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Post Info TOPIC: Halley's Comet
Blobrana


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RE: Halley's Comet
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Comet 1P/Halley is at Opposition (33.265 AU) on the 30th January 2016



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Blobrana


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Comet 1P/Halley
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Title: Molecular Oxygen in Oort Cloud Comet 1P/Halley
Author: Martin Rubin, Kathrin Altwegg, Ewine F. van Dishoeck, Gerhard Schwehm

Recently the ROSINA mass spectrometer suite on board the European Space Agency's Rosetta spacecraft discovered an abundant amount of molecular oxygen, O2, in the coma of Jupiter family comet 67P/Churyumov-Gerasimenko of O2/H2O = 3.80±0.85%. It could be shown that O2 is indeed a parent species and that the derived abundances point to a primordial origin. One crucial question is whether the O2 abundance is peculiar to comet 67P/Churyumov-Gerasimenko or Jupiter family comets in general or whether also Oort cloud comets such as comet 1P/Halley contain similar amounts of molecular oxygen. We investigated mass spectra obtained by the Neutral Mass Spectrometer instrument obtained during the flyby by the European Space Agency's Giotto probe at comet 1P/Halley. Our investigation indicates that a production rate of O2 of 3.7±1.7% with respect to water is indeed compatible with the obtained Halley data and therefore that O2 might be a rather common and abundant parent species.

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Title: The Evolving Photometric Lightcurve of Comet 1P/Halley's Coma During the 1985/86 Apparition
Author: David G. Schleicher, Allison N. Bair, Siobhan Sackey, Lorinda A. Alciator Stinnett, Rebecca M. E. Williams, Bridget R. Smith-Konter

We present new analyses of the photometric lightcurve of Comet 1P/Halley during its 1985/86 apparition. As part of a world-wide campaign coordinated by the International Halley Watch (IHW), narrowband photometry was obtained with telescopes at 18 observatories. Following submissions to and basic reductions by the Photometry and Polarimetry Network of the IHW, we computed production rates and created composite lightcurves for each species. These were used to measure how the apparent rotational period (~7.35 day), along with its shape, evolved with time during the apparition. The lightcurve shape systematically varied from double-peaked to triple-peaked and back again every 8-9 weeks, due to Halley's non-principal axis (complex) rotation and the associated component periods. Unexpectedly, we found a phase shift of one-half cycle also took place during this interval, and therefore the actual beat frequency between the component periods is twice this interval or 16-18 weeks. Preliminary modelling suggests that a single source might produce the entire post-perihelion lightcurve variability and associated evolution. The detailed evolution of the apparent period varied in a non-smooth manner between 7.2 and 7.6 day, likely due to a combination of synodic effects and the interaction of solar illumination with isolated source regions on a body in complex rotation. The need to simultaneously reproduce each of these characteristics will provide very strong additional constraints on Halley's component periods associated with its complex rotation. To assist in these and future analyses, we created a synthetic lightcurve based directly on the measured data. We unexpectedly discovered a strong correlation of ion tail disconnection event start times with minima in the comet's gas production, implying that a decrease in outgassing is another cause of these events.

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Blobrana


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Halley's comet (1P/ 374 E1) made a close approach to the Earth (0.0884 AU) on the 1st April 374 AD



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Blobrana


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Comet 1P/Halley is at Opposition (33.006 AU) on the 30th January 2015.

Ephemeris

Date    TT    R. A. (2000) Decl.     Delta      r    Elong.  Phase   Mag
2015 01 29    08 27 59.3 +01 18 34  33.0054 33.9472   162.7     0.5  25.3
2015 01 30    08 27 52.0 +01 19 02  33.0061 33.9479   162.7     0.5  25.3
2015 01 31    08 27 44.8 +01 19 31  33.0070 33.9487   162.7     0.5  25.3
2015 02 01    08 27 37.5 +01 20 00  33.0083 33.9495   162.6     0.5  25.3
2015 02 02    08 27 30.3 +01 20 30  33.0098 33.9502   162.4     0.5  25.3
2015 02 03    08 27 23.1 +01 21 01  33.0116 33.9510   162.1     0.5  25.3
2015 02 04    08 27 15.9 +01 21 32  33.0138 33.9517   161.8     0.5  25.3
2015 02 05    08 27 08.8 +01 22 03  33.0162 33.9525   161.5     0.5  25.3
2015 02 06    08 27 01.6 +01 22 35  33.0190 33.9532   161.1     0.5  25.3
2015 02 07    08 26 54.5 +01 23 07  33.0220 33.9540   160.6     0.6  25.3
2015 02 08    08 26 47.5 +01 23 40  33.0253 33.9547   160.2     0.6  25.3
2015 02 09    08 26 40.4 +01 24 13  33.0289 33.9555   159.6     0.6  25.3
2015 02 10    08 26 33.4 +01 24 47  33.0329 33.9563   159.1     0.6  25.3


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Comet 1P/Halley
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Title: Chaotic Dynamics of Comet 1P/Halley; Lyapunov Exponent and Survival Time Expectancy
Author: M. A. Muñoz-Gutiérrez, M. Reyes-Ruiz, B. Pichardo

The orbital elements of comet Halley are known to a very high precision, suggesting that the calculation of its future dynamical evolution is straightforward. In this paper we seek to characterize the chaotic nature of the present day orbit of comet Halley and to quantify the timescale over which its motion can be predicted confidently. In addition, we attempt to determine the timescale over which its present day orbit will remain stable. Numerical simulations of the dynamics of test particles in orbits similar to that of comet Halley are carried out with the Mercury 6.2 code. On the basis of these we construct survival time maps to assess the absolute stability of Halley's orbit, frequency analysis maps, to study the variability of the orbit and we calculate the Lyapunov exponent for the orbit for variations in initial conditions at the level of the present day uncertainties in our knowledge of its orbital parameters. On the basis of our calculations of the Lyapunov exponent for comet Halley, the chaotic nature of its motion is demonstrated. The e-folding timescale for the divergence of initially very similar orbits is approximately 70 years. The sensitivity of the dynamics on initial conditions is also evident in the self-similarity character of the survival time and frequency analysis maps in the vicinity of Halley's orbit, which indicates that, on average, it is unstable on a timescale of hundreds of thousands of years. The chaotic nature of Halley's present day orbit implies that a precise determination of its motion, at the level of the present day observational uncertainty, is difficult to predict on a timescale of approximately 100 years. Furthermore, we also find that the ejection of Halley from the solar system or its collision with another body could occur on a timescale as short as 10,000 years.

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Blobrana


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Halley's Comet was at perihelion on the 9th February, 1986.

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Blobrana


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Wednesday 11 May 1910
Halley's Comet.
Fine view this morning.

Those who reluctantly left their warm beds between the hours of 4.30 and 5.30 this morning were amply recompensed for the temporary discomfort by the glorious spectacle presented by Halley's Comet and the planet Venus in the eastern sky. The two objects are still close companions and as the comet has greatly increased in brightness during the past week, the sight is one to be remembered. The tail of the comet has become very bright, and is now of great size.
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Perihelion passage of Halley's Comet on the 26th January, 66AD

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On October 16, 1982, a team of astronomers led by David Jewett and G. Edward Danielson recovered Comet Halley using the 200-inch telescope on Palomar Mountain in Southern California. 
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