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49-458: KPC may refer to: kiloparsec (kpc), a unit of measurement used in astronomy Kaltim Prima Coal , a thermal coal mine in Kalimantan Timur , Indonesia Kampala Pentecostal Church , an English speaking church in downtown Kampala, Uganda King's Privy Council for Canada , an advisory body to the monarch of Canada Kenai Peninsula College ,

98-469: A u ≈ 206 264.81   a u . {\displaystyle {\begin{aligned}\mathrm {SD} &={\frac {\mathrm {ES} }{\tan 1''}}\\&={\frac {\mathrm {ES} }{\tan \left({\frac {1}{60\times 60}}\times {\frac {\pi }{180}}\right)}}\\&\approx {\frac {1\,\mathrm {au} }{{\frac {1}{60\times 60}}\times {\frac {\pi }{180}}}}={\frac {648\,000}{\pi }}\,\mathrm {au} \approx 206\,264.81~\mathrm {au} .\end{aligned}}} Because

147-793: A u = 180 × 60 × 60 × 149 597 870 700   m = 96 939 420 213 600 000   m {\displaystyle \pi ~\mathrm {pc} =180\times 60\times 60~\mathrm {au} =180\times 60\times 60\times 149\,597\,870\,700~\mathrm {m} =96\,939\,420\,213\,600\,000~\mathrm {m} } (exact by the 2015 definition) Therefore, 1   p c = 96 939 420 213 600 000 π   m = 30 856 775 814 913 673   m {\displaystyle 1~\mathrm {pc} ={\frac {96\,939\,420\,213\,600\,000}{\pi }}~\mathrm {m} =30\,856\,775\,814\,913\,673~\mathrm {m} } (to

196-645: A degree ). The nearest star, Proxima Centauri , is about 1.3 parsecs (4.2 light-years) from the Sun : from that distance, the gap between the Earth and the Sun spans slightly less than ⁠ 1 / 3600 ⁠ of one degree of view. Most stars visible to the naked eye are within a few hundred parsecs of the Sun, with the most distant at a few thousand parsecs, and the Andromeda Galaxy at over 700,000 parsecs. The word parsec

245-764: A college with three campuses on the Kenai Peninsula in Alaska Key purchasing criteria , a business term defining factors that contribute to a consumer's buying decision KPC Media Group , a media company based in Kendallville, Indiana Kenya Pipeline Company , a state corporation of Kenya Kiribati Protestant Church, the former name of the Kiribati Uniting Church , the second-largest religious group in Kiribati Klebsiella pneumoniae carbapenemase ,

294-447: A distance d using the formula d ≈ ⁠ c / H ⁠ × z . One gigaparsec (Gpc) is one billion parsecs — one of the largest units of length commonly used. One gigaparsec is about 3.26 billion ly, or roughly ⁠ 1 / 14 ⁠ of the distance to the horizon of the observable universe (dictated by the cosmic microwave background radiation ). Astronomers typically use gigaparsecs to express

343-453: A new record as the farthest object that can be seen from Earth with the naked eye. It occurred about 7.5 billion years ago, the light taking that long to reach Earth. Many other things can be estimated without an instrument. If an arm is stretched the span of the hand corresponds to an angle of 18 to 20°. The distance of a person, just covered up by the outstretched thumbnail, is about 100 meters. The vertical can be estimated to about 2° and, in

392-479: A viewing distance of 16" = ~ 400 mm, which is considered a normal reading distance in the US, the smallest object resolution will be ~ 0.116 mm. For inspection purposes laboratories use a viewing distance of 200–250 mm, which gives the smallest size of the object recognizable to the naked eye of ~0.058–0.072 mm (58–72 micrometers). The accuracy of a measurement ranges from 0.1 to 0.3 mm and depends on

441-467: Is a portmanteau of "parallax of one second" and was coined by the British astronomer Herbert Hall Turner in 1913 to simplify astronomers' calculations of astronomical distances from only raw observational data. Partly for this reason, it is the unit preferred in astronomy and astrophysics , though the light-year remains prominent in popular science texts and common usage. Although parsecs are used for

490-508: Is a unit of length used to measure the large distances to astronomical objects outside the Solar System , approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9  trillion kilometres (19.2 trillion miles ). The parsec unit is obtained by the use of parallax and trigonometry , and is defined as the distance at which 1 AU subtends an angle of one arcsecond ( ⁠ 1 / 3600 ⁠ of

539-419: Is determined in a similar fashion. To determine the number of galaxies in superclusters , volumes in cubic megaparsecs (Mpc ) are selected. All the galaxies in these volumes are classified and tallied. The total number of galaxies can then be determined statistically. The huge Boötes void is measured in cubic megaparsecs. In physical cosmology , volumes of cubic gigaparsecs (Gpc ) are selected to determine

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588-510: Is easy to see, even in direct vision. Many other Messier objects are also visible under such conditions. The most distant objects that have been seen by the naked eye are nearby bright galaxies such as Centaurus A , Bode's Galaxy , Sculptor Galaxy , and Messier 83 . Five planets can be recognized as planets from Earth with the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. Under typical dark sky conditions Uranus (magnitude +5.8) can be seen as well with averted vision, as can

637-499: Is intended to measure one billion stellar distances to within 20 microarcsecond s, producing errors of 10% in measurements as far as the Galactic Centre , about 8000 pc away in the constellation of Sagittarius . Distances expressed in fractions of a parsec usually involve objects within a single star system. So, for example: Distances expressed in parsecs (pc) include distances between nearby stars, such as those in

686-506: Is limited by the fact that the eye uses rods instead of cones to view fainter stars. The visibility of diffuse objects such as star clusters and galaxies is much more strongly affected by light pollution than is that of planets and stars. Under typical dark conditions only a few such objects are visible. These include the Pleiades , h/χ Persei , the Andromeda Galaxy , the Carina Nebula ,

735-572: Is one million parsecs, or about 3,260,000 light years. Sometimes, galactic distances are given in units of Mpc/ h (as in "50/ h  Mpc", also written " 50 Mpc h "). h is a constant (the " dimensionless Hubble constant ") in the range 0.5 < h < 0.75 reflecting the uncertainty in the value of the Hubble constant H for the rate of expansion of the universe: h = ⁠ H / 100 (km/s)/Mpc ⁠ . The Hubble constant becomes relevant when converting an observed redshift z into

784-446: Is possible. This represents only 200 meters at the moon's distance of 385,000 km. Observing a nearby small object without a magnifying glass or a microscope , the size of the object depends on the viewing distance. Under normal lighting conditions (light source ~ 1000 lumens at height 600–700 mm, viewing angle ~ 35 degrees) the angular size recognized by naked eye will be round 1 arc minute = 1/60 degrees = 0.0003 radians. At

833-435: Is the fundamental calibration step for distance determination in astrophysics ; however, the accuracy of ground-based telescope measurements of parallax angle is limited to about 0.01″ , and thus to stars no more than 100 pc distant. This is because the Earth's atmosphere limits the sharpness of a star's image. Space-based telescopes are not limited by this effect and can accurately measure distances to objects beyond

882-741: The Orion Nebula , Omega Centauri , 47 Tucanae , the Ptolemy Cluster Messier 7 near the tail of Scorpius and the globular cluster M13 in Hercules . The Triangulum Galaxy (M33) is a difficult averted vision object and only visible at all if it is higher than 50° in the sky. The globular clusters M 3 in Canes Venatici and M 92 in Hercules are also visible with the naked eye under such conditions. Under really dark sky conditions, however, M33

931-646: The phases of Venus , among other things. Meteor showers are better observed by naked eye than with binoculars. Such showers include the Perseids (10–12 August) and the December Geminids . Some 100 satellites per night, the International Space Station and the Milky Way are other popular objects visible to the naked eye. On 19 March 2008, a major gamma-ray burst (GRB) known as GRB 080319B , set

980-413: The 3.5-parsec distance of 61 Cygni . The parallax of a star is defined as half of the angular distance that a star appears to move relative to the celestial sphere as Earth orbits the Sun. Equivalently, it is the subtended angle, from that star's perspective, of the semimajor axis of the Earth's orbit. Substituting the star's parallax for the one arcsecond angle in the imaginary right triangle,

1029-536: The Earth when the two measurements were taken is twice the distance between the Earth and the Sun. The difference in angle between the two measurements is twice the parallax angle, which is formed by lines from the Sun and Earth to the star at the distant vertex . Then the distance to the star could be calculated using trigonometry. The first successful published direct measurements of an object at interstellar distances were undertaken by German astronomer Friedrich Wilhelm Bessel in 1838, who used this approach to calculate

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1078-525: The Galilean moons of Jupiter before telescopes were invented. Uranus and Vesta had most probably been seen but could not be recognized as planets because they appear so faint even at maximum brightness; Uranus's magnitude varies from +5.3 to +5.9 , and Vesta's from +5.2 to +8.5 (so that it is only visible near its opposition dates). Uranus, when discovered in 1781, was the first planet discovered using technology (a telescope ) rather than being spotted by

1127-712: The asteroid Vesta at its brighter oppositions. Under perfect dark sky conditions Neptune may be visible to the Naked eye only if Neptune is at its maximum brightness (magnitude +7.8). The Sun and the Moon—the remaining noticeable naked-eye objects of the solar system—are sometimes added to make seven "planets". During daylight only the Moon and Sun are obvious naked eye objects, but in many cases Venus can be spotted in daylight and in rarer cases Jupiter . Close to sunset and sunrise, bright stars like Sirius or even Canopus can be spotted with

1176-493: The astronomical unit is defined to be 149 597 870 700   m , the following can be calculated: Therefore, if 1  ly ≈ 9.46 × 10  m, A corollary states that a parsec is also the distance from which a disc that is one au in diameter must be viewed for it to have an angular diameter of one arcsecond (by placing the observer at D and a disc spanning ES ). Mathematically, to calculate distance, given obtained angular measurements from instruments in arcseconds,

1225-430: The best observing conditions within their reach. Under such "typical" dark sky conditions, the naked eye can see stars with an apparent magnitude up to +6 . Under perfect dark sky conditions where all light pollution is absent, stars as faint as +8 might be visible. The angular resolution of the naked eye is about 1 ′ ; however, some people have sharper vision than that. There is anecdotal evidence that people had seen

1274-529: The definition of a standardized absolute and apparent bolometric magnitude scale, mentioned an existing explicit definition of the parsec as exactly ⁠ 648 000 / π ⁠  au, or approximately 3.085 677 581 491 3673 × 10  metres (based on the IAU 2012 definition of the astronomical unit). This corresponds to the small-angle definition of the parsec found in many astronomical references. Imagining an elongated right triangle in space, where

1323-509: The distance SD is calculated as follows: S D = E S tan ⁡ 1 ″ = E S tan ⁡ ( 1 60 × 60 × π 180 ) ≈ 1 a u 1 60 × 60 × π 180 = 648 000 π

1372-402: The distribution of matter in the visible universe and to determine the number of galaxies and quasars. The Sun is currently the only star in its cubic parsec, (pc ) but in globular clusters the stellar density could be from 100–1000 pc . The observational volume of gravitational wave interferometers (e.g., LIGO , Virgo ) is stated in terms of cubic megaparsecs (Mpc ) and is essentially

1421-455: The experience of the observer. The latter figure is the usual positional accuracy of faint details in maps and technical plans. A clean atmosphere is indicated by the fact that the Milky Way is visible. Comparing the zenith with the horizon shows how the "blue quality" is degraded depending on the amount of air pollution and dust. The twinkling of a star is an indication of the turbulence of

1470-473: The formula would be: Distance star = Distance earth-sun tan ⁡ θ 3600 {\displaystyle {\text{Distance}}_{\text{star}}={\frac {{\text{Distance}}_{\text{earth-sun}}}{\tan {\frac {\theta }{3600}}}}} where θ is the measured angle in arcseconds, Distance earth-sun is a constant ( 1 au or 1.5813 × 10  ly). The calculated stellar distance will be in

1519-437: The gene for an enzyme produced by some highly antibiotic-resistant bacteria Kosovo Protection Corps Kuwait Petroleum Corporation , an umbrella company which takes control of all petroleum and oil-related aspects of Kuwait Kunzang Palyul Choling , a Tibetan Buddhist organization headed by Jetsunma Ahkon Lhamo Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with

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1568-428: The human eye are: Visual perception allows a person to gain much information about their surroundings: The visibility of astronomical objects is strongly affected by light pollution . Even a few hundred kilometers away from a metropolitan area where the sky can appear to be very dark, it is still the residual light pollution that sets the limit on the visibility of faint objects. For most people, these are likely to be

1617-517: The limit of ground-based observations. Between 1989 and 1993, the Hipparcos satellite, launched by the European Space Agency (ESA), measured parallaxes for about 100 000 stars with an astrometric precision of about 0.97  mas , and obtained accurate measurements for stellar distances of stars up to 1000 pc away. ESA's Gaia satellite , which launched on 19 December 2013,

1666-433: The long leg of the triangle will measure the distance from the Sun to the star. A parsec can be defined as the length of the right triangle side adjacent to the vertex occupied by a star whose parallax angle is one arcsecond. The use of the parsec as a unit of distance follows naturally from Bessel's method, because the distance in parsecs can be computed simply as the reciprocal of the parallax angle in arcseconds (i.e.: if

1715-402: The naked eye as long as one knows the exact position in which to look. Historically, the zenith of naked-eye astronomy was the work of Tycho Brahe (1546–1601). He built an extensive observatory to make precise measurements of the heavens without any instruments for magnification. In 1610, Galileo Galilei pointed a telescope towards the sky. He immediately discovered the moons of Jupiter and

1764-495: The naked eye. Theoretically, in a typical dark sky, the dark adapted human eye would see the about 5,600 stars brighter than +6 while in perfect dark sky conditions about 45,000 stars brighter than +8 might be visible. In practice, the atmospheric extinction and dust reduces this number somewhat. In the center of a city, where the naked-eye limiting magnitude due to extreme amounts of light pollution can be as low as 2 , as few as 50 stars are visible. Colors can be seen but this

1813-426: The nearest metre ). Approximately, In the diagram above (not to scale), S represents the Sun, and E the Earth at one point in its orbit (such as to form a right angle at S ). Thus the distance ES is one astronomical unit (au). The angle SDE is one arcsecond ( ⁠ 1 / 3600 ⁠ of a degree ) so by definition D is a point in space at a distance of one parsec from the Sun. Through trigonometry,

1862-592: The need of a name for that unit of distance. He proposed the name astron , but mentioned that Carl Charlier had suggested siriometer and Herbert Hall Turner had proposed parsec . It was Turner's proposal that stuck. By the 2015 definition, 1 au of arc length subtends an angle of 1″ at the center of the circle of radius 1 pc . That is, 1 pc = 1 au/tan( 1″ ) ≈ 206,264.8 au by definition. Converting from degree/minute/second units to radians , Therefore, π   p c = 180 × 60 × 60  

1911-492: The northern hemisphere, observing the Pole Star and using a protractor can give the observer's geographic latitude , up to 1 degree of accuracy. The Babylonians , Mayans , ancient Egyptians , ancient Indians , and Chinese measured all the basics of their respective time and calendar systems by naked eye: In a similar manner star occultations by the moon can be observed. By using a digital clock an accuracy of 0.2 second

1960-399: The oldest methods used by astronomers to calculate the distance to a star is to record the difference in angle between two measurements of the position of the star in the sky. The first measurement is taken from the Earth on one side of the Sun, and the second is taken approximately half a year later, when the Earth is on the opposite side of the Sun. The distance between the two positions of

2009-521: The parallax angle is 1 arcsecond, the object is 1 pc from the Sun; if the parallax angle is 0.5 arcseconds, the object is 2 pc away; etc.). No trigonometric functions are required in this relationship because the very small angles involved mean that the approximate solution of the skinny triangle can be applied. Though it may have been used before, the term parsec was first mentioned in an astronomical publication in 1913. Astronomer Royal Frank Watson Dyson expressed his concern for

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2058-399: The same spiral arm or globular cluster . A distance of 1,000 parsecs (3,262 ly) is denoted by the kiloparsec (kpc). Astronomers typically use kiloparsecs to express distances between parts of a galaxy or within groups of galaxies . So, for example : Astronomers typically express the distances between neighbouring galaxies and galaxy clusters in megaparsecs (Mpc). A megaparsec

2107-517: The same measurement unit as used in Distance earth-sun (e.g. if Distance earth-sun = 1 au , unit for Distance star is in astronomical units; if Distance earth-sun = 1.5813 × 10  ly, unit for Distance star is in light-years). The length of the parsec used in IAU 2015 Resolution B2 (exactly ⁠ 648 000 / π ⁠ astronomical units) corresponds exactly to that derived using

2156-507: The shorter distances within the Milky Way , multiples of parsecs are required for the larger scales in the universe, including kilo parsecs (kpc) for the more distant objects within and around the Milky Way, mega parsecs (Mpc) for mid-distance galaxies, and giga parsecs (Gpc) for many quasars and the most distant galaxies. In August 2015, the International Astronomical Union (IAU) passed Resolution B2 which, as part of

2205-436: The shorter leg measures one au ( astronomical unit , the average Earth – Sun distance) and the subtended angle of the vertex opposite that leg measures one arcsecond ( 1 ⁄ 3600 of a degree), the parsec is defined as the length of the adjacent leg. The value of a parsec can be derived through the rules of trigonometry . The distance from Earth whereupon the radius of its solar orbit subtends one arcsecond. One of

2254-532: The sizes of large-scale structures such as the size of, and distance to, the CfA2 Great Wall ; the distances between galaxy clusters; and the distance to quasars . For example: To determine the number of stars in the Milky Way, volumes in cubic kiloparsecs (kpc ) are selected in various directions. All the stars in these volumes are counted and the total number of stars statistically determined. The number of globular clusters, dust clouds, and interstellar gas

2303-424: The small-angle calculation. This differs from the classic inverse- tangent definition by about 200 km , i.e.: only after the 11th significant figure . As the astronomical unit was defined by the IAU (2012) as an exact length in metres, so now the parsec corresponds to an exact length in metres. To the nearest meter, the small-angle parsec corresponds to 30 856 775 814 913 673  m . The parallax method

2352-483: The title KPC . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=KPC&oldid=1110162067 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Parsec#Parsecs and kiloparsecs The parsec (symbol: pc )

2401-421: The value of the effective distance cubed. Naked-eye stars In astronomy , the naked eye may be used to observe celestial events and objects visible without equipment, such as conjunctions , passing comets , meteor showers , and the brightest asteroids , including 4 Vesta . Sky lore and various tests demonstrate an impressive variety of phenomena visible to the unaided eye. Some basic properties of

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