In observational astronomy , culmination is the passage of a celestial object (such as the Sun , the Moon , a planet , a star , constellation or a deep-sky object ) across the observer's local meridian . These events are also known as meridian transits , used in timekeeping and navigation , and measured precisely using a transit telescope .
32-508: During each day, every celestial object appears to move along a circular path on the celestial sphere due to the Earth's rotation creating two moments when it crosses the meridian. Except at the geographic poles , any celestial object passing through the meridian has an upper culmination , when it reaches its highest point (the moment when it is nearest to the Zenith ), and nearly twelve hours later,
64-440: A culmination and the next is a sidereal day , which is exactly 24 sidereal hours and 4 minutes less than 24 common solar hours , while the period between an upper culmination and a lower one is 12 sidereal hours. The period between successive day to day (rotational) culminations is effected mainly by Earth's orbital proper motion , which produces the different lengths between the solar day (the interval between culminations of
96-535: A much smaller impact on sidereal observation, impacting Earth's climate through the Milankovitch cycles significantly more. Though at such timescales stars themself change position, particularly those stars which have, as viewed from the Solar System , a high proper motion . Stellar parallax appears to be a similar motion like all these apparent movements, but has only from non-averaged sidereal day to sidereal day
128-511: A slight effect, returning to its original apparent position, completing a cycle every orbit, with a slight additional lasting change to the position due to the precessions. This phenomenon results from Earth changing position on its orbital path. From the tropics and middle latitudes , the Sun is visible in the sky at its upper culmination (at solar noon ) and invisible (below the horizon) at its lower culmination (at solar midnight ). When viewed from
160-758: Is a polar region around Earth 's South Pole , opposite the Arctic region around the North Pole . The Antarctic comprises the continent of Antarctica , the Kerguelen Plateau , and other island territories located on the Antarctic Plate or south of the Antarctic Convergence . The Antarctic region includes the ice shelves , waters, and all the island territories in the Southern Ocean situated south of
192-585: Is commonly accepted to have occurred in 1820 by the Russian expedition of Fabian Gottlieb von Bellingshausen and Mikhail Lazarev on Vostok and Mirny . The Australian James Kerguelen Robinson (1859–1914) was the first human born in the Antarctic, on board the sealing ship Offley in the Gulf of Morbihan (Royal Sound then), Kerguelen Island on 11 March 1859. The first human born and raised on an Antarctic island
224-533: Is credited to the Spaniard Gabriel de Castilla , who reported seeing distant southern snow-capped mountains in 1603. The first Antarctic land discovered was the island of South Georgia , visited by the English merchant Anthony de la Roché in 1675. Although such myths and speculation about a Terra Australis ("Southern Land") date back to antiquity, the first confirmed sighting of the continent of Antarctica
256-466: Is followed by a lower culmination , when it reaches its lowest point (nearest to the Nadir ). The time of culmination (when the object culminates) is often used to mean upper culmination. An object's altitude ( A ) in degrees at its upper culmination is equal to 90 minus the observer's latitude ( L ) plus the object's declination ( δ ): Three cases are dependent on the observer's latitude ( L ) and
288-428: Is low on the islands: studies have theorized that the harsh climate was a major contributor towards species richness, but multiple correlations have been found with area, temperature, remoteness of islands, and food chain stability. For example, herbivorous insects are poor in number due to low plant richness, and likewise, indigenous bird numbers are related to insects, which are a major food source. The Antarctic hosts
320-487: Is managed through an international commission headquartered in Hobart , Australia, by an efficient system of annual fishing quotas, licenses, and international inspectors on the fishing vessels, as well as satellite surveillance. The islands situated between 60°S latitude parallel to the south and the Antarctic Convergence to the north and their respective 200-nautical-mile (370 km) exclusive economic zones fall under
352-493: Is no bright pole star, but the constellation Octans circles clockwise around the south celestial pole and remains visible at both culminations. Any astronomical objects that always remain above the local horizon, as viewed from the observer's latitude, are described as circumpolar . Diurnal motion Too Many Requests If you report this error to the Wikimedia System Administrators, please include
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#1732859402516384-721: Is no permanent country in Antarctica . As defined by the Antarctic Treaty System , the Antarctic region is everything south of the 60°S latitude . The Treaty area covers Antarctica and the archipelagos of the Balleny Islands , Peter I Island , Scott Island , the South Orkney Islands , and the South Shetland Islands . However, this area does not include the Antarctic Convergence , a transition zone where
416-702: Is set to expire in 35 years. ) To protect the area, all Antarctic ships over 500 tonnes are subject to mandatory regulations under the Polar Code , adopted by the International Maritime Organization (in force since 1 January 2017). Climate change caused by greenhouse gas emissions from human activities occurs everywhere on Earth, and while Antarctica is less vulnerable to it than any other continent, climate change in Antarctica has been observed. Since 1959, there has been an average temperature increase of >0.05 °C/decade since 1957 across
448-487: The Antarctic Convergence , a zone approximately 32 to 48 km (20 to 30 mi) wide and varying in latitude seasonally. The region covers some 20 percent of the Southern Hemisphere , of which 5.5 percent (14 million km ) is the surface area of the Antarctica continent itself. All of the land and ice shelves south of 60°S latitude are administered under the Antarctic Treaty System . Biogeographically ,
480-491: The Antarctic realm is one of eight biogeographic realms on Earth's land surface. Climate change in Antarctica is particularly important because the melting of the Antarctic ice sheet has a high potential to add to the global sea level rise . Further, this melting also disrupts the flow of Southern Ocean overturning circulation , which would have significant effects on the local climate and marine ecosystem functioning.There
512-429: The declination ( δ ) of the celestial object : The third case applies for objects in a part of the full sky equal to the cosine of the latitude (at the equator it applies for all objects, because the sky turns around the horizontal north–south line; at the poles it applies for none, because the sky turns around the vertical line). The first and second case each apply for half of the remaining sky. The period between
544-564: The region within either polar circle around the winter solstice of that hemisphere (the December solstice in the Arctic and the June solstice in the Antarctic ), the Sun is below the horizon at both of its culminations. Supposing that the declination of the Sun is +20° when it crosses the local meridian, then the complementary angle of 70° (from the Sun to the pole) is added to and subtracted from
576-534: The Convergence and thus outside the Antarctic region. A variety of animals live in Antarctica for at least some of the year, including: Most of the Antarctica continent is permanently covered by ice and snow, leaving less than 1 percent of the land exposed. There are only two species of flowering plant, Antarctic hair grass and Antarctic pearlwort , but a range of mosses , liverworts , lichens and macrofungi . Biodiversity among terrestrial flora and fauna
608-446: The Sun) and the sidereal day (the interval between culminations of any reference star ) or the slightly more precise, precession unaffected, stellar day . This results in culminations occurring every solar day at different times, taking a sidereal year (366.3 days), a year that is one day longer than the solar year , for a culmination to reoccur. Therefore, only once every 366.3 solar days
640-551: The West Antarctic, the ocean has warmed by 1 °C (1.8 °F) since 1955. The fresh, 1100-1500 billion tons (GT) per year of meltwater from the ice dilutes the saline Antarctic bottom water , weakening the lower cell of the Southern Ocean overturning circulation (SOOC). According to some research, a full collapse of the SOOC may occur a between 1.7 °C (3.1 °F) and 3 °C (5.4 °F) of global warming, although
672-511: The cold waters of the Southern Ocean collide with the warmer waters of the north, forming a natural border to the region. Because the Convergence changes seasonally, the Convention for the Conservation of Antarctic Marine Living Resources approximates the Convergence line by joining specified points along parallels of latitude and meridians of longitude . The implementation of the convention
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#1732859402516704-496: The continent, although it had been uneven. West Antarctica warmed by over 0.1 °C/decade from the 1950s to the 2000s, and the exposed Antarctic Peninsula has warmed by 3 °C (5.4 °F) since the mid-20th century. The colder, stabler East Antarctica had been experiencing cooling until the 2000s. Around Antarctica, the Southern Ocean has absorbed more oceanic heat than any other ocean, and has seen strong warming at depths below 2,000 m (6,600 ft). Around
736-411: The culmination reoccurs at the same time of a solar day, while reoccurring every sidereal day. The remaining small changes in the culmination period time from sidereal year to sidereal year is on the other hand mainly caused by nutation (with a 18.6 years cycle), resulting in the longer time scale axial precession of Earth (with a 26,000 years cycle), while apsidal precession and other mechanics have
768-446: The details below. Request from 172.68.168.226 via cp1108 cp1108, Varnish XID 765271113 Upstream caches: cp1108 int Error: 429, Too Many Requests at Fri, 29 Nov 2024 05:50:02 GMT Antarctic The Antarctic ( / æ n ˈ t ɑːr t ɪ k / or / æ n ˈ t ɑːr k t ɪ k / , American English also / æ n t ˈ ɑːr t ɪ k / or / æ n t ˈ ɑːr k t ɪ k / ; commonly / æ ˈ n ɑːr t ɪ k / )
800-736: The full effects are expected to occur over multiple centuries; these include less precipitation in the Southern Hemisphere but more in the Northern Hemisphere , an eventual decline of fisheries in the Southern Ocean and a potential collapse of certain marine ecosystems . While many Antarctic species remain undiscovered, there are documented increases in Antarctic flora , and large fauna such as penguins are already having difficulty retaining suitable habitat. On ice-free land, permafrost thaws release greenhouse gases and formerly frozen pollution. The first recorded sighting of Antarctica
832-584: The most popular destinations being the Antarctic Peninsula area (especially the South Shetland Islands ) and South Georgia Island . In December 2009, the growth of tourism , with consequences for both the ecology and the safety of the travellers in its great and remote wilderness, was noted at a conference in New Zealand by experts from signatories to the Antarctic Treaty . The definitive results of
864-818: The national jurisdiction of the countries that possess them: South Georgia and the South Sandwich Islands (United Kingdom), Bouvet Island (Norway), and Heard and McDonald Islands (Australia). Kerguelen Islands (France; also an EU Overseas territory) are situated in the Antarctic Convergence area, while the Isla Grande de Tierra del Fuego , Falkland Islands , Isla de los Estados , Hornos Island with Cape Horn , Diego Ramírez Islands , Campbell Island , Macquarie Island , Amsterdam and Saint Paul Islands, Crozet Islands , Prince Edward Islands , Gough Island , and Tristan da Cunha group remain north of
896-459: The observer's latitude to find the solar altitudes at upper and lower culminations, respectively. From most of the Northern Hemisphere , Polaris (the North Star) and the other stars of the constellation Ursa Minor circles counterclockwise around the north celestial pole and remain visible at both culminations (as long as the sky is clear and dark enough). In the Southern Hemisphere there
928-462: The southernmost. In late 1977, Silvia Morella de Palma, who was then seven months pregnant, was airlifted to Esperanza Base , in order to complete her pregnancy in the base. The airlift was a part of the Argentine solutions to the sovereignty dispute over territory in Antarctica. Emilio was automatically granted Argentine citizenship by the government since his parents were both Argentine citizens, and he
960-719: The world's largest protected area comprising 1.07 million km , the South Georgia and the South Sandwich Islands Marine Protection Area created in 2012. The latter exceeds the surface area of another vast protected territory, the Greenland National Park 's 972,000 km (375,000 sq mi). (While the Ross Sea Marine Protection Area established in 2016 is still larger at 1.55 million km , its protection
992-636: Was Solveig Gunbjørg Jacobsen born on 8 October 1913 in Grytviken , South Georgia. Emilio Marcos Palma (born 7 January 1978) is an Argentine man who was the first documented person born on the continent of Antarctica at the Esperanza Base . His father, Captain Jorge Palma, was head of the Argentine Army detachment at the base. While ten people have been born in Antarctica since, Palma's birthplace remains
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1024-449: Was born in the claimed Argentine Antarctica . Palma can be considered to be the first native Antarctican. The Antarctic region had no indigenous population when first discovered, and its present inhabitants comprise a few thousand transient scientific and other personnel working on tours of duty at the several dozen research stations maintained by various countries. However, the region is visited by more than 40,000 tourists annually,
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