Электронная библиотека астронома-любителя. Книги по астрономии, телескопостроению, оптике.


Ru.Space.News:
Апрель 1998
ПнВтСрЧтПтСбВс
 
12345
6789101112
13141516171819
20212223242526
27282930
 

год:


  • Обзоры оружия и снаряжения
  • m31.spb.ru



  • AstroTop-100

    Яндекс цитирования


    0.016


    Архив RU.SPACE.NEWS за 01 апреля 1998


    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: A Bull's Eye For MERLIN and Hubble Привет всем! Вот, свалилось из Internet... University of Manchester Nuffield Radio Astronomy Laboratories Jodrell Bank Macclesfield Cheshire SK11 9DL England PRESS RELEASE: PR9801 27th March 1998 A Bull's Eye for MERLIN and the Hubble A team of British astronomers using the UK's MERLIN radio array and the Hubble Space Telescope have found an ``Einstein Ring'' -- a gravitational effect predicted by Albert Einstein over 60 years ago as a consequence of his General Theory of Relativity. The Hubble picture is a beautiful demonstration of Einstein's ideas since, for the first time, it shows a complete ring surrounding the galaxy that created it. The effect is a cosmic mirage caused by the gravity of a massive galaxy bending the light from an object behind it and acting as a ``gravitational lens''. On the rare occasions when the distant object, the lens galaxy and the telescope are exactly aligned an ``Einstein ring'' is created. Dr. Ian Browne of the University of Manchester admits ``At first sight it looks artificial and we thought it was some sort of defect in the image but then we realised we were actually looking at a perfect Einstein ring!''. Commenting later on the pictures Bristol University astronomer Professor Mark Birkinshaw said ``MERLIN and the Hubble have scored a bulls-eye!''. The size of the ring on the sky is tiny -- roughly a second of arc or about the size of a penny viewed from a distance of over two miles -- even though the lens consists of an entire galaxy. The blurring effect of the atmosphere makes such fine detail hard for astronomers to spot using optical telescopes on the Earth. The British team found it by using the 135 mile-wide MERLIN radio telescope to image distant radio sources. MERLIN is a network of six radio telescopes spread out across England and operated as a national facility by the University of Manchester's Jodrell Bank observatory. MERLIN's resolution is the same as that of the Hubble Space Telescope but at a completely different wavelength -- the two make perfect astronomical partners. The Hubble, orbiting above the atmosphere, took a detailed picture of the object and this revealed the spectacular bulls-eye. This is only one of over 20 galaxy lenses now known. In an ironic twist, counting the number of gravitational lenses in the sky, including the rare Einstein rings, is the best way of seeing whether Einstein really made his ``greatest blunder''. When he applied his General Theory of Relativity to the Universe as it was known 80 years ago, Einstein had to invent a repulsive force which overcomes gravity at very large distances. This new force was soon dismissed by other astronomers but many modern cosmologists now think that Einstein may have been right first time -- the lens searches will soon tell us where the truth lies. Background information on gravitational lenses is available by clicking HERE. [http://www.jb.man.ac.uk/merlin/press/PR9801/press2.html] The results of this work will be published in Letters section of the April 1 Issue of the Monthly Notices of the Royal Astronomical Society. L.J. King et al. ``A complete infrared Einstein ring in the gravitational lens sytem B1938+666'' The MERLIN radio array is a UK National Facility operated by the University of Manchester on behalf of the Particle Physics and Astronomy Research Council. The Very Large Array is a US National Facility operated by the National Radio Astronomy Observatory on behalf of Associcated Universities Inc. The astronomers involved work at the following institutes: University of Manchester; University of Oxford; California Institute of Technology (Pasadena); Netherlands Foundation for Radio Astronomy; University of Groningen; Institut d'Astrophysique de Paris. For further information contact any of the following team members: The following may be contacted at Jodrell Bank, at Telephone: 01477 571321 FAX: 01477 571618 Address: Nuffield Radio Astronomy Laboratories Jodrell Bank Macclesfield Cheshire SK11 9DL * Dr. Neal Jackson, Lecturer, Dept. of Physics and Astronomy, Univ. Manchester Email: njj@jb.man.ac.uk * Dr. Peter Wilkinson, Acting Director, MERLIN/VLBI National Facility Email: pnw@jb.man.ac.uk NOTE: During the period Tuesday 31 March to Friday 3 April Dr. Wilkinson will be attending the UK National Astronomy Meeting (NAM) at the University of St. Andrews. He can be contacted at via the NAM press room, whose hours are: Tuesday to Thursday, 8.30 - 18.00, and 9.00 - 12.00 Friday. Telephone: 01334-462168 and 462169 FAX: 01334-463130 PHOTO CAPTION: Figure 1 [http://www.jb.man.ac.uk/merlin/press/PR9801/picture1.html] Hubble and MERLIN image of 1938+666. A postscript version is available for Figure 1. (Upper) The Hubble Space Telescope picture of the distant galaxy 1938+666 which has been imaged into an Einstein ring by an intervening galaxy. The intervening galaxy shows up as the bright spot in the centre of the ring. The picture was taken in the infra-red region of the spectrum and the computer-generated colour of the image has been chosen simply for ease of viewing. (Lower) The MERLIN radio picture of the radio source 1938+666 embedded in the distant galaxy. The incomplete ring (or arc) shows that the radio source is not perfectly aligned with the lens galaxy and the Earth. The lens galaxy does not contain a radio source and hence does not show up in this picture. The colours are computer-generated and represent different levels of radio brightness. Figure 2 [http://www.jb.man.ac.uk/merlin/press/PR9801/picture2.html] Diagram demonstrating the principle of a gravitational lens. A postscript version is available for Figure 2. Diagram showing the formation of a gravitational lens images. In the upper diagram the distant object, the lens galaxy and the Earth are perfectly aligned. The lens galaxy formed a perfect ring-like image known as an Einstein Ring. In the lower diagram the distant object, the lens galaxy and the Earth are not perfectly aligned. In this case the lens galaxy forms multiple images of the distant object. ***** PRESS RELEASE: PR9801 12th March 1998 A Bull's Eye for MERLIN and the Hubble Background Information The observations Because of the blurring effect of the atmosphere on optical telescopes, the astronomers use high resolution radio telescopes -- the Very Large Array in New Mexico and the MERLIN array in the UK (see the main MERLIN WWW page at http://www.jb.man.ac.uk/merlin/) -- to pick out gravitational lens systems. Only about one in every five hundred distant radio sources (galaxies and quasars) is lensed and so thousands of radio sources have to be searched to have a good chance of success. The British team, working together with an international team of colleagues, have now found thirteen such systems -- more than doubling the number previously known. The radio picture produced by MERLIN (Figure 1), which allowed the system to be recognised in the first place, shows only part of a ring. The reason is that, while the source of radio emission is embedded in the distant galaxy, it is not exactly aligned with the lens galaxy. The ``optical'' picture produced by the Hubble (Figure 1) is actually in the infra-red region of the spectrum taken with the NICMOS camera. The wavelength used is about twice that of red light. The infra-red emission from the distant galaxy is more extended than the radio emission. Some of it comes from directly behind the lens galaxy and hence a complete ring is formed. Gravitational Lensing Unlike the lenses with which we are familiar, in spectacles for example, a gravitational lens can produce not one but several images of a given object; these images may be highly distorted and magnified. Whereas a conventional glass or plastic lens has a simply curved shape the analogy with a gravitational lens is a piece of glass shaped like the base and stem of a wine glass with the bowl cut off. Even without breaking the glass the ring effect can easily be seen by tipping the glass and looking at a mark on a piece of paper (or a table cloth) through the base. The way in which a gravitional lens produces multiple images, including the special Einstein ring case, is illustrated in the explanatory diagram (Figure 2). Why study gravitational lenses? By studying this and other gravitational lenses astronomers can not only measure the masses and shapes of distant galaxies, including any ``dark'' matter which will not show up in the optical or radio pictures, but also can measure Hubble's constant which is related to the time elapsed since the Big Bang. Einstein's ``greatest blunder'' refers to the elusive Cosmological Constant. This describes the strength of the long-range repulsive force he introduced into the General Relativity equations in 1916. Other astronomers soon showed, however, that this force was not needed to explain the properties of the Universe as it was then known. Einstein ruefully wrote ``away with the cosmological term''. But like a genie, once released it has proved hard to put away and many astronomers now invoke the Cosmological Constant to account for modern observations of the distant universe. A Universe in which the Cosmological Constant is not identically zero has different geometrical properties to one governed solely by gravity. Counting gravitational lenses, in other words counting the number of lines-of-sight ``blocked'' by intervening galaxies, is acknowledged to be the best way of measuring the geometry of the Universe at large distances. By the end of this year we expect to be able to place the best limit so far on the Cosmological Constant. Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: A New View Of Mass Ejections: Watching The Sun Cough Привет всем! Вот, свалилось из Internet... Royal Astronomical Society Press Notices Date: 27 March 1998 Ref. PN 98/08 (NAM5) Issued by: Dr Jacqueline Mitton RAS Public Relations Officer Phone: Cambridge ((0)1223) 564914 FAX: Cambridge ((0)1223) 572892 E-mail: jmitton@ast.cam.ac.uk and Peter Bond Space Science Advisor Phone: (0)1483-268672 Fax: (0)1483-274047 E-mail: 100604.1111@compuserve.com A NEW VIEW OF MASS EJECTIONS: WATCHING THE SUN COUGH It seems that the behaviour of the Sun in some ways resembles that of humans with a dry throat: the first spasm leads to a further series of coughs in a kind of chain reaction. In the case of the Sun, huge clouds of hot gas are ejected during each spasm in the form of Coronal Mass Ejections. This, and other new results from the LASCO (Large Angle Spectrometric Coronagraph) instrument on board the European Space Agency/NASA spacecraft SOHO (Solar and Heliospheric Observatory), will be presented at the UK National Astronomy Meeting at the University of St Andrews by Dr Mark Lyons from the University of Birmingham. What Are CMEs? Astronomers have known since the early 1970s that Coronal Mass Ejections (CMEs) are regularly thrown out into space by the Sun. These huge clouds of gas consist of electrically charged particles (protons and electrons) and have a typical mass of hundreds of millions of tonnes. In some cases they are directed towards the Earth and they travel so rapidly that they usually cross the 150 million km gap within three days of their launch from the Sun. Scientists would very much like to be able to forecast these events since, on arrival, they interact with the Earth's magnetic field, producing geomagnetic disturbances which can disrupt electricity supplies and cause damage to satellites. In addition, understanding how CMEs are produced is crucial to understanding the overall workings of the Sun. They are a dominant feature of the solar corona (the white halo seen around the Sun during solar eclipses) and may play a major role in the behaviour of the solar magnetic field. LASCO The latest tool being used to advance the research into CMEs is the LASCO instrument carried on board the SOHO satellite. LASCO is a joint project between the University of Birmingham, the Naval Research Laboratory (Washington DC), the Max-Planck-Institut fur Aeronomie (Germany) and the Laboratoire d'Astronomie Spatiale (France). It consists of three telescopes (known as coronagraphs) which are capable of blocking out the bright disk of the Sun and allowing the fainter light from the corona to be observed. Combined, the three coronagraphs of LASCO give images of the solar corona from 1.1 to 30 solar radii (from just above the visible surface to a distance of about 20 million km from the Sun). This wide angle view and its high sensitivity give LASCO a tremendous advantage over previous instruments. In general, a CME is thought to occur when closed magnetic configurations in the solar corona are destabilised by some trigger. This destabilisation then leads to the expulsion of matter from the solar atmosphere. The latest research at Birmingham is revealing that the entire Sun can be affected by CMEs. This is displayed most strikingly by events observed by LASCO where an initial mass ejection is closely followed by a series of others. In some cases CMEs occur at widely separated points almost simultaneously. For the first time LASCO is showing us that the corona behaves as a single unit, capable of storing large amounts of magnetic energy which can be released from more than one point by some initial triggering mechanism. Further evidence for a global reaction of the corona was provided by an event observed on the 23rd February 1997. LASCO C1 images (covering a region from 1.1 to 3 solar radii) showed the expansion of a CME in the lower corona moving with a speed of 880 km/s from the north-east limb of the Sun. This quickly destabilised a sequence of much larger magnetic loop structures to the south which then became the dominant feature of the CME. This sequence of events implies that a higher magnetic loop system spans the solar equator to physically connect regions in opposite hemispheres. The Solar Wind For a long time the Sun has been known to produce a 'wind' of charged particles. Mass ejections from the Sun are known to contribute a significant fraction of the total material of solar wind. LASCO observations are now providing new information about the flow of the solar wind nearer to solar surface where its properties have not been closely studied. A study of CME events carried out by Professor George Simnett at Birmingham University has shown that they begin to undergo an acceleration at a distance of about 6 solar radii. So the LASCO observations indicate that this is probably where the solar wind begins. Notes for Editors The SOHO satellite was launched in December 1995. It orbits a stable point (the Lagrangian L1 point), situated approximately 1.5 million km from Earth towards the Sun at which the gravitational pull on the satellite from the Earth and the Sun are equal. This position ensures that LASCO has an uninterrupted view of the Sun. LASCO observations will continue as solar activity moves towards a maximum in its 11 year cycle by the end of the century. Dr Mark Lyons is a research fellow working on the LASCO project at the University of Birmingham. The solar group at the University of Birmingham, headed by Prof. George Simnett, is using images from LASCO to provide new insights into the CME process. More information about the LASCO research carried out by the solar group at the University of Birmingham and about the SOHO project, including images of CMEs, can be found on the following Web sites. * http://www/research/solar.html * http://lasco-www.nrl.navy.mil/lasco.html Contact Dr Mark Lyons, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT. Tel: +44 (0)121 414-4608 E-mail: mal@star.sr.bham.ac.uk Press room at the National Astronomy Meeting, University of St Andrews (8.30 - 18.00 Tue 31 March to Thur 2 April; 9.00 - 12.00 Fri 3 April): Phone: 01334-462168 and 01334-462169 Fax: 01334-463130 Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: Hubble Images Of Comet Hyakutake Released Привет всем! Вот, свалилось из Internet... The University of Michigan News and Information Services 412 Maynard Ann Arbor, Michigan 48109-1399 Contact: Adam Marcus Phone: (734) 647-7046 E-mail: marcusa@umich.edu News Release: March 27, 1998 Hubble pictures from study of Comet Hyakutake released EDITORS: A complete description of the results of the program and the individual images can be accessed via the World Wide Web from URL http://www.sprl.umich.edu/SPRL/Comets/Hyakutake.html ANN ARBOR -- University of Michigan astronomer Michael Combi has released two images of the inner coma, or gassy head, of Comet Hyakutake, which passed within about 16 million kilometers of Earth in 1996. The computer-generated pictures were taken with NASA's Hubble Space Telescope on April 4, 1996, during observations led by Combi, a research scientist at the U-M College of Engineering. These images, made using Hubble's Wide Field Planetary Camera 2, were part of a study of water photochemistry in comets. Hydrogen atoms are the most abundant gas in the entire coma of the comet. They are produced when solar ultraviolet light divides molecules of water, the major constituent of the nucleus of the comet. Using Hubble's High Resolution Spectrograph, Combi and his colleagues were able to determine that Hyakutake was churning out between 7 and 8 tons of water per second, by matching a computer model of the comet the researchers had created earlier to the observations. "The importance of such a detailed model is that it permits the accurate calculation of the production rate of water from observations," Combi said. The results appear in an article in the Feb. 20, 1998, issue of the Astrophysical Journal (vol 494, pages 816-821). The first image, shown in red, was taken through a narrow-band red filter that shows only sunlight scattered by dust particles in the inner coma of the comet. The second, shown in blue, was taken with an ultraviolet "Woods" filter image that shows the distribution of scattered ultraviolet radiation from hydrogen atoms in the inner coma. The inner yellow region near the center of the red dust image is dominated by the contribution from the dust which shows sunward directed spiral jets toward the upper right, and the thin straight particle trail pointing toward the lower left. The trail was a permanent feature of the comet around the time of its close approach to the earth in late March and early April. Also barely visible just beyond the lower left end of the trail are two of the many condensations which were seen to travel slowly down the tail are believed to be clumps of material released from the comet's nucleus -- a 2-3 km chunk of dirty ice. The inner white region of the blue image appears to show that the hydrogen atoms like the dust might be preferentially ejected toward the sunward or day side of the nucleus. However, this is not true. The asymmetric ultraviolet radiation pattern is produced by a roughly spherical distribution of hydrogen atoms because they are so efficient at scattering the incoming solar ultraviolet light. The atoms on the sunward side actually shadow the atoms on the tailward or night side of the coma. The same detailed model analysis of the coma which explains the expansion of the hydrogen atoms in the coma also explains the appearance of the image. Combi's team included Michael Brown of the California Institute of Technology, Paul Feldman of the Johns Hopkins University, H. Uwe Keller of the Max Planck Institute, Lindau, Robert Meier of the Naval Research Laboratory, and William Smyth of Atmospheric and Environmental Research, Inc. [NOTE: Images supporting this release can be accessed directly at http://www-personal.engin.umich.edu/~mcombi/HST/hyaku.html] Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: Hunt Is On For More Extrasolar Planets Привет всем! Вот, свалилось из Internet... Royal Astronomical Society Press Notices Date: 30th March 1998 For immediate release Ref. PN 98/11 (NAM8) Issued by: Dr Jacqueline Mitton RAS Public Relations Officer Phone: Cambridge ((0)1223) 564914 FAX: Cambridge ((0)1223) 572892 E-mail: jmitton@ast.cam.ac.uk HUNT IS ON FOR MORE EXTRASOLAR PLANETS The UK National Astronomy Meeting (NAM) at the University of St Andrews opens on Tuesday 31st March with astronomers expressing high hopes of finding more extrasolar planets in the near future, and of learning much more about planetary systems beyond our own, as major new research projects get under way at the Anglo-Australian Observatory (AAO) in New South Wales, and at the observatory on La Palma in the Canary Islands. The Anglo-Australian Planet Search Project Commenting on the AAO programme, AAO astronomer Chris Tinney said, "This southern hemisphere program is exciting, because it is the first time the virgin territory of the southern sky has been searched. Every southern star we observe is being checked for the first time. And the experience of the northern hemisphere shows we can expect to find the first new planets within about a year. Altogether, we hope to double the number of nearby stars with known planets over the next five years." The AAO observations form part of an international project to examine nearby stars similar to the Sun for the presence of planets. The project stems from the highly successful search by Geoffrey Marcy and Paul Butler at Lick Observatory in California. Marcy and Butler are the world's leading discoverers of extrasolar planets with 6 independent finds to their credit. Because many stars in the far southern sky are not visible from Lick, Paul Butler will be working on the 3.9-metre Anglo-Australian Telescope at the AAO in collaboration with Chris Tinney, Hugh Jones (Liverpool John Moores University) and Alan Penny (Rutherford Appleton Laboratory), who will talk about the project at the NAM. The LA Palma Exoplanet Programme Observations to start in May on La Palma will be described by Professor Keith Horne of the University of St Andrews, who is a member of a 20-strong team of astronomers from 15 different institutions, mainly in Europe. He explains, "We were awarded the 1998 'International Time Project' at La Palma and we have about 5% of the 1998 telescope time on all of the La Palma telescopes." Professor Horne is involved with searching for extrasolar planets by two different techniques -- looking for any that act as gravitational lenses, and looking for evidence that a planet is passing in front of its parent star as it travels in orbit. Other members of the La Palma consortium will observe stars with known planets, where there is a very large planet orbiting close to the star. They will be looking for signs of gas boiling off a giant planet similar to Jupiter. A third study is concerned with disks of dust around stars where planetary systems may still be forming. The researchers will investigate the presence of comet-like objects which have already been discovered in the disk around the star Beta Pictoris. Making Sense of Extrasolar Planets Dr William Cochran of the University of Texas, co-discoverer of the planet orbiting the star 16 Cygni B, opens the NAM on Tuesday 31st March with an invited talk in which he takes a long hard look at the facts on extrasolar planets as they stand today, about a year since the last discovery was announced. He will look at whether any of the 'planets' may really be brown dwarfs (failed stars) and whether it is possible to tell the difference. Dr Cochran says, "The question of whether these objects are planets or brown dwarfs is much more than an issue of semantics. I define a brown dwarf as a sub-stellar object formed in the same manner as a star. On the other hand, a planet is an object formed in the way we believe the planets in our solar system formed, by accretion in a circumstellar disk. Very different physical processes were involved. So there is no reason to believe that there should be a nice clean boundary between the masses of planets and brown dwarfs. The mass ranges of the two kinds of object may overlap, or there may be a 'mass gap' between planets and brown dwarfs. Those of us who have discovered the low mass objects have labelled them as planets, but mostly through wishful thinking. For example, the companion to 70 Virginis is commonly called a "planet", while the virtually identical object in orbit around the star HD114762 was called a "brown dwarf" by its discoverer. I believe that two different physical processes are indeed at work in the formation of these objects, and that the dividing line is somewhere around 10 Jupiter masses. The companions to 70 Virginis and HD114762 could well be either planets or brown dwarfs, but the lower mass companions are most likely true planets." Further Information on the Internet Further information on these topics can be found at the following WWW sites: Anglo-Australian Telescope Planet Search Programme: http://www.aao.gov.au/local/www/cgt/planet/aat.html G. Marcy and P. Butler's programme at Lick Observatory: http://cannon.sfse.edu/~williams/planetsearch/news.html Contact Information for the National Astronomy Meeting, University of St Andrews: Press room (open 8.30 - 18.00 Tue 31 March to Thur 2 April; 9.00 - 12.00 Fri 3 April): Phone: 01334-462168 and 01334-462169; Fax: 01334-463130 Contacts (usual phone nos etc.) Dr Alan Penny Rutherford Appleton Laboratory Didcot, Oxfordshire OX11 0QX, UK E-mail: alan.penny@rl.ac.uk Phone +44 (0)1235 445675 Fax: +44 (0)1235 446667 Dr Chris Tinney Anglo-Australian Observatory E-mail: cgt.@aaoepp.aao.gov.au Phone: +61 2 9372 4849 Professor Keith Horne University of St Andrews E-mail: kdh1@st-andrews.ac.uk Phone: +44 (0)1334 463322 Dr William Cochran McDonald Observatory The University of Texas at Austin Austin, TX 78712-1083 USA E-mail: wdc@shiraz.as.utexas.edu Phone: +1 512-471-6474 Fax: +1 512-471-6016 Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: Magnetism The Key To Mysteries Of The Sun Привет всем! Вот, свалилось из Internet... Royal Astronomical Society Press Notices Date: 27 March 1998 Ref. PN 98/10 (NAM 7) Issued by: Dr Jacqueline Mitton RAS Public Relations Officer Phone: Cambridge ((0)1223) 564914 FAX: Cambridge ((0)1223) 572892 E-mail: jmitton@ast.cam.ac.uk MAGNETISM THE KEY TO MYSTERIES OF THE SUN Solar physicists at the University of St Andrews are combining theory with results from the European Space Agency/NASA Solar and Heliospheric Observatory (SOHO) to solve a long-standing mystery about the Sun -- why is the solar corona so hot? According to Professor Eric Priest and his colleagues, energy from the Sun's magnetic surface is channelled into the corona by a process called 'magnetic reconnection'. In the corona, the magnetic field is broken down, releasing heat and raising the temperature of the gas to millions of degrees. And using SOHO observations they have also been able to show that there is little evidence so far to support a competing theory. This new work will be included by Professor Priest in his talk, 'A startling new Sun', at the National Astronomy Meeting at the University of St Andrews on Wednesday 1st April. The surface of the Sun has a temperature of only 6000 degrees kelvin (5730 degrees C), but its outermost layers of tenuous gas -- the corona, which is visible at a total solar eclipse -- is surprisingly very much hotter. Its temperature is several million degrees. How the corona is heated represents one of the most important unsolved mysteries in astrophysics which has tantalized solar physicists for the past 40 years. "But the coronal heating problem is a really tough and complex one to tackle" says Professor Priest. "The corona consists of several types of structure which may be heated by different mechanisms. There are huge magnetic loops arching high above the solar surface, tiny intense cores of emission called X-ray bright points, and dark regions, called coronal holes, where the nature of the magnetic field allows hot gas (plasma) to stream out into interplanetary space." Two main theories have been proposed to explain the high temperature of the solar corona. One of them involves magnetic waves travelling upwards from the surface of the Sun. Like water waves, magnetic waves carry energy. The other, the 'magnetic reconnection' theory, involves the generation of intense electric currents to discharge the energy directly into the corona. To test the wave theory, Dr Robert Walsh and Dr Jack Ireland at St Andrews used the Coronal Diagnostic Spectrometer (CDS) instrument on SOHO to search for magnetic waves with periods between 30 and 1000 seconds in an active region of the Sun's surface where the magnetic field is strong. The magnetic structure of the region was also mapped out using data from the Michelson Doppler Imager (MDI) instrument, also on SOHO. The results were startling: in the layers of gas nearest the visible surface of the Sun (the chromosphere), where the temperature is about 10,000 degrees kelvin, there are clear wave-like motions with periods of about 300 seconds and 600 seconds; further up (the transition region) where the temperature is 200,000 degrees kelvin the waves can also be seen. But by the time the one- million-degree corona is reached no such wave motions were detected. It appears that waves are travelling up some distance, but they are not getting far enough to heat the corona. However, the St Andrews team discovered that intense coronal brightenings known as X-ray bright points are heated by magnetic reconnection. Observations from a rocket instrument called NIXT have shown that such bright points have a complex internal structure of interacting magnetic loops. This structure agrees very well with predictions made by Professor Priest, Dr Clare Parnell and Dr Sara Martin. "Magnetic reconnection gives a unified explanation for many diverse observations from SOHO that all fall into place when viewed together" says Professor Priest. For example: * Recently, Karel Schrijver, Alan Title and colleagues at Lockheed Martin discovered from MDI observations that the solar surface consists of a "magnetic carpet", in which the magnetic structure is completely replenished every 40 hours. The mechanism for changing the magnetic connections so rapidly is the magnetic reconnection process. * With the SUMER instrument, rapid jets of plasma in explosive events have been discovered and these are also naturally produced by magnetic reconnection. * The discovery made with the CDS instrument of bright spots that have been called "blinkers" are an inevitable consequence of magnetic reconnection. Said Professor Priest, "It is only now that we are beginning to analyse and digest the results from SOHO, but there are some amazing surprises that are revolutionising our understanding of the Sun -- our closest star". Images to support this story can be found at: * http://www-solar.dcs.st-andrews.ac.uk/~robert/press.html The general SOHO Web site is at: * http://sohowww.nascom.nasa.gov/ Note The SOHO satellite was launched 2 years ago as a major joint project between the European Space Agency (ESA) and NASA, with ESA as the major partner. Contacts All at the University of St Andrews Fax: 01334 463748 Prof. Eric Priest Phone: 01334-463709 or 01334-474975 E-mail: eric@dcs.st-and.ac.uk Dr Jack Ireland Phone: 01334-463750 E-mail: jack@dcs.st-and.ac.uk Dr Clare Parnell Phone: 01334-463706 E-mail: clare@dcs.st-and.ac.uk Dr Robert Walsh Phone: 01334-463711 E-mail: robert@dcs.st-andrews.ac.uk Press room at the National Astronomy Meeting, University of St Andrews (8.30 - 18.00 Tue 31 March to Thur 2 April; 9.00 - 12.00 Fri 3 April): Phone: 01334-462168 and 01334-462169 Fax: 01334-463130 Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: Milky Way May Be Smaller Than We Thought Привет всем! Вот, свалилось из Internet... Royal Astronomical Society Press Notices Date: 27 March 1998 Ref. PN 98/06 (NAM 3) Issued by: Dr Jacqueline Mitton RAS Public Relations Officer Phone: Cambridge ((0)1223) 564914 FAX: Cambridge ((0)1223) 572892 E-mail: jmitton@ast.cam.ac.uk MILKY WAY GALAXY MAY BE SMALLER THAN WE THOUGHT In a new study, astronomers Dr Michael Merrifield and Dr Robert Olling of the University of Southampton have come up with revised estimates for the size of our galaxy, the Milky Way, and for the rate at which it is turning. They have found that the Milky Way is significantly smaller, and is spinning more slowly, than has previously been assumed. These results are being presented by Dr Merrifield on Thursday 2nd April at the UK National Astronomy Meeting at the University of St Andrews. Astronomers have known for almost a century that the solar system is located toward the outskirts the Milky Way, and that it follows a roughly circular path around the galactic centre. However, the quantitative details of this picture -- how far we are from the centre of the Galaxy and how fast we are travelling on our orbit -- have proved hard to pin down. For example, recent estimates of the distance to the galactic centre have ranged from 21,000 light years up to 30,000 light years, with a "best" estimate of around 28,000 light years. These uncertainties are particularly troubling to astronomers trying to understand the motions of stars in the Milky Way. The way stars move through space is largely controlled by the gravitational pull of our Galaxy as a whole, and the strength of that pull can only be estimated when astronomers know the size of our galaxy, and how rapidly the Sun is orbiting around its centre. Michael Merrifield and Robert Olling have shown how this problem can be turned on its head. They have looked at several studies of the actual observed motions of stars in the Milky Way. They say that the motion of the stars can only be understood if the Sun is located some 23,000 light years from the centre of the Milky Way, travelling at approximately 185 kilometres per second. Although within the range of existing estimates, these new results suggest that the values usually quoted for our distance from the galactic centre (28,000 light years) and the Sun's speed of rotation in its galactic orbit (220 kilometres per second) are significantly too high. A lower value for the size of our galaxy has repercussions on a much larger scale: the size of other objects in the Universe are often measured relative to the size of the Milky Way. Thus, if astronomers have previously overestimated the size of our galaxy, they will also have overestimated the sizes of other objects, and, indeed, of the Universe as a whole. It is therefore quite possible that the Universe is some 15% smaller than has been previously believed. Contact Dr Michael Merrifield Department of Physics and Astronomy University of Southampton Highfield Southampton SO17 1BJ Phone no: 01703 592092 Fax no: 01703 593910 E-mail: mm@astro.soton.ac.uk Note: Dr Merrifield will be at the National Astronomy Meeting, 31 March to 2 April. Press room at the National Astronomy Meeting, University of St Andrews (8.30 - 18.00 Tue 31 March to Thur 2 April; 9.00 - 12.00 Fri 3 April): Phone: 01334-462168 and 01334-462169 Fax: 01334-463130 Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: Oxford Scientists Uncover Strange Workings Of Jupiter's Great Red Spot Subject: Oxford Scientists Uncover Strange Workings Of Jupiter's Great Red Spot Привет всем! Вот, свалилось из Internet... Royal Astronomical Society Press Notices Date: 27 March 1998 Ref. PN 98/12 (NAM9) Issued by: Dr Jacqueline Mitton RAS Public Relations Officer Phone: Cambridge ((0)1223) 564914 FAX: Cambridge ((0)1223) 572892 E-mail: jmitton@ast.cam.ac.uk and Peter Bond Space Science Advisor Phone: (0)1483-268672 Fax: (0)1483-274047 E-mail: 100604.1111@compuserve.com OXFORD SCIENTISTS UNCOVER THE STRANGE WORKINGS OF JUPITER'S GREAT RED SPOT -- AND OTHER SECRETS OF THE JOVIAN ATMOSPHERE For well over two years, scientists from the department of Atmospheric, Oceanic & Planetary Physics at Oxford University have been studying weather and cloud formations on a world more than 600 million km away -- the planet Jupiter. The latest results of their research will be presented at the UK National Astronomy Meeting on Tuesday 31st March by Professor Fred Taylor, co-investigator for the NIMS instrument on the Galileo spacecraft, which is currently orbiting Jupiter. These results include the revelation of remarkable structure in Jupiter's Great Red Spot. The giant planet Jupiter is famous for its colourful, swirling clouds. The most notable feature among this ever-changing turbulence is the Great Red Spot, a huge storm system that could swallow up three Earths and is known to have existed for at least three centuries. One of the instruments on board the Galileo orbiter being used to study the Jovian atmosphere and the Great Red Spot is the Near-Infrared Mapping Spectrometer (NIMS). The capability of NIMS to obtain spatial and spectral information simultaneously is ideal for investigating the composition, vertical layering, optical thickness, and fine structure of Jupiter's mysterious cloud layers. The scientists hope that continued observations with NIMS will help to explain a number of the following mysteries: 1) Although theories abound, it is still not known what gives rise to the bright colorations of the Jovian clouds -- for example, the red pigment in the Great Red Spot or the various yellows and browns. 2) The nature of the circulation which gives rise to the east-west, belt-zone cloud structure is controversial. 3) What creates and sustains the various giant weather systems (of which the Great Red Spot is just one example of a whole family of different types of giant eddies). The analysis of the data is still at a relatively early stage, but several preliminary results will be presented at NAM. Winds, Storms and the Great Red Spot Jupiter has high winds, and a large number of very large, very long-lived storm systems can be seen on the planet at any one time. The most famous of these is the Great Red Spot (GRS), which is revealed as having a most remarkable structure in the new data. Most astronomers believed it was a deep mass of cloud. Instead, it has a spiral arm structure of clouds, with gaps between which enable NIMS to see through the GRS into the deep, relatively clear atmosphere below. Futhermore, the cloud structure is higher in the centre by more than 10 km and tilted towards one side, something like a crooked spiral staircase. What seems to be happening is that wet air from the deep atmosphere is rising rapidly in a relatively narrow region in the centre of the GRS, and then spraying out above the tops of the ammonia clouds while rotating, rather like a giant garden sprinkler. In some ways this is similar to what happens in a terrestrial hurricane, but the Jovian storm is much bigger than the entire Earth. The Nature of Jupiter's Cloud Layers As expected, the main cloud layer on Jupiter is made up of frozen ammonia crystals, and lies at a pressure level of around half a bar (1 bar is the mean pressure at the surface of the Earth). Although anticipated to resemble terrestrial cirrus clouds, the Jovian, ammonia-ice version is made of particles around a hundred times smaller than those in water-ice clouds on Earth. The ammonia clouds are overlain by a thick haze at much higher levels in Jupiter's atmosphere. This appears to be a photochemical smog made up of liquid hydrocarbon droplets. A similar layer blankets Saturn's moon Titan and prevents us from seeing Titan's surface. Although thinner than Titan's, the Jovian haze is unexpectedly substantial, and varies with time and place across the planet. There is a thicker cloud layer below both the haze and the ammonia cloud. This may be the theoretically-predicted hydrogen sulphide (as NH4SH) cloud at around the one-and-a-half bar level (one and a half times the sea level air pressure on Earth), or a combination of that and an even deeper water cloud. New data is being acquired to try to resolve this point. The Composition of Jupiter's Atmosphere Jupiter's atmosphere is mainly hydrogen, with about 15% helium and a number of minor constituents, the most important of which are measured and mapped by NIMS. Weather on Earth centres around the condensation and evaporation of water. On Jupiter three species, ammonia, phosphine, and water vapour, can condense, making for a remarkably complicated climate. The new data have shown that water, in particular, is very variable. This helps explain the very low water abundance measured by the Galileo probe when it plunged into Jupiters clouds in December 1995. It happened, by chance, to enter a particularly dry region. Notes The Oxford researchers are part of an international science team for the Near Infrared Mapping Spectrometer on the Galileo orbiter (Principal Investigator is Dr. Robert W. Carlson of the Jet Propulsion Laboratory in Pasadena, California). Galileo is a $1.5 billion NASA mission to explore the Jupiter system at close quarters over a long period. The orbiter has been returning data on the planet and its four largest moons since 7 December, 1995. A probe was also released into Jupiter's atmosphere which returned unique information on the structure and composition of the planets cloud layers. Although the primary mission is now over, the orbiter and the NIMS experiment are in good health and an extended mission is under way. This is focusing on detailed studies of the icy satellite Europa, which is thought to have a sub-surface ocean. Images NIMS images showing full hemisphere views of Jupiter are available on the Web site at: * http://www.atm.ox.ac.uk/user/irwin/ Contact Professor Fred W. Taylor, Head of Atmospheric, Oceanic and Planetary Physics, University of Oxford. Telephone: +44 (1865) 272903 Fax: +44 (1865) 272924 E-mail: F.Taylor@physics.oxford.ac.uk Press room at the National Astronomy Meeting, University of St Andrews (8.30 - 18.00 Tue 31 March to Thur 2 April; 9.00 - 12.00 Fri 3 April): Phone: 01334-462168 and 01334-462169 Fax: 01334-463130 Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: Quasar Discovered With X-Rays Is Long Ago And Far Away Привет всем! Вот, свалилось из Internet... Pennsylvania State University Contact: Barbara K. Kennedy (814-863-4682) or Donald P. Schneider (814-863-9554) and go to the Web at http://www.astro.psu.edu/users/dps/ 3-31-98 Quasar Discovered With X-Rays Is Long Ago And Far Away University Park, Pa. -- The most distant object ever found by probing the universe with x-rays has been discovered by an international team of astronomers using the x-ray satellite, ROSAT. The object, a quasar whose 12-billion-year-old radiation has been speeding toward Earth since the universe was in its infancy, was detected with the deepest x-ray exposure ever made, according to a paper to be published in the April issue of the Astronomical Journal. "This quasar is one of the faintest x-ray sources ever detected," says Donald Schneider, associate professor of astronomy and astrophysics at Penn State and an author of the paper describing the discovery. Quasars, which are the most luminous objects in the universe and are thought to contain the black-hole seeds from which all galaxies formed, are among the most distant objects known. "A quasar produces about 100 times as much energy as our entire galaxy but its volume typically is less than the size of our solar system," explains Schneider. Because radiation from quasars takes billions of years to reach the Earth, scientists see distant quasars as they were billions of years ago and use them as probes to study the early history of the universe. The researchers discovered the distant quasar, christened "RX J105225.9+571905," by pointing ROSAT's High-Resolution Imager (HRI) x-ray camera at a patch of sky for about a million seconds -- a very long time by astronomers' standards -- in a study known as the ROSAT Deep Survey. The group, including astronomers from the United States, Germany, and Italy, obtained enough time on the telescope to look deeper into space in x-rays than anyone ever had done before. "The purpose of this x-ray survey was to determine the nature of faint x-ray sources, says Guenther Hasinger, director of the Astrophysical Institute in Potsdam, Germany. "It surprised us by revealing one of the most distant objects known." In addition to Schneider and Hasinger, other astronomers involved with this work are Maarten Schmidt at Caltech, Ingo Lehmann at Potsdam, James Gunn at Princeton University, Riccardo Giacconi at the European Southern Observatory, J. Tr=FCmper at the Max Plank Institute, and Gianni Zamorani in Bologna. The enormous energies released by a quasar result from matter tumultuously tumbling into its central black hole during the initial formation of a galaxy, many astronomers believe. Quasars are observed to be plentiful early in the history of the universe but to be quite rare today. The black holes still exist, but have had time by now to devour all the matter within their reach. "There is good evidence that a black hole resides at the center of our Milky Way galaxy, but we do not see a quasar because there is no material currently falling into the black hole," Schneider says. In order to gauge the distance from Earth to the objects revealed by ROSAT's x-ray observatory, the scientists had to study them with one of the world's largest optical telescopes, the Keck telescope in Hawaii. "The X-ray satellite reveals that there is an X-ray source in this part of the sky, but it doesn't tell us what it is and it doesn't tell us how far away it is -- we determine that from its visible light," said Hasinger. The most distant objects are speeding away the fastest, so their visible light appears to be more "redshifted," or skewed toward the red end of the spectrum. "This quasar is so faint in visible light, it is near the limit of what the giant Keck telescope can measure and -- because there are large numbers of optical objects at these brightnesses -- our x-ray resolution had to be very accurate in order to determine which object our x-ray source matches in the Keck optical image," Hasinger explains. The German team, led by Hasinger, developed the techniques that made it possible for the astronomers to assign very accurate celestial positions to x-ray sources in the ROSAT survey. "The HRI now yields positions that are accurate to about 2 arc seconds -- less than one-one-thousandth of a degree -- whereas before we were getting positions accurate only within 5 to 10 arc-seconds." The researchers discovered that the new quasar is located at redshift 4.45, which is so far away that we see it as it appeared when the universe was only about nine percent of its current age. "Most of the other objects in the survey turned out to be galaxies or quasars much closer to Earth, with redshifts less than two," Schneider says. While a few objects more distant than the new quasar have been discovered, this is the most distant object ever discovered in an x-ray survey, according to the astronomers. Neil Brandt, assistant professor of astronomy and astrophysics at Penn State, has been investigating the x-ray properties of distant quasars. "Altogether, there are about 100 high-redshift quasars now known and x-rays have been detected coming from only about 9 of them," Brandt says. "We suspect the others are producing x-rays that are just too weak to be detected with our current instruments and typical exposure times." Astronomers may have to wait only until the end of this year to get a next-generation x-ray camera that will produce much sharper images than are possible now. The "AXAF Charge-coupled device Imaging Spectrometer" (ACIS), which is scheduled for a Space Shuttle launch this fall, is one of the instruments on the world's most powerful X-ray-astronomy observatory, NASA's Advanced X-ray Astrophysics Facility (AXAF). AXAF will be the third of NASA's "Great Observatories" to be launched, following the Hubble Space Telescope, which detects ultraviolet, visible, and infrared rays, and the Compton Gamma-Ray Observatory, which detects gamma rays. "Among the wonders the ACIS camera is designed to see is the early growth of the seeds of quasars in the infant universe," says Gordon Garmire, the Evan Pugh Professor of Astronomy and Astrophysics at Penn State and the principal investigator who conceived and designed the camera. "This research holds great promise for our future work at Penn State," Schneider comments. "With Dr. Garmire's ASIS camera and the next generation of large optical telescopes including the new Hobby-Eberly Telescope, in which Penn State is a major partner, we expect to be able to discover, identify, and locate many more very faint x-ray objects," he says. "We will be quite surprised if a number of them are not much closer to the beginning of time than the quasar found in our current survey." This research was supported by the National Science Foundation, the National Aeronautics and Space Administration (NASA), the German Center for Space Research, and the Italian Space Agency. Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: This Week On Galileo - March 31 - April 5, 1998 Привет всем! Вот, свалилось из Internet... THIS WEEK ON GALILEO March 31 - April 5, 1998 The remaining five days of this week continue to be busy for the Galileo spacecraft, even though it has just completed a science encounter. Among other activities, Galileo begins to process and transmit to Earth pictures and science information gathered this past weekend as the spacecraft flew past Jupiter and its moons. The series of flybys included flying over Europa's surface at a distance of 1645 kilometers (1022 miles). During the week, the spacecraft will execute two activities designed to further understand and possibly circumvent the anomalous behavior exhibited by the attitude control subsystem. The first of these, performed on Tuesday, is designed to collect gyroscope data to track the degradation of the gyro's performance. A repeat of the performance test is planned later in the orbit, far from Jupiter's intense radiation environment, in hopes of determining whether the degradation rate is time dependent or radiation dependent, or possibly dependent on both. The second activity is performed on Wednesday and will provide engineers with data they require to complete the design of a flight software upgrade that could allow the spacecraft to operate on the single gyroscope that is functioning correctly. This week's processing and transmission to Earth of science information contains two sets of pictures obtained by the spacecraft's camera of Jupiter's fiery moon Io. The first set of pictures shows color views of Io's north and south pole regions. The pictures will improve the color knowledge of these regions by providing more than a factor of 3 greater resolution than obtained during Galileo's primary mission, 3 kilometers (1.8 miles) per picture element and 10 kilometers (6.2 miles) per picture element, respectively. Monochrome pictures as good as 2.5 kilometers (1.5 miles) per picture element were obtained in the primary mission, but the color in these new images will be critical to identifying surface materials. The second set of images provides a preliminary look at a region of Io that is planned to be imaged at much higher resolution in October 1999. Both of these image sets will also help scientists to refine observation plans for Io in late 1999. Data processing and transmission to Earth is paused for a few hours on Thursday as the spacecraft executes a flight path correction. This is the first flight path correction since before this past weekend's flybys. For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page: http://www.jpl.nasa.gov/galileo/ Hа сегодня все, пока! =SANA=
    Дата: 01 апреля 1998 (1998-04-01) От: Alexander Bondugin Тема: NASA Program Spawns New Safety Sofware For Pilots Привет всем! Вот, свалилось из Internet... Don Nolan-Proxmire Headquarters, Washington, DC March 31, 1998 (Phone: 202/358-1983) John G. Watson Jet Propulsion Laboratory, Pasadena, CA (Phone: 818/354-5011) RELEASE: 98-52 NASA PROGRAM SPAWNS NEW SAFETY SOFTWARE FOR PILOTS Two new software packages enabling pilots to use laptops to avoid hazardous terrain and find their place on maps are the latest success stories of a NASA program bringing together entrepreneurs and space engineers. Pilots of small planes, for whom such tools have been largely unavailable until now due to cost and the sheer size of bulky hardware, may soon be able to carry onboard the personal computer equivalent of collision-avoidance systems now used by the military and commercial airlines. "TerrAvoid" and "Position Integrity" combine Global Positioning Satellite (GPS) data with high-resolution maps of the Earth's topography. Dubbs and Severino, Inc., based in Irvine, CA, has developed software that allows the system to be run on a battery-powered laptop in the cockpit. The packages, designed primarily for military sponsors and now positioned to hit the consumer market in coming months, came about as the result of the Technology Affiliates Program at NASA's Jet Propulsion Laboratory's (JPL), Pasadena, CA. Intended to give American industry assistance from NASA experts and to facilitate business use of intellectual property developed for the space program, the Technology Affiliates Program introduced the start-up company of Dubbs and Severino to JPL's Dr. Nevin Bryant four years ago. Dubbs and Severino had an idea for mapping software to help private airplane pilots, inspired in part by the fatal crash of a pilot friend of company president Bob Severino. The twist: the package was to be completely software-driven, instead of requiring expensive hardware, as was the norm up to that time. Bryant's Cartographic Applications Group at JPL had developed GeoTIFF, an architecture standard providing geo-location tools for mapping applications. GeoTIFF proved to be the crucial key that the start-up company needed to bring the idea to fruition, allowing the firm to develop low-cost software packages. GeoTIFF is now in the public domain, and its use for commercial product development has evolved into an industry standard over the last year. Through the Technology Affiliates Program, Dubbs and Severino obtained JPL's assistance early on and thus gained a jump-start in adapting the architecture for their products' specific needs. "JPL gave us a demonstration and opened up the red carpet. It was a match made in heaven," says Severino. Merle McKenzie, manager of JPL's Commercial Technology Program, said that Dubbs and Severino's ability to utilize technology originally developed for NASA provides a strong example of the many advantages of technology transfer programs. "This is a win-win partnership through which yet another American business gets a boost from the space program," McKenzie said. "TerrAvoid" is a terrain avoidance system that graphically shows pilots if they are flying dangerously close to mountains: safe sections can be seen in green, while hazardous sections show up in red, with those proportions changing in real time as the pilot moves through hilly terrain. In a sense, the system "looks" out over a plane's flight path, sweeping 360 degrees, warning the pilot if there are any upcoming hazards. Ithe software integrates GPS tracking data with maps on CD-ROM, and is approximately 1/20th the cost of its nearest competitor. "Position Integrity," which also co-registers real-time GPS data with local maps on CD-ROM, is a moving map detailing the exact position of the pilot. Because of the unique features of GeoTIFF, this software can be adapted to operate with any map, chart or photo image in the world, while comparable versions are limited solely to either military, scientific or commercial maps. GeoTIFF also enables the package to feature four windows at once, a useful and unique option for pilots who need to work simultaneously with maps, charts, photo images and sketches at different scales and zoom levels. Further details about JPL's technology transfer activities, including the Technology Affiliates Program, are available online at http://techtrans.jpl.nasa.gov/tu.html JPL is a division of the California Institute of Technology. -end- Hа сегодня все, пока! =SANA=

    сайт служит астрономическому сообществу с 2005 года