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Johann Franz Encke
No full textJOHANN FRANZ ENCKE
Johann Franz Encke / Bruhns, Carl (Public Domain) ( - )
Stempel: Geprüft. Keine Beanstandungen. Kommission zur Säuberung der Büchereien. Ort, Datum: 21.11.46. Unterschrift: [...] ( - )
Title page ( - )
Preface ( - )
Contents ([IX])
I. Encke's erste Jugend (1)
II. Encke's Studienzeit (16)
III. Encke als Astronom auf dem Seeberge bei Gotha (37)
a. Encke's Zusammenleben mit Lindenau, seine Arbeiten im Jahre 1816 (37)
b. Encke allein auf dem Seeberge; seine Ernennung zum Professor nach Ablehnung des Rufes nach Greifswalde; seine Arbeiten in den Jahren 1817 und 1818 (43)
c) Encke's erste Arbeiten über den Kometen von kurzer Umlaufszeit (59)
d) Encke's Arbeiten über andere Kometen, über Vesta und Pallas. Seine Mitwirkung an der Gauss'schen Gradmessung, die Bearbeitung der Venusdurchgänge von 1761 und 1769 (68)
[e.] f. Encke's Privatleben auf demSeeberge. Die mehrfache Verbesserung seiner Stellung. Seine Berufung nach Berlin (91)
[IV.] VI. Encke in Berlin (112)
a. Encke als Akademiker (113)
b. Encke als Lehrer (156)
c. Encke als Director der Sternwarte (177)
d. Encke als Herausgeber des Astronomischen Jahrbuchs (203)
e. Encke's sonstige Arbeiten (250)
[f.] e. Encke ausser der Wissenschaft (263)
1. Encke's Aemter, Würden, Auszeichnungen (263)
2. Encke's Verhältniss zu auswärtigen Astronomen (267)
a) Encke und Bessel (267)
b) Encke und Gauss (287)
c) Encke und Gerling (294)
d) Encke und Olbers (300)
e) Encke und W. Struve (302)
f) Encke und Lindenau (306)
g) Encke und Hansen (308)
h) Encke's Verhältniss zu andern Astronomen und Gelehrten (310)
3. Encke's Beziehungen in Berlin (312)
4. Encke's Privatleben (318)
Verzeichniss der von Johann Franz Encke publicirten Schriften ([336])
Nachtrag zu Seite 94 (350)
Berichtigung zu Seite 315 (350)
Imprint (350
A proposed alternative dynamical history for 2P/Encke which explains the taurid meteoroid complex
No full textInternational audienceAbstract The Taurid Meteoroid Complex (TMC) is a broad stream of meteoroids that produces several annual meteor showers on Earth. If the linkage between these showers and 2P/Encke is at the centre of most TMC models, the small size and low activity of the comet suggest that 2P/Encke is not the unique parent body of the Taurids. Here we simulate the formation of the TMC from 2P/Encke and several NEAs. In total, we explored more than a hundred stream formation scenarios using clones of 2P/Encke. Each modelled stream was integrated and compared with present-day Taurid observations. As previously reported, we find that even slight variations of 2P/Encke’s orbit modifies considerably the characteristics of the simulated showers. Most of the comet’s clones, including the nominal one, appear to reproduce the radiant structure of the Taurid meteors but do not match the observed time and duration of the showers. However, the radiants and timing of most Taurid showers are well reproduced by a particular clone of the comet. Our analysis thus suggest that with this specific dynamical history, 2P/Encke is the sole parent of the four major TMC showers which have ages from 7-21 ka. Our modelling also predicts that the 2022 Taurid Resonant Swarm return will be comparable in strength to the 1998, 2005 and 2015 returns. While purely dynamical models of Encke’s orbit -limited by chaos- may fail to reveal the comet’s origin, its meteor showers may provide the trail of breadcrumbs needed to backtrack our way out of the labyrinth
From Jupiter-family to Encke-like orbits
No full textWe investigate numerically the transfer routes from Jupiter-family
towards Encke-like cometary orbits, including in the model all the planets
as well as non-gravitational forces. The numerical integrations are
started from orbital elements similar to those of 2P/Encke, changing the
perihelion distance q, to obtain starting orbits in the Jupiter family,
and the non-gravitational parameter A2. The results show that some of
the model orbits reach the Encke-like stage within a reasonable time,
comparable to a typical active cometary lifetime; along the way, at the
crossing of mean motion resonances with Jupiter, temporary captures in
resonance may occur. Thus, resonances and non-gravitational forces appear
to be key factors in the transfer of orbits from the Jupiter family to the
Encke region
Mission design for a ballistic slow flyby Comet Encke 1980
No full textPreliminary mission analyses for a proposed 1980 slow flyby (7-9 km/s) of comet Encke are presented. Among the topics covered are science objectives, Encke's physical activity and ephemeris accuracy, trajectory and launch-window analysis, terminal guidance, and spacecraft concepts. The nominal mission plan calls for a near-perihelion intercept with two spacecraft launched on a single launch vehicle. Both spacecraft will arrive at the same time, one passing within 500 km from Encke's nucleus on its sunward side, the other cutting through the tail region. By applying a small propulsive correction about three weeks after the encounter, it is possible to retarget both spacecraft for a second Encke intercept in 1984. The potential science return from the ballistic slow flyby is compared with other proposed mission modes for the 1980 Encke flyby mission, including the widely advocated slow flyby using solar-electric propulsion. It is shown that the ballistic slow flyby is superior in every respect
Encke gap : diffusion map
No full textThe Encke Gap is located in Saturn’s A ring at 133584km from the planet. It contains the satelite Pan and an internal ring system including the inner ring, outer ring, central ring and fourth ring, located at 133484km, 133720km, 133584km and 133584km from Saturn’s center. In this work we will define diferent dinamical regimes present when a satellite is immersed in a planetery ring: chaos, horseshoe orbit and waves. We will also do numerical simulations aiming at reproducing the dinamical system of the Encke Gap, and conclude that the regions of chaos and horseshoe orbit occur at 111.64km and 25.76km from Pan, respectively. A diffusion map will be used to check the stability of the rings inside the Encke Gap. The central ring is the most stable since it shares its orbit with Pan in the horseshoe region. The inner ring and the fourth ring are in the chaotic region of the gap and are very unstable presenting log D = −2. We will also see that the outer ring is unstable with log D = −3 despite being outside the chaotic region.A Falha de Encke está localizada no anel A de Saturno a uma distância de 133584km do planeta. Ela contem o satélite Pan e um sistema de anéis internos, que são: anel interno, anel externo, anel central e quarto anel; às distâncias de 133484km, 133720km, 133584km e 133680km de Saturno. Nesse trabalho de conclusão de curso definiremos os diferentes regimes dinâmicos presentes quando um satélite é imerso em um anel: caos, ferradura e ondas. Realizaremos simulações numéricas com o objetivo de reproduzir o sistema dinâmico da Falha de Encke e verificaremos que as regiões de caos e ferradura ocorrem até 111.64km e 25.76km de Pan, respectivamente. Um mapa de difusão foi usado na verificação da estabilidade dos anéis presentes no interior da falha. O anel central é o mais estável dos quatro anéis por dividir órbita com Pan em região de ferradura. O anel interno e quarto anel estão localizados em região de caos e apresentam log D = −2. Apesar do anel externo estar fora da região caótica, ele também tem difusão alta (log D = −3).Não recebi financiament
A model of the physical properties of comet Encke
No full textThe available observational data on periodic comet Encke were collected and interpreted in order to construct a model of the comet. The model is intended for use in the design of scientific experiments and spacecraft systems to be used on future missions to Encke. Numerical values and ranges of uncertainty are given for all of the important structural, compositional, and photometric parameters with references to the original research from which these were calculated or estimated
Ballistic Missions To Comet Encke In 1980 -A New Phase Of Solar System Exploration
No full textA prime mission candidate for initiating exploration of both a comet and asteroids with unmanned spacecraft is available during the 1980 apparition of the short-period Comet Encke. Direct investigation of such bodies is expected to provide the best insight into conditions existing during the early periods of solar system evolution.
A discussion is presented on low-cost ballistic mission options to Comet Encke. Particular emphasis is given to the results of a recentlycompleted study of ballistically-launched, spinstabilized spacecraft for 1980 missions to Comet Encke and the asteroids Geographos and Toro. Characteristics and utilization of a small, separable probe to enhance comet science return are also described. In conclusion, it is shown that the Encke ballistic flyby can provide the necessary technical foundation to support the planning of more advanced Encke follow-on missions as well as the challenging flyby of Comet Halley in 1986
King David's Altar in Jerusalem Dated by the Bright Appearance of Comet Encke in 964 BC
No full textAt the time corresponding to our end of May and beginning of June in 964 BC a bright comet with a very long tail dominated the night sky of the northern hemisphere. It was Comet Encke that was very bright during the Bronze Age, but today it is scarcely visible to the naked eye. It first appeared as a small comet close to the zenith, but for every night it became greater and brighter and moved slowly to the north with its tail pointing southwards. In the first week of June the tail was stretched out across the whole sky and at midnight it was visible close to the meridian. In this paper the author wishes to test the hypothesis that this appearance of Comet Encke corresponds to the motion in the sky above Jerusalem of “the sword of the Angel of the Lord”, mentioned in 1 Chronicles, in the Old Testament. Encke was first circumpolar and finally set at the northern horizon on 8 June in 964 BC at 22. This happened according to the historical chronology between 965 and 960 BC. The calculations of the orbit of Comet Encke have been performed by a computer program developed by the author. It has been calibrated from depictions on Swedish rock-carvings, Chinese texts and Sumerian cylinder seals and gives useful results at least back to 2654 BC
Encke Virtual University Collaboration: Bringing Educators Together in Second Life
No full textThe Encke Virtual University Collaboration brought educators from
around the world to an island in Second Life to listen to some
presentations from experts in the field, embark on a series of field
trips but most importantly to collaborate in teams around a number
of topics including bots, communities of practice and gamification.
Like the comet Encke, the Encke Virtual University Collaboration
had a long tail, with a number of workshops and events, and
collaborations developing over the following months
Photometry and polarimetry of the nucleus of comet 2P/Encke ⋆
No full textContext. Comet 2P/Encke, a short-period comet, is a favorable target for studies of light scattering by bare cometary nuclei. These studies enable assessment of the nucleus size, the material albedo, and the light-scattering properties of the cometary surface. Observations of 2P/Encke were completed between October to December 2006 when the comet approached the Sun between 2.7 and 2.1 AU. Aims. We characterize the activity of the cometary coma and the physical properties of the nucleus of 2P/Encke such as its size, albedo, colors, spectral slope, surface roughness, porosity, and single-particle properties. Methods. Broadband imaging photometry and broadband and narrowband linear polarimetry is measured for the nucleus of 2P/Encke over the phase-angle range 4 – 28 deg. Results. An analysis of the point spread function of the comet in polarimetric images reveal only weak coma activity in 2P/Encke, corresponding to dust production of the order of 0.05 kg/s. Over the measured phase-angle range the nucleus displays a color independent photometric phase function of almost linear slope (β = 0.050±0.004 mag/deg). The absolute R filter magnitude at zero phase angle is 15.05±0.05 mag and corresponds to an equivalent radius for the nucleus of 2.43±0.06km (adopted albedo of 0.047). The nucleus color V – R was measured to be 0.47±0.07, suggesting a spectral slope S ’ of 11±8%/100nm. The phase function of linear polarimetry in the V and R filter shows a widely color independent linear increase with phase angle (0.12±0.02 %/deg). The test of the empirical albedo-polarization relationship for asteroids reveals unreasonably high albedo values for the nucleus. We find discrepancies in the photometric and polarimetric parameters between 2P/Enck
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