What unit of length is defined as the mean distance between the earth and the sun (approximately 149,597,871 km)?
"definition being already fixed: mass (of the Sun), and time (the day of seconds). This transferred the uncertainty from the gravitational constant to an uncertainty in the semi-major axis of the Earth-Sun system, which was no longer exactly one a.u. (the a.u. being defined as depending on the value of the gravitational constant). The astronomical unit thus became a measured quantity rather than a defined, fixed one. In 1976, the IAU reconfirmed the Gaussian constant's status at the XVIth General Assembly in Grenoble, declaring it to be a defining constant, and that From this definition, the mean distance of Earth"
"approximately 5778 K () and ""V"" indicates that the Sun, like most stars, is a main-sequence star, and thus generates its energy via fusing hydrogen into helium. In its core, the Sun fuses about 620 million metric tons of hydrogen each second. The Earth's mean distance from the Sun is approximately , though the distance varies as the Earth moves from perihelion in January to aphelion in July. At this average distance, light travels from the Sun to Earth in about 8 minutes, 19 seconds. The energy of this sunlight supports almost all life on Earth by photosynthesis, and drives"
"solar activity will allow us to better protect these assets. Astronauts on deep space missions will not have Earth's protections so understanding the factors that may affect their exposure to cosmic rays and the solar wind is critical to manned space exploration. Astronomers measure distances within the Solar System in astronomical units (AU). One AU equals the average distance between the centers of Earth and the Sun, or 149,598,000 km. Pluto is about 38 AU from the Sun and Jupiter is about 5.2 AU from the Sun. One light-year is 63,240 AU. Energetic neutral atom Energetic neutral atom (ENA) imaging,"
"Metre The metre (British spelling and BIPM spelling) or meter (American spelling) (from the French unit ""mètre"", from the Greek noun μέτρον, ""measure"") is the base unit of length in some metric systems, including the International System of Units (SI). The SI unit symbol is m. The metre is defined as the length of the path travelled by light in a vacuum in second. The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole – as a result the Earth's circumference is approximately 40,000 km today. In 1799, it was"
"Earth's mean distance. Its length is: The Besselian year is a tropical year that starts when the (fictitious) mean Sun reaches an ecliptic longitude of 280°. This is currently on or close to January 1. It is named after the 19th-century German astronomer and mathematician Friedrich Bessel. The following equation can be used to compute the current Besselian epoch (in years): The TT subscript indicates that for this formula, the Julian date should use the Terrestrial Time scale, or its predecessor, ephemeris time. The exact length of an astronomical year changes over time. Mean year lengths in this section are"
"as the Julian day, but adjusted to the frame of reference of the Sun, and thus can differ from the Julian day by as much as 8.3 minutes (498 seconds), that being the time it takes the Sun's light to reach Earth. To illustrate the ambiguity that could arise, consider the two separate astronomical measurements of an astronomical object from the earth: Assume that three objects—the Earth, the Sun, and the astronomical object targeted, that is whose distance is to be measured—happen to be in a straight line for both measures. However, for the first measurement, the Earth is between"
"reasonably accurate value for the astronomical unit (AU) to be calculated to a precision of about ±30 meters. As a result, the need for parallax calculations has been superseded. A number of scientific organizations headed by the European Southern Observatory (ESO) organized a network of amateur astronomers and students to measure Earth's distance from the Sun during the transit. The participants' observations allowed a calculation of the astronomical unit (AU) of 149,608,708 km ± 11,835 km which had only a 0.007% difference to the accepted value. There was a good deal of interest in the 2004 transit as scientists attempted"
"the definition of the Astronomical Unit, or the AU, which defines a standard mean distance between the Sun and the Earth, conducted under the auspices of the Congressionally funded U.S. Transit of Venus Commission. The astronomical measurements taken of the transit of Venus by a number of countries since 1639 resulted in a progressively more accurate definition of the AU. Relying heavily on photographic methods, the naval observers returned 350 photographic plates in 1874, and 1,380 measurable plates in 1882. The results of the surveys conducted simultaneously from several locations around the world (for each of the two transits) produced"
"while voyaging to (unsuccessfully) observe the 1761 Transit in Sumatra. Using the solar parallax values obtained from the 1769 transit, Hornsby wrote in ""Philosophical Transitions"" December 1771 that ""the mean distance from the Earth to the Sun (is) 93,726,900 English miles."" The radar-based value used today for the astronomical unit is . This is only a difference of eight-tenths of one percent. Considering what these astronomers had to work with, their results were ""absolutely remarkable"". 1769 Transit of Venus observed from Tahiti On June 3, 1769, British navigator Captain James Cook, British naturalist Joseph Banks, British astronomer Charles Green and"
"Julian date for your desired time then The mean longitude of the Sun, corrected for the aberration of light, is: The mean anomaly of the Sun (actually, of the Earth in its orbit around the Sun, but it is convenient to pretend the Sun orbits the Earth), is: Put formula_4 and formula_5 in the range 0° to 360° by adding or subtracting multiples of 360° as needed. Finally, the ecliptic longitude of the Sun is: The ecliptic latitude of the Sun is nearly: as the ecliptic latitude of the Sun never exceeds 0.00033°, and the distance of the Sun from"
"billion km or 670 astronomical units). To help compare different distances this section lists lengths starting at 10 m (1 Pm or 1 trillion km or 6685 astronomical units (AU) or 0.11 light years). To help compare different distances this section lists lengths starting at 10 m (10 Pm or 66,800 AU, 1.06 light years). To help compare different distances this section lists lengths between 10 m (100 Pm or 11 light years) and 10 m (106 light years). This list includes distances between 1 and 10 exametres (10 m). To help compare different distances this section lists lengths between"
"Lunar distance (astronomy) Lunar distance (LD or formula_1), also called Earth–Moon distance, Earth–Moon characteristic distance, or distance to the Moon, is a unit of measure in astronomy. It is the average distance from the center of Earth to the center of the Moon. More technically, it is the mean semi-major axis of the geocentric lunar orbit. It may also refer to the time-averaged distance between the centers of the Earth and the Moon, or less commonly, the instantaneous Earth–Moon distance. The lunar distance is approximately a quarter of a million miles (). The mean semi-major axis has a value of"
"instead a giant flaming ball of metal even larger than the land of the Peloponnesus and that the Moon reflected the light of the Sun. For teaching this heresy, he was imprisoned by the authorities and sentenced to death, though he was later released through the intervention of Pericles. Eratosthenes estimated the distance between Earth and the Sun in the 3rd century BC as ""of stadia myriads 400 and 80000"", the translation of which is ambiguous, implying either 4,080,000 stadia (755,000 km) or 804,000,000 stadia (148 to 153 million kilometers or 0.99 to 1.02 AU); the latter value is correct"
"the exception of Mars) would be the same angular size when viewed from the Sun, this being 28 arc seconds. This meant that the assumption Kepler had made about the sizes of the planets held true, and led Horrocks to the false conclusion that the distance between each planet and the Sun was about 15,000 times its radius. Thus he estimated the average distance from the Earth to the Sun to be approximately 60 million miles (97 million km), suggesting that the Solar System was ten times larger than traditionally believed. His figure was much lower than the 93 million"
"interval of one day (""D"") of 86400 seconds. The astronomical unit of mass is the mass of the Sun (""S""). The astronomical unit of length is that length (""A"") for which the Gaussian gravitational constant (""k"") takes the value when the units of measurement are the astronomical units of length, mass and time. † The definitions of these derived constants have been taken from the references cited, but the values have been recalculated to take account of the more precise values of the primary constants cited in the table. Astronomical constant An astronomical constant is a physical constant used in"
"Earth's orbit All celestial bodies in the Solar System, including planets such as our own, orbit around the Solar System's centre of mass. The sun makes up 99.76% of this mass which is why the centre of mass is extremely close to the sun. Earth's orbit is the trajectory along which Earth travels around the Sun. The average distance between the Earth and the Sun is 149.60 million km (92.96 million mi), and one complete orbit takes days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). Earth's orbit has an eccentricity of 0.0167."
"is based on the solar day, which is the period between one solar noon (passage of the real Sun across the meridian) and the next. A solar day is approximately 24 hours of mean time. Because the Earth's orbit around the sun is elliptical, and because of the obliquity of the Earth's axis relative to the plane of the orbit (the ecliptic), the apparent solar day varies a few dozen seconds above or below the mean value of 24 hours. As the variation accumulates over a few weeks, there are differences as large as 16 minutes between apparent solar time"
"annual range). The solar constant does not remain constant over long periods of time (see Solar variation), but over a year the solar constant varies much less than the solar irradiance measured at the top of the atmosphere. This is because the solar constant is evaluated at a fixed distance of 1 Astronomical Unit (AU) while the solar irradiance will be affected by the eccentricity of the Earth's orbit. Its distance to the Sun varies annually between 147.1·10 km at aphelion and 152.1·10 km at perihelion. The Earth receives a total amount of radiation determined by its cross section (π·R²),"
"and the Sun is 778 million km (about 5.2 times the average distance between Earth and the Sun, or 5.2 AU) and it completes an orbit every 11.86 years. This is approximately two-fifths the orbital period of Saturn, forming a near orbital resonance between the two largest planets in the Solar System. The elliptical orbit of Jupiter is inclined 1.31° compared to Earth. Because the eccentricity of its orbit is 0.048, Jupiter's distance from the Sun varies by 75 million km between its nearest approach (perihelion) and furthest distance (aphelion). The axial tilt of Jupiter is relatively small: only 3.13°."
"July. At this average distance, light travels from the Sun's horizon to Earth's horizon in about 8 minutes and 19 seconds, while light from the closest points of the Sun and Earth takes about two seconds less. The energy of this sunlight supports almost all life on Earth by photosynthesis, and drives Earth's climate and weather. The Sun does not have a definite boundary, but its density decreases exponentially with increasing height above the photosphere. For the purpose of measurement, however, the Sun's radius is considered to be the distance from its center to the edge of the photosphere, the"
"Siriometer The siriometer is an obsolete astronomical unit of length, defined to be equal to one million astronomical units (au). One siriometer is approximately . The distance from Earth to the star Sirius is then approximately 0.54 siriometers. The unit was proposed in 1911 by Carl V. L. Charlier who used the symbol 'sir.' Others have suggested denoting the unit with the symbol 'Sm'. The siriometer never gained widespread usage. The first General Assembly of the International Astronomical Union in 1922 adopted the parsec as the standard unit of stellar distances, which simplified the definition of absolute magnitude. Use of"
"Light-year The light-year is a unit of length used to express astronomical distances and measures about 9.46 trillion kilometres or 5.88 trillion miles. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Because it includes the word ""year"", the term light-year is sometimes misinterpreted as a unit of time. The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in nonspecialist and popular science publications. The unit most commonly used in professional astrometry is the parsec"
"1 sea mile"", followed by ""For most practical purposes distance is measured from the latitude scale, assuming that one minute of latitude equals one nautical mile"". One tenth of a nautical mile is a cable length. The derived unit of speed is the knot, defined as one nautical mile per hour. The metre was originally defined as of the meridian arc from the North pole to the equator passing through Dunkirk. The Earth’s circumference is therefore approximately 40,000 km. The equatorial circumference is slightly longer than the polar circumference – the measurement based on this (40,075.017 km x x ="
"the siriometer seems to have disappeared from the astronomical literature by . Professional astronomers use the parsec as their primary unit of distances larger than the Solar System. Siriometer The siriometer is an obsolete astronomical unit of length, defined to be equal to one million astronomical units (au). One siriometer is approximately . The distance from Earth to the star Sirius is then approximately 0.54 siriometers. The unit was proposed in 1911 by Carl V. L. Charlier who used the symbol 'sir.' Others have suggested denoting the unit with the symbol 'Sm'. The siriometer never gained widespread usage. The first"
"by the Apollo program. </math>, where ""m"" is the mass of Earth, ""a"" is an astronomical unit, and ""M"" is the mass of the Sun. So the radius in AU is about formula_1.</ref> Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year."
"the Sun is over 1.4 billion kilometers (9 AU). With an average orbital speed of 9.68 km/s, it takes Saturn 10,759 Earth days (or about years) to finish one revolution around the Sun. As a consequence, it forms a near 5:2 mean-motion resonance with Jupiter. The elliptical orbit of Saturn is inclined 2.48° relative to the orbital plane of the Earth. The perihelion and aphelion distances are, respectively, 9.195 and 9.957 AU, on average. The visible features on Saturn rotate at different rates depending on latitude and multiple rotation periods have been assigned to various regions (as in Jupiter's case)."
"metre (as well as to some other length units which were then in use, such as the yard). However, it was soon discovered that the length of a seconds pendulum varies from place to place: French astronomer Jean Richer had measured the 0.3% difference in length between Cayenne (in French Guiana) and Paris. Jean Richer and Giovanni Domenico Cassini measured the parallax of Mars between Paris and Cayenne in French Guiana when Mars was at its closest to Earth in 1672. They arrived at a figure for the solar parallax of 91/2 inches, equivalent to an Earth–Sun distance of about"
"Unit of length A unit of length refers to any discrete, pre-established length or distance having a constant magnitude which is used as a reference or convention to express linear dimension. The most common units in modern use are U.S. customary units in the United States and metric units elsewhere. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units. The base unit in the International System of Units (SI) is the metre, defined as ""the length of the path travelled by light"
"as myrio-) is obsolete and not included among the prefixes when the International System of Units was introduced in 1960. 10 kilometres is equal to: A length of 100 kilometres (about 62 miles), as a rough amount, is relatively common in measurements on Earth and for some astronomical objects. It is the altitude at which the FAI defines spaceflight to begin. To help compare orders of magnitude, this section lists lengths between 100 and 1,000 kilometres (10 and 10 metres). A distance of 100 kilometres is equal to about 62 miles (or ). To help compare different orders of magnitude"
"the Sun with a semi-major axis of 30.027 AU at a distance of 29.3–30.7 AU once every 164 years and 6 months (60,099 days). Its orbit has an eccentricity of 0.02 and an inclination of 1° with respect to the ecliptic. The discoverers estimate that the body has a mean-diameter of 100 kilometers based on a magnitude of 23.3. Based on a generic magnitude-to-diameter conversion, it measures approximately 74 kilometers in diameter using an absolute magnitude of 8.8 and an assumed albedo of 0.10. This minor planet was the first Neptune trojan to be named in November 2015. It was"
"parallax of 1 arcsecond. The light-year is often used in popular works, but is not an approved non-SI unit and is rarely used by professional astronomers. When simulating a numerical model of the Solar System, the astronomical unit provides an appropriate scale that minimizes (overflow, underflow and truncation) errors in floating point calculations. According to Archimedes in the ""Sandreckoner"" (2.1), Aristarchus of Samos estimated the distance to the Sun to be times Earth's radius (the true value is about ). However, the book ""On the Sizes and Distances of the Sun and Moon"", which has long been ascribed to Aristarchus,"
"a unit of distance in cosmology, defined as formula_77 — the speed of light multiplied by the Hubble time. It is equivalent to 4,550 million parsecs or 14.4 billion light years. (The numerical value of the Hubble length in light years is, by definition, equal to that of the Hubble time in years.) The Hubble distance would be the distance between the Earth and the galaxies which are ""currently"" receding from us at the speed of light, as can be seen by substituting formula_78 into the equation for Hubble's law, . The Hubble volume is sometimes defined as a volume"
"as 1/86400 of a mean solar day) was made one of the original base units of the modern metric system, or International System of Units (SI), at the 10th General Conference on Weights and Measures (CGPM) in 1954. Because the planet Earth's rotation is slowly decelerating at an irregular rate and was thus unsuitable as a reference point for precise measurements, the SI second was later redefined more precisely as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom. The international standard atomic clocks"