Misplaced Pages

#812187

81-624: Spica, along with Arcturus and Denebola —or Regulus , depending on the source—forms the Spring Triangle asterism , and, by extension, is also part of the Great Diamond together with the star Cor Caroli . In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included

162-501: A main-sequence star . The evolutionary stage has been calculated to be near or slightly past the end of the main-sequence phase. This is a massive star with more than 10 times the mass of the Sun and seven times its radius . The bolometric luminosity of the primary is about 20,500 times that of the Sun , and nine times the luminosity of its companion. The primary is one of the nearest stars to

243-526: A B-V color index of +1.23, roughly midway between Pollux (B-V +1.00) and Aldebaran (B-V +1.54). η Boötis , or Muphrid, is only 3.3 light-years distant from Arcturus, and would have a visual magnitude −2.5, about as bright as Jupiter at its brightest from Earth, whereas an observer on the former system would find Arcturus with a magnitude -5.0, slightly brighter than Venus as seen from Earth, but with an orangish color. Based upon an annual parallax shift of 88.83  milliarcseconds , as measured by

324-522: A crowd-funded space program, is named Spica. Spica aims to make Denmark the first country to launch its own astronaut to space after Russia, the US and China. Spica is one of the Behenian fixed stars . In his Three Books of Occult Philosophy , Cornelius Agrippa attributes Spica's kabbalistic symbol [REDACTED] to Hermes Trismegistus . Arcturus Arcturus is the brightest star in

405-423: A duration that is probably less than 14 years. A weak magnetic field has been detected in the photosphere with a strength of around half a gauss . The magnetic activity appears to lie along four latitudes and is rotationally modulated. Arcturus is estimated to be around 6 to 8.5 billion years old, but there is some uncertainty about its evolutionary status. Based upon the color characteristics of Arcturus, it

486-477: A few microhertz (μHz), the highest peak corresponding to 4.3 μHz (2.7 days) with an amplitude of 60 ms , with a frequency separation of c. 5 μHz. They suggested that the most plausible explanation for the variability of Arcturus is stellar oscillations. Asteroseismological measurements allow direct calculation of the mass and radius, giving values of 0.8 ± 0.2  M ☉ and 27.9 ± 3.4  R ☉ . This form of modelling

567-544: A few bands can be observed from the Earth's surface. These bands are visible – near-infrared and a portion of the radio-wave part of the spectrum. For this reason there are no X-ray or far-infrared ground-based telescopes as these have to be observed from orbit. Even if a wavelength is observable from the ground, it might still be advantageous to place a telescope on a satellite due to issues such as clouds, astronomical seeing and light pollution . The disadvantages of launching

648-504: A focal point. Optical telescopes are used for astronomy and in many non-astronomical instruments, including: theodolites (including transits ), spotting scopes , monoculars , binoculars , camera lenses , and spyglasses . There are three main optical types: A Fresnel imager is a proposed ultra-lightweight design for a space telescope that uses a Fresnel lens to focus light. Beyond these basic optical types there are many sub-types of varying optical design classified by

729-406: A long-period radial velocity oscillation, which could be interpreted as a substellar companion . This substellar object would be nearly 12 times the mass of Jupiter and be located roughly at the same orbital distance from Arcturus as the Earth is from the Sun, at 1.1  astronomical units . However, all three stars surveyed showed similar oscillations yielding similar companion masses, and

810-419: A mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors —reduction of spherical aberration and no chromatic aberration —led to many proposed designs and several attempts to build reflecting telescopes . In 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name,

891-475: A single receiver and records a single time-varying signal characteristic of the observed region; this signal may be sampled at various frequencies. In some newer radio telescope designs, a single dish contains an array of several receivers; this is known as a focal-plane array . By collecting and correlating signals simultaneously received by several dishes, high-resolution images can be computed. Such multi-dish arrays are known as astronomical interferometers and

SECTION 10

#1732780906813

972-625: A space telescope include cost, size, maintainability and upgradability. Some examples of space telescopes from NASA are the Hubble Space Telescope that detects visible light, ultraviolet, and near-infrared wavelengths, the Spitzer Space Telescope that detects infrared radiation, and the Kepler Space Telescope that discovered thousands of exoplanets. The latest telescope that was launched was

1053-435: A surrounding shell. Examination of carbon monoxide lines show the molecular component of the atmosphere extending outward to 2–3 times the radius of the star, with the chromospheric wind steeply accelerating to 35–40 km/s in this region. Astronomers term "metals" those elements with higher atomic numbers than helium . The atmosphere of Arcturus has an enrichment of alpha elements relative to iron but only about

1134-467: A table of the first two batches of names approved by the WGSN, which included Arcturus for α Boötis. With an apparent visual magnitude of −0.05, Arcturus is the brightest star in the northern celestial hemisphere and the fourth-brightest star in the night sky, after Sirius (−1.46 apparent magnitude), Canopus (−0.72) and α Centauri (combined magnitude of −0.27). However, α Centauri AB

1215-1006: A table of the first two batches of names approved by the WGSN; which included Spica for this star. It is now so entered in the IAU Catalog of Star Names. The name is derived from the Latin spīca virginis "the virgin's ear of [wheat] grain". It was also anglicized as Virgin's Spike . α Virginis ( Latinised to Alpha Virginis ) is the system's Bayer designation . Johann Bayer cited the name Arista . Other traditional names are Azimech / ˈ æ z ɪ m ɛ k / , from Arabic السماك الأعزل al-simāk al-ʼaʽzal 'the unarmed simāk (of unknown meaning, cf. Eta Boötis ); Alarph , Arabic for 'the grape-gatherer' or 'gleaner', and Sumbalet ( Sombalet , Sembalet and variants), from Arabic سنبلة sunbulah "ear of grain". In Chinese , 角宿 ( Jiǎo Xiù ), meaning Horn (asterism) , refers to an asterism consisting of Spica and ζ Virginis . Consequently,

1296-477: A telescope was a 1608 patent submitted to the government in the Netherlands by Middelburg spectacle maker Hans Lipperhey for a refracting telescope . The actual inventor is unknown but word of it spread through Europe. Galileo heard about it and, in 1609, built his own version, and made his telescopic observations of celestial objects. The idea that the objective , or light-gathering element, could be

1377-458: A third of solar metallicity . Arcturus is possibly a Population II star . As one of the brightest stars in the sky, Arcturus has been the subject of a number of studies in the emerging field of asteroseismology . Belmonte and colleagues carried out a radial velocity (Doppler shift of spectral lines) study of the star in April and May 1988, which showed variability with a frequency of the order of

1458-428: Is a binary star , whose components are each fainter than Arcturus. This makes Arcturus the third-brightest individual star, just ahead of α Centauri A (officially named Rigil Kentaurus ), whose apparent magnitude is −0.01 . The French mathematician and astronomer Jean-Baptiste Morin observed Arcturus in the daytime with a telescope in 1635. This was the first recorded full daylight viewing for any star other than

1539-448: Is a rotating ellipsoidal variable , which is a non-eclipsing close binary star system where the stars are mutually distorted through their gravitational interaction. This effect causes the apparent magnitude of the star system to vary by 0.03 over an interval that matches the orbital period. This slight dip in magnitude is barely noticeable visually. Both stars rotate faster than their mutual orbital period. This lack of synchronization and

1620-580: Is a device used to observe distant objects by their emission, absorption , or reflection of electromagnetic radiation . Originally, it was an optical instrument using lenses , curved mirrors , or a combination of both to observe distant objects – an optical telescope . Nowadays, the word "telescope" is defined as a wide range of instruments capable of detecting different regions of the electromagnetic spectrum , and in some cases other types of detectors. The first known practical telescopes were refracting telescopes with glass lenses and were invented in

1701-677: Is called Da Jiao ( Chinese : 大角 ; pinyin : Dàjiǎo ; lit. 'great horn'), because it is the brightest star in the Chinese constellation called Jiao Xiu (Chinese: 角宿 ; pinyin: Jiǎo Xiǔ ; lit. 'horn star'). Later it became a part of another constellation Kang Xiu (Chinese: 亢宿 ; pinyin: Kàng Xiǔ ). The Wotjobaluk Koori people of southeastern Australia knew Arcturus as Marpean-kurrk , mother of Djuit ( Antares ) and another star in Boötes, Weet-kurrk (Muphrid). Its appearance in

SECTION 20

#1732780906813

1782-412: Is called an observatory . Radio telescopes are directional radio antennas that typically employ a large dish to collect radio waves. The dishes are sometimes constructed of a conductive wire mesh whose openings are smaller than the wavelength being observed. Unlike an optical telescope, which produces a magnified image of the patch of sky being observed, a traditional radio telescope dish contains

1863-451: Is currently ascending the red-giant branch and will continue to do so until it accumulates a large enough degenerate helium core to ignite the helium flash . It has likely exhausted the hydrogen from its core and is now in its active hydrogen shell burning phase. However, Charbonnel et al. (1998) placed it slightly above the horizontal branch , and suggested it has already completed the helium flash stage. Arcturus has evolved off

1944-422: Is due to a lower efficacy as the star has a lower surface temperature than the Sun. There have been suggestions that Arcturus might be a member of a binary system with a faint, cool companion, but no companion has been directly detected. In the absence of a binary companion, the mass of Arcturus cannot be measured directly, but models suggest it is slightly greater than that of the Sun. Evolutionary matching to

2025-528: Is now also being applied to optical telescopes using optical interferometers (arrays of optical telescopes) and aperture masking interferometry at single reflecting telescopes. Radio telescopes are also used to collect microwave radiation , which has the advantage of being able to pass through the atmosphere and interstellar gas and dust clouds. Some radio telescopes such as the Allen Telescope Array are used by programs such as SETI and

2106-482: Is possible to make very tiny antenna). The near-infrared can be collected much like visible light; however, in the far-infrared and submillimetre range, telescopes can operate more like a radio telescope. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm (0.003 mm) to 2000 μm (2 mm), but uses a parabolic aluminum antenna. On the other hand,

2187-544: Is specified as السماك الرامح as-simāk ar-rāmiħ "the uplifted one of the lancer". The term Al Simak Al Ramih has appeared in Al Achsasi Al Mouakket catalogue (translated into Latin as Al Simak Lanceator ). This has been variously romanized in the past, leading to obsolete variants such as Aramec and Azimech . For example, the name Alramih is used in Geoffrey Chaucer 's A Treatise on

2268-520: Is still relatively inaccurate, but a useful check on other models. Hipparcos satellite astrometry suggested that Arcturus is a binary star , with the companion about twenty times dimmer than the primary and orbiting close enough to be at the very limits of humans' current ability to make it out. Recent results remain inconclusive, but do support the marginal Hipparcos detection of a binary companion. In 1993, radial velocity measurements of Aldebaran, Arcturus and Pollux showed that Arcturus exhibited

2349-577: Is to follow the arc of the handle of the Big Dipper (or Plough in the UK ). By continuing in this path, one can find Spica , "Arc to Arcturus, then spike (or speed on) to Spica". Together with the bright stars Spica and Regulus (or Denebola , depending on the source), Arcturus is part of the Spring Triangle asterism . With Cor Caroli , these four stars form the Great Diamond asterism. Ptolemy described Arcturus as subrufa ("slightly red"): it has

2430-406: Is underway on several 30–40m designs. The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays . The first purpose-built radio telescope went into operation in 1937. Since then, a large variety of complex astronomical instruments have been developed. Since the atmosphere is opaque for most of the electromagnetic spectrum, only

2511-645: The Arecibo Observatory to search for extraterrestrial life. An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum. Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness . For the image to be observed, photographed, studied, and sent to a computer, telescopes work by employing one or more curved optical elements, usually made from glass lenses and/or mirrors , to gather light and other electromagnetic radiation to bring that light or radiation to

Spica - Misplaced Pages Continue

2592-588: The Chinese name for Spica is 角宿一 ( Jiǎo Sù yī , English: the First Star of Horn ). In Hindu astronomy , Spica corresponds to the Nakshatra Chitrā . As one of the nearest massive binary star systems to the Sun, Spica has been the subject of many observational studies. Spica is believed to be the star that gave Hipparchus the data that led him to discover the precession of the equinoxes . A temple to Menat (an early Hathor ) at Thebes

2673-822: The Earth's atmosphere is opaque to this part of the electromagnetic spectrum. An example of this type of telescope is the Fermi Gamma-ray Space Telescope which was launched in June 2008. The detection of very high energy gamma rays, with shorter wavelength and higher frequency than regular gamma rays, requires further specialization. Such detections can be made either with the Imaging Atmospheric Cherenkov Telescopes (IACTs) or with Water Cherenkov Detectors (WCDs). Examples of IACTs are H.E.S.S. and VERITAS with

2754-515: The Hipparcos satellite, Arcturus is 36.7 light-years (11.26 parsecs ) from the Sun. The parallax margin of error is 0.54 milliarcseconds, translating to a distance margin of error of ±0.23 light-years (0.069 parsecs). Because of its proximity, Arcturus has a high proper motion , two arcseconds a year, greater than any first magnitude star other than α Centauri. Arcturus is moving rapidly (122 km/s or 270,000 mph) relative to

2835-405: The Netherlands at the beginning of the 17th century. They were used for both terrestrial applications and astronomy . The reflecting telescope , which uses mirrors to collect and focus light, was invented within a few decades of the first refracting telescope. In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in

2916-504: The Newtonian reflector . The invention of the achromatic lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, more functional refracting telescopes. Reflecting telescopes, though not limited by the color problems seen in refractors, were hampered by the use of fast tarnishing speculum metal mirrors employed during the 18th and early 19th century—a problem alleviated by

2997-658: The Society Islands , Arcturus, called Ana-tahua-taata-metua-te-tupu-mavae ("a pillar to stand by"), was one of the ten "pillars of the sky", bright stars that represented the ten heavens of the Tahitian afterlife. In Hawaii , the pattern of Boötes was called Hoku-iwa , meaning "stars of the frigatebird". This constellation marked the path for Hawaiʻiloa on his return to Hawaii from the South Pacific Ocean. The Hawaiians called Arcturus Hoku-leʻa . It

3078-572: The Spitzer Space Telescope , observing from about 3 μm (0.003 mm) to 180 μm (0.18 mm) uses a mirror (reflecting optics). Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the frequency range from about 0.2 μm (0.0002 mm) to 1.7 μm (0.0017 mm) (from ultra-violet to infrared light). With photons of the shorter wavelengths, with

3159-412: The Sun and supernovae . Arcturus has been seen at or just before sunset with the naked eye. Arcturus is visible from both of Earth 's hemispheres as it is located 19° north of the celestial equator . The star culminates at midnight on 27 April, and at 9 p.m. on June 10 being visible during the late northern spring or the southern autumn. From the northern hemisphere , an easy way to find Arcturus

3240-451: The Sun , Arcturus is a red giant of spectral type K1.5III—an aging star around 7.1 billion years old that has used up its core hydrogen and evolved off the main sequence . It is about the same mass as the Sun , but has expanded to 25 times its size (around 35 million kilometers) and is around 170 times as luminous. The traditional name Arcturus is Latinised from the ancient Greek Ἀρκτοῦρος ( Arktouros ) and means "Guardian of

3321-485: The northern constellation of Boötes . With an apparent visual magnitude of −0.05, it is the fourth-brightest star in the night sky , and the brightest in the northern celestial hemisphere . The name Arcturus originated from ancient Greece ; it was then cataloged as α Boötis by Johann Bayer in 1603, which is Latinized to Alpha Boötis . Arcturus forms one corner of the Spring Triangle asterism . Located relatively close at 36.7 light-years from

Spica - Misplaced Pages Continue

3402-409: The ultraviolet to infrared . The spectrum shows a dramatic transition from emission lines in the ultraviolet to atomic absorption lines in the visible range and molecular absorption lines in the infrared. This is due to the optical depth of the atmosphere varying with wavelength. The spectrum shows very strong absorption in some molecular lines that are not produced in the photosphere but in

3483-609: The "Star of Joy". Arcturus is the zenith star of the Hawaiian Islands . Using Hōkūleʻa and other stars, the Polynesians launched their double-hulled canoes from Tahiti and the Marquesas Islands . Traveling east and north they eventually crossed the equator and reached the latitude at which Arcturus would appear directly overhead in the summer night sky. Knowing they had arrived at the exact latitude of

3564-713: The 1960s. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei 's instruments presented at a banquet at the Accademia dei Lincei . In the Starry Messenger , Galileo had used the Latin term perspicillum . The root of the word is from the Ancient Greek τῆλε, romanized tele 'far' and σκοπεῖν, skopein 'to look or see'; τηλεσκόπος, teleskopos 'far-seeing'. The earliest existing record of

3645-614: The Astrolabe (1391). Another Arabic name is Haris-el-sema , from حارس السماء ħāris al-samā’ "the keeper of heaven". or حارس الشمال ħāris al-shamāl’ "the keeper of north". In Indian astronomy , Arcturus is called Swati or Svati (Devanagari स्वाति, Transliteration IAST svāti, svātī́), possibly 'su' + 'ati' ("great goer", in reference to its remoteness) meaning very beneficent. It has been referred to as "the real pearl" in Bhartṛhari 's kāvyas. In Chinese astronomy , Arcturus

3726-459: The Bear", ultimately from ἄρκτος ( arktos ), "bear" and οὖρος ( ouros ), "watcher, guardian". The designation of Arcturus as α Boötis ( Latinised to Alpha Boötis ) was made by Johann Bayer in 1603. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included

3807-627: The James Webb Space Telescope on December 25, 2021, in Kourou, French Guiana. The Webb telescope detects infrared light. The name "telescope" covers a wide range of instruments. Most detect electromagnetic radiation , but there are major differences in how astronomers must go about collecting light (electromagnetic radiation) in different frequency bands. As wavelengths become longer, it becomes easier to use antenna technology to interact with electromagnetic radiation (although it

3888-406: The Sun that has enough mass to end its life in a Type II supernova explosion. However, since Spica has recently left the main sequence, this event is not likely to occur for several more million years. The primary is classified as a Beta Cephei variable star that varies in brightness over a 0.1738-day period. The spectrum shows a radial velocity variation with the same period, indicating that

3969-563: The Sun, and is now almost at its closest point to the Sun. Closest approach will happen in about 4,000 years, when the star will be a few hundredths of a light-year closer to Earth than it is today. (In antiquity, Arcturus was closer to the centre of the constellation. ) Arcturus is thought to be an old-disk star , and appears to be moving with a group of 52 other such stars, known as the Arcturus stream . With an absolute magnitude of −0.30, Arcturus is, together with Vega and Sirius, one of

4050-427: The authors concluded that the variation was likely to be intrinsic to the star rather than due to the gravitational effect of a companion. So far no substellar companion has been confirmed. One astronomical tradition associates Arcturus with the mythology around Arcas , who was about to shoot and kill his own mother Callisto who had been transformed into a bear. Zeus averted their imminent tragic fate by transforming

4131-561: The boy into the constellation Boötes, called Arctophylax "bear guardian" by the Greeks, and his mother into Ursa Major (Greek: Arctos "the bear"). The account is given in Hyginus 's Astronomy . Aratus in his Phaenomena said that the star Arcturus lay below the belt of Arctophylax, and according to Ptolemy in the Almagest it lay between his thighs. An alternative lore associates

SECTION 50

#1732780906813

4212-407: The current astronomical epoch . Spica is a close binary star whose components orbit each other every four days. They stay close enough together that they cannot be resolved as two stars through a telescope . The changes in the orbital motion of this pair results in a Doppler shift in the absorption lines of their respective spectra , making them a double-lined spectroscopic binary. Initially,

4293-417: The first ever to have their reflectivity (or geometric albedo ) measured. The geometric albedos of Spica A and B are, respectively, 3.61 percent and 1.36 percent, values that are low compared to planets. The MK spectral classification of Spica is typically considered to be an early B-type main-sequence star. Individual spectral types for the two components are difficult to assign accurately, especially for

4374-486: The high ellipticity of their orbit may indicate that this is a young star system. Over time, the mutual tidal interaction of the pair may lead to rotational synchronization and orbit circularization . Spica is a polarimetric variable, first discovered to be such in 2016. The majority of the polarimetric signal is the result of the reflection of the light from one star off the other (and vice versa). The two stars in Spica were

4455-682: The higher frequencies, glancing-incident optics, rather than fully reflecting optics are used. Telescopes such as TRACE and SOHO use special mirrors to reflect extreme ultraviolet , producing higher resolution and brighter images than are otherwise possible. A larger aperture does not just mean that more light is collected, it also enables a finer angular resolution. Telescopes may also be classified by location: ground telescope, space telescope , or flying telescope . They may also be classified by whether they are operated by professional astronomers or amateur astronomers . A vehicle or permanent campus containing one or more telescopes or other instruments

4536-415: The introduction of silver coated glass mirrors in 1857, and aluminized mirrors in 1932. The maximum physical size limit for refracting telescopes is about 1 meter (39 inches), dictating that the vast majority of large optical researching telescopes built since the turn of the 20th century have been reflectors. The largest reflecting telescopes currently have objectives larger than 10 meters (33 feet), and work

4617-785: The island chain, they sailed due west on the trade winds to landfall. If Hōkūleʻa could be kept directly overhead, they landed on the southeastern shores of the Big Island of Hawaii. For a return trip to Tahiti the navigators could use Sirius, the zenith star of that island. Since 1976, the Polynesian Voyaging Society 's Hōkūleʻa has crossed the Pacific Ocean many times under navigators who have incorporated this wayfinding technique in their non-instrument navigation. Arcturus had several other names that described its significance to indigenous Polynesians . In

4698-440: The main sequence to the red giant branch , reaching an early K-type stellar classification . It is frequently assigned the spectral type of K0III, but in 1989 was used as the spectral standard for type K1.5III Fe−0.5, with the suffix notation indicating a mild underabundance of iron compared to typical stars of its type. As the brightest K-type giant in the sky, it has been the subject of multiple atlases with coverage from

4779-439: The most luminous stars in the Sun's neighborhood. It is about 110 times brighter than the Sun in visible light wavelengths, but this underestimates its strength as much of the light it gives off is in the infrared ; total ( bolometric ) power output is about 180 times that of the Sun. With a near-infrared J band magnitude of −2.2, only Betelgeuse (−2.9) and R Doradus (−2.6) are brighter. The lower output in visible light

4860-478: The myth of King Arthur is based was originally named for the star. In the Middle Ages , Arcturus was considered a Behenian fixed star and attributed to the stone jasper and the plantain herb. Cornelius Agrippa listed its kabbalistic sign [REDACTED] under the alternate name Alchameth . Arcturus's light was employed in the mechanism used to open the 1933 Chicago World's Fair . The star

4941-420: The name with the legend around Icarius , who gave the gift of wine to other men, but was murdered by them, because they had had no experience with intoxication and mistook the wine for poison. It is stated that Icarius became Arcturus while his dog, Maira , became Canicula ( Procyon ), although "Arcturus" here may be used in the sense of the constellation rather than the star. As one of the brightest stars in

SECTION 60

#1732780906813

5022-607: The north signified the arrival of the larvae of the wood ant (a food item) in spring. The beginning of summer was marked by the star's setting with the Sun in the west and the disappearance of the larvae. The people of Milingimbi Island in Arnhem Land saw Arcturus and Muphrid as man and woman, and took the appearance of Arcturus at sunrise as a sign to go and harvest rakia or spikerush . The Weilwan of northern New South Wales knew Arcturus as Guembila "red". Prehistoric Polynesian navigators knew Arcturus as Hōkūleʻa ,

5103-428: The observed physical parameters gives a mass of 1.08 ± 0.06  M ☉ , while the oxygen isotope ratio for a first dredge-up star gives a mass of 1.2  M ☉ . The star, given its evolutionary state, is expected to have undergone significant mass loss in the past. The star displays magnetic activity that is heating the coronal structures, and it undergoes a solar-type magnetic cycle with

5184-573: The orbital parameters for this system were inferred using spectroscopic measurements. Between 1966 and 1970, the Narrabri Stellar Intensity Interferometer was used to observe the pair and to directly measure the orbital characteristics and the angular diameter of the primary, which was found to be (0.90 ± 0.04) × 10 arcseconds , and the angular size of the semi-major axis of the orbit was found to be only slightly larger at (1.54 ± 0.05) × 10 arcseconds . Spica

5265-415: The prologue to Plautus ' comedy Rudens (circa 211 BC). The Kāraṇḍavyūha Sūtra , compiled at the end of the 4th century or beginning of the 5th century, names one of Avalokiteśvaras meditative absorptions as "The face of Arcturus". One of the possible etymologies offered for the name " Arthur " assumes that it is derived from "Arcturus" and that the late 5th to early 6th-century figure on whom

5346-624: The rays just a few degrees . The mirrors are usually a section of a rotated parabola and a hyperbola , or ellipse . In 1952, Hans Wolter outlined 3 ways a telescope could be built using only this kind of mirror. Examples of space observatories using this type of telescope are the Einstein Observatory , ROSAT , and the Chandra X-ray Observatory . In 2012 the NuSTAR X-ray Telescope

5427-461: The secondary due to the Struve–Sahade effect . The Bright Star Catalogue derived a spectral class of B2III-IV for the primary and B4-7V for the secondary, but later studies have given various different values. The primary star has a stellar classification of B2III-IV. The luminosity class matches the spectrum of a star that is midway between a subgiant and a giant star , and it is no longer

5508-573: The sky, Arcturus has been significant to observers since antiquity. In ancient Mesopotamia , it was linked to the god Enlil , and also known as Shudun, "yoke", or SHU-PA of unknown derivation in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC. In ancient Greek, the star is found in ancient astronomical literature, e.g. Hesiod's Work and Days , circa 700 BC, as well as Hipparchus's and Ptolemy's star catalogs. The folk-etymology connecting

5589-418: The star (as seen from Earth ) on November 10, 1783. The next occultation will occur on September 2, 2197, when Venus again passes in front of Spica. The Sun passes a little more than 2° north of Spica around October 16 every year, and the star's heliacal rising occurs about two weeks later. Every 8 years, Venus passes Spica around the time of the star's heliacal rising, as in 2009 when it passed 3.5° north of

5670-467: The star commonly referred to in Armenian folklore as Gutani astgh ( Armenian : Գութանի աստղ; lit. star of the plow) was in fact Arcturus, as the constellation of Boötes was called "Ezogh" ( Armenian : Եզող; lit. the person who is plowing) by Armenians. In Ancient Rome , the star's celestial activity was supposed to portend tempestuous weather, and a personification of the star acts as narrator of

5751-442: The star is moving away from the observer. It may be caused by a strong stellar wind from the primary scattering the light from secondary when it is receding. This star is smaller than the primary, with about 4 times the mass of the Sun and 3.6 times the Sun's radius. Its stellar classification is B4-7 V, making this a main-sequence star . Both a rocket and crew capsule designed and under development by Copenhagen Suborbitals ,

5832-524: The star name with the bears (Greek: ἄρκτος, arktos) was probably invented much later. It fell out of use in favour of Arabic names until it was revived in the Renaissance . Arcturus is also mentioned in Plato's "Laws" (844e) as a herald for the season of vintage, specifically figs and grapes. In Arabic , Arcturus is one of two stars called al-simāk "the uplifted ones" (the other is Spica ). Arcturus

5913-563: The star on November 3. A method of finding Spica is to follow the arc of the handle of the Big Dipper (or Plough) to Arcturus, and then continue on the same angular distance to Spica. This can be recalled by the mnemonic phrase, "arc to Arcturus and spike to Spica." Stars that can set (not in a circumpolar constellation for the viewer) culminate at midnight—noticeable where viewed away from any polar region experiencing midnight sun —when at opposition , meaning they can be viewed from dusk until dawn. This applies to α Virginis on 12 April, in

5994-476: The surface of the star is regularly pulsating outward and then contracting. This star is rotating rapidly, with a rotational velocity of 199 km/s along the equator . The secondary member of this system is one of the few stars whose spectrum is affected by the Struve–Sahade effect. This is an anomalous change in the strength of the spectral lines over the course of an orbit, where the lines become weaker as

6075-511: The task they perform such as astrographs , comet seekers and solar telescopes . Most ultraviolet light is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. X-rays are much harder to collect and focus than electromagnetic radiation of longer wavelengths. X-ray telescopes can use X-ray optics , such as Wolter telescopes composed of ring-shaped 'glancing' mirrors made of heavy metals that are able to reflect

6156-519: The technique is called aperture synthesis . The 'virtual' apertures of these arrays are similar in size to the distance between the telescopes. As of 2005, the record array size is many times the diameter of the Earth – using space-based very-long-baseline interferometry (VLBI) telescopes such as the Japanese HALCA (Highly Advanced Laboratory for Communications and Astronomy) VSOP (VLBI Space Observatory Program) satellite. Aperture synthesis

6237-705: Was chosen as it was thought that light from Arcturus had started its journey at about the time of the previous Chicago World's Fair in 1893 (at 36.7 light-years away, the light actually started in 1896). At the height of the American Civil War, President Abraham Lincoln observed Arcturus through a 9.6-inch refractor telescope when he visited the Naval Observatory in Washington, D.C., in August 1863. Telescope A telescope

6318-523: Was equated to the Tuamotuan constellation Te Kiva , meaning " frigatebird ", which could either represent the figure of Boötes or just Arcturus. However, Arcturus may instead be the Tuamotuan star called Turu . The Hawaiian name for Arcturus as a single star was likely Hoku-leʻa , which means "star of gladness", or "clear star". In the Marquesas Islands , Arcturus was probably called Tau-tou and

6399-447: Was launched which uses Wolter telescope design optics at the end of a long deployable mast to enable photon energies of 79 keV. Higher energy X-ray and gamma ray telescopes refrain from focusing completely and use coded aperture masks: the patterns of the shadow the mask creates can be reconstructed to form an image. X-ray and Gamma-ray telescopes are usually installed on high-flying balloons or Earth-orbiting satellites since

6480-523: Was oriented with reference to Spica when it was built in 3200 BC, and, over time, precession slowly but noticeably changed Spica's location relative to the temple. Nicolaus Copernicus made many observations of Spica with his home-made triquetrum for his researches on precession. Spica is 2.06 degrees from the ecliptic and can be occulted by the Moon and sometimes by planets . The last planetary occultation of Spica occurred when Venus passed in front of

6561-689: Was the star that ruled the month approximating January. The Māori and Moriori called it Tautoru , a variant of the Marquesan name and a name shared with Orion's Belt . In Inuit astronomy , Arcturus is called the Old Man ( Uttuqalualuk in Inuit languages ) and The First Ones ( Sivulliik in Inuit languages). The Miꞌkmaq of eastern Canada saw Arcturus as Kookoogwéss , the owl. Early-20th-century Armenian scientist Nazaret Daghavarian theorized that

#812187