Occultation — LLMpedia

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Occultation An occultation is an astronomical event in which one celestial body passes in front of another, temporarily obscuring it from an observer's viewpoint. Observations of occultations have informed studies across Ptolemy, Hipparchus, Al-Battani, Tycho Brahe, and modern observatories such as Palomar Observatory, Arecibo Observatory, and Mauna Kea Observatories. Occultations link techniques used by Royal Astronomical Society, International Astronomical Union, Minor Planet Center, European Southern Observatory, and missions like Voyager program, Cassini–Huygens, and New Horizons.

Definition and Types

Occultations are classified by geometry and participants: stellar occultations by stars as seen by Cassini–Huygens or ground facilities; lunar occultations by the Moon against stars observed from Greenwich Observatory or Mt. Wilson Observatory; planetary occultations when a planet hides a star as recorded by Hubble Space Telescope or Keck Observatory; and asteroid occultations monitored by networks including International Occultation Timing Association and European Asteroidal Occultation Network. Subtypes include grazing occultations at the Mare Imbrium limb, central occultations like those measured during Voyager program encounters with Jupiter, and mutual occultations among Galilean moons observed during Galileo (spacecraft) operations. Techniques distinguish between total, annular, partial, and grazing events, paralleling categorizations used in studies by Royal Astronomical Society of Canada and publications in Monthly Notices of the Royal Astronomical Society.

Ancient records from Babylon, Assyria, Alexandria, and observers such as Hipparchus and Ptolemy documented lunar occultations to refine star catalogs housed at institutions like Library of Alexandria. Medieval Islamic astronomers including Al-Battani and Al-Sufi used occultation phenomena to correct ephemerides employed by House of Wisdom. Early modern efforts by Tycho Brahe and Johannes Kepler integrated occultation timings into orbital models influencing navigation used by British Royal Navy and expeditions of James Cook. Cultural interpretations appear in accounts from Inca Empire and Maya civilization rituals that recorded solar and lunar occultations alongside chronicles held in Codex Borgia and Codex Dresden. Historical tests of general relativity via occultation-like observations involved researchers at Princeton University and Cambridge University, while more recent public outreach campaigns have been led by Smithsonian Institution and Griffith Observatory.

Professional occultation work uses high-speed photometers at facilities like Very Large Telescope, Subaru Telescope, Gran Telescopio Canarias, and radio receivers at Arecibo Observatory and Very Large Array. Timing precision relies on Global Positioning System clocks, atomic standards from National Institute of Standards and Technology, and data pipelines developed at Jet Propulsion Laboratory and European Space Agency. Imaging systems include CCDs from Charge-Coupled Device manufacturers used at Kitt Peak National Observatory and electron-multiplying devices applied in Keck Observatory instrumentation. Occultation campaigns coordinate via organizations such as International Occultation Timing Association, Minor Planet Center, American Association of Variable Star Observers, and utilize software like Occult (software), orbit models from JPL Horizons, and astrometric catalogs such as Gaia, Hipparcos, and UCAC. Amateur networks contribute using portable setups popularized by groups like Astronomical Society of the Pacific and maker communities around Raspberry Pi and Arduino.

Occultations measure sizes and shapes of Kuiper belt, trans-Neptunian objects, and asteroids; reveal atmospheres of Pluto and Titan as studied by teams for New Horizons and Cassini–Huygens; and probe rings around Saturn, Uranus, and Chariklo first detected via occultation data analyzed at Institute of Astronomy, Cambridge and Max Planck Institute for Solar System Research. Stellar occultations constrain limb darkening for targets observed by Hubble Space Telescope and inform exoplanet transit models used by Kepler (spacecraft), TESS, and JWST. Occultation-derived shape models support missions like OSIRIS-REx and Hayabusa2 and underpin density estimates that connect to laboratory studies at Jet Propulsion Laboratory and theoretical work by researchers at Caltech and MIT.

Prediction pipelines use astrometry from Gaia and orbital solutions from JPL Small-Body Database and Minor Planet Center to compute shadow paths via software distributed by International Astronomical Union working groups. Models incorporate limb profiles of Moon topography from LRO (Lunar Reconnaissance Orbiter), stellar diameters from Hipparcos catalogs, and atmospheric refraction for bodies like Titan via radiative transfer codes developed at University of Oxford and University of Colorado Boulder. Uncertainty budgets reference covariance analyses from Jet Propulsion Laboratory and observing geometry studies published in Astronomy & Astrophysics and The Astrophysical Journal. Campaign logistics coordinate with national agencies such as NASA, European Space Agency, Japan Aerospace Exploration Agency, and observatories including Palomar Observatory.

Key events include the 1977 discovery of Uranian rings via stellar occultation analyzed by teams from University of Hawaii and Cardiff University; detection of Chariklo’s rings during a 2013 occultation reported by researchers at Observatoire de Paris and Instituto de Astrofísica de Canarias; Pluto’s atmosphere revealed in occultations leading up to New Horizons investigated by groups at Observatoire de Paris and South African Astronomical Observatory; the 1961 lunar occultation campaigns that refined stellar positions involving Royal Greenwich Observatory; and occultation-based size estimates that guided Rosetta (spacecraft) mission target selection coordinated with European Space Agency. Other milestones include astrometric refinement of (486958) Arrokoth prior to New Horizons flyby, grazing occultation measurements by Pulkovo Observatory, and occultation-derived discoveries published by Nature and Science.

Category:Astronomical phenomena