Astronomy fanatica
-
Astronomy Picture of the Day
2005 July 14
Star Trails Over Vienna
Explanation: As the Earth spins on its axis, the sky seems to rotate around us. This motion, called diurnal motion, produces the beautiful concentric trails traced by stars during time exposures. In the middle of the picture is the North Celestial Pole (NCP), easily identified as the point in the sky at the center of all the star trail arcs. The star Polaris, commonly known as the North Star, made the very short bright circle near the NCP. Full circle star trails are pictured over Vienna, Austria. This image, a relatively short exposure followed by a digital trick, could not have been taken during a single night because 24-hours are needed for one full rotation, and the Sun is sure to dominate the frame at some time.
Credit & Copyright: Peter Wienerroither (U. Wien) -
Large Binocular Telescope
The Large Binocular Telescope (originally named the Columbus Project) is a joint project of the Italian astronomical community (represented by the Istituto Nazionale di Astrofisica (INAF)), the University of Arizona, Arizona State University, Northern Arizona University, the LBT Beteiligungsgesellschaft in Germany Max-Planck-Institut für Astronomie in Heidelberg, Landessternwarte in Heidelberg, Astrophysikalisches Institut in Potsdam, Max-Planck-Institut für Extraterrestrische Physik in Munich, and Max-Planck-Institut für Radioastronomie in Bonn), The Ohio State University, Research Corporation in Tucson, and the University of Notre Dame.
The Large Binocular Telescope
The final configuration will be a telescope with two 8.4-meter mirrors mounted on a common base (hence the name "binocular"), taking full advantage of the active and adaptive optics provided by Arcetri Observatory. Also, an interferometric mode will be available, with a baseline of 23 meters.
When the LBT is fully operational, it will be the world's most technologically advanced optical telescope, creating images in the near-infrared expected to be nearly 10 times sharper than images from the Hubble Space Telescope.
LBT on the cover of VMEbus Systems magazine
It is located on the 10,700-foot Mount Graham in southeastern Arizona. The choice of location sparked considerable local controversy, both among the San Carlos Apache Tribe who claimed the mountain as sacred and environmentalists who contended that the observatory would cause the demise of the endangered Mount Graham red squirrel. Environmentalists and members of the tribe filed some 40 lawsuits - eight of which ended up before a federal appeals court - but the project ultimately prevailed after an act of Congress.
The telescope and mountain observatory also survived two major forest fires in eight years, the most recent in the summer of 2004.
Forest fire approaches the LBT in July 2004.
The telescope was dedicated in October 2004 and is expected to be complete in 2005.
Issue #140 -
Astronomy Picture of the Day
2005 July 15
Reflections on the Inner Solar System
Explanation: Only Mars is missing from this reflective view of the major rocky bodies of the inner solar system. Captured on July 8th, the serene, twilight picture looks out over the Flat Tops Wilderness area from near Toponas, Colorado, USA and includes planets Mercury, Venus, Earth, and Earth's large natural satellite, the Moon. The Moon is in a young crescent phase about three degrees above bright planet Venus. Forest fires contribute to a layer of smoke in Earth's sky that almost hides planet Mercury, still visible very near the horizon. Just a week earlier Venus and Mercury were joined by Saturn, forming a notable grouping in the west also enjoyed by skygazers across planet Earth.
Credit & Copyright: Jimmy Westlake (Colorado Mountain College) -
Subaru Telescope
Subaru Telescope is the 8.3 meter flagship telescope of the National Astronomical Observatory of Japan. It is named for the open star cluster known in English as the Pleiades. It is located on top of Mauna Kea in Hawaii.
The Subaru Telescope at sunset
Issue #141 -
Astronomy Picture of the Day
2005 July 16
Galaxy Group HCG 87
Explanation: Posing for this cosmic family photo are the galaxies of HCG (Hickson Compact Group) 87, about four hundred million light-years distant toward the amphibious constellation Capricornus. The large edge-on spiral near picture center, the fuzzy elliptical galaxy immediately to its right, and the spiral near the top of the image are identified members of the group, while the small spiral galaxy in the middle is likely a more distant background galaxy. In any event, a careful examination of the deep image reveals other galaxies which certainly lie far beyond HCG 87. While not exactly locked in a group hug, the HCG 87 galaxies are interacting gravitationally, influencing their fellow group members' structure and evolution. This image is from the commissioning phase of an instrument on the Gemini Observatory's South Telescope at Cerro Pachon, Chile. It compares favorably with views of this photogenic galaxy group recorded by the Hubble Space Telescope.
Credit: GMOS-S Commissioning Team, Gemini Observatory -
Very Large Telescope
The Very Large Telescope Project (VLT) consists of a system of four separate optical telescopes (the Antu telescope, the Kueyen telescope, the Melipal telescope, and the Yepun telescope) organized in an array formation. Each telescope has an 8.2 m aperture. The project is organized by the European Southern Observatory.
VLT is located at the Paranal Observatory on Cerro Paranal, a 2,635 m high mountain in the Atacama desert in northern Chile.
The four telescopes of the European Southern Observatory Paranal site. The VLTI (Very Large Telescope Interferometer) building is the low structure in front of the telescopes. Image courtesy of the European Southern Observatory.
General Information
Organization: European Southern Observatory
Location: Cerro Paranal, Atacama desert, Chile
Coordinates: 24° 37' 38" S 70° 24' 17" W
Altitude: 2,635 m
Weather: >340 clear nights/year
Webpage: Paranal observatory
Telescopes
Antu: 8,2 m reflector
Kueyen: 8,2 m reflector
Melipal: 8,2 m reflector
Yepun: 8,2 m reflector
General information
The VLT consists of a cluster of four large (8 meter diameter) telescopes, and an interferometer (VLTI) which will be used to resolve fine features. The interferometer will include a set of 1.8 meter diameter telescopes dedicated to interferometric observations. The 8 meter telescopes have been named after the names of some astronomical objects in the local Mapuche language: Antu (The Sun), Kueyen (The Moon), Melipal (The Southern Cross), and Yepun (Venus).
One of the four telescopes that make up the VLT, named Kueyen. The 8.2 m mirror can be seen below the large horizontal grey beam (as an oval patch of lightness). Image courtesy of the European Southern Observatory.
The VLT 8 meter telescopes can be operated in three modes:
- as a set of independent telescopes (this is the primary mode of operation)
- as a single large incoherent instrument, for extra light-gathering capacity (this mode has now been abandoned)
- as a single large coherent interferometric instrument (the VLT Interferometer or VLTI), for extra resolution (this is occasionally used, usually for observations of relatively bright sources)
The principle role of the VLT is to operate as four independent telescopes, and the interferometry (combining light from multiple telescopes) is a minor secondary role.
The VLT is operated by the European Southern Observatory.
In 2005, VLT telescopes produced some of the first infrared images of extrasolar planets GQ Lupi b and 2M1207b.
Interferometry and the VLTI
Most interferometry will be done using 1.8 meter Auxiliary Telescopes (ATs), which will be dedicated to full-time interferometric measurements. The first observations using a pair of ATs were conducted in February 2005, and additional ATs are expected to be installed soon. For many interferometric observations there is little benefit in using 8 meter telescopes rather than 1.8 meter telescopes.
In its full interferometric operating mode, the four telescopes provide the same light gathering ability (neglecting light losses from the throughput of the instrument) as a single 16 m telescope, making it theoretically the largest optical telescope in the world (the interferometric technique used at the VLTI is not suitable for observing very faint sources, so it actually has poorer sensitivity than the single 8m telescopes). The light from the telescopes is reflected off mirrors and directed through tunnels to a central beam combining laboratory. The VLT is intended to achieve an effective angular resolution of 0.001 arcsecond at a wavelength of 1 µm, comparable to that achieved using other arrays such as the Navy Prototype Optical Interferometer and the CHARA Array.
The poor brightness sensitivity of interferometric observations mean that they could not be used for imaging objects with low surface brightness such as the moon. Only targets which are at temperatures of more than 1000 °C have a surface brightness high enough to be observed in the mid-infrared, and objects must be at several thousands of degrees for near-infrared observations using the VLTI. This sensitivity limit rules out interferometric observations of most solar-system objects apart from the Sun. All the stars visible to the naked eye have temperatures of several thousand degrees, and have large enough surface brightnesses and angular sizes to be observed by the VLTI. Although the use of large telescope diameters and adaptive optics correction can improve the sensitivity a small amount, this cannot extend the reach of optical interferometry beyond nearby stars and the brightest active galactic nucleii.
The first two instruments at the VLTI were VINCI and MIDI, which only allowed two telescopes to be used at any one time. With the installation of the three-telescope AMBER closure-phase instrument in 2005, the first imaging observations from the VLTI are expected soon. In 2008 the PRIMA instrument will further enhance the imaging capabilities of the VLTI by allowing phase-referenced imaging.
After falling drastically behind schedule and failing to meet some specifications, in December 2004 the VLT Interferometer became the target of a second ESO recovery plan. This involves additional effort concentrated on more rapid improvements to fringe tracking and the performance of the main delay lines. Note that this only applies to the interferometer and not other instruments on Paranal.
Issue #142 -
Astronomy Picture of the Day
2005 July 17
The Center of Centaurus A
Explanation: A fantastic jumble of young blue star clusters, gigantic glowing gas clouds, and imposing dark dust lanes surrounds the central region of the active galaxy Centaurus A. This mosaic of Hubble Space Telescope images taken in blue, green, and red light has been processed to present a natural color picture of this cosmic maelstrom. Infrared images from the Hubble have also shown that hidden at the center of this activity are what seem to be disks of matter spiraling into a black hole with a billion times the mass of the Sun! Centaurus A itself is apparently the result of a collision of two galaxies and the left over debris is steadily being consumed by the black hole. Astronomers believe that such black hole central engines generate the radio, X-ray, and gamma-ray energy radiated by Centaurus A and other active galaxies. But for an active galaxy Centaurus A is close, a mere 10 million light-years away, and is a relatively convenient laboratory for exploring these powerful sources of energy.
Credit: E.J. Schreier (STScI) et al., HST, NASA -
William Herschel Telescope
The William Herschel Telescope or WHT was first conceived in the late 1960s, when the Anglo-Australian Observatory was being designed. The British astronomical community saw the need for telescopes of comparable power in the Northern Hemisphere. Planning began in 1974, but by 1979 the project was on the verge of being scrapped due to a ballooning budget. A re-design cut the price-tage substantially, and Dutch astronomers took a 20% stake in the project, allowing the project to be given the go-ahead in 1981. That year was the 200th anniverary of the discovery of Uranus by William Herschel, and it was decided to name the telescope in his honour. The telescope is a member of the Isaac Newton Group of Telescopes.
Moonrise over the William Herschel Telescope, La Palma, Spain.
The telescopes are (from left to right):
1. The Swedish Solar Telescope
2. The Dutch Open Telescope
3. The Nordic Optical Telescope
4. The William Herschel Telescope
General Information
Organization: Isaac Newton Group of Telescopes
Location: Roque de los Muchachos Observatory, La Palma, Canary Islands
Wavelength regime: Optical
Completion date: June 1st, 1987
Webpage: WHT Homepage
Physical characteristics
Telescope style: Cassegrain-Nasmyth Reflector
Diameter: 4.2 m
Collecting area: 13.8 m²
Mounting: Alt-azimuth
Construction began in 1983, and the telescope was shipped to La Palma in 1985. It saw first light in 1987. The telescope has an altazimuth mount. The mirror is maintained so that its theoretical maximum resolution is less than 0.2 arcseconds. The typical seeing at La Palma is of the order of one arcsecond, so the telescope is limited by that.
As one of the best telescopes in the world, the WHT is heavily over-subscribed, and typically three times more applications for telescope time are received than can be accommodated. Notable discoveries made using the WHT include that of a hot bubble of expanding gas at the centre of the galaxy, suggestive of the presence of a supermassive black hole; the first observation of the optical counterpart of a gamma-ray burst; and recently, the discovery of a Wolf-Rayet star with the fastest-known stellar wind.
Issue #143 -
Astronomy Picture of the Day
2005 July 18
Deep Impact on Comet Tempel 1 from Hubble
Explanation: It was a human-made event visible across the Solar System. At the direction of terrestrial scientists, a refrigerator-sized probe from the Deep Impact mission struck Comet Tempel 1 on July 4 at over 35,000 kilometers per hour. The unexpectedly bright explosion was not nuclear but rather originated from a large plume that reflected back sunlight. Pictured above is how the event looked to the Earth-orbiting Hubble Space Telescope. A large cloud of bright material is seen emanating from the comet's nucleus and then dispersing. The area encompassing the comet became over three times brighter in the hours after the impact. Astronomers will continue to study the images and data returned by Deep Impact to better determine the nature of Comet Tempel 1 and discern clues about the formation dynamics of the early Solar System.
Credit: P. Feldman (JHU) & H. Weaver (APL), ESA, NASA -
Paris 1900 Exposition Refractor
The largest refractor ever constructed was French. It was on display at the 1900 Paris Exposition. Its lens was stationary, prefigured so as to sag into the correct shape. The telescope was aimed with the aid of a Foucault sidérostat, which is a movable plane mirror of diameter 2 m (6.56 feet), mounted in a large cast-iron frame. The horizontal tube was 60 m (197 feet) long and the objective had 1.25 m (4.1 feet) in diameter. The results were poor. When the year-long exposition was over, its builders were unable to sell it. It was ultimately broken up for scrap.
Paris 1900 exposition refractor
Issue #144 -
Astronomy Picture of the Day
2005 July 19
A Nearby Supernova in M51
Explanation: One of the nearest supernovas of recent years was discovered late last month in the bright nearby galaxy M51. It is visible on the right of the above before and after images of the picturesque spiral. Can you spot it? The supernova, discovered originally by Wolfgang Kloehr and now dubbed 2005cs, is still near its maximum brightness and visible with a telescope toward the constellation of the Hunting Dogs (Canes Venatici). The supernova has been identified as a Type II but has an unusual brightness history, creating speculation that is similar in nature to the brightest supernova of modern times: 1987A. The progenitor star has been identified as a bright blue star. Although hundreds of supernovas are discovered each year by automated searches, nearby supernova are rare and important because they frequently become bright enough to be studied by many telescopes and are near enough for their (former) host star and immediate surroundings to be spatially resolved. Supernova 2005cs may have left behind a core that has been compressed into a neutron star or black hole.
Credit & Copyright: R Jay GaBany (Cosmotography.com) -
Astronomy Picture of the Day
2005 July 20
Water Ice in a Martian Crater
Explanation: What lies on the floor of this Martian crater? A frozen patch of water ice. The robotic Mars Express spacecraft took the above image in early February. The ice pocket was found in a 35-kilometer wide crater that resides 70 degrees north of the Martian equator. There, sunlight is blocked by the 300-meter tall crater wall from vaporizing the water-ice on the crater floor into the thin Martian atmosphere. The ice pocket may be as deep as 200 meters thick. Frost can be seen around the inner edge on the upper right part of the crater, while part of the lower left crater wall is bathed in sunlight. The existence of water-ice pockets inside craters near the Martian North Pole, like that pictured above and others noted previously, give clues not only about surface conditions in the Martian past but also possible places where future water-based astronauts might do well to land.
Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA;
Image created for and Copyright: Nature -
Nordic Optical Telescope
The Nordic Optical Telescope (NOT) is an astronomical telescope located at Roque de los Muchachos Observatory, La Palma in the Canary Islands. First light came in 1988, with regular observing beginning in 1989. It is funded by Denmark, Sweden, Iceland, Norway and Finland. Access is provided to astronomers of all nationalities through internation time allocation committees.
Looking down on the dome of the Nordic Optical Telescope, with the Atlantic Ocean behind.
The NOT was the first major telescope facility to use active optics to correct the shape of a thin, lightweight primary mirror.
The service building and dome of Nordic Optical Telescope situated above the clouds at the top of Roque de los Muchachos, La Palma.
The NOT is a 2.56 m telescope with the following instrumentation:
- ALFOSC -- CCD (visible light) faint object spectrograph and 4 Megapixel camera
- NOTCam -- 1 Megapixel HgCdTe Hawaii infrared camera and spectrograph
- MOSCA -- 16 Megapixel CCD camera
- SOFIN -- High resolution CCD spectrograph (up to R=170,000)
- StanCam -- Stand-by 1 Megapixel CCD camera
- LuckyCam -- High frame rate, low noise L3Vision CCD camera for lucky imaging
- TURPOL -- UBVRI Photopolarimeter
The interior of the telescope, showing an instrument on the Cassegrain focus
Issue #145 -
Astronomy Picture of the Day
2005 July 21
X-Ray Stars of 47 Tuc
Explanation: Visible light images show the central region of globular cluster 47 Tucanae is closely packed, with stars less than a tenth of a light-year apart. This Chandra false-color x-ray view of central 47 Tuc also shows the cluster is a popular neighborhood for x-ray stars, many of which are "normal" stars co-orbiting with extremely dense neutron stars -- stars with the mass of the Sun but the diameter of Manhattan Island. One of the most remarkable of these exotic binary systems is cataloged as 47 Tuc W, a bright source near the center of this image. The system consists of a low mass star and a a neutron star that spins once every 2.35 milliseconds. Such neutron stars are known to radio astronomers as millisecond pulsars, believed to be driven to such rapid rotation by material falling from the normal star onto its dense companion. In fact, x-ray observations of the 47 Tuc W system link this spin-up mechanism observed to operate in other x-ray binary stars with fast rotating millisecond pulsars.
Credit: C.Heinke (Northwestern U.) et al. CXC, NASA -
Overwhelmingly Large Telescope
The Overwhelmingly Large Telescope (OWL) is a conceptual design by the European Southern Observatory organization for a telescope which is intended to have a single aperture of 100 meters in diameter.
Computer model of Overwhelmingly Large Telescope's external appearance.
Whilst this design would not exceed the angular resolving power of interferometric telescopes, it would have exceptional light-gathering and imaging capacity which would greatly increase the depth to which mankind could explore the universe.
If built, it would be the largest optical telescope ever constructed. It has been claimed that OWL would have more mirror surface than that of all previous professional telescopes put together.
All proposed designs for the OWL are variations on a segmented mirror, since there is no technology available to build a monolithic 100-meter mirror. The operation of a segmented mirror is somewhat more complicated than a monolithic one, requiring careful alignment of the segments (a technique called cophasing). Experience gained in existing segmented mirrors (for example, the Keck telescope) suggests that the mirror proposed for the OWL is feasible.
Issue #146 -
Astronomy Picture of the Day
2005 July 22
Tethys, Rings, and Shadows
Explanation: Seen from ice moon Tethys, rings and shadows would play across fantastic views of the Saturnian system. Haven't dropped in on Tethys lately? Then this gorgeous ringscape from the Cassini spacecraft will have to do for now. Caught in sunlight just below and left of picture center, Tethys itself is about 1,000 kilometers in diameter and orbits not quite five saturn-radii from the center of the gas giant planet. At that distance (around 300,000 kilometers) it is well outside Saturn's main bright rings, but Tethys is still one of five major moons that find themselves within the boundaries of the faint and tenuous outer E ring. Discovered in the 1980s, two very small moons Telesto and Calypso are locked in stable locations along Tethys' orbit. Telesto precedes and Calypso follows Tethys as the trio circles Saturn.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA -
2MASS
Observations for the Two Micron All-Sky Survey (2MASS) began in 1997 and were completed in 2001 at two telescopes located one each in the northern and southern hemispheres (Mt. Hopkins Arizona and Cerro Tololo/CTIO Chile, respectively) to ensure coverage of the entire sky. The most ambitious project to map the night sky to date, the final (post-processing) data release for 2MASS occurred in 2003. The whole sky was covered in three infrared wavebands around 2 µm (micrometres), J (1.25 µm), H (1.65 µm), and Ks (2.17 µm).
2MASS logo
General Information
Organization: UMass, IPAC (JPL/Caltech), NASA, NSF
Wavelength regime: IR (2 µm, 1.25 µm,1.65 µm, 2.17 µm)
Data source: two 1.3 m Cassegrain reflector equatorial mount telescopes (Mt. Hopkins, Tucson, AZ; Cerro Tololo, La Serena, Chile)
Survey goals: galaxies, brown dwarfs
Dataproducts: images, point source catalogue, extended object catalogue
Other names: Two Micron All-Sky Survey
Webpage:
About 2MASS
The catalogue of point sources
The catalogue of extended sources
The goals of this survey included:
- Detection of galaxies in the "zone of avoidance," a strip of sky obscured in visible light by our own Galaxy, the Milky Way.
- First detection of brown dwarfs.
- An extensive survey of low mass stars, the most common type of star both in our own galaxy and others.
- Cataloging of all detected stars and galaxies.
This last goal has been admirably achieved. Numerical descriptions of point sources (stars, planets, asteroids) and extended sources (galaxies, nebulae) were catalogued by automated computer programs to an average limiting magnitude of about 14. More than 300 million point sources and 1 million extended sources were catalogued. In November of 2003, a team of scientists announced the discovery of the Canis Major Dwarf Galaxy, at that time the closest known satellite galaxy to the milky way, based on analysis of 2MASS stellar data.
The resulting data and images from the survey are currently in the public domain, and may be accessed online for free by anyone at The Two Micron All Sky Survey at IPAC website (although interpretation and use of this data may require an advanced degree). There is also a list of 2MASS science publications with links to free pre-publication copies of the papers.
2MASS is sponsored by the University of Massachusetts (aka UMass, and the origin of the survey name), the Infrared Processing and Analysis Center (IPAC, run by JPL and Caltech), NASA, and the NSF.
Issue #147 -
Astronomy Picture of the Day
2005 July 23
Ringed Nebulae
Explanation: This gorgeous celestial vista is centered on one of the Milky Way's own planetary nebulae, M57, the famous Ring Nebula. The wide view is a composite of three exposures; one to record the details of the inner roughly one light-year span of the familiar nebula, one to record the surprisingly intricate but faint outer rings of glowing hydrogen gas, and one to pick up the rich assortment of distant background galaxies. By chance, one of the background galaxies, IC 1296 at the upper left, is close enough to show its barred, spiral structure making an attractive visual comparison with M57. Interestingly, though IC 1296 is 200 million light-years away compared to only 2 thousand light-years for M57, a faint ring is also apparent around the outer reaches of the distant spiral galaxy.
Credit & Copyright: Tony and Daphne Hallas -
3C
The Third Cambridge Catalog of Radio Sources (3C) is an astronomical catalogue of celestial radio sources as measured at 159-MHz. It was published in 1959 by the Radio Astronomy Group of the University of Cambridge. References to entries in this catalogue use the prefix 3C followed by the entry number, with no space perforce. ie. 3C273. The catalogue was produced by the Cambridge Interferometer on the west side of Cambridge. (The interferometer had previously been used for the 2C survey, published in 1955).
The Catalogue was subsequently revised by Bennett in 1962, and for many years 3CR was considered as the definitive listing of the brighter radio sources in the Northern Hemisphere. The revision resulted in a number of sources being deleted from the catalogue (as being below the flux limit of 9Jy or as now-resolved blends of adjacent sources) and others being added. To avoid renumbering the existing sources (which were listed in RA order) these new sources were added using a decimal extension. Eg 3CR323.1 follows 3C323 in Right Ascension and precedes 3C324.
General Information
Organization: Radio Astronomy Group, University of Cambridge
Wavelength regime: 159-MHz radio
Data source: Mullard Radio Astronomy Observatory
Survey goals: First detailed survey of radio sources
Data products: 3C Catalogue
Webpage:
The Third Cambridge Catalog of Radio Sources
Issue #148 -
Astronomy Picture of the Day
2005 July 24
A Chicago Meteorite Fall
Explanation: If you wait long enough, a piece of outer space itself will come right to you. As Colby Navarro worked innocently on the computer, a rock from space crashed through the roof, struck the printer, banged off the wall, and came to rest near the filing cabinet. This occurred around midnight on March 26 in Park Forest, Illinois, USA, near Chicago. The meteorite, measuring about 10 cm across, was one of several that fell near Chicago that day as part of a tremendous fireball. Pictured above is the resulting hole in the ceiling, while the inset image shows the wall dent and the meteorite itself. Although the vast majority of meteors is much smaller and burn up in the Earth's atmosphere, the average homeowner should expect to repair direct meteor damage every hundred million years.
Credit & Copyright: Ivan and Colby Navarro -
4C
The Fourth Cambridge Survey (4C) is an astronomical catalogue of celestial radio sources as measured at 178 MHz using the 4C Array. It was published in two parts, in 1965 (for declinations +20 to +40) and 1967 (declinations -7 to + 20 and +40 to +80), by the Radio Astronomy Group of the University of Cambridge. References to entries in this catalogue use the prefix 4C followed by the declination in degrees, followed by a period, and then followed by the source number on that declination strip, e.g. 4C-06.23.
The 4C Array, which used the technique of aperture synthesis, could reliably position sources of less than 2 Jy, to within about 0.35 arcmin in Right ascension and 2.5 arcmin in declination.
General Information
Organization: Radio Astronomy Group, University of Cambridge
Wavelength regime: 178 MHz radio
Data source: 4C Array, Mullard Radio Astronomy Observatory
Survey goals: Deep survey of radio sources
Dataproducts: 4C Catalogue
Webpage: The Fourth Cambridge Survey
Issue #149 -
Astronomy Picture of the Day
2005 July 25
Unusual Gas Filaments Surround Galaxy NGC 1275
Explanation: How were the unusual gas filaments surrounding galaxy NGC 1275 created? No one is sure. Galaxy NGC 1275 is the central dominant galaxy of the Perseus Cluster of Galaxies, a cluster with many member galaxies visible in the above image. In visible light, NGC 1275 appears to show a spectacular collision between two distinct galaxies. The galaxy and cluster are also bright emitters of X-rays. The unusual gas filaments are shown above in a very specific color of light emitted by hydrogen, here artificially colored pink. Possible origins for the filaments may involve details of the collision between the two galaxies, or alternatively, interactions between a galactic center black hole and the surrounding intracluster gas. NGC 1275, pictured above, spans about 100,000 light years and lies about 230 million light years distant toward the constellation of Perseus.
Credit & Copyright: C. Conselice (Caltech), WIYN, AURA, NOAO, NSF -
5C
The Fifth Cambridge Catalog of Radio Sources (5C) is an astronomical catalogue of celestial radio sources as measured at 408-MHz and 1407-MHz. It was published in a number of parts between 1975 and 1995 by the Radio Astronomy Group of the University of Cambridge. The One-Mile Telescope used to produce this catalogue had an angular resolutions of 80 arcseconds and 23 arcseconds at 408 MHz and 1407 MHz respectively, and cataloged radio sources as faint as 2 milli-Janskys, considerably fainter than any previously cataloged radio source
References to entries in this catalogue use the prefix 5C followed by the catalogue part, a . and then the entry number, with no space perforce. ie. 5C12.311 for the 311th entry in part 12 of the 5C catalogue.
General Information
Organization: Radio Astronomy Group, University of Cambridge
Wavelength regime: 408-MHz and 1407-MHz radio
Data source: One-Mile Telescope, Mullard Radio Astronomy Observatory
Survey goals: Deep survey of radio sources
Dataproducts: 5C Catalogue
Webpage:
The 5C5 survey of radio sources
The 5C6 and 5C7 surveys of radio sources
The 5C12 survey near the North Galactic Pole
The 5C13 deep radio survey
The 5C14/5C15/5C16 Radio Survey at 408 and 1407 MHz
Issue #150 -
Astronomy Picture of the Day
2005 July 26
Hyperion: Sponge Moon of Saturn
Explanation: Why is Saturn's moon Hyperion textured like a sponge? Recent high-resolution images from the robot Cassini spacecraft orbiting Saturn show Hyperion to be an even stranger place than thought before. Previously, it was known that the length of a day on Hyperion is unpredictable. The moon's highly elliptical orbit around Saturn, its highly non-spherical shape, and its locked 4:3 orbital resonance with Titan torque Hyperion around so much it is hard to predict when the Sun will rise next. The newly imaged craters on the unusually coarse surface are surely the result of impacts, but for some reason have dark centers. The low density of Hyperion indicates it might even be a spelunker's paradise, riddled with tremendous caverns.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA -
8C
The Eighth Cambridge Survey (8C) is an astronomical catalogue of celestial radio sources as measured at 38-MHz. It was published in 1990 by the Radio Astronomy Group of the University of Cambridge. Sources are labelled 8C HHMM+DDd where HHMM is the Right Ascension in hours and minutes, and DDd is the Declination in degrees and tenths of a degree, e.g. 8C 0014+861 for a source at Right Ascension 00 14 and 86.1 degrees Declination in 1950 coordinates.
General Information
Organization: Radio Astronomy Group, University of Cambridge
Wavelength regime: 38-MHz radio
Data source: Cambridge Low Frequency Synthesis Telescope, Mullard Radio Astronomy Observatory
Survey goals: Deep, low frequency survey of radio sources
Data products: 8C Catalogue
Webpage: The Rees 38-MHz survey
Issue #151
