"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"
"they appeared 13 billion years ago, when the universe was less than a billion years old. The fact that more distant objects appear to be younger, due to the finite speed of light, allows astronomers to infer the evolution of stars, of galaxies, and of the universe itself. Astronomical distances are sometimes expressed in light-years, especially in popular science publications and media. A light-year is the distance light travels in one year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. In round figures, a light year is nearly 10 trillion kilometres or nearly 6 trillion miles. Proxima Centauri,"
"36 Andromedae 36 Andromedae is a visual binary star system in the northern constellation of Andromeda. The designation is from the star catalogue of English astronomer John Flamsteed, first published in 1712. It is faintly visible to the naked eye with an apparent visual magnitude of 5.45. An annual parallax shift of 26.33 mas yields a distance estimate of about 124 light years. The system is moving closer to the Sun with a radial velocity of −0.8 km/s. The binary nature of this system was discovered in 1832 by the German-Russian astronomer Wilhelm von Struve. It is a wide binary"
"36 Andromedae 36 Andromedae is a visual binary star system in the northern constellation of Andromeda. The designation is from the star catalogue of English astronomer John Flamsteed, first published in 1712. It is faintly visible to the naked eye with an apparent visual magnitude of 5.45. An annual parallax shift of 26.33 mas yields a distance estimate of about 124 light years. The system is moving closer to the Sun with a radial velocity of −0.8 km/s. The binary nature of this system was discovered in 1832 by the German-Russian astronomer Wilhelm von Struve. It is a wide binary"
"of 3.27 Astronomical Units (AU). HD 33636 HD 33636 is a binary system located approximately 94 light-years away in Orion constellation. The visible member HD 33636 A is a 7th magnitude yellow main-sequence star. It is located at a distance of 91.6 light years from Earth. It has a metallicity of −0.05 ± 0.07. A companion was discovered in 2002 with a minimum mass of planet size. This was ascertained to be a low-mass star in 2007, making it HD 33636 B. HD 33636 B was discovered in 2002 by the Keck telescope in Hawaii. It was independently detected at"
"equivalent distance of the solar system's asteroid belt. It is not currently known why both of these star systems should have such configurations; i.e. a protoplanetary disk around part of the system while other stars in the system lack one. HD 113766 HD 113766 is a binary star system located 424 light years from Earth in the direction of the constellation Centaurus. The star system is approximately 10 million years old and both stars are slightly more massive than our sun. The two are separated by an angle of 1.3 arcseconds, which, at the distance of this system, corresponds to"
"36 Tauri 36 Tauri (abbreviated to 36 Tau) is a binary star in the constellation of Taurus. Parallax measurements made by the Hipparcos spacecraft put it at a distance of over 1,000 light years (350 parsecs) from Earth. The combined apparent magnitude of the system is about 5.5, meaning it can barely be seen with the naked eye, according to the Bortle scale. 36 Tauri is a spectroscopic binary. The two stars are close enough that periodic Doppler shifts in their spectra can be made out. In this case, light from both stars can be detected (and they overlap in"
"31 Aquilae 31 Aquilae (abbreviated 31 Aql) is a star in the equatorial constellation of Aquila. ""31 Aquilae"" is its Flamsteed designation though it also bears the Bayer designation b Aquilae. This star has an apparent visual magnitude of 5.16 and is 49.5 light years from Earth. It has no known companions. 31 Aquilae has an apparent visual magnitude of 5.16, making it bright enough to be seen with the naked eye in dark skies. The annual parallax shift of 65.89 mas yields a distance estimate of from Earth. It is a variable star with a magnitude change of less"
"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"
"(symbol: pc, about 3.26 light-years; the distance at which one astronomical unit subtends an angle of one second of arc). As defined by the IAU, the light-year is the product of the Julian year (365.25 days as opposed to the 365.2425-day Gregorian year) and the speed of light (). 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 IAU recognized abbreviation for light-year is ly, although other standards like ISO 80000 use ""l.y."" and localized symbols are frequent, such as ""al"" in French"
"36 Aquilae 36 Aquilae (abbreviated 36 Aql) is a star in the equatorial constellation of Aquila. ""36 Aquilae"" is its Flamsteed designation though it also bears the Bayer designation e Aquilae. With an apparent visual magnitude of 5.02, this star is faintly visible to the naked eye. It has an annual parallax shift of 6.17 mas, indicating a physical distance of with a 30 light-year margin of error. The spectrum of this star matches a stellar classification of M1 III. It is a red giant star with 54 times the radius of the Sun that is currently on the asymptotic"
"26 Aquilae 26 Aquilae (abbreviated 26 Aql) is a binary star system in the equatorial constellation of Aquila. ""20 Aquilae"" is its Flamsteed designation though it also bears the Bayer designation f Aquilae. It has an apparent visual magnitude of 5.00, which means it is faintly visible to the naked eye. As the Earth orbits the Sun, this star system undergoes a parallax shift of 21.15 mas. This means it is located at a distance of approximately from Earth, give or take a 3 light-year margin of error. This is a single-lined spectroscopic binary system, meaning that the presence of"
"year as our galaxy, but they were much smaller and less massive, making it ""intensely star forming"". The light travel distance of the light that we observe from UDFy-38135539 (HUF.YD3) is more than 4 billion parsecs (13.1 billion light years), and it has a luminosity distance of 86.9 billion parsecs (about 283 billion light years). There are a number of different distance measures in cosmology, and both ""light travel distance"" and ""luminosity distance"" are different from the comoving distance or ""proper distance"" generally used in defining the size of the observable universe (comoving distance and proper distance are defined to"
"the Sun of spectral type G5V and magnitude 6.18. The two are 10.6 astronomical units (au) apart and orbit each other every 21.78 years. The system is 52.4 ± 0.6 light-years distant from Earth. Likewise 16 Lyncis was originally known as Psi Aurigae and conversely, 37, 39, 41 and 44 Lyncis became part of Ursa Major. Y Lyncis is a popular target among amateur astronomers, as it is a semiregular variable ranging in brightness from magnitude 6.2 to 8.9. These shifts in brightness are complex, with a shorter period of 110 days due to the star's pulsations, and a longer"
"26 Andromedae 26 Andromedae, abbreviated 26 And, is an astrometric binary star system in the constellation Andromeda. ""26 Andromedae"" is the Flamsteed designation. It has a combined apparent visual magnitude of 6.10, which is near the lower limit of visibility to the naked eye. The distance to this system can be estimated from its annual parallax shift of , which yields a range of 610 light years. At that distance, the visual magnitude of the stars is diminished from an extinction of 0.04 due to interstellar dust. The system is moving further from the Earth with a heliocentric radial velocity"
"at least three different measures of time. The astronomical unit of time is the Day, defined as seconds. 365.25 days make up one Julian year. The symbol ""D"" is used in astronomy to refer to this unit. The astronomical unit of mass is the solar mass. The symbol is often used to refer to this unit. The solar mass (), , is a standard way to express mass in astronomy, used to describe the masses of other stars and galaxies. It is equal to the mass of the Sun, about times the mass of the Earth or 1 048 times"
"HD 24160 HD 24160 is a single star in the equatorial constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 4.17. The distance to HD 24160 can be estimated from its annual parallax shift of , yielding a separation of 217 light years. It is moving further from the Earth with a heliocentric radial velocity of +2 km/s. This object is a coronal member of the Ursa Major Moving Group of stars that share a common motion through space. At the age of 1.76 billion years old, HD 24160 is an evolved G-type"
"around 22.7 billion light-years (6947 Mpc). PKS 2000-330 PKS 2000-330 (also known as QSO B2000-330) is a quasar located in the constellation Sagittarius. When identified in 1982, it was the most distant and most luminous object known. The ""distance"" of a far away galaxy depends on what distance measurement you use. With a redshift of 3.77, light from this active galaxy is estimated to have taken around 11.7 billion years to reach us. But since this galaxy is receding from Earth at an estimated rate of 274,681 km/s (the speed of light is 299,792 km/s), the present (co-moving) distance to"
"System. Lying 222 ± 7 light-years away with an apparent magnitude of 4.39, HD 66141 is 6.8 billion years old and has evolved into an orange giant of spectral type K2III with a diameter around 22 times that of the Sun, and weighing 1.1 solar masses. It is 174 times as luminous as the Sun, with an absolute magnitude of −0.15. HD 66141 was mistakenly named 13 Puppis, as its celestial coordinates were recorded incorrectly when catalogued and hence mistakenly thought to be in the constellation of Puppis; Bode gave it the name Lambda Canis Minoris, which is now obsolete."
"HD 113766 HD 113766 is a binary star system located 424 light years from Earth in the direction of the constellation Centaurus. The star system is approximately 10 million years old and both stars are slightly more massive than our sun. The two are separated by an angle of 1.3 arcseconds, which, at the distance of this system, corresponds to a projected separation of at least 170 AU. What makes HD 113766 special is the presence of a large belt of warm (~440 K) dust surrounding the star HD 113766 A. The dense dust belt, more than 100 times more"
"a star with a parallax angle of only one arcsecond measured on a baseline of one AU is a unit known as the parsec (pc) in astronomy and is equal to about 3.26 light years. There is an inverse relationship between the distance in parsecs and the angle in arcseconds. For instance, two arcseconds corresponds to a distance of and 0.5 arcsecond corresponds to a distance of two parsecs. The skinny triangle is useful in gunnery in that it allows a relationship to be calculated between the range and size of the target without the shooter needing to compute or"
"others think HD 168625 is farther, at a distance estimated to be 2.8 kiloparsecs (kpc) (9,100 light years) and unrelated to the former objects. The parallax published in Gaia Data Release 2 indicates a distance close to 1,600 kpc, consistent with HD 168607. Assuming a distance of 2.2 kiloparsecs, HD 168625 is 220,000 times brighter than the Sun, having a surface temperature of 12,000 K. It is losing mass through a very strong stellar wind at a rate of roughly 1.46×10 solar masses per year and observations realized in 2012 with the help of the VLT show it's actually a"
"(exactly astronomical units) corresponds exactly to that derived using 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 SI length in metres, so now the parsec corresponds to an exact SI length in metres. To the nearest meter, the small-angle parsec corresponds to 30,856,775,814,913,673 m. The parallax method 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 arcseconds, and"
"Light-second The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exactly metres by the definition of metre (just over miles). Just as the second forms the basis for other units of time, the light-second can form the basis for other units of length, ranging from the light-nanosecond (299.8 mm or just under one international foot) to the light-minute, light-hour and light-day, which are sometimes used in popular science publications. The more commonly used light-year is also"
"Light-second The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exactly metres by the definition of metre (just over miles). Just as the second forms the basis for other units of time, the light-second can form the basis for other units of length, ranging from the light-nanosecond (299.8 mm or just under one international foot) to the light-minute, light-hour and light-day, which are sometimes used in popular science publications. The more commonly used light-year is also"
"16 Cygni 16 Cygni or 16 Cyg is the Flamsteed designation of a triple star system approximately 69 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C. In 1996 an extrasolar planet was discovered in an eccentric orbit around 16 Cygni B. The parallax of the two brightest stars were measured as part of the Hipparcos astrometry mission. This yielded a parallax of 47.44 milliarcseconds for 16 Cygni A and 47.14 milliarcseconds for 16 Cygni B. Since"
"for historical or archaeological purposes; however, the classical second has been retained as the basis of timekeeping. Second : The time taken for light to travel 299,792,458 meters in vacuum. Kilosecond : 16 minutes Diurn ""100 kiloseconds"" : 27 hours, 1 day and 3 hours Megasecond (Cycle) ""10 diurns"" : 11 days and 6 hours M-year ""30 megaseconds"" : 337 Earth days, 11 months Gigasecond : approximately 31 Earth years Terasecond : approximately 31,000 Earth years (half age of human species) Petasecond : approximately 31,000,000 Earth years (half elapsed time since end of Cretaceous era) T-gates : (Transporter gates). These"
"HD 162826 HD 162826 (HR 6669, HIPP 87382) is a star in the constellation Hercules. It is about away from Earth. With an apparent magnitude of 6.46, the star can be found with binoculars or a low-power telescope by reference to nearby Vega in the constellation Lyra. It is very similar to the Sun; the Sun is a G2V star with a temperature of 5778 K and 4.6 billion years old while HD 162826 is a F8V star with a temperature of 6210 K, 4.5 billion years old, and is just 15% more massive than the Sun and 3% more"
"66 Andromedae 66 Andromedae is a binary star in the constellation Andromeda. The designation is from the star catalogue of English astronomer John Flamsteed, first published in 1712. It has a combined apparent magnitude of 6.16, which is just below the nominal brightness limit of stars that are visible to the naked eye under good seeing conditions. An annual parallax shift of 17.69 mas provides a distance estimate of around 184 light years. This is a double-lined spectroscopic binary system with an orbital period of 11 days and an eccentricity of 0.19. The two components are similar stars with a"
"Myr The abbreviation myr, ""million years"", is a unit of a quantity of (i.e. ) years, or 31.6 teraseconds. Myr is in common use where the term is often written, such as in Earth science and cosmology. Myr is seen with ""mya"", ""million years ago"". Together they make a reference system, one to a quantity, the other to a particular place in a year numbering system that is ""time before the present"". Myr is deprecated in geology, but in astronomy ""myr"" is standard. Where ""myr"" ""is"" seen in geology it is usually ""Myr"" (a unit of mega-years). In astronomy it"
"10 watts, equal to an absolute bolometric magnitude of -31.5. If the quasar were at a distance of 280 light-years from Earth, it would give out as much energy per square meter as the Sun does at Earth, despite being 18 million times more distant. The quasar's luminosity is therefore about 3 × 10 (300 trillion) times the Sun, or over 25,000 times as luminous as all the 100 to 400 billion stars of the Milky Way Galaxy combined, making it one of the most powerful objects in the observable universe. However, because of its huge distance of 12.1 billion"
"a star other than the Sun, by Friedrich Bessel in 1838. The star was 61 Cygni, and he used a heliometer designed by Joseph von Fraunhofer. The largest unit for expressing distances across space at that time was the astronomical unit, equal to the radius of the Earth's orbit or In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be astronomical units ( or ). Bessel added that light employs 10.3 years to traverse this distance. He recognized that his readers would enjoy the mental picture of the approximate"
"Astronomical unit The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun. However, that distance varies as Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year. Originally conceived as the average of Earth's aphelion and perihelion, since 2012 it has been defined as exactly metres or about . The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length,"