-------------------------------------- | | | Biuletyn PTA nr 14 | | | -------------------------------------- Biuletyn informacyjny Zarzadu Glownego Polskiego Towarzystwa Astro- nomicznego (Adres kontaktowy: M. Ostrowski, pta@oa.uj.edu.pl , a w bardzo pilnych sprawach: mio@oa.uj.edu.pl ) ======================================================================= Spis tresci: I. Nota redakcyjna II. Nowy Zarzad Polskiego Towarzystwa Astronomicznego III. Seminaria IV. Nowinki naukowe ======================================================================= I. Nota redakcyjna Przypominam, ze Biuletyn PTA jest wydawany jako forum do prezentacji aktualnych informacji, ktore moga interesowac ogol polskich astronomow. Nie jest on organem PTA, a nasze Towarzystwo przesylan swoim czlonkom komunikaty w postaci internetowej lub drukowanej jako Komunikaty PTA. Bardzo prosze o przesylanie na podany wyzej adres wszelkich istatnych informacji, ktore moga byc interesujace dla naszego srodowiska. Informacje do Biuletynu nalezy przesylac w postaci zwyklych zbiorow ASCII, bez polskich liter (!). Osoby pragnace otrzymywac Biuletyn (takze studenci) proszeni sa o nadsylanie krotkich "mejli" z taka prosba. M. Ostrowski ======================================================================= II. Nowy Zarzad Polskiego Towarzystwa Astronomicznego wybrany na Zjezdzie w Olsztynie. Prezes: Andrzej Woszczyk Wiceprezes: Janusz Ziolkowski Sekretarz: Adam Michalec Skarbnik: Andrzej Niedzielski Czlonkowie Zarzadu: Ewa Janaszak Tadeusz Michalowski Michal Ostrowski From: Adam Michalec ======================================================================= III. Seminaria SEMINARIUM "FIZYKA MATERII MIEDZYGWIAZDOWEJ" Kolejne seminarium poswiecone zagadnieniom fizyki materii miedzygwiazdowej odbylo sie 5 listopada 1999 w Obserwatorium Astronomicznym Uniwersytetu Mikolaja Kopernika w Piwnicach kolo Torunia. Referaty: Piotr Gnancinski (IFTiA Uniwersytet Gdanski) Wyznaczanie obfitosci miedzygwiazdowego wegla z ultrafioletowych linii CI i CII Jacek Krelowskiego i Jan Fulara (CA Uniwersytet M. Kopernika i Instytut Fizyki PAN Warszawa) Precyzyjne profile rozmytych linii miedzygwiazdowych i co mozna z nich wywnioskowac Funkcje LKO pelni Jacek Krelowski (jacek@astri.uni.torun.pl). Na ten adres nalezy nadsylac zgloszenia uczestnictwa oraz dezyderaty: czy zamowic obiad, oraz odnosnie menu - ryba vs. nalesniki. Prosimy tez o podanie dokladnego terminu przyjazdu i wyjazdu, a takze srodka komunikacji. Uczestnikom z "daleka" oferujemy mozliwosc przenocowania w Piwnicach. Zapytania o dalsze spotkania nalezy nadsylac do Jacka Krelowskiego. From: jacek@astri.uni.torun.pl Przeredagowal M. Ostrowski, ktory przeprasza za opoznienie z rozpowsze- chnieniem tej informacji. ======================================================================= IV. Nowinki naukowe Uwaga: Zrodlem ponizszych nowinek naukowych jest PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News by Phillip F. Schewe and Ben Stein Przedruk za zgoda wydawcy. THE SHADOW OF A PLANET slipping across the face of a distant star has been detected, for the first time, by veteran extrasolar-planet stalkers Geoffrey Marcy of UC Berkeley and Paul Butler of the Carnegie Institution, working with Greg Henry of Tennessee State University. Prior indirect "sightings" of extrasolar planets consisted of small feints in the apparent position of the stars caused by the suspected gravity pull of an orbiting planet. Astronomers have felt that from among the growing sample of such planets (up to 25 as of now) a few (whose orbits would be viewed at Earth edge-on) might be detected directly as they pass in front of the star. One such candidate was HD 209458. Prediction of a planetary transit for the night of November 7 proved accurate and a 1.7% dimming in the star's light was seen. (Announcement made in an International Astronomical Union circular.) IO SODIUM JET. Astronomers have previously known of a sodium cloud which precedes the moon Io in its orbit around Jupiter. The cloud is believed to arise from slow escape of sodium from Io. Now the Galileo spacecraft is providing details of another sodium feature at Io, more of a fast-escaping spray or jet, thought to come about when Io plows through Jupiter's potent magnetic field, a process which induces mega-amp currents through Io's atmosphere (see schematic at www.aip.org/physnews/graphics). New pictures, reported by scientists at the University of Colorado (Matthew Burger, burger@ganesh.colorado.edu, 303-492-3395, and Nicholas Schneider) and Boston University (Jody Wilson), localize the source of the sodium to a region smaller than Io's diameter, suggesting that Io's atmosphere might not be global; that is, the atmosphere might be patchy and not extend all the way to the poles. (Geophysical Research Letters, 15 November.) ORIGIN OF RADIO JETS NEAR A BLACK HOLE. Black holes don't just sit there spiderlike swallowing stars. They also fling out vast plumes of light-emitting material; these collimated streams can stretch for hundreds of thousands of light years. One of the closest of these conspicuous jets is to be found at the heart of galaxy M87, about 50 million light years away from Earth. Presumably the jet originates at an accretion disk surrounding a supermassive black hole. Previously radio mapping of this spot in the sky did not possess sufficient resolving power to see precisely where the jet begins. But now, by pooling the extended radiowave gathering power of the Very Long Baseline Array (VLBA), the Very Large Array (VLA), and telescopes in Italy Sweden, Finland, Germany, and Spain, astronomers have nailed down the jet origin to within tenths of a light year of the black hole's location. The resulting image (see www.aip.org/physnews/graphics) shows that the jet's initial opening angle is 60 degrees, the widest ever seen for a jet, although the jet becomes much more focused (6 degrees) further downstream. (Junor et al., Nature, 28 Oct.) GRAVITY'S GRAVITY. A new experiment at the University of Washington seeks to determine whether the gravitational binding energy of an object generates gravity of its own. As formulated by Albert Einstein, the Equivalence Principle (EP) states that if we stand in a closed room we cannot tell whether the weight we feel is the result of gravity pulling down or the force of a rocket carrying us forward through otherwise empty space. All of this gets complicated in some theories of gravity, which predict that the EP will be violated to a small degree since in addition to the usual gravity, carried from place to place by spin-two particles called gravitons, there should exist another, fainter kind of gravity carried by spin-zero particles (sometimes called dilatons). For this reason, and because recent observations of supernovas suggest that some repulsive gravitational effects might be at work in the cosmos, scientists want to explore the possibility of EP violations. Three decades of lunar laser ranging (bouncing light off reflectors placed on the Moon) show that the Moon and the Earth fall toward the Sun with the same acceleration to within half a part in a trillion (10^12). What the Washington physicists (Eric Adelberger, 206-543-4294, eric@gluon.npl.washington.edu) have done is focus attention on the subject of gravitational binding energy, or self-energy, and whether it too obeys the EP. To illustrate the concept of binding energy, consider that the mass of an alpha particle is actually about 28 MeV less than the sum of its constituents. This energy (about 7.6 parts in a thousand of the alpha mass) represents the energy (vested in the strong nuclear force) needed to hold two protons and two neutrons together inside the alpha. Gravity being very much weaker than the strong nuclear force, the gravitational binding energy, the self-energy of gravity attraction, is almost infinitesimal. For example, self- energy effectively reduces the mass energy of the Earth by a factor of only about 4.6 parts in 10^10. Is this tiny "mass" also subject to the EP? Supplementing existing lunar laser ranging results with new data from special test masses mounted on a sensitive torsion balance (see www.aip.org/physnews/graphics) to take into account the different compositions of the Earth and Moon, the Washington physicists show that gravitational self energy does obey the equivalence principle at the level of at least one part in a thousand. Thus gravitational self energy does indeed generate its own gravity. (Baessler et al., Physical Review Letters, 1 November; see also Clifford Will's article, Physics Today, Oct 1999.) NEPTUNE DIAMONDS. The crushing conditions inside Neptune and Uranus are recreated at UC Berkeley, where a tiny sample of methane is squeezed in a diamond anvil press up to pressures of 30- 50 GPa (more than 10 million atm) and heated with laser light to temperatures to 3000 K. Scattered x rays and infrared light indicate that some of the methane is being converted into 10-micron-sized diamonds and certain polymers at pressures much below what had been expected. This result might lead to some re-assessment of planetary interiors since a widespread dissociation of methane would release considerable energy, affecting the dynamics and evolution of the planet in a big way. (Benedetti et al., Science, 1 October 1999.) CORRECTIONS: 1. Diamonds precipitated from methane in an anvil press (Update 451) squeezed up to pressures of 50 GPa, equivalent to 0.5 (not 10) million atm. CHILLING MIRRORS WITH LIGHT. In astronomy the effect of atmospheric turbulence on the quality of images acquired by ground-based telescopes can be greatly reduced by "adaptive optics," a corrective process in which parts of the telescope mirror are flexed mechanically by piezoelectric motors in an amount typically equal to a fraction of the wavelength of the incoming light. In interferometric measurements adjustments in mirrors are also desirable, not because of turbulence in the intervening medium but because of thermal noise in the mirror itself. The LIGO and VIRGO interferometers (Update 442), searching for gravity waves, need very still mirrors, the better to observe the flexing of space-time on a scale far smaller than the size of an atom. A new technique might help in this regard. Physicists at the Ecole Normale Superieure and Universit‚ P. et M. Curie in Paris (Antoine Heidmann and Michel Pinard, heidmann@spectro.jussieu.fr, 011-33.1-4427-4405), can measure the thermal agitation of mirrors and reduce this unwanted noise by a factor of 20, with pressure from laser light. This corresponds to a spatial sensitivity of the mirror at a level of a billionth of an angstrom. (P.F. Cohadon et al., upcoming article in Physical Review Letters; see figure at www.aip.org/physnews/graphics.) ANOMALOUS ACCELERATION UPDATE. Last year a team of scientists published an assessment of the longterm trajectories of certain spacecraft, including Pioneer 10 and 11, showing that even after all known sources of gravity (sun, planets, comets, etc.) and other forces were taken into account, an extra acceleration seemed to be present (Anderson et al., Physical Review Letters, 5 Oct 98; Update 391). Now a series of letters concerning this assessment appears in the same journal (30 August 1999). John Murphy of Johns Hopkins (301-953-6214) argues that the explanation lies in the asymmetric radiation given off by the crafts' electronics as waste heat. Jonathan Katz of Washington University (314-935-6202) implicates the recoil of radiation (from radioactive thermal generators, or RTG, powering the craft) off the rear of the high-gain antenna. The authors of the original paper (contact John Anderson, JPL, 818-354-3956) basically assert that these two particular explanations fall short of accounting for the anomalous acceleration by roughly a factor of five or more. (All PRL papers are available to journalists from AIP Public Information.) DARK MATTER ANNIHILATION AT THE GALACTIC CENTER. How does the presumed massive black hole at the center of our galaxy shape the distribution of the presumed halo of dark matter in its vicinity? Paolo Gondolo of the Max Planck Institute of Physics (Munich, Germany) and Joseph Silk of Oxford (UK; also UC Berkeley) suggest the black hole sculpts the dark matter into a dense spike where particle annihilation (or, more to the point, self- annihilation, since one of the leading hypothetical dark-matter particles is the "neutralino," which is its own antiparticle) would be enhanced. Of all the annihilation products (e.g., electrons, positrons, protons, etc.) issuing from the galactic center (a region half a light year wide) neutrinos would be the most serviceable since they can travel to Earth undeflected by magnetic fields. Gondolo and Silk have calculated how present and future neutrino telescopes can probe the density of inner halo dark matter. (Physical Review Letters, 30 August; gondolo@mppmu.mpg.de, 011-49-893-235-4427.) GRAVITY WAVE ANALYSIS FROM LIGO PROTOTYPE. The Laser Interferometer Gravitational-wave Observatory (LIGO), when fully deployed, will consist of two facilities (Hanford, WA and Livingston, LA). At each site laser beams pass up and down two perpendicular 4-km-long vacuum pipes, reflecting repeatedly from mirrors hung from wires. The presence of a passing gravitational wave would announce itself by a flexing of space- time which would very slightly lengthen the path of light in one arm and shorten the path in the other arm, causing a subtle change in the interference pattern made by the converging light beams from the two arms. The full LIGO, by about November 2001, should be able to detect a strain, defined as the fractional change in the position of the mirrors divided by the length of the arm (4 km), of 10^-21. This is the expected disturbance one expects from the gravity waves emitted by the coalescence of two solar-sized stars at a distance from Earth of 30-50 million light years. But before LIGO scientists possess their full instrument, they do have a 40-m prototype at Caltech, built for doing engineering studies but also capable of sensing gravity waves, albeit with the lesser strain sensitivity of a few times 10^-19. Thus the LIGO team, while testing methods for searching (directly via gravity waves) for binary coalescences, have thereby rendered an upper limit for such events of less than one every two hours in our galaxy. This result is useful for the test of the procedures, but is not significant for astronomers, who have previously established more stringent upper bounds with electromagnetic waves (visible and radio). (Contact Barry Barish at Caltech, 626-395-3853 or 818-601-2643; Stan Whitcomb 626-395-2131; or Bruce Allen, University of Wisconsin-Milwaukee, 626-893-2003 or 414-229-6439; Allen et al., Physical Review Letters, 16 August 1999.) THE CHANDRA X-RAY TELESCOPE is now installed in its highly elliptical orbit, where the Earth itself, and not just its atmosphere, will not interfere with x-ray reception. Named for astrophysicist Subrahmanyan Chandrasekher, the 14-m-long telescope is considered one of NASA's three "great observatories"; the other telescopes in this battleship class are the Hubble Space Telescope and the Compton Gamma Ray Observatory. Chandra will have superb angular resolution (half an arc-second, 8 times better than previous x-ray telescopes), sensitivity to faint objects (20 times better), and spectral resolution (1 eV). The object of the mission is unflinchingly to explore graphic violence wherever it can be found at x-ray wavelengths: quasars, black holes, pulsars, supernovas, and intergalactic plasmas. (http://www1.msfc.nasa.gov/NEWSROOM/background/facts/cxoqu ick.htm) THE SURFACE OF MARS has been mapped to 13-meter precision, better than for some places on Earth. Laser light sent from and returning to the orbiting Mars Global Surveyor spacecraft reveals that the southern hemisphere is one big highland (6 km higher) compared to the northern hemisphere. Surface water, if there was any, would have collected in the North, although there is not yet definitive proof of any boreal ocean. One thing that is known about the northern lowland: it is the flattest place in the solar system. The South's elevation is due at least in part to an immense amount of material raised during an ancient impact which fashioned a huge crater known as the Hellas basin. (Science, 28 May 1999.) MEASURED VALUES FOR THE HUBBLE CONSTANT are converging nicely. At a press conference on May 25, Wendy Freedman of the Carnegie Institution reported a new value of 70 km/sec/megaparsec (with an uncertainty of 10%), down from a value of 80 reported back in 1994. She is one of the leaders of a group that uses the Hubble Space Telescope (HST) to track the light emission of Cepheid variable stars in nearby galaxies. Another Carnegie astronomer, Allan Sandage, has been a leader of a group that consistently measures a smaller value for the Hubble constant, the latest number being about 59, up from an earlier value of 57. Thus the observed Hubble constant, which is a measure of the overall expansion of the cosmos, is now providing an estimate for the age of the universe about 12 billion years that is no longer in contradiction with the apparent age of the oldest stars. (NASA press release, 25 May 1999.) =======================================================================