Secular phenomena: Difference between revisions
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== In the solar system == |
== In the solar system == |
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Secular phenomena create variations in the orbits of the Moon and the planets. The [[Sun|solar]] [[emission spectrum]] and the [[solar wind]] are undergoing [[Sun#Possible long-term cycle|secular trends]] due to [[Habitable zone#Galactic habitable zone|migration]] through the [[galactic plane]], leading to [[Sun#Motion and location within the galaxy|effects]], that may impact on [[climate]] and cause [[extinction event]]s. [[Solar system]] efemerides are essencial for [[spacecraft]] [[navigation]] and [[astronomical observation]]s. |
Secular phenomena create variations in the orbits of the Moon and the planets. The [[Sun|solar]] [[emission spectrum]] and the [[solar wind]] are undergoing [[Sun#Possible long-term cycle|secular trends]] due to [[Habitable zone#Galactic habitable zone|migration]] through the [[galactic plane]], leading to [[Sun#Motion and location within the galaxy|effects]], that may impact on [[climate]] and cause [[extinction event]]s. [[Solar system]] efemerides are essencial for [[spacecraft]] [[navigation]] and [[astronomical observation]]s. |
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The secular effects of solar [[accretion]] of [[Dark Matter]] at some rate, during billions of years, is also attracting interest.<ref>L.Iorio; [http://arxiv.org/PS_cache/arxiv/pdf/1001/1001.1697v7.pdf ''Effect of Sun and Planet-Bound Dark Matter on Planet and Satellite Dynamics in the Solar System''], arXiv (May 2010)</ref> |
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=== Moon === |
=== Moon === |
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''Variations Séculaires des Orbites Planétaires'' (VSOP) is a modern [[numerical model]]<ref>P. Bretagnon; [http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1982A%26A...114..278B&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf "Théorie du mouvement de l'ensemble des planètes. Solution VSOP82"], (PDF 1.23MB), ''[[Astronomy & Astrophysics]]'' '''114''' (1982) 278–288.</ref>, that tries to address the problem. |
''Variations Séculaires des Orbites Planétaires'' (VSOP) is a modern [[numerical model]]<ref>P. Bretagnon; [http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1982A%26A...114..278B&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf "Théorie du mouvement de l'ensemble des planètes. Solution VSOP82"], (PDF 1.23MB), ''[[Astronomy & Astrophysics]]'' '''114''' (1982) 278–288.</ref>, that tries to address the problem. |
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[[Jet Propulsion Laboratory]] has an important role in providing scientific efemeris data. In spite of methods to deal with perturbations of numerous [[asteroids]], most of whose masses and orbits are poorly known, remains a tiny secular trend, causing the [[JPL]] to revise its published ephemerides at intervals of 20 years. Russian astronomers have taken notice of this problem. <ref>Kharin, A. S. and [[Yuri B. Kolesnik|Kolesnik, Y. B.]]; ''On the Errors of the Ephemerides Derived from Optical Observations of Planets.'' (1990), [[IAU]] SYMP.141 P.189, 1989.</ref><ref>[[Georgij A. Krasinsky]] and [[Victor A. Brumberg]], ''Secular Increase of Astronomical Unit from Analysis of the Major Planet Motions, and its Interpretation'' [http://iau-comm4.jpl.nasa.gov/GAKVAB.pdf Celestial Mechanics and Dynamical Astronomy 90: 267–288, (2004)].</ref> |
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Kolesnik has followed this up with an ambitious undertaking, which can be condensed in an [[empiric]] formula, that may help solving JPL's problem.<ref>[[Yuri B. Kolesnik]]; [http://adsabs.harvard.edu/abs/2002HiA....12..330K ''Analysis of the secular variations of longitudes of the Sun, Mercury and Venus from optical observations''], in Highlights of Astronomy, Vol. 12, as presented at the XXIVth General Assembly of the IAU - 2000 [Manchester, UK, 7 - 18 August 2000]. Edited by H. Rickman. San Francisco, CA: Astronomical Society of the Pacific, ISBN 1-58381-086-2, 2002, p. 330 – 333.</ref> |
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The net result is that the planet accelerates in its orbit, while slowly falling toward the sun. The relation for the change in angular velocity is given by |
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:<math>\frac{d\omega}{dt}= 3\omega{H_0}</math> |
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where 1/<math>{H_0}</math> is the [[Hubble's law#Units derived from the Hubble constant|Hubble time]] and '''ω''' is the increasing [[angular velocity]]. This tiny change will cause the Earth to fall roughly 22 meters closer to the Sun per year. <ref>Y. B Kolesnik;[http://adsabs.harvard.edu/full/2001ASPC..245...83K ''On the Relationship Between Dynamical Time and Atomic Time''], Astrophysical Ages and Times Scales, ASP Conference Series Vol. 245. Edited by Ted von Hippel, Chris Simpson, and Nadine Manset. San Francisco: Astronomical Society of the Pacific, ISBN: 1-58381-083-8, 2001., p.83</ref> One theoretical explanation claims that this secular acceleration is of a [[Physical cosmology|cosmological]] origin. <ref>Masreliez C. J.; [http://redshift.vif.com/JournalFiles/V11NO4PDF/V11N4MA2.pdf ''Scale Expanding Cosmos Theory II–Cosmic Drag''], [[Apeiron (tidskrift)|Apeiron]] Okt (2004)</ref> |
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== See also == |
== See also == |
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Revision as of 23:15, 2 June 2011
 | This article needs additional citations for verification. (April 2011) |
In astronomy, secular phenomena are contrasted with phenomena observed to repeat periodically. In particular, astronomical ephemerides use secular to label the longest-lasting or non-oscillatory perturbations in the motion of planets, as opposed to periodic perturbations which exhibit repetition over the course of a time frame of interest. Solar system ephemerides are essential for the navigation of spacecraft and for all kinds of space observations of the planets, their natural satellites, stars and galaxies.
Most of the known perturbations to motion in stable, regular, and well-determined dynamical systems tend to be periodic at some level, but in many-body systems, chaotic dynamics result in some effects which are one-way (for example, planetary migration).
In the solar system
Secular phenomena create variations in the orbits of the Moon and the planets. The solar emission spectrum and the solar wind are undergoing secular trends due to migration through the galactic plane, leading to effects, that may impact on climate and cause extinction events. Solar system efemerides are essencial for spacecraft navigation and astronomical observations.
Moon
The secular acceleration of the Moon depends on tidal forces. It was discovered early and has received a number of explanations.[1]
Earth
Depending on what time frames are considered, perturbations can appear secular even if they are actually periodic. An example of this is the precession of the Earth's axis considered over the time frame of a few hundred or thousand years. When viewed in this time frame the so-called "precession of the equinoxes" can appear to mimic a secular phenomenon since the axial precession takes 25,771.5 years and monitoring it over a much smaller timeframe appears to simply result in a "drift" of the position of the equinox in the plane of the ecliptic of approximately one degree every 71.6 years,[2] influencing the Milankovitch cycles.[3]
Magnetic declination varies both from place to place, and with the passage of time. The spatial variation reflects irregularities of the flows deep in the earth; in some areas, deposits of iron ore or magnetite in the Earth's crust may contribute substantially and secular changes to these flows result in slow changes to the field strength and direction at the same point on the Earth. The declination in a given area will most likely change slowly over time, the order of 2–2.5 degrees every hundred years or so, depending on distance from the magnetic poles.
The planets
Secular variations of the planetary orbits is a concept describing long-term trends in the orbits of the planets Mercury to Neptune. Several attempts have from time to time been undertaken to analyze and predict such gravitational deviations from ordinary satellite orbits. Others are often referred to as post keplerian effects.
Variations Séculaires des Orbites Planétaires (VSOP) is a modern numerical model[4], that tries to address the problem.
See also
Notes and References
- ^ Jyri B. Kolesnik; Revision of the tidal acceleration of the Moon and the tidal deceleration of the Earth's rotation from historical optical observations of planets, in ISBN 2-901057-45-4 (2001) pp. 231 - 234.
- ^ Lowrie, William (2004). Fundamentals of Geophysics. Cambridge University Press. ISBN 0521461642.
- ^ Jurij B. Kolesnik; A new appraoch to interpretation of the non-precessional equinox motion, in Journées 2000 - systèmes de référence spatio-temporels. J2000, a fundamental epoch for origins of reference systems and astronomical models, Paris, Septembre 2000, edited by N. Capitaine, Observatoire de Paris (2001), pp. 119 – 120. ISBN 2-901057-45-4
- ^ P. Bretagnon; "Théorie du mouvement de l'ensemble des planètes. Solution VSOP82", (PDF 1.23MB), Astronomy & Astrophysics 114 (1982) 278–288.
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