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The Hubble Deep Field (HDF) is the result of a series of observations by the Hubble Space Telescope of a small region of the northern celestial hemisphere. It covers an area of sky 144 arcseconds across, equivalent in angular size to a tennis ball at a distance of 100 metres, and was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over 10 consecutive days between December 18 and December 28, 1995. Download high resolution version (800x840, 82 KB)Hubble Deep Field (full mosaic) released by NASA on January 15, 1996. ...
Download high resolution version (800x840, 82 KB)Hubble Deep Field (full mosaic) released by NASA on January 15, 1996. ...
The Hubble Space Telescope is a telescope in orbit around the Earth. ...
In astronomy and navigation, the celestial sphere is an imaginary rotating sphere of gigantic radius, concentric with the Earth. ...
A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ...
A Hubble Space Telescope image of the Hubble Deep Field showing the characteristic stairstep composition of WFPC2 images The Wide Field and Planetary Camera 2 (WFPC2) is a camera installed on the Hubble Space Telescope. ...
December 18 is the 352nd day of the year (353rd in leap years) in the Gregorian Calendar. ...
December 28 is the 362nd day of the year (363rd in leap years) in the Gregorian Calendar, with 3 days remaining. ...
1995 was a common year starting on Sunday of the Gregorian calendar. ...
The field is small so 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 a landmark image in the study of the early universe, and it has been the source of almost 400 scientific papers since it was created. The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ...
A NASA artists conception of what the Milky Way would look like if seen off-axis. ...
Cosmology, from the Greek: κοσμολογία (cosmologia, κόσμος (cosmos) world + λογια (logia) discourse) is the study of the universe in its totality and by extension mans place in it. ...
In scientific publishing, a paper is a scientific article that is published in a scientific journal. ...
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). 2004 saw the construction of a yet deeper image, known as the Hubble Ultra Deep Field, from a total of 11 days of observations. The Hubble Deep Field South The Hubble Deep Field South is a composite of several hundred individual images taken using the Hubble Space Telescopes Wide Field and Planetary Camera 2 over 10 days in September and October 1998. ...
The deepest visible-light image of the cosmos. ...
Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ...
The Cosmological Principle is a principle invoked in cosmology that severely restricts the large variety of possible cosmological theories: On large scales, the Universe is homogeneous and isotropic. ...
This snapshot of the HUDF includes galaxies of various ages, sizes, shapes, and colors. ...
Conception  The dramatic improvement in Hubble's imaging capabilities after corrective optics were installed encouraged attempts to obtain very deep images of distant galaxies One of the key aims of 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. Although 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 a better understanding of how they evolve. Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ...
NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 56,000 light years in diameter and approximately 60 million light years distant. ...
Spherical aberration is an inherent property of telescopes using spherical mirrors with focal ratios shorter than f/10. ...
After the spherical aberration was corrected during Space Shuttle mission STS-61 in 1993, the now excellent 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 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. The Space Shuttle Columbia seconds after engine ignition, 1981 (NASA). ...
Crew Commander: Richard O. Covey (4) Pilot: Kenneth D. Bowersox (2) Payload Commander: F. Story Musgrave (5) Mission Specialist 1: Kathryn C. Thornton (3) Mission Specialist 2: Claude Nicollier (2) - ESA Switzerland Mission Specialist 3: Jeffrey A. Hoffman (4) Mission Specialist 5: Thomas D. Akers (3) Mission Parameters Mass: Orbiter...
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, 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. This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
The Space Telescope Science Institute (STScI) is an organization founded by NASA to manage and direct research done with the Hubble Space Telescope. ...
An optical filter is a device which selectively transmits light having certain properties (often, a particular range of wavelengths, i. ...
Target selection
 The HDF field is at the centre of this image, one degree across, which shows the unremarkable nature of this patch of sky. The field selected for the observations needed to fulfil 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. 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 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). Image File history File links Download high resolution version (800x801, 135 KB)Star field in which the Hubble Deep Field was taken. ...
Image File history File links Download high resolution version (800x801, 135 KB)Star field in which the Hubble Deep Field was taken. ...
A degree (in full, a degree of arc), usually symbolized °, is a measurement of plane angle, representing 1ï¼360 of a full rotation. ...
A NASA artists conception of what the Milky Way would look like if seen off-axis. ...
The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ...
Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...
Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ...
In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...
Cirrus can refer to: a type of cloud, cirrus cloud a German rocket, cirrus (rocket) a trance music group, Cirrus (music group) an ATM network (cash machines) by MasterCard This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
For the fictional fundamental particle in Philip Pullmans His Dark Materials, see Dust (His Dark Materials). ...
General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...
An H I region is an interstellar cloud composed of warm neutral atomic hydrogen (H1). ...
These criteria considerably restricted the field of potential target areas. It was further decided that the target should be in Hubble's 'continuous viewing zones' (CVZs)—the areas of sky which are not occulted by the Earth or the moon during Hubble's orbit. The working group decided to concentrate on the northern CVZ, so that northern-hemisphere telescopes, such as the Keck telescopes and the Very Large Array, could conduct follow-up observations. In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ...
Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ...
The Mauna Kea Observatory, an institute of the University of Hawaii, is considered one of the most important land-based observatories in the world for its isolated, unobstructed views of space without interference from man-made light sources. ...
The NRAOs Very Large Array (configuration D) For other uses of the acronym VLA see VLA (disambiguation) The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro...
Twenty fields satisfying all of these criteria were initially identified, from which three optimal candidate fields were selected, all within the constellation of Ursa Major. Radio snapshot observations ruled out one of these fields because it contained a bright radio source, and the final decision between the other two was made on 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 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 12h 36m 49.4s and a declination of +62° 12′ 48″ [1]. Ursa Major (Ursa Maior in Latin) is a constellation visible throughout the year in the northern hemisphere. ...
Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ...
In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ...
Observations
 The HDF was located in Hubble's northern Continuous Viewing Zone, as shown by this diagram Once a field had been selected, an observing strategy had to be 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 colours of stars and galaxies. The choice of filters to be used for the HDF depended on 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. Image File history File links Download high resolution version (670x873, 58 KB)Diagram showing the observing geometry for the observations used to create the Hubble Deep Field. ...
Image File history File links Download high resolution version (670x873, 58 KB)Diagram showing the observing geometry for the observations used to create the Hubble Deep Field. ...
The term filter may refer to: A device to separate mixtures. ...
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ...
The frequency axis of this symbolic diagram would be logarithmically scaled. ...
In the end, four broadband filters were chosen, centred at wavelengths of 3000Å (near-ultraviolet), 4500Å (blue light), 6060Å (red light) and 8140Å (near-infrared). Because the quantum efficiency of Hubble's detectors is quite low at 3000Å, 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. An angstrom or ångström (Å) is a non-SI unit of length equal to 10−10 metres, 0. ...
Quantum efficiency (QE) is a figure given for a photosensitive device (charge-coupled device (CCD), for example) which is the percentage of photons hitting the photoreactive surface that will produce an electron-hole pair. ...
A specially developed CCD used for ultraviolet imaging in a wire bonded package. ...
Images of the target area in the chosen filters were taken over 10 consecutive days, during which Hubble orbited the Earth about 150 times. The total exposure times at each wavelength were 42.7 hours (3000Å), 33.5 hours (4500Å), 30.3 hours (6060Å) and 34.3 hours (8140Å), 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. Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...
Data processing
 A section of the HDF about 14 arcseconds across in each of the four wavelengths used to construct the final version: 3000 Å (top left), 4500Å (top right), 6060Å (bottom left) and 8140Å (bottom right). The production of 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. Image File history File links Download high resolution version (723x733, 79 KB)A region of the HDF at each of the four wavelengths used to construct the final image - 3000Ã… (top left), 4500Ã… (top right), 6060Ã… (bottom left) and 8140Ã… (bottom right). ...
Image File history File links Download high resolution version (723x733, 79 KB)A region of the HDF at each of the four wavelengths used to construct the final image - 3000Ã… (top left), 4500Ã… (top right), 6060Ã… (bottom left) and 8140Ã… (bottom right). ...
A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ...
An angstrom or ångström (Å) is a non-SI unit of length equal to 10−10 metres, 0. ...
A pixel (a portmanteau of picture element) is one of the many tiny dots that make up the representation of a picture in a computers memory. ...
Space debris or orbital debris, also called space junk, are the objects in orbit around Earth created by man that no longer serve any useful purpose. ...
For other uses, please see Satellite (disambiguation) A satellite is an object that orbits another object (known as its primary). ...
Scattered light from the Earth was evident in about a quarter of the data frames. 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 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 in diameter, but by changing 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. A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ...
The data processing yielded four monochrome images, one at each wavelength. The combining of these into the full colour images released to the public was a fairly arbitrary process, with one image designated as each of red, green and blue, and the three images combined to give a colour image. Because the wavelengths at which the images were taken do not correspond to the wavelengths of red, green and blue light, the colours in the final image only give an approximate representation of the actual colours of the galaxies in the image; the choice of filters for the HDF (and the majority of Hubble images) was primarily designed to maximise the scientific utility of the observations rather than to create colours corresponding to what the human eye would actually perceive. Something which is monochromatic has a single color. ...
Contents of the Deep Field The final images revealed a plethora of distant, faint galaxies. About 3,000 distinct galaxies could be identified in 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 10 galactic foreground stars; by far the majority of objects in the field are distant galaxies. An irregular galaxy is a galaxy that does not fall into the Hubble classification for galaxies. ...
A spiral galaxy is a type of galaxy in the Hubble sequence which is characterized by the following physical properties: Spiral Galaxy M74 presents a face-on view of its spiral arms. ...
There are about 50 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 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 [2]. Star formation is the process by which gas in molecular clouds gets transformed into stars. ...
This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ...
White dwarf Sirius-B in x-rays A white dwarf is an astronomical object which is produced when a low or medium mass star dies. ...
Scientific results
 Details from the HDF illustrate the wide variety of galaxy shapes, sizes and colours found in the distant universe The HDF data provided extremely rich material for cosmologists to analyse, and as of 2005, almost 400 papers based on the HDF have appeared in the astronomical literature. One of the most fundamental findings was the discovery of large numbers of galaxies with high redshift values. Image File history File links Download high resolution version (700x875, 157 KB)Wide variety of galaxies in selected Hubble Deep Field regions. ...
Image File history File links Download high resolution version (700x875, 157 KB)Wide variety of galaxies in selected Hubble Deep Field regions. ...
Cosmology, from the Greek: κοσμολογία (cosmologia, κόσμος (cosmos) world + λογια (logia) discourse) is the study of the universe in its totality and by extension mans place in it. ...
2005 is a common year starting on Saturday of the Gregorian calendar. ...
Redshift describes a change in the wavelength of light, in which the wavelength is longer, or redder, than when it was emitted at the source. ...
As the universe expands, more distant objects recedes from the Earth faster, in what is called the Hubble Flow. The light from very distant galaxies is significantly affected by doppler shifting, which reddens the radiation that we receive from them. Before the production of the HDF images, while quasars with high redshifts were known, very few galaxies with redshifts greater than 1 were known; however, the HDF contained many galaxies with redshifts as high as 6, corresponding to a distance of about 12 billion light years [3]. Hubble flow refers to the apparent radial motions (or redshifts) of galaxies due to the expansion of the universe. ...
The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ...
This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ...
A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ...
The HDF galaxies contained a larger proportion of disturbed and irregular galaxies than does the local universe. The young universe was much smaller than today's universe, and thus galaxy collisions and mergers were more common. It is believed that giant elliptical galaxies form when spirals and irregular galaxies collide. An elliptical galaxy is a type of galaxy in the Hubble sequence characterized by the following physical properties: The giant elliptical galaxy NGC 4881 (the spherical glow at upper left) lies at the edge of the Coma Cluster of Galaxies. ...
The wealth of galaxies at different stages of their evolution also allowed astronomers to estimate 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 [4]. Star formation is the process by which gas in molecular clouds gets transformed into stars. ...
Another important result from the HDF was the very small number of foreground stars present. For years astronomers had been puzzling over the nature of the so-called dark matter, which observations showed make up about 90% of the mass of the universe, but which was not detectable in visible light. One theory was that it could 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 that there were not significant numbers of red dwarfs in the outer parts of our galaxy. In cosmology, dark matter refers to hypothetical matter particles, of unknown composition, that do not emit enough electromagnetic radiation to be detected directly, but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. ...
Being macho is overconforming to traditional male gender roles or hypermasculinity and often implies misogyny. ...
Red Dwarf is a British science fiction comedy, created and originally written by Rob Grant and Doug Naylor. ...
We are forever reading in our newspapers that our planets are made up of rock. ...
Subsequent observations The HDF is a landmark in observational cosmology and much still remains to be learned from it. Since 1995, the field has been observed by many ground-based telescopes as well as some further space telescopes, at wavelengths from radio to X-ray. Image File history File links Download high resolution version (729x699, 41 KB) Summary Full mosaic of the Hubble Deep Field South. ...
Image File history File links Download high resolution version (729x699, 41 KB) Summary Full mosaic of the Hubble Deep Field South. ...
The Cosmological Principle is a principle invoked in cosmology that severely restricts the large variety of possible cosmological theories: On large scales, the Universe is homogeneous and isotropic. ...
Important space-based observations have included those by the Chandra X-ray Observatory and the Infrared Space Observatory. X-ray observations 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 a distant galaxy containing a large amount of dust which absorbs its blue light emissions [5]. Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. ...
The Infrared Space Observatory (ISO)is a space telescope for infrared light designed and operated by the European Space Agency (ESA). ...
An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ...
For the fictional fundamental particle in Philip Pullmans His Dark Materials, see Dust (His Dark Materials). ...
ISO observations indicated infrared emission from 13 galaxies visible in the optical images, which was attributed to large quantities of dust associated with intense star formation. 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.
1998 saw the creation of an HDF counterpart in the southern celestial hemisphere: the HDF-South. Created with a similar observing strategy, the HDF-S was very similar in appearance to the original HDF. This supports the cosmological principle that the universe is homogenous at the largest scales. The Cosmological Principle is a principle invoked in cosmology that severely restricts the large variety of possible cosmological theories: On large scales, the Universe is homogeneous and isotropic. ...
Homogeneous is an adjective that has several meanings. ...
References - Williams RE et al. (1996), The Hubble Deep Field: Observations, data reduction, and galaxy photometry, Astronomical Journal, 112:1335
- Ferguson HC (2000), The Hubble Deep Fields, Astronomical Data Analysis Software and Systems IX, ASP Conference Proceedings, Vol. 216, N Manset, C Veillet, and D Crabtree (eds). Astronomical Society of the Pacific, ISBN 1-58381-047-1, p.395
- ^ Hansen BMS (1998), Observational signatures of old white dwarfs, 19th Texas Symposium on Relativistic Astrophysics and Cosmology, J Paul, T Montmerle, and E Aubourg (eds)
- ^ Hornschemeier A et al. (2000), X-Ray sources in the Hubble Deep Field detected by Chandra, Astrophysical Journal, 541:49–53
- ^ Connolly AJ et al. (1997), The evolution of the global star formation history as measured from the Hubble Deep Field, Astrophysical Journal Letters, 486:L11
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