple models assuming that accretion is a homogeneous and axisymmetric process. Although these models have been successful in explaining some observational signatures of TTS such as the shape of emission lines, the static nature of these models makes them unsuitable for describing the strong variability of the veiling spectrum and emission lines of TTS. An improved understanding of this variability is of key importance to study the dynamic processes related to the accretion flow and the winds. This study is based on a set of high-quality spectroscopic observations with the UVES spectrograph at the 8-m VLT in 2000 and 2002. These spectra, with exposure times as short as 10-15 minutes, have high spectral resolution and high signal-to-noise ratios and cover a large part of the optical wavelength range. From this dataset we determine the basic physical parameters of several TTS and model their photospheres. These models then serve as a basis for a detailed investigation of variations of the veiling continuum and line emission. We confirm that the level of veiling correlates with some of the strongest emission lines and that coherent changes in accretion occur on a timescale of a few hours, comparable to the free-fall time from the disk to the star. From the properties of the emission lines formed close to the central star and in the stellar wind we derive restrictions on the geometry of the observed systems. Because the intrinsic axial symmetry of a single star makes it almost impossible to disentangle rotational modulation from inhomogeneity and axial asymmetry of the accretion flow, we study a series of spectra of a close spectroscopic binary at different orbital phases and derive the 3D structure of flows between the disk and the star. Finally, we calculate the profiles of hydrogen emission lines by iteratively solving 3D NLTE radiative transfer in a state-of-the-art magnetospheric model.

The properties of Mercury's regolith have been investigated at optical and near-infrared wavelengths with high-resolution imaging, photometric, and spectroscopic observations with the Swedish Vacuum Solar Telescope and the Nordic Optical Telescope. A new global optical map at a spatial resolution of 200 km shows that the well known (from Mariner 10) and poorly known hemispheres are indistinguishable with respect to the distribution, number density, and morphological parameters of bright albedo features. This indicates a globally uniform recent (

Quasars form one of the most energetic phenomena in the universe, and can be traced out to very large redshifts. By studying the galaxies which host the active nuclei, important insights can be gained into the processes that trigger and maintain the quasar powerhouse. The evolution rate of the quasar population is furthermore similar to that of ordinary galaxies, which implies a connection between black hole accretion and star formation in the host galaxies. While the properties of quasar host galaxies at low redshift have become better constrained in recent years, less is known about hosts at earlier cosmic epochs. In addition, though radio-quiet quasars are by far more common than their radio-loud counterparts their host galaxies have not been studied to the same extent, in particular not at higher redshifts. An imaging campaign of a large sample of quasars at intermediate redshift (0.4 < z < 0.8) was carried out at optical wavelengths using the Nordic Optical Telescope, and is studied in this thesis together with two smaller samples. The joint material forms more than half of the total number of observed sources in this redshift interval and increases the number of resolved radio-quiet hosts at z>0.4 considerably. The morphology and mean magnitudes are found to be similar for radio-loud and radio-quiet host galaxies. Both types of host are shown to have optical colours as blue as those of present-day late-type spirals and starburst galaxies, which is likely the result of ongoing star formation. With increasing redshift, observations of host galaxies become more difficult. High spatial resolution can be achieved with adaptive optics, but the variation of the point spread function in the near-infrared wavelength band which is most suited for detection is large and rapid. A statistical approach to the problem of characterizing the point spread function has been developed, making use of simulated objects which are matched to the different atmospheric conditions. Bright, compact host galaxies showing signs of merging and interaction were detected in this way for three quasars at z~2.2, which were observed with the ESO 3.6 m telescope. The method is not restricted to host galaxy analysis but can be utilized in other applications as well, provided that the underlying extended source can be described by an analytical model.

Comets are the most primordial and least evolved bodies in the Solar System. As such, they are unique sources of information regarding the early history of the Solar System. However, little is known about cometary nuclei since they are very difficult to observe due to the obscuring coma. Indirect methods are therefore often used to extract knowledge about nucleus parameters such as size, shape, density, material strength, and rotational properties. For example, tidal and non-tidal splitting of cometary nuclei can provide important information about nuclear densities and material strengths, but only if the criteria for mechanical stability are well known. Masses and densities of cometary nuclei can also be obtained by studying orbital modifications due to non-gravitational forces, but only if the thermophysics of comets can be modelled accurately. A detailed investigation is made regarding the mechanical stability of small Solar System bodies. New expressions for the Roche distance are derived, as functions of the size, shape, density, material strength, rotational period, and spin axis orientation of a body. The critical rotational period for centrifugal breakup in free space is also considered, and the resulting formulae are applied to comets for which the size, shape and rotational period have been estimated observationally, in order to place constraints on their densities and material strengths. A new thermophysical model of cometary nuclei is developed, focusing on two rarely studied features - layer absorption of solar energy, and parallel modelling of the nucleus and innermost coma. Sophisticated modelling of radiative transfer processes and the kinetics of gas in thermodynamic non-equilibrium form the basis for this work. The new model is applied to Comet 19P/Borrelly, and its density is estimated by reproducing the non-gravitational changes of its orbit.

We present an investigation of the magnetic field geometries and inhomogeneous distribution of chemical elements in the atmospheres of peculiar A and B stars. Our study combines high-quality spectroscopic and spectropolarimetric stellar observations with the development and application of novel techniques for theoretical interpretation of the shapes and variability of stellar line profiles. In particular, we extend the method of Doppler imaging to the analysis of spectra in the four Stokes parameters, making it possible to derive detailed and reliable stellar magnetic maps simultaneously with the imaging chemical inhomogeneities. The magnetic Doppler imaging is applied to study of magnetic topologies and distributions of chemical elements in the peculiar stars α2 CVn and 53 Cam. We found that the magnetic field geometry of 53 Cam is considerably more complex than a low-order multipolar topology, commonly assumed for magnetic A and B stars. Our Doppler imaging analysis also led to a discovery and study of spots of enhanced mercury abundance in the atmosphere of α And, a star where the presence of a global magnetic field is unlikely. The ESO 3.6-m telescope is used to collect unique, very high spectral- and time-resolution observations of rapidly oscillating peculiar A (roAp) stars and to reveal line profile variations due to stellar pulsations. We present a detailed characterization of the spectroscopic pulsational behaviour and demonstrate a remarkable diversity of pulsations in different spectral lines. The outstanding variability of the lines of rare-earth elements is used to study propagation of pulsation waves through the stellar atmospheres and identify pulsation modes. This analysis led to a discovery of a non-axisymmetric character of pulsations in roAp stars. Our study of chemical stratification in the atmosphere of the roAp star γ Equ provides a compelling evidence for significant variation of the chemical composition with depth. We find a combined effect of extreme chemical anomalies and a growth of pulsation amplitude in the outermost atmospheric layers to be the most likely origin of the high-amplitude pulsational variations of the lines of rare-earth elements. Observations of cool magnetic CP stars are obtained with the ESO Very Large Telescope and are used for empirical investigation of the anomalies in the atmospheric temperature structure. We show that the core-wing anomaly of the hydrogen Balmer lines observed in some cool CP stars can be attributed to a hot layer at an intermediate atmospheric depth.

A major fraction of stars will pass through a short period of dramatic events in their final evolutionary stage. Low- to intermediate-mass stars, studied here, are stripped of their outer parts in a slow massive wind. This mass loss reshapes both the star and the surrounding medium. The formation of the wind is a consequence of the non-linear interaction of a number of physical processes. Stellar pulsations and efficient dust formation are examples of such key processes. Time-dependent theoretical models, in combination with observations, are useful tools for understanding these winds. The main object of this thesis has been the physical improvement of a theoretical wind model. Here the coupling between the dust and gas in the wind is studied in further detail, allowing drift. The methods that have been developed earlier to describe the micro-physical interaction are overviewed and summarized. Previously dust has often been assumed to move at the same velocity as gas. New time-dependent wind models are presented where grain drift has been treated self-consistently. Specifically, the coupling between dust and gas in the wind has been modeled more realistically, with descriptions of both the modified momentum and energy balances, and drift dependent dust formation. The results of these new ``drift models'' have been compared with the results of non-drift models. A general result of the study is that the effects of drift are significant and difficult to predict if a simple analytical theory is used. It has been found that dust in drift models tends to accumulate in certain dense regions, an accumulation that was not possible without drift. Moreover the new models show an increased variability in the wind structure. The use of drift in dust formation tends to markedly increase the produced dust. Some sets of model parameters lead to a wind without including drift, but a corresponding wind does not form when drift is included -- and vice versa. The effects of drift are important and can probably not be ignored in realistic models.