Messier 15 or M15 (also designated NGC 7078 and sometimes known as the Great Pegasus Cluster ) is a globular cluster in the constellation Pegasus . It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier 's catalogue of comet -like objects in 1764. At an estimated 12.5 ± 1.3 billion years old, it is one of the oldest known globular clusters.
24-486: M15 or M-15 may refer to: In science [ edit ] Messier 15 (M15), a globular cluster in the constellation Pegasus In firearms and military equipment [ edit ] M15 mine , a United States anti-tank mine M15 rifle , a variant of the M14, a United States military rifle Grigorovich M-15 , a Russian World War I-era biplane flying boat M15 pistol ,
48-527: A Magic: The Gathering expansion set [REDACTED] Topics referred to by the same term This disambiguation page lists articles associated with the same title formed as a letter–number combination. 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=M15&oldid=1239350717 " Category : Letter–number combination disambiguation pages Hidden categories: Short description
72-407: A star system tend to be small fractions of a light-year, and are usually expressed in astronomical units . However, smaller units of length can similarly be formed usefully by multiplying units of time by the speed of light. For example, the light-second , useful in astronomy, telecommunications and relativistic physics, is exactly 299 792 458 metres or 1 / 31 557 600 of
96-711: A General Officer's variant of the M1911A1 M15 Half-track M15/42 tank , an Italian medium tank In transportation [ edit ] M-15 (Michigan highway) , a highway in the lower peninsula of Michigan, US M15 motorway (Hungary) , a motorway in Hungary M15 road (East London) , a Metropolitan Route in East London, South Africa M15 (Cape Town) , a Metropolitan Route in Cape Town, South Africa M15 road (Pretoria) ,
120-786: A Metropolitan Route in Pretoria, South Africa M15 road (Durban) , a Metropolitan Route in Durban, South Africa M15 road (Bloemfontein) , a Metropolitan Route in Bloemfontein, South Africa M15 (Port Elizabeth) , a Metropolitan Route in Port Elizabeth, South Africa The Hunter Expressway in New South Wales, Australia M15 motorway (Great Britain) , an unbuilt motorway in London M15 (New York City bus) ,
144-608: A New York City Bus route in Manhattan, US Select Bus Service § M15 , a New York City Bus route in Manhattan, US Noble M15 , a British sport car built by Noble Automotive Ltd FAA location identifier for James Tucker Airport , a rural airport in Linden, Tennessee, US GER Class M15 , a class of British 2-4-2T steam locomotive WSK-Mielec PZL M-15 Belphegor , a Polish-designed jet-engined agricultural biplane M15 fuel mixed with 15% of methanol M15 road (Zambia) ,
168-412: A light-year. Units such as the light-minute, light-hour and light-day are sometimes used in popular science publications. The light-month, roughly one-twelfth of a light-year, is also used occasionally for approximate measures. The Hayden Planetarium specifies the light month more precisely as 30 days of light travel time. Light travels approximately one foot in a nanosecond ; the term "light-foot"
192-604: A road in Zambia In sports [ edit ] Markku Uusipaavalniemi (nicknamed "M-15"), a Finnish curler In computing [ edit ] An ergonomic model of IBM's Model M keyboard, produced in the mid-1990s. See also [ edit ] 15-M, Anti-austerity movement in Spain MI5 , the United Kingdom's counter-intelligence and security agency Shorthand for Model 15 Magic 2015 ,
216-533: Is an odd name. In 1868 an English journal labelled the light-year as a unit used by the Germans. Eddington called the light-year an inconvenient and irrelevant unit, which had sometimes crept from popular use into technical investigations. Although modern astronomers often prefer to use the parsec , light-years are also popularly used to gauge the expanses of interstellar and intergalactic space. Distances expressed in light-years include those between stars in
240-467: Is different from Wikidata All article disambiguation pages All disambiguation pages Messier 15 M 15 is about 35,700 light-years from Earth , and 175 light-years in diameter. It has an absolute magnitude of −9.2, which translates to a total luminosity of 360,000 times that of the Sun . Messier 15 is one of the most densely packed globulars known in
264-598: Is the product of the J1900.0 mean tropical year and the defined speed of light. Abbreviations used for light-years and multiples of light-years are: The light-year unit appeared a few years after the first successful measurement of the distance to a star other than the Sun, by Friedrich Bessel in 1838. The star was 61 Cygni , and he used a 160-millimetre (6.2 in) heliometre designed by Joseph von Fraunhofer . The largest unit for expressing distances across space at that time
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#1732771743480288-470: The Milky Way galaxy . Its core has undergone a contraction known as " core collapse " and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole. Home to over 100,000 stars, the cluster is notable for containing a large number of variable stars (112) and pulsars (8), including one double neutron star system, M15-C. It also contains Pease 1 ,
312-545: The IAU (1964) System of Astronomical Constants, used from 1968 to 1983. The product of Simon Newcomb 's J1900.0 mean tropical year of 31 556 925 .9747 ephemeris seconds and a speed of light of 299 792 .5 km/s produced a light-year of 9.460 530 × 10 m (rounded to the seven significant digits in the speed of light) found in several modern sources was probably derived from an old source such as C. W. Allen 's 1973 Astrophysical Quantities reference work, which
336-583: The IAU for light-year is "ly", International standards like ISO 80000:2006 (now superseded) have used "l.y." and localized abbreviations are frequent, such as "al" in French, Spanish, and Italian (from année-lumière , año luz and anno luce , respectively), "Lj" in German (from Lichtjahr ), etc. Before 1984, the tropical year (not the Julian year) and a measured (not defined) speed of light were included in
360-402: The brightest of which are of magnitude +12.6. The cluster appears 18 arc minutes in size (three tenths of a degree across). M15 is around 4° WNW of the brightest star of Pegasus, Epsilon Pegasi . Earth-orbiting satellites Uhuru and Chandra X-ray Observatory have detected two bright X-ray sources in this cluster: Messier 15 X-1 (4U 2129+12) and Messier 15 X-2. The former appears to be
384-639: The first astronomical X-ray source detected in Pegasus. Light-year A light-year , alternatively spelled light year ( ly or lyr ), is a unit of length used to express astronomical distances and is equal to exactly 9 460 730 472 580 .8 km , which is approximately 5.88 trillion mi. 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). Despite its inclusion of
408-415: The first planetary nebula discovered within a globular cluster in 1928. Just three others have been found in globular clusters since then. At magnitude 6.2, M15 approaches naked eye visibility under good conditions and can be observed with binoculars or a small telescope, appearing as a fuzzy star. Telescopes with a larger aperture (at least 6 in. (150 mm)) will start to reveal individual stars,
432-513: The light-year is the product of the Julian year (365.25 days, as opposed to the 365.2425-day Gregorian year or the 365.24219-day Tropical year that both approximate) and the speed of light ( 299 792 458 m/s ). Both of these values are included in the IAU (1976) System of Astronomical Constants , used since 1984. From this, the following conversions can be derived: The abbreviation used by
456-438: The mental picture of the approximate transit time for light, but he refrained from using the light-year as a unit. He may have resisted expressing distances in light-years because it would reduce the accuracy of his parallax data due to multiplying with the uncertain parameter of the speed of light. The speed of light was not yet precisely known in 1838; the estimate of its value changed in 1849 ( Fizeau ) and 1862 ( Foucault ). It
480-493: The same general area, such as those belonging to the same spiral arm or globular cluster . Galaxies themselves span from a few thousand to a few hundred thousand light-years in diameter, and are separated from neighbouring galaxies and galaxy clusters by millions of light-years. Distances to objects such as quasars and the Sloan Great Wall run up into the billions of light-years. Distances between objects within
504-442: The word "year", the term should not be 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 non-specialist contexts and popular science publications. The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years). As defined by the International Astronomical Union (IAU),
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#1732771743480528-432: Was not yet considered to be a fundamental constant of nature, and the propagation of light through the aether or space was still enigmatic. The light-year unit appeared in 1851 in a German popular astronomical article by Otto Ule . Ule explained the oddity of a distance unit name ending in "year" by comparing it to a walking hour ( Wegstunde ). A contemporary German popular astronomical book also noticed that light-year
552-492: Was the astronomical unit , equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660 000 astronomical units (9.9 × 10 km; 6.1 × 10 mi). Bessel added that light takes 10.3 years to traverse this distance. He recognized that his readers would enjoy
576-438: Was updated in 2000, including the IAU (1976) value cited above (truncated to 10 significant digits). Other high-precision values are not derived from a coherent IAU system. A value of 9.460 536 207 × 10 m found in some modern sources is the product of a mean Gregorian year (365.2425 days or 31 556 952 s ) and the defined speed of light ( 299 792 458 m/s ). Another value, 9.460 528 405 × 10 m ,
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