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94-494: The Hubble Deep Field ( HDF ) is an image of a small region in the constellation Ursa Major , constructed from a series of observations by the Hubble Space Telescope . It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with

188-425: A celestial coordinate system lies in one of the modern constellations. Some astronomical naming systems include the constellation where a given celestial object is found to convey its approximate location in the sky. The Flamsteed designation of a star, for example, consists of a number and the genitive form of the constellation's name. Other star patterns or groups called asterisms are not constellations under

282-498: A better understanding of how they evolve. After the spherical aberration was corrected during Space Shuttle mission STS-61 in 1993, the improved imaging capabilities of the telescope were used to study increasingly distant and faint galaxies. The Medium Deep Survey (MDS) used the Wide Field and Planetary Camera 2 (WFPC2) to take deep images of random fields while other instruments were being used for scheduled observations. At

376-741: A distant galaxy containing a large amount of dust absorbing its blue light emissions. Ground-based radio images taken using the VLA revealed seven radio sources in the HDF, all of which correspond to galaxies visible in the optical images. The field has also been surveyed with the Westerbork Synthesis Radio Telescope and the MERLIN array of radio telescopes at 1.4 GHz; the combination of VLA and MERLIN maps made at wavelengths of 3.5 and 20 cm have located 16 radio sources in

470-442: A final combined image at each wavelength was a complex process. Bright pixels caused by cosmic ray impacts during exposures were removed by comparing exposures of equal length taken one after the other, and identifying pixels that were affected by cosmic rays in one exposure but not the other. Trails of space debris and artificial satellites were present in the original images, and were carefully removed. Scattered light from

564-638: A landmark image in the study of the early universe . Three years after the HDF observations were taken, a region in the south celestial hemisphere was imaged in a similar way and named the Hubble Deep Field South . The similarities between the two regions strengthened the belief that the universe is uniform over large scales and that the Earth occupies a typical region in the Universe (the cosmological principle ). A wider but shallower survey

658-452: A list of 88 constellations with three-letter abbreviations for them. However, these constellations did not have clear borders between them. In 1928, the IAU formally accepted the 88 modern constellations, with contiguous boundaries along vertical and horizontal lines of right ascension and declination developed by Eugene Delporte that, together, cover the entire celestial sphere; this list

752-421: A long tradition of observing celestial phenomena. Nonspecific Chinese star names , later categorized in the twenty-eight mansions , have been found on oracle bones from Anyang , dating back to the middle Shang dynasty . These constellations are some of the most important observations of Chinese sky, attested from the 5th century BC. Parallels to the earliest Babylonian (Sumerian) star catalogues suggest that

846-419: Is occasionally seen. Radio source Sagittarius A* , which is the best physical marker of the true Galactic Center , is located at 17  45  40.0409 , −29° 00′ 28.118″ (J2000). Rounded to the same number of digits as the table, 17  45.7 , −29.01° (J2000), there is an offset of about 0.07° from the defined coordinate center, well within the 1958 error estimate of ±0.1°. Due to

940-645: Is the Suzhou Astronomical Chart , which was prepared with carvings of stars on the planisphere of the Chinese sky on a stone plate; it is done accurately based on observations, and it shows the supernova of the year of 1054 in Taurus. Influenced by European astronomy during the late Ming dynasty , charts depicted more stars but retained the traditional constellations. Newly observed stars were incorporated as supplementary to old constellations in

1034-481: The xyz -axes are designated UVW , but the definitions vary by author. In one system, the U axis is directed toward the Galactic Center ( l = 0°), and it is a right-handed system (positive towards the east and towards the north galactic pole); in the other, the U axis is directed toward the galactic anticenter ( l = 180°), and it is a left-handed system (positive towards the east and towards

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1128-647: The Hubble eXtreme Deep Field was completed in 2012. Images from the Extreme Deep Field, or XDF, were released on September 26, 2012, to a number of media agencies. Images released in the XDF show galaxies which are now believed to have formed in the first 500 million years following the Big Bang. [REDACTED] Media related to Hubble Deep Field at Wikimedia Commons Constellation Four views of

1222-609: The Inca civilization identified various dark areas or dark nebulae in the Milky Way as animals and associated their appearance with the seasonal rains. Australian Aboriginal astronomy also describes dark cloud constellations, the most famous being the "emu in the sky" whose head is formed by the Coalsack , a dark nebula, instead of the stars. Footnotes Citations Galactic latitude Longitude (symbol l ) measures

1316-579: The International Astronomical Union (IAU) defined the galactic coordinate system in reference to radio observations of galactic neutral hydrogen through the hydrogen line , changing the definition of the Galactic longitude by 32° and the latitude by 1.5°. In the equatorial coordinate system , for equinox and equator of 1950.0 , the north galactic pole is defined at right ascension 12  49 , declination +27.4°, in

1410-670: The James Webb Space Telescope was a mid-infrared image of the Hubble Ultra-Deep Field. The HDF galaxies contained a considerably larger proportion of disturbed and irregular galaxies than the local universe; galaxy collisions and mergers were more common in the young universe as it was much smaller than today. It is believed that giant elliptical galaxies form when spirals and irregular galaxies collide. The wealth of galaxies at different stages of their evolution also allowed astronomers to estimate

1504-616: The KJV , but ‘Ayish "the bier" actually corresponding to Ursa Major. The term Mazzaroth מַזָּרוֹת , translated as a garland of crowns , is a hapax legomenon in Job 38:32, and it might refer to the zodiacal constellations. There is only limited information on ancient Greek constellations, with some fragmentary evidence being found in the Works and Days of the Greek poet Hesiod , who mentioned

1598-860: The Spitzer Space Telescope . Submillimeter observations of the field have been made with SCUBA on the James Clerk Maxwell Telescope , initially detecting 5 sources, although with very low resolution. Observations have also been made with the Subaru telescope in Hawaii. X-ray observations by the Chandra X-ray Observatory revealed six sources in the HDF, which were found to correspond to three elliptical galaxies, one spiral galaxy, one active galactic nucleus and one extremely red object, thought to be

1692-675: The Zodiac of Dendera ; it remains unclear when this occurred, but most were placed during the Roman period between 2nd to 4th centuries AD. The oldest known depiction of the zodiac showing all the now familiar constellations, along with some original Egyptian constellations, decans , and planets . Ptolemy's Almagest remained the standard definition of constellations in the medieval period both in Europe and in Islamic astronomy . Ancient China had

1786-450: The angular distance of an object eastward along the galactic equator from the Galactic Center. Analogous to terrestrial longitude , galactic longitude is usually measured in degrees (°). Latitude (symbol b ) measures the angle of an object northward of the galactic equator (or midplane) as viewed from Earth. Analogous to terrestrial latitude , galactic latitude is usually measured in degrees (°). The first galactic coordinate system

1880-592: The horizon when viewed from a particular latitude on Earth is termed circumpolar . From the North Pole or South Pole , all constellations south or north of the celestial equator are circumpolar . Depending on the definition, equatorial constellations may include those that lie between declinations 45° north and 45° south, or those that pass through the declination range of the ecliptic (or zodiac ) ranging between 23.5° north and 23.5° south . Stars in constellations can appear near each other in

1974-408: The quantum efficiency of Hubble's detectors at 300 nm wavelength is quite low, the noise in observations at this wavelength is primarily due to CCD noise rather than sky background; thus, these observations could be conducted at times when high background noise would have harmed the efficiency of observations in other passbands. Between December 18 and 28, 1995—during which time Hubble orbited

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2068-399: The throughput of each filter—the total proportion of light that it allows through—and the spectral coverage available. Filters with bandpasses overlapping as little as possible were desirable. In the end, four broadband filters were chosen, centred at wavelengths of 300 nm (near- ultraviolet ), 450 nm (blue light), 606 nm (red light) and 814 nm (near- infrared ). Because

2162-583: The zodiac (straddling the ecliptic , which the Sun , Moon , and planets all traverse). The origins of the zodiac remain historically uncertain; its astrological divisions became prominent c. 400 BC in Babylonian or Chaldean astronomy. Constellations appear in Western culture via Greece and are mentioned in the works of Hesiod , Eudoxus and Aratus . The traditional 48 constellations, consisting of

2256-458: The "heavenly bodies". Greek astronomy essentially adopted the older Babylonian system in the Hellenistic era , first introduced to Greece by Eudoxus of Cnidus in the 4th century BC. The original work of Eudoxus is lost, but it survives as a versification by Aratus , dating to the 3rd century BC. The most complete existing works dealing with the mythical origins of the constellations are by

2350-520: The 14th century. The Ancient Greek word for constellation is ἄστρον ( astron ). These terms historically referred to any recognisable pattern of stars whose appearance was associated with mythological characters or creatures, earthbound animals, or objects. Over time, among European astronomers, the constellations became clearly defined and widely recognised. In the 20th century, the International Astronomical Union (IAU) recognized 88 constellations . A constellation or star that never sets below

2444-529: The 17,000-year-old cave paintings in Lascaux , southern France, depict star constellations such as Taurus, Orion's Belt, and the Pleiades. However, this view is not generally accepted among scientists. Inscribed stones and clay writing tablets from Mesopotamia (in modern Iraq) dating to 3000 BC provide the earliest generally accepted evidence for humankind's identification of constellations. It seems that

2538-556: The 88 IAU-recognized constellations in this region first appeared on celestial globes developed in the late 16th century by Petrus Plancius , based mainly on observations of the Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman . These became widely known through Johann Bayer 's star atlas Uranometria of 1603. Fourteen more were created in 1763 by the French astronomer Nicolas Louis de Lacaille , who also split

2632-573: The Earth about 150 times—342 images of the target area in the chosen filters were taken. The total exposure times at each wavelength were 42.7 hours (300 nm), 33.5 hours (450 nm), 30.3 hours (606 nm) and 34.3 hours (814 nm), divided into 342 individual exposures to prevent significant damage to individual images by cosmic rays , which cause bright streaks to appear when they strike CCD detectors. A further 10 Hubble orbits were used to make short exposures of flanking fields to aid follow-up observations by other instruments. The production of

2726-645: The Earth or the moon during Hubble's orbit. The working group decided to concentrate on the northern continuous viewing zone, so that northern-hemisphere telescopes such as the Keck telescopes , the Kitt Peak National Observatory telescopes, and the Very Large Array (VLA) could conduct follow-up observations. Twenty fields satisfying these criteria were identified, from which three optimal candidate fields were selected, all within

2820-417: The Earth was evident in about a quarter of the data frames, creating a visible "X" pattern on the images. This was removed by taking an image affected by scattered light, aligning it with an unaffected image, and subtracting the unaffected image from the affected one. The resulting image was smoothed, and could then be subtracted from the bright frame. This procedure removed almost all of the scattered light from

2914-486: The HDF images were produced. The HDF, however, contained many galaxies with redshifts as high as six, corresponding to distances of about 12 billion light-years . Due to redshift the most distant objects in the HDF ( Lyman-break galaxies ) are not actually visible in the Hubble images; they can only be detected in images of the HDF taken at longer wavelengths by ground-based telescopes. One of the first observations planned for

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3008-643: The HDF-N field, with many more in the flanking fields. Radio images of some individual sources in the field have been made with the European VLBI Network at 1.6 GHz with a higher resolution than the Hubble maps. An HDF counterpart in the southern celestial hemisphere was created in 1998: the HDF-South (HDF-S). Created using a similar observing strategy, the HDF-S was very similar in appearance to

3102-742: The Hellenistic writer termed pseudo-Eratosthenes and an early Roman writer styled pseudo- Hyginus . The basis of Western astronomy as taught during Late Antiquity and until the Early Modern period is the Almagest by Ptolemy , written in the 2nd century. In the Ptolemaic Kingdom , native Egyptian tradition of anthropomorphic figures represented the planets, stars, and various constellations. Some of these were combined with Greek and Babylonian astronomical systems culminating in

3196-504: The IAU as well as those by cultures throughout history are imagined figures and shapes derived from the patterns of stars in the observable sky. Many officially recognized constellations are based on the imaginations of ancient, Near Eastern and Mediterranean mythologies. Some of these stories seem to relate to the appearance of the constellations, e.g. the assassination of Orion by Scorpius, their constellations appearing at opposite times of year. Constellation positions change throughout

3290-634: The NICMOS and STIS instruments. Several supernova events were detected by comparing the first and second epoch observations of the HDF-N. A wider survey, but less sensitive, was carried out as part of the Great Observatories Origins Deep Survey ; a section of this was then observed for longer to create the Hubble Ultra-Deep Field , which was the most sensitive optical deep field image for years until

3384-572: The Navigator in c. 500 BC. The history of southern constellations is not straightforward. Different groupings and different names were proposed by various observers, some reflecting national traditions or designed to promote various sponsors. Southern constellations were important from the 14th to 16th centuries, when sailors used the stars for celestial navigation . Italian explorers who recorded new southern constellations include Andrea Corsali , Antonio Pigafetta , and Amerigo Vespucci . Many of

3478-534: The Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and 28, 1995. The field is so small that only a few foreground stars in the Milky Way lie within it; thus, almost all of the 3,000 objects in the image are galaxies , some of which are among the youngest and most distant known. By revealing such large numbers of very young galaxies, the HDF has become

3572-470: The Sun's position, which currently lies 56.75 ± 6.20  ly north of the midplane, and the heliocentric definition adopted by the IAU, the galactic coordinates of Sgr A* are latitude +0° 07′ 12″ south, longitude 0° 04′ 06″ . Since as defined the galactic coordinate system does not rotate with time, Sgr A* is actually decreasing in longitude at the rate of galactic rotation at

3666-476: The affected images. Once the 342 individual images were cleaned of cosmic-ray hits and corrected for scattered light, they had to be combined. Scientists involved in the HDF observations pioneered a technique called ' drizzling ', in which the pointing of the telescope was varied minutely between sets of exposures. Each pixel on the WFPC2 CCD chips recorded an area of sky 0.09 arcseconds across, but by changing

3760-647: The ancient Chinese system did not arise independently. Three schools of classical Chinese astronomy in the Han period are attributed to astronomers of the earlier Warring States period . The constellations of the three schools were conflated into a single system by Chen Zhuo , an astronomer of the 3rd century ( Three Kingdoms period ). Chen Zhuo's work has been lost, but information on his system of constellations survives in Tang period records, notably by Qutan Xida . The oldest extant Chinese star chart dates to that period and

3854-409: The ancient constellation Argo Navis into three; these new figures appeared in his star catalogue, published in 1756. Several modern proposals have not survived. The French astronomers Pierre Lemonnier and Joseph Lalande , for example, proposed constellations that were once popular but have since been dropped. The northern constellation Quadrans Muralis survived into the 19th century (when its name

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3948-576: The associated scientific paper for the image had received over 900 citations. One of the most fundamental findings was the discovery of large numbers of galaxies with high redshift values. As the Universe expands, more distant objects recede from the Earth faster, in what is called the Hubble Flow . The light from very distant galaxies is significantly affected by the cosmological redshift . While quasars with high redshifts were known, very few galaxies with redshifts greater than one were known before

4042-620: The astronomers who designed the Hubble Space Telescope was to use its high optical resolution to study distant galaxies to a level of detail that was not possible from the ground. Positioned above the atmosphere , Hubble avoids atmospheric airglow allowing it to take more sensitive visible and ultraviolet light images than can be obtained with seeing-limited ground-based telescopes (when good adaptive optics correction at visible wavelengths becomes possible, 10 m ground-based telescopes may become competitive). Although

4136-733: The bulk of the Mesopotamian constellations were created within a relatively short interval from around 1300 to 1000 BC. Mesopotamian constellations appeared later in many of the classical Greek constellations. The oldest Babylonian catalogues of stars and constellations date back to the beginning of the Middle Bronze Age , most notably the Three Stars Each texts and the MUL.APIN , an expanded and revised version based on more accurate observation from around 1000 BC. However,

4230-655: The celestial equator), and southern constellations Puppis , Vela , Carina , Crux , Centaurus , Triangulum Australe , and Ara . Polaris , being the North Star, is the approximate center of the northern celestial hemisphere. It is part of Ursa Minor , constituting the end of the Little Dipper's handle. From latitudes of around 35° north, in January, Ursa Major (containing the Big Dipper ) appears to

4324-529: The choice of filters for the HDF (and the majority of Hubble images) was primarily designed to maximize the scientific utility of the observations rather than to create colors corresponding to what the human eye would actually perceive. The final images were released at a meeting of the American Astronomical Society in January 1996, and revealed a plethora of distant, faint galaxies. About 3,000 distinct galaxies could be identified in

4418-407: The constellation Coma Berenices , with a probable error of ±0.1°. Longitude 0° is the great semicircle that originates from this point along the line in position angle 123° with respect to the equatorial pole . The galactic longitude increases in the same direction as right ascension. Galactic latitude is positive towards the north galactic pole, with a plane passing through the Sun and parallel to

4512-491: The constellation Orion : A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellations were likely defined in prehistory . People used them to relate stories of their beliefs, experiences, creation , and mythology . Different cultures and countries invented their own constellations, some of which lasted into

4606-415: The constellation of Ursa Major . Radio snapshot observations with the VLA ruled out one of these fields because it contained a bright radio source, and the final decision between the other two was made on the basis of the availability of guide stars near the field: Hubble observations normally require a pair of nearby stars on which the telescope's Fine Guidance Sensors can lock during an exposure, but given

4700-661: The daytime and lower at night, while in winter the reverse is true, for both hemispheres. Due to the Solar System 's 60° tilt, the galactic plane of the Milky Way is inclined 60° from the ecliptic, between Taurus and Gemini (north) and Scorpius and Sagittarius (south and near which the Galactic Center can be found). The galaxy appears to pass through Aquila (near the celestial equator) and northern constellations Cygnus , Cassiopeia , Perseus , Auriga , and Orion (near Betelgeuse ), as well as Monoceros (near

4794-524: The development of today's accepted modern constellations. The southern sky, below about −65° declination , was only partially catalogued by ancient Babylonians, Egyptians, Greeks, Chinese, and Persian astronomers of the north. The knowledge that northern and southern star patterns differed goes back to Classical writers, who describe, for example, the African circumnavigation expedition commissioned by Egyptian Pharaoh Necho II in c. 600 BC and those of Hanno

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4888-466: The direction in which the telescope was pointing by less than that between exposures, the resulting images were combined using sophisticated image-processing techniques to yield a final angular resolution better than this value. The HDF images produced at each wavelength had final pixel sizes of 0.03985 arcseconds. The data processing yielded four monochrome images (at 300 nm, 450 nm, 606 nm and 814 nm), one at each wavelength. One image

4982-432: The early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many changed in size or shape. Some became popular, only to drop into obscurity. Some were limited to a single culture or nation. Naming constellations also helped astronomers and navigators identify stars more easily. Twelve (or thirteen) ancient constellations belong to

5076-399: The early constellations were never universally adopted. Stars were often grouped into constellations differently by different observers, and the arbitrary constellation boundaries often led to confusion as to which constellation a celestial object belonged. Before astronomers delineated precise boundaries (starting in the 19th century), constellations generally appeared as ill-defined regions of

5170-425: The ecliptic), approximating a great circle . Zodiacal constellations of the northern sky are Pisces , Aries , Taurus , Gemini , Cancer , and Leo . In the southern sky are Virgo , Libra , Scorpius , Sagittarius , Capricornus , and Aquarius . The zodiac appears directly overhead from latitudes of 23.5° north to 23.5° south, depending on the time of year. In summer, the ecliptic appears higher up in

5264-482: The following conversion formulas. Where: In some applications use is made of rectangular coordinates based on galactic longitude and latitude and distance. In some work regarding the distant past or future the galactic coordinate system is taken as rotating so that the x -axis always goes to the centre of the galaxy. There are two major rectangular variations of galactic coordinates, commonly used for computing space velocities of galactic objects. In these systems

5358-507: The form of star charts , whose oldest representation appears on the statue known as the Farnese Atlas , based perhaps on the star catalogue of the Greek astronomer Hipparchus . Southern constellations are more modern inventions, sometimes as substitutes for ancient constellations (e.g. Argo Navis ). Some southern constellations had long names that were shortened to more usable forms; e.g. Musca Australis became simply Musca. Some of

5452-621: The formal definition, but are also used by observers to navigate the night sky. Asterisms may be several stars within a constellation, or they may share stars with more than one constellation. Examples of asterisms include the teapot within the constellation Sagittarius , or the big dipper in the constellation of Ursa Major . The word constellation comes from the Late Latin term cōnstellātiō , which can be translated as "set of stars"; it came into use in Middle English during

5546-447: The galactic equator being 0°, whilst the poles are ±90°. Based on this definition, the galactic poles and equator can be found from spherical trigonometry and can be precessed to other epochs ; see the table. The IAU recommended that during the transition period from the old, pre-1958 system to the new, the old longitude and latitude should be designated l and b while the new should be designated l and b . This convention

5640-558: The images, with both irregular and spiral galaxies clearly visible, although some galaxies in the field are only a few pixels across. In all, the HDF is thought to contain fewer than twenty galactic foreground stars; by far the majority of objects in the field are distant galaxies. There are about fifty blue point-like objects in the HDF. Many seem to be associated with nearby galaxies, which together form chains and arcs: these are likely to be regions of intense star formation . Others may be distant quasars . Astronomers initially ruled out

5734-453: The importance of the HDF observations, the working group required a second set of back-up guide stars. The field that was eventually selected is located at a right ascension of 12 36 49.4 and a declination of +62° 12′ 58″; it is about 2.6 arcminutes in width, or 1/12 the width of the Moon. The area is about 1/24,000,000 of the total area of the sky. Once a field

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5828-480: The mid-18th century when European explorers began traveling to the Southern Hemisphere . Due to Roman and European transmission, each constellation has a Latin name. In 1922, the International Astronomical Union (IAU) formally accepted the modern list of 88 constellations , and in 1928 adopted official constellation boundaries that together cover the entire celestial sphere. Any given point in

5922-432: The nature of dark matter , mass which seems to be undetectable but which observations implied made up about 85% of all matter in the Universe by mass. One theory was that dark matter might consist of Massive Astrophysical Compact Halo Objects ( MACHOs )—faint but massive objects such as red dwarfs and planets in the outer regions of galaxies. The HDF showed, however, that there were not significant numbers of red dwarfs in

6016-449: The northeast, while Cassiopeia is the northwest. To the west are Pisces (above the horizon) and Aries. To the southwest Cetus is near the horizon. Up high and to the south are Orion and Taurus. To the southeast above the horizon is Canis Major . Appearing above and to the east of Orion is Gemini : also in the east (and progressively closer to the horizon) are Cancer and Leo. In addition to Taurus, Perseus and Auriga appear overhead. From

6110-602: The numerous Sumerian names in these catalogues suggest that they built on older, but otherwise unattested, Sumerian traditions of the Early Bronze Age . The classical Zodiac is a revision of Neo-Babylonian constellations from the 6th century BC. The Greeks adopted the Babylonian constellations in the 4th century BC. Twenty Ptolemaic constellations are from the Ancient Near East. Another ten have

6204-422: The objects in the deep field, and also needed to be in a region with a low background infrared cirrus , the diffuse, wispy infrared emission believed to be caused by warm dust grains in cool clouds of hydrogen gas ( H I regions ). These criteria restricted the field of potential target areas. It was decided that the target should be in Hubble's continuous viewing zones: the areas of sky that are not occulted by

6298-466: The observations needed to fulfill several criteria. It had to be at a high galactic latitude because dust and obscuring matter in the plane of the Milky Way 's disc prevents observations of distant galaxies at low galactic latitudes (see Zone of Avoidance ). The target field had to avoid known bright sources of visible light (such as foreground stars), and infrared , ultraviolet , and X-ray emissions, to facilitate later studies at many wavelengths of

6392-634: The original HDF. This supports the cosmological principle that at its largest scale the Universe is homogeneous . The HDF-S survey used the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instruments installed on the HST in 1997; the region of the original Hubble Deep Field (HDF-N) has since been re-observed several times using WFPC2, as well as by

6486-551: The outer parts of our galaxy. Very-high redshift objects (Lyman-break galaxies) cannot be seen in visible light and generally are detected in infrared or submillimetre wavelength surveys of the HDF instead. Observations with the Infrared Space Observatory (ISO) indicated infrared emission from 13 galaxies visible in the optical images, attributed to large quantities of dust associated with intense star formation. Infrared observations have also been made with

6580-538: The parts of the southern sky unknown to Ptolemy) by Petrus Plancius (1592, 1597/98 and 1613), Johannes Hevelius (1690) and Nicolas Louis de Lacaille (1763), who introduced fourteen new constellations. Lacaille studied the stars of the southern hemisphere from 1751 until 1752 from the Cape of Good Hope , when he was said to have observed more than 10,000 stars using a refracting telescope with an aperture of 0.5 inches (13 mm). In 1922, Henry Norris Russell produced

6674-455: The pole star include Chamaeleon , Apus and Triangulum Australe (near Centaurus), Pavo , Hydrus , and Mensa . Sigma Octantis is the closest star approximating a southern pole star, but is faint in the night sky. Thus, the pole can be triangulated using the constellation Crux as well as the stars Alpha and Beta Centauri (about 30° counterclockwise from Crux) of the constellation Centaurus (arching over Crux). It has been suggested that

6768-423: The possibility that some of the point-like objects are white dwarfs , because they are too blue to be consistent with theories of white dwarf evolution prevalent at the time. However, more recent work has found that many white dwarfs become bluer as they age, lending support to the idea that the HDF might contain white dwarfs. The HDF data provided extremely rich material for cosmologists to analyse and by late 2014

6862-695: The same latitude, in July, Cassiopeia (low in the sky) and Cepheus appear to the northeast. Ursa Major is now in the northwest. Boötes is high up in the west. Virgo is to the west, with Libra southwest and Scorpius south. Sagittarius and Capricorn are southeast. Cygnus (containing the Northern Cross ) is to the east. Hercules is high in the sky along with Corona Borealis . January constellations include Pictor and Reticulum (near Hydrus and Mensa, respectively). In July, Ara (adjacent to Triangulum Australe) and Scorpius can be seen. Constellations near

6956-836: The same stars but different names. Biblical scholar E. W. Bullinger interpreted some of the creatures mentioned in the books of Ezekiel and Revelation as the middle signs of the four-quarters of the Zodiac, with the Lion as Leo , the Bull as Taurus , the Man representing Aquarius , and the Eagle standing in for Scorpio . The biblical Book of Job also makes reference to a number of constellations, including עיש ‘Ayish "bier", כסיל chesil "fool" and כימה chimah "heap" (Job 9:9, 38:31–32), rendered as "Arcturus, Orion and Pleiades" by

7050-554: The same time, other dedicated programs focused on galaxies that were already known through ground-based observation. All of these studies revealed substantial differences between the properties of galaxies today and those that existed several billion years ago. Up to 10% of the HST's observation time is designated as Director's Discretionary (DD) Time, and is typically awarded to astronomers who wish to study unexpected transient phenomena, such as supernovae . Once Hubble's corrective optics were shown to be performing well, Robert Williams ,

7144-518: The sky, but they usually lie at a variety of distances away from the Earth. Since each star has its own independent motion, all constellations will change slowly over time. After tens to hundreds of thousands of years, familiar outlines will become unrecognizable. Astronomers can predict the past or future constellation outlines by measuring common proper motions of individual stars by accurate astrometry and their radial velocities by astronomical spectroscopy . The 88 constellations recognized by

7238-564: The sky. Today they now follow officially accepted designated lines of right ascension and declination based on those defined by Benjamin Gould in epoch 1875.0 in his star catalogue Uranometria Argentina . The 1603 star atlas " Uranometria " of Johann Bayer assigned stars to individual constellations and formalized the division by assigning a series of Greek and Latin letters to the stars within each constellation. These are known today as Bayer designations . Subsequent star atlases led to

7332-536: The southern hemisphere of the sky based on the knowledge of Western star charts; with this improvement, the Chinese Sky was integrated with the World astronomy. Historically, the origins of the constellations of the northern and southern skies are distinctly different. Most northern constellations date to antiquity, with names based mostly on Classical Greek legends. Evidence of these constellations has survived in

7426-595: The southern sky, which did not depict the traditional stars recorded by ancient Chinese astronomers. Further improvements were made during the later part of the Ming dynasty by Xu Guangqi and Johann Adam Schall von Bell , the German Jesuit and was recorded in Chongzhen Lishu (Calendrical Treatise of Chongzhen period , 1628). Traditional Chinese star maps incorporated 23 new constellations with 125 stars of

7520-460: The sun, Ω , approximately 5.7 milliarcseconds per year (see Oort constants ). An object's location expressed in the equatorial coordinate system can be transformed into the galactic coordinate system. In these equations, α is right ascension , δ is declination . NGP refers to the coordinate values of the north galactic pole and NCP to those of the north celestial pole. The reverse (galactic to equatorial) can also be accomplished with

7614-414: The telescope's mirror suffered from spherical aberration when the telescope was launched in 1990, it could still be used to take images of more distant galaxies than had previously been obtainable. Because light takes billions of years to reach Earth from very distant galaxies, we see them as they were billions of years ago; thus, extending the scope of such research to increasingly distant galaxies allows

7708-567: The then-director of the Space Telescope Science Institute , decided to devote a substantial fraction of his DD time during 1995 to the study of distant galaxies. A special Institute Advisory Committee recommended that the WFPC2 be used to image a "typical" patch of sky at a high galactic latitude , using several optical filters . A working group was set up to develop and implement the project. The field selected for

7802-442: The variation in the rate of star formation over the lifetime of the Universe. While estimates of the redshifts of HDF galaxies are somewhat crude, astronomers believe that star formation was occurring at its maximum rate 8–10 billion years ago, and has decreased by a factor of about 10 since then. Another important result from the HDF was the very small number of foreground stars present. For years astronomers had been puzzling over

7896-409: The year due to night on Earth occurring at gradually different portions of its orbit around the Sun. As Earth rotates toward the east, the celestial sphere appears to rotate west, with stars circling counterclockwise around the northern pole star and clockwise around the southern pole star. Because of Earth's 23.5° axial tilt , the zodiac is distributed equally across hemispheres (along

7990-451: The years and centuries to come. The constellations have no official symbols, though those of the ecliptic may take the signs of the zodiac. Symbols for the other modern constellations, as well as older ones that still occur in modern nomenclature, have occasionally been published. The Great Rift, a series of dark patches in the Milky Way, is most visible in the southern sky. Some cultures have discerned shapes in these patches. Members of

8084-525: The zodiac and 36 more (now 38, following the division of Argo Navis into three constellations) are listed by Ptolemy , a Greco-Roman astronomer from Alexandria , Egypt, in his Almagest . The formation of constellations was the subject of extensive mythology , most notably in the Metamorphoses of the Latin poet Ovid . Constellations in the far southern sky were added from the 15th century until

8178-410: Was also made as part of the Great Observatories Origins Deep Survey . In 2004 a deeper image, known as the Hubble Ultra-Deep Field (HUDF), was constructed from a few months of light exposure. The HUDF image was at the time the most sensitive astronomical image ever made at visible wavelengths, and it remained so until the Hubble eXtreme Deep Field (XDF) was released in 2012. One of the key aims of

8272-467: Was attached to the Quadrantid meteor shower), but is now divided between Boötes and Draco . A list of 88 constellations was produced for the IAU in 1922. It is roughly based on the traditional Greek constellations listed by Ptolemy in his Almagest in the 2nd century and Aratus ' work Phenomena , with early modern modifications and additions (most importantly introducing constellations covering

8366-408: Was designated as red (814 nm), the second as green (606 nm) and the third as blue (450 nm), and the three images were combined to give a color image. Because the wavelengths at which the images were taken do not correspond to the wavelengths of red, green and blue light, the colors in the final image only give an approximate representation of the actual colors of the galaxies in the image;

8460-498: Was finally published in 1930. Where possible, these modern constellations usually share the names of their Graeco-Roman predecessors, such as Orion, Leo, or Scorpius. The aim of this system is area-mapping, i.e. the division of the celestial sphere into contiguous fields. Out of the 88 modern constellations, 36 lie predominantly in the northern sky, and the other 52 predominantly in the southern. The boundaries developed by Delporte used data that originated back to epoch B1875.0 , which

8554-688: Was preserved as part of the Dunhuang Manuscripts . Native Chinese astronomy flourished during the Song dynasty , and during the Yuan dynasty became increasingly influenced by medieval Islamic astronomy (see Treatise on Astrology of the Kaiyuan Era ). As maps were prepared during this period on more scientific lines, they were considered as more reliable. A well-known map from the Song period

8648-405: Was selected, an observing strategy was developed. An important decision was to determine which filters the observations would use; WFPC2 is equipped with 48 filters, including narrowband filters isolating particular emission lines of astrophysical interest, and broadband filters useful for the study of the colors of stars and galaxies. The choice of filters to be used for the HDF depended on

8742-509: Was used by William Herschel in 1785. A number of different coordinate systems, each differing by a few degrees, were used until 1932, when Lund Observatory assembled a set of conversion tables that defined a standard galactic coordinate system based on a galactic north pole at RA 12  40 , dec +28° (in the B1900.0 epoch convention) and a 0° longitude at the point where the galactic plane and equatorial plane intersected. In 1958,

8836-406: Was when Benjamin A. Gould first made his proposal to designate boundaries for the celestial sphere, a suggestion on which Delporte based his work. The consequence of this early date is that because of the precession of the equinoxes , the borders on a modern star map, such as epoch J2000 , are already somewhat skewed and no longer perfectly vertical or horizontal. This effect will increase over

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