Misplaced Pages

#79920

40-459: Comet Encke and the Taurid complex are believed to be remnants of a disrupted 40-km-class comet from about 10,000 years ago, breaking into several pieces and releasing material by normal cometary activity , mass loss via YORP spin-up, or occasionally by close encounters with the tidal force of Earth or other planets ( Whipple , 1940; Klačka, 1999). In total, this meteoroid stream is the largest in

80-537: A close flyby of the comet in 1986. A hydrogen gas halo was detected to be 15 times the diameter of Sun (12.5 million miles). This triggered NASA to point the Pioneer Venus mission at the Comet, and it was determined that the Comet was emitting 12 tons of water per second. The hydrogen gas emission has not been detected from Earth's surface because those wavelengths are blocked by the atmosphere. The process by which water

120-619: A panel in the same caves depicting a charging bison, a man with a bird's head and the head of a bird on top of a piece of wood, together may depict the Summer Triangle , which at the time was a circumpolar formation . Rappenglueck also discovered a drawing of the Northern Crown constellation in the cave of El Castillo (North of Spain), made in the same period as the Lascaux chart. Another star chart panel, created more than 21,000 years ago,

160-488: A plate of the southern constellations and two plates showing the entire northern and southern hemispheres in stereographic polar projection. Polish astronomer Johannes Hevelius published his Firmamentum Sobiescianum star atlas posthumously in 1690. It contained 56 large, double page star maps and improved the accuracy in the position of the southern stars. He introduced 11 more constellations, including Scutum , Lacerta , and Canes Venatici . In 1824 Sidney Hall produced

200-604: A sun or full moon, a lunar crescent, several stars including the Pleiades cluster and possibly the Milky Way. The oldest accurately dated star chart appeared in ancient Egyptian astronomy in 1534 BC. The earliest known star catalogues were compiled by the ancient Babylonian astronomers of Mesopotamia in the late 2nd millennium BC, during the Kassite Period ( ca. 1531–1155 BC). The oldest records of Chinese astronomy date to

240-642: Is 32,500 years old and has a carving that resembles the constellation Orion , although it could not be confirmed and could also be a pregnancy chart. German researcher Dr Michael Rappenglueck, of the University of Munich, has suggested that drawing on the wall of the Lascaux caves in France could be a graphical representation of the Pleiades open cluster of stars. This is dated from 33,000 to 10,000 years ago. He also suggested

280-477: Is a listing or tabulation of astronomical objects for a particular purpose. Tools using a star chart include the astrolabe and planisphere . A variety of archaeological sites and artifacts found are thought to indicate ancient made star charts. The oldest known star chart may be a carved ivory Mammoth tusk, drawn by early people from Asia who moved into Europe, that was discovered in Germany in 1979. This artifact

320-619: Is broken down into hydrogen and oxygen was studied by the ALICE instrument aboard the Rosetta spacecraft. One of the issues is where the hydrogen is coming from and how (e.g. Water splitting ): First, an ultraviolet photon from the Sun hits a water molecule in the comet's coma and ionises it, knocking out an energetic electron. This electron then hits another water molecule in the coma, breaking it apart into two hydrogen atoms and one oxygen, and energising them in

360-630: Is uncertain, but is estimated as 705–10 AD. During the Song dynasty (960–1279), the Chinese astronomer Su Song wrote a book titled Xin Yixiang Fa Yao (New Design for the Armillary Clock) containing five maps of 1,464 stars. This has been dated to 1092. In 1193, the astronomer Huang Shang prepared a planisphere along with explanatory text. It was engraved in stone in 1247, and this chart still exists in

400-498: The ALICE spectrograph on the Rosetta space probe studying comet 67P/Churyumov–Gerasimenko determined that electrons (within 1 km (0.62 mi) above the comet nucleus ) produced from photoionization of water molecules by solar radiation , and not photons from the Sun as thought earlier, are responsible for the liberation of water and carbon dioxide molecules released from

440-508: The Chinese constellations by name and does not show individual stars. The Farnese Atlas is a 2nd-century AD Roman copy of a Hellenistic era Greek statue depicting the Titan Atlas holding the celestial sphere on his shoulder. It is the oldest surviving depiction of the ancient Greek constellations, and includes grid circles that provide coordinate positions. Because of precession ,

SECTION 10

#1732848418080

480-617: The Dutch East Indies . Their compilations resulted in the 1601 globe of Jodocus Hondius , who added 12 new southern constellations. Several other such maps were produced, including Johann Bayer 's Uranometria in 1603. The latter was the first atlas to chart both celestial hemispheres and it introduced the Bayer designations for identifying the brightest stars using the Greek alphabet. The Uranometria contained 48 maps of Ptolemaic constellations,

520-452: The Sun in its highly elliptical orbit . As the comet warms, parts of it sublimate ; this gives a comet a diffuse appearance when viewed through telescopes and distinguishes it from stars . The word coma comes from the Greek κόμη ( kómē ), which means "hair" and is the origin of the word comet itself. The coma is generally made of ice and comet dust . Water composes up to 90% of

560-616: The Tang dynasty (618–907) and discovered in the Mogao Caves of Dunhuang in Gansu , Western China along the Silk Road . This is a scroll 210 cm in length and 24.4 cm wide showing the sky between declinations 40° south to 40° north in twelve panels, plus a thirteenth panel showing the northern circumpolar sky. A total of 1,345 stars are drawn, grouped into 257 asterisms . The date of this chart

600-514: The Warring States period (476–221 BC), but the earliest preserved Chinese star catalogues of astronomers Shi Shen and Gan De are found in the 2nd-century BC Shiji by the Western Han historian Sima Qian . The oldest Chinese graphical representation of the night sky is a lacquerware box from the 5th-century BC Tomb of Marquis Yi of Zeng , although this depiction shows the positions of

640-575: The ecliptic . This may have served as a prototype for the oldest European printed star chart, a 1515 set of woodcut portraits produced by Albrecht Dürer in Nuremberg , Germany . During the European Age of Discovery , expeditions to the southern hemisphere began to result in the addition of new constellations. These most likely came from the records of two Dutch sailors, Pieter Dirkszoon Keyser and Frederick de Houtman , who in 1595 traveled together to

680-426: The volatiles that outflow from the nucleus when the comet is within 3–4  au (280–370 million  mi ; 450–600 million  km ) from the Sun. The H 2 O parent molecule is destroyed primarily through photodissociation and to a much smaller extent photoionization . The solar wind plays a minor role in the destruction of water compared to photochemistry . Larger dust particles are left along

720-546: The ESA Rosetta spacecraft to comet 67/P, detected hydrogen, oxygen, carbon and nitrogen in the coma, which they also called the comet's atmosphere. Alice is an ultraviolet spectrograph, and it found that electrons created by UV light were colliding and breaking up molecules of water and carbon monoxide. OAO-2 ('Stargazer') discovered large halos of hydrogen gas around comets. Space probe Giotto detected hydrogen ions at distance of 7.8 million km away from Halley when it did

760-813: The Earth in June/July, are also cross sections of the stream that approach from the Earth's daytime side and, as such, cannot be observed visually in the way the (night-time) Northern and Southern Taurids of October/November can. Astronomers Duncan Steel and Bill Napier even suggest the Beta Taurids could be the cause of the Tunguska event of June 30, 1908. In 1962 and 1963, the Mars 1 probe recorded one micrometeorite strike every two minutes at altitudes ranging from 6,000 to 40,000 km (3,700 to 24,900 mi) from Earth's surface due to

800-453: The Moon for meteor strikes. After consulting star charts , they concluded that the impact body was likely part of the Taurid meteor shower. This may be the first photographic record of such a strike, which some witnesses claim to have visually observed on rare occasions. Coma (cometary) The coma is the nebulous envelope around the nucleus of a comet , formed when the comet passes near

840-625: The Sun. The hydrogen atom are very light so they can travel a long distance before they are themselves ionized by the Sun. When the hydrogen atoms are ionized they are especially swept away by the solar wind. The Rosetta mission found carbon monoxide, carbon dioxide, ammonia, methane and methanol in the Coma of Comet 67P, as well as small amounts of formaldehyde, hydrogen sulfide, hydrogen cyanide, sulfur dioxide and carbon disulfide. The four top gases in 67P's halo were water, carbon dioxide, carbon monoxide, and oxygen. The ratio of oxygen to water coming off

SECTION 20

#1732848418080

880-610: The Taurids have spread out over time, allowing separate segments labeled the Northern Taurids (NTA) and Southern Taurids (STA) to become observable. The Southern Taurids are active from about September 23 to December 8, while the Northern Taurids are active from about October 13 to December 2. Essentially these are two cross sections of a single, broad, continuous stream in space. The Beta Taurids and Zeta Perseids , encountered by

920-402: The Taurids meteor shower, and also recorded similar densities at distances from 20 to 40 million km (12 to 25 million mi) from Earth. The Taurid stream has a cycle of activity that peaks roughly every 2,500 to 3,000 years, when the core of the stream passes nearer to Earth and produces more intense showers. In fact, because of the separate "branches" (night-time in one part of

960-548: The Wen Miao temple in Suzhou . In Muslim astronomy , the first star chart to be drawn accurately was most likely the illustrations produced by the Persian astronomer Abd al-Rahman al-Sufi in his 964 work titled Book of Fixed Stars . This book was an update of parts VII.5 and VIII.1 of the 2nd century Almagest star catalogue by Ptolemy . The work of al-Sufi contained illustrations of

1000-479: The coma can become quite large, its size can actually decrease about the time it crosses the orbit of Mars around 1.5  AU from the Sun. At this distance the solar wind becomes strong enough to blow the gas and dust away from the coma, enlarging the tail . Comets were found to emit X-rays in late-March 1996. This surprised researchers, because X-ray emission is usually associated with very high-temperature bodies . The X-rays are thought to be generated by

1040-450: The comet nucleus into its coma. Comas typically grow in size as comets approach the Sun, and they can be as large as the diameter of Jupiter, even though the density is very low. About a month after an outburst in October 2007, comet 17P/Holmes briefly had a tenuous dust atmosphere larger than the Sun. The Great Comet of 1811 also had a coma roughly the diameter of the Sun. Even though

1080-419: The comet remained constant for several months. Star chart A star chart is a celestial map of the night sky with astronomical objects laid out on a grid system. They are used to identify and locate constellations , stars , nebulae , galaxies , and planets . They have been used for human navigation since time immemorial. Note that a star chart differs from an astronomical catalog , which

1120-525: The comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure . On 11 August 2014, astronomers released studies, using the Atacama Large Millimeter/Submillimeter Array (ALMA) for the first time, that detailed the distribution of HCN , HNC , H 2 CO , and dust inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) . On 2 June 2015, NASA reported that

1160-538: The constellations and portrayed the brighter stars as dots. The original book did not survive, but a copy from about 1009 is preserved at the Oxford University . Perhaps the oldest European star map was a parchment manuscript titled De Composicione Spere Solide . It was most likely produced in Vienna , Austria in 1440 and consisted of a two-part map depicting the constellations of the northern celestial hemisphere and

1200-402: The drift method, one locks the telescope in position and measures the time for the visible disc to pass through the field of view. That time multiplied by the cosine of the comet's declination, times .25, should equal the coma's diameter in arcminutes. If the distance to the comet is known, then the apparent size of the coma can be determined. In 2015, it was noted that the ALICE instrument on

1240-415: The inner Solar System . Since the stream is rather spread out in space, Earth takes several weeks to pass through it, causing an extended period of meteor activity, compared with the much smaller periods of activity in other showers. The Taurids are also made up of weightier material, pebbles instead of dust grains. The daytime showers are active from May to July ( Beta Taurids and Zeta Perseids ), while

Taurids - Misplaced Pages Continue

1280-408: The interaction between comets and the solar wind: when highly charged ions fly through a cometary atmosphere, they collide with cometary atoms and molecules, "ripping off" one or more electrons from the comet. This ripping off leads to the emission of X-rays and far ultraviolet photons . With a basic Earth-surface based telescope and some technique, the size of the coma can be calculated. Called

1320-432: The nighttime showers are active from September to December. Typically, Taurids appear at a rate of about 5 per hour, moving slowly across the sky at about 28 kilometers per second (17 mi/s), or 100,800 km/h (65,000 mph). If larger than a pebble, these meteors may become bolides as bright as the Moon and leave behind smoke trails. Due to the gravitational perturbations of planets , especially Jupiter ,

1360-421: The positions of the constellations slowly change over time. By comparing the positions of the 41 constellations against the grid circles, an accurate determination can be made of the epoch when the original observations were performed. Based upon this information, the constellations were catalogued at 125 ± 55 BC . This evidence indicates that the star catalogue of the 2nd-century BC Greek astronomer Hipparchus

1400-505: The process. These atoms then emit ultraviolet light that is detected at characteristic wavelengths by Alice. A hydrogen gas halo three times the size of the Sun was detected by Skylab around Comet Kohoutek in the 1970s. SOHO detected a hydrogen gas halo bigger than 1 AU in radius around Comet Hale–Bopp . Water emitted by the comet is broken up by sunlight, and the hydrogen in turn emits ultra-violet light. The halos have been measured to be ten billion meters across, many times bigger than

1440-437: The swarm and showed that many such as the 2212 Hephaistos group and the 169P/NEAT group exhibit cometary activity. On November 11, 2019, a Taurid fireball was seen over St. Louis, MO . A brief flash of light from a lunar impact event was recorded by NASA scientist Rob Suggs and astronomer Bill Cooke on November 7, 2005, while testing a new 250 mm (10 in) telescope and video camera they had built to monitor

1480-460: The year and daytime in another; and Northern/Southern in each case) there are two (possibly overlapping) peaks separated by a few centuries, every 3000 years. The next peak is expected around 3000 AD . The Taurids also have more frequent peaks which may result from a heavier concentration of material in the stream, which only encounter Earth during some passes. Over Poland in 1995, all-sky cameras imaged an absolute magnitude –17 Taurid bolide that

1520-582: Was estimated to be 900 kg and perhaps a meter in diameter. In 1993, it was predicted that there would be a swarm of activity in 2005. Around Halloween in 2005, many fireballs were witnessed that affected people's night vision. Astronomers have taken to calling these the "Halloween fireballs." During the Southern Taurid meteor shower in 2013, fireball sightings were spotted over southern California, Arizona, Nevada, and Utah. A 2021 study by Ignacio Ferrín and Vincenzo Orofino catalogued 88 probable members of

1560-566: Was found in the La Tête du Lion cave ( fr ). The bovine in this panel may represent the constellation Taurus , with a pattern representing the Pleiades just above it. A star chart drawn 5000 years ago by the Indians in Kashmir, which also depict a supernova for the first time in human history. The Nebra sky disk , a 30 cm wide bronze disk dated to 1600 BC, bears gold symbols generally interpreted as

1600-612: Was used. A Roman era example of a graphical representation of the night sky is the Ptolemaic Egyptian Dendera zodiac , dating from 50 BC. This is a bas relief sculpting on a ceiling at the Dendera Temple complex . It is a planisphere depicting the zodiac in graphical representations. However, individual stars are not plotted. The oldest surviving manuscript star chart was the Dunhuang Star Chart , dated to

#79920