The capture of comets

1974 ◽  
Vol 22 ◽  
pp. 187-191
Author(s):  
Hans Rickman
Keyword(s):  
The Sun ◽  
Capture Process ◽  
Long Period ◽  
Limited Role ◽  
Period Orbit ◽  
Short Period

The expression: “Capture of a comet” may lead thoughts primarily to the single encounter mechanism, when a comet happens to pass very close to Jupiter and is at once “captured” into Jupiter’s family of comets, getting an aphelion just outside Jupiter’s orbit, but I would rather suggest that any evolution from a long-period orbit far from the Sun to a short-period orbit, making use of different kinds of perturbations, may be termed a “capture process”, and it is evident that single encounters must play a rather limited role in such evolutions.

Discussion following the presentation by F. Deubner

1977 ◽  
Vol 36 ◽  
pp. 69-74
Keyword(s):  
List Type ◽  
The Sun ◽  
Type Number ◽  
Harmonic Motion ◽  
Locally Excited ◽  
Long Period ◽  
Coherent Wave ◽  
Short Period ◽  
Global Modes

The discussion was separated into 3 different topics according to the separation made by the reviewer between the different periods of waves observed in the sun :1) global modes (long period oscillations) with predominantly radial harmonic motion.2) modes with large coherent - wave systems but not necessarily global excitation (300 s oscillation).3) locally excited - short period waves.

scholarly journals On the secondary’s rotation in a synchronous binary asteroid

2020 ◽  
Vol 493 (1) ◽  
pp. 171-183
Author(s):  
H S Wang ◽  
X Y Hou
Keyword(s):  
Periodic Orbits ◽  
Body Problem ◽  
Spin Orbit ◽  
Binary Asteroid ◽  
Classical Spin ◽  
Long Period ◽  
Period Orbit ◽  
Short Period ◽  
Orbit Eccentricity ◽  
Binary Asteroid System

ABSTRACT This article studies the secondary’s rotation in a synchronous binary asteroid system in which the secondary enters the 1:1 spin-orbit resonance. The model used is the planar full two-body problem, composed of a spherical primary plus a triaxial ellipsoid secondary. Compared with classical spin-orbit work, there are two differences: (1) influence of the secondary’s rotation on the mutual orbit is considered and (2) instead of the Hamiltonian approach, the approach of periodic orbits is adopted. Our studies find the following. (1) The genealogy of the two families of periodic orbits is the same as that of the families around triangular libration points in the restricted three-body problem. That is, the long-period family terminates on to a short-period orbit travelling N times. (2) In the limiting case where the secondary’s mass is negligible, our results can be reduced to classical spin-orbit theory, by equating the long-period orbit with free libration and the short-period orbit with the forced libration caused by orbit eccentricity. However, the two models show obvious differences when the secondary’s mass is non-negligible. (3) By studying the stability of periodic orbits for a specific binary asteroid system, we are able to obtain the maximum libration amplitude of the secondary (which is usually less than 90°) and the maximum mutual orbit eccentricity that does not break the secondary’s synchronous state. We also find an anti-correlation between the secondary’s libration amplitude and the orbit eccentricity. The (65803) Didymos system is taken as an example to show the results.

scholarly journals New Trends in the Discovery of Comets by Amateurs

1988 ◽  
Vol 98 ◽  
pp. 163-163 ◽  
Author(s):  
J.C. Merlin
Keyword(s):  
Strong Correlation ◽  
Considerable Proportion ◽  
The Sun ◽  
Long Period ◽  
Short Period

AbstractThe ways in which amateurs may increase their chances of discovering comets were described. Amateurs discover a considerable proportion of comets, but their contribution is greater among long-period comets. The relative proportions of short-period comets is revealing: 1 in 2 for professional astronomers, 1 in 8 for amateurs. Professional discoveries are largely a by-product of searches for asteroids: the comets have low inclinations (i < 30°) and are faint (m1 > 14). Amateurs are most successful in areas close (<60°) to the Sun. Typical apertures are 150-mm, and most comets are brighter than magnitude 10.Past results show that there is a strong correlation between number of observers and number of discoveries. Several amateurs have discovered comets at great elongations with larger telescopes (≥ 400 mm). The comets tend to be fainter (10 < m1 < 12). Several comets have been discovered with simple equipment (200- or 300-mm telephoto lenses) down to magnitude 13.Calculations of the distribution of discoverable comets show that an average of 14 comets (9 < m1 < 14) are missed per year.

scholarly journals Report to the solar physics committee on a comparison between apparent inequalities of short period in sun-spot areas and in diurnal temperature-ranges at Toronto and Kew

1884 ◽  
Vol 37 (232-234) ◽  
pp. 290-316
Keyword(s):  
Solar Physics ◽  
The State ◽  
The Sun ◽  
Diurnal Temperature ◽  
Terrestrial Magnetism ◽  
Long Period ◽  
Short Period ◽  
Temperature Ranges

1. It has been known for some time, through the researches of Sabine and others, that there is a close connexion between the Inequalities in the state of the sun’s surface as denoted by sun-spot areas and those in terrestrial magnetism as denoted by the diurnal ranges of oscillation of the declination magnet; and moreover, the observations,of Baxendell, Meldrum, and various other meteorologists have induced us to suspect that there may likewise be a connexion between solar inequalities and those in terrestrial meteorology. This latter connexion, however, assuming it to exist, is not so well established as the former—at least if we compare together Inequalities of long period. Attempts have been made to explain this by imagining that for long periods the state of the atmosphere, as regards absorption, may change in such a manner as to diminish or even cloak the effects of solar variation by increasing the absorption when the sun is strongest and diminishing the absorption when the sun is weakest.

scholarly journals On the Rate of Ejection of Dust by Long-Period Comets

1972 ◽  
Vol 45 ◽  
pp. 442-446
Author(s):  
V. N. Lebedinets
Keyword(s):  
Dust Cloud ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
The Sun ◽  
Long Period ◽  
Spherical Component ◽  
Short Period ◽  
Spherical Cloud ◽  
Radar Meteor ◽  
Meteoric Dust

A model of the interplanetary dust medium that includes two subsystems, a spherical component and a flat one, has been proposed by the author as a result of analysis of radar meteor orbits. The disintegration of short-period comets is the main source of the flat dust cloud, while the disintegration of long-period comets is the main source of the spherical cloud. Assuming that dust particles fall into the Sun due to the Poynting-Robertson effect, one can estimate the intensity of ejection of dust from long-period comets necessary for the maintenance of the observed density of interplanetary dust. It has been found that the long-period comets should eject between 7 × 1014 and 2 × 1015 g of meteoric dust per year.

scholarly journals Report to the solar physics Committee on a comparison between apparent inequalities of short period in sun-spot areas and in diurnal temperature-ranges at Toronto and Kew

1884 ◽  
Vol 37 (232-234) ◽  
pp. 251-290 ◽  
Keyword(s):  
Solar Physics ◽  
The State ◽  
The Sun ◽  
Diurnal Temperature ◽  
Terrestrial Magnetism ◽  
Long Period ◽  
Short Period ◽  
Temperature Ranges

1. It has been known for some time, through the researches of Sabine and others, that there is a close connexion between the Inequalities in the state of the sun’s surface as denoted by sun-spot areas and those in terrestrial magnetism as denoted by the diurnal ranges of oscillation of the declination magnet; and moreover, the observations,of Baxendell, Meldrum, and various other meteorologists have induced us to suspect that there may likewise be a connexion between solar inequalities and-those in terrestrial meteorology. This latter connexion, however, assuming it to exist, is not so well established as the former—at least if we compare together Inequalities of long period. Attempts have been made to explain this by imagining that for long periods the state of the atmosphere, as regards absorption, may change in such a manner as to diminish or even cloak the effects of solar variation by increasing the absorption when the sun is strongest and diminishing the absorption when the sun is weakest.

From the Oort cloud to Halley-type comets

1999 ◽  
Vol 173 ◽  
pp. 327-338 ◽  
Author(s):  
J.A. Fernández ◽  
T. Gallardo
Keyword(s):  
Total Population ◽  
Complex Function ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Capture Process ◽  
Influx Rate ◽  
Short Period ◽  
Dynamical Properties ◽  
Orbital Periods ◽  
Probability Of Capture

AbstractThe Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods &lt; 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq &lt;2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods &lt; 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.

scholarly journals Isolation and Analysis of Six timeless Alleles That Cause Short- or Long-Period Circadian Rhythms in Drosophila

Genetics ◽  
2000 ◽  
Vol 156 (2) ◽  
pp. 665-675
Author(s):  
Adrian Rothenfluh ◽  
Marla Abodeely ◽  
Jeffrey L Price ◽  
Michael W Young
Keyword(s):  
Nuclear Translocation ◽  
Phase Response Curve ◽  
Fixed Number ◽  
Constant Darkness ◽  
Genetic Screens ◽  
Protein Levels ◽  
Long Period ◽  
Short Period ◽  
Molecular Oscillation ◽  
New Alleles

Abstract In genetic screens for Drosophila mutations affecting circadian locomotion rhythms, we have isolated six new alleles of the timeless (tim) gene. Two of these mutations cause short-period rhythms of 21–22 hr in constant darkness, and four result in long-period cycles of 26–28 hr. All alleles are semidominant. Studies of the genetic interactions of some of the tim alleles with period-altering period (per) mutations indicate that these interactions are close to multiplicative; a given allele changes the period length of the genetic background by a fixed percentage, rather than by a fixed number of hours. The timL1 allele was studied in molecular detail. The long behavioral period of timL1 is reflected in a lengthened molecular oscillation of per and tim RNA and protein levels. The lengthened period is partly caused by delayed nuclear translocation of TIML1 protein, shown directly by immunocytochemistry and indirectly by an analysis of the phase response curve of timL1 flies.

scholarly journals PHL 417: a zirconium-rich pulsating hot subdwarf (V366 Aquarid) discovered in K2 data

2020 ◽  
Vol 499 (3) ◽  
pp. 3738-3748
Author(s):  
R H Østensen ◽  
C S Jeffery ◽  
H Saio ◽  
J J Hermes ◽  
J H Telting ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Helium Abundance ◽  
The Sun ◽  
The Third ◽  
Short Period ◽  
Standard Models ◽  
Hot Subdwarfs ◽  
Amplitude Mode ◽  
Rare Group

ABSTRACT The Kepler spacecraft observed the hot subdwarf star PHL 417 during its extended K2 mission, and the high-precision photometric light curve reveals the presence of 17 pulsation modes with periods between 38 and 105 min. From follow-up ground-based spectroscopy, we find that the object has a relatively high temperature of 35 600 K, a surface gravity of $\log g / {\rm cm\, s^{-2}}\, =\, 5.75$ and a supersolar helium abundance. Remarkably, it also shows strong zirconium lines corresponding to an apparent +3.9 dex overabundance compared with the Sun. These properties clearly identify this object as the third member of the rare group of pulsating heavy-metal stars, the V366-Aquarii pulsators. These stars are intriguing in that the pulsations are inconsistent with the standard models for pulsations in hot subdwarfs, which predicts that they should display short-period pulsations rather than the observed longer periods. We perform a stability analysis of the pulsation modes based on data from two campaigns with K2. The highest amplitude mode is found to be stable with a period drift, $\dot{P}$, of less than 1.1 × 10−9 s s−1. This result rules out pulsations driven during the rapid stages of helium flash ignition.

scholarly journals Wave Force Characteristics of Large-Sized Offshore Wind Support Structures to Sea Levels and Wave Conditions

2019 ◽  
Vol 9 (9) ◽  
pp. 1855
Author(s):  
Youn-Ju Jeong ◽  
Min-Su Park ◽  
Jeongsoo Kim ◽  
Sung-Hoon Song
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Wave Force ◽  
Diffraction Effect ◽  
Support Structures ◽  
Sea Levels ◽  
Irregular Wave ◽  
Long Period ◽  
Short Period ◽  
Period Wave

This paper presents the results of wave force tests conducted on three types of offshore support structures considering eight waves and three sea levels to investigate the corresponding wave forces. As a result of this study, it is found that the occurrence of shoaling in shallow water induces a significant increase of the wave force. Most of the test models at the shallow water undergo a nonlinear increase of the wave force with higher wave height increasing. In addition, the larger the diameter of the support structure within the range of this study, the larger the diffraction effect is, and the increase in wave force due to shoaling is suppressed. Under an irregular wave at the shallow water, the wave force to the long-period wave tends to be slightly higher than that of the short period wave since the higher wave height component included in the irregular wave has an influence on the shoaling. In addition, it is found that the influence of shoaling under irregular wave becomes more apparent in the long period.

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