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Astrophysics in 1998 VIRGINIA TRIMBLE1 and MARKUS ASCHWANDEN2 Received 1998 December 10; Accepted 1998 December 11

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Astrophysics in 1998 VIRGINIA TRIMBLE1 and MARKUS ASCHWANDEN2 Received 1998 December 10; Accepted 1998 December 11 PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 111:385È437, 1999 April ( 1999. The Astronomical Society of the PaciÐc. All rights reserved. Printed in U.S.A. Invited Review Astrophysics in 1998 VIRGINIA TRIMBLE1 AND MARKUS ASCHWANDEN2 Received 1998 December 10; accepted 1998 December 11 ABSTRACT. From Alpha (Orionis and the parameter in mixing-length theory) to Omega (Centauri and the density of the universe), the Greeks had a letter for it. In between, we look at the Sun and planets, some very distant galaxies and nearby stars, neutrinos, gamma rays, and some of the anomalies that arise in a very large universe being studied by roughly one astronomer per 107 Galactic stars. 1. INTRODUCTION trated in a few highly regarded journals, and, of course, for power to be concentrated in fewer and fewer editorial Astrophysics in 1998 welcomes a new co-author, Markus hands. Aschwanden, formerly of the University of Maryland astronomy department, and as a direct result, gives some attention to solar physics, which has been relatively neglected in recent years. Lucy-Ann McFadden, meanwhile, 1.1. Up, Up, and Away is up to her very capable shoulders in the Near Earth Aster- oid Rendezvous (NEAR) project, a Maryland honors A great many things got started during the year. Cassini program, a science museum for families, and heaven knows was launched safely toward Saturn on 1997 October 15. what else. Astrophysics in 1991 to 1997 appeared in PASP The Planet B mission to Mars took o† in July, 1998 and so on page l of volumes 104È107, page 8 of volume 108, page was renamed Nozomi (Hope), following an excellent custom 78 of 109, and page 223 of 110, respectively. They are cited that has saved the Japanese space program from having had below as Ap91, Ap92, etc. a named mission blow up on the launch pad or enter a The journals scanned were the issues that reached library geostationary orbit on the ocean Ñoor for a very long time. shelves between 1997 October 1 and 1998 September 30 of The Ðrst data came back from HAL CA, the space-based Nature, Physical Review L etters, Science, T he Astrophysical radio interferometer (Hirabayashi et al. 1998). With a base- Journal (plus L etters and Supplements), Monthly Notices of line to earth-bound radio dishes exceeding 25,000 km, it has the Royal Astronomical Society, Astronomy and Astro- tightened the limits on the sizes of some components in physics (plus Supplements and Reviews), Solar Physics, Acta quasar jets and driven their apparent brightness tem- Astronomica, Astrophysics and Space Science, Astronomy peratures above 1012 K (the limit for incoherent synchro- Reports, Astronomy L etters, AstroÐzica, Astronomische tron emission). Nachrichten, Journal of Astrophysics and Astronomy, Pub- Early data were also reported from the recommissioned lications of the Astronomical Society of Japan, Bulletin of the Hooker 100A telescope on Mount Wilson (Hartkopf et al. Astronomical Society of India, Baltic Astronomy, Astro- 1997); from the second OGLE survey for gravitational physical L etters and Communications, New Astronomy, IAU lensing events due to MACHOSÈand for variable starsÈ Circulars, and (of course) Publications of the Astronomical (Udalski et al. 1997a; it uses a dedicated 1.3 m telescope at Society of the PaciÐc. Several of these have become quite Las Campanas); from the Ðrst of the four 8 meter mirrors difficult to locate, as more and more subscriptions are that will make up the Very Large Telescope (Kaper 1998); dropped, and coverage of AstroÐzica, Astronomische Nach- from the Sloan Digital Sky Survey (Turner 1998); from the richten, and Astrophysical L etters and Communications is second Ñight of the ORFEUS extreme-ultraviolet telescope not complete. This is part of a trend in astronomical pub- (Hurwitz et al. 1998a and about seven following papers; it lication that can be traced back at least to the late 19th saw a lot of O VI); and from a very large number of adaptive century, for major papers to be more and more concen- optics systems, including one on the Russian 6 meter tele- scope (Weigelt et al. 1998), though they are not the solution ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ to all the astronomical problems you ever thought of 1 Department of Astronomy, University of Maryland, College Park, (Esslinger & Edmunds 1998). MD 20742; and Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697. Alpha Orionis (Betelgeuse) has been resolved at the 0A.2 2 Lockheed-Martin ATC Solar and Astrophysics Laboratory, Depart- level with a nulling interferometer, which greatly suppresses ment H1-12, Building 252, 3251 Hanover Street, Palo Alto, CA 94304. the Ñux from the central star, allowing one to see the sur- 385 386 TRIMBLE & ASCHWANDEN rounding disk, and, someday, perhaps, planets (Hinz et al. Solar and Heliospheric Observatory (SOHO), which probed 1998). almost everything from the interior of the Sun (via Rugate is a Ðlter to suppress the near-infrared OH lines helioseismology) out to 30 solar radii in the heliosphere, produced by the earthÏs atmosphere (O†er & Bland- accompanied by an armada of other space-borne instru- Hawthorn 1998). It is a Latin word, not a relative of the ments: Yohkoh, the Compton Gamma Ray Observatory Rugrats. Oya et al. (1998) report data from a device with (CGRO), the T ransition Region and Coronal Explorer similar function (and a design with some resemblance to a (T RACE), W ind, Ulysses, and so forth. Short dives into radial-velocity spectrometer), but without a Latin name. space yielding unique solar glimpses have also been accom- COME-ON-PLUS is a coronagraph to be used with plish by rocket Ñight such as NRL HRTS, NRL ETI, and adaptive optics (Beuzit et al. 1997), and we suspect that the GSFC SERTS, and the shuttle payload SPARTAN 201. name was selected by someone who was not a native WhatÏs the scientiÐc harvest? Despite the overwhelming speaker of American English. multicolor vision in invisible wavelengths, the complex A replica of the telescope with which Karl Jansky did his intricacies of solar plasma physics could not yet be suffi- pioneering work in radio astronomy has been erected close ciently disentangled to yield solutions to the problems to the original site in New Jersey (Tyson & Wilson 1998). It posed by coronal heating, acceleration of the solar wind, or is not intended as a working model. particle acceleration in solar Ñares. However, encouraging Finally, as drivers of relatively sedate vehicles (““ my other new Ðndings were presented. car is a Volvo ÏÏ), we wish to record with awe a disk wind Coronal heating by dissipativeAlfven waves in multiple that goes from 0 to 3000 km s~1 in 6È8 minutes. It belongs resonance layers that drift throughout coronal loops is pre- to the cataclysmic variable BZ Cam (Ringwald & Naylor dicted by recent theories (Ofman et al. 1998). Obser- 1998). vationally, quasi-periodic wave trains have been detected in solar plumes; they carry an energy Ñux that is almost enough to heat coronal holes (DeForest & Gurman 1998). 1.2. LÏEnvoi Falconer et al. (1998) localize the sources of coronal heating concentrations in the magnetic network. Krucker & Benz Some things also came to an end. After a long (in both (1998) inquire into the faintest extreme-ultraviolet (EUV) time and wavelength) and, we hope, happy life, the Infrared brightness Ñuctuations in the quiet Sun and Ðnd that a Space Observatory (ISO) was turned o† (Bonnet 1998). surprisingly high percentage, at least 85% of all pixels in the ROSAT made the mistake of an inexperienced eclipse EUV images they investigated, vary signiÐcantly all the observer and looked too closely at the Sun (with the time. Such small EUV brightenings have been interpreted in declared termination of the guest observer program coming terms of ““ miniÑares ÏÏ or ““ network Ñares ÏÏ that heat the just after our year ended). SOHO, in contrast, sort of forgot plasma of tiny, low-lying loops to EUV([1 MK) tem- to look at the Sun until its batteries had run down badly, peratures but do not show up in(Z2 MK) soft X-rays but seems to have made a remarkable recovery. (Berghmans et al. 1998). The energy for these tiny EUV It was not quite so devastating a year as 1997 for the brightenings is believed to come from magnetic reconnec- American astronomical community, but deaths reported to tion events of low-lying quiet-Sun loops, which reconnect the AAS and/or ASP during the reference year included preferentially near the chromospheric network and require Richard Herr, Barry Rappaport, Victor Szebehely, Andrew a magnetic Ñux replacement within 48 hr on average Michalitsianos, Walter McAfee, Charles Worley, Anthony (Schrijver et al. 1998). The Ðnest structures of the magnetic Jenzano, Georgeanne Caughlan, David Schramm, John Ðeld detected with SOHO/MDI down to a resolution of 1A Baer, Frank Bradshaw Wood, Gabriel Kojoian, Emil are now described as ““ magnetic carpet ÏÏ textures. Herzog, Robert L. Wildey, John Wang, Charles Franklin Exciting progress was also reported from helio- Prosser, Jr., Karl Kamper, Alexander Rodgers, Robert seismology. Global p-mode oscillations of the solar interior Light, James B. Willett, Guenter Brueckner, William Titte- are now so accurately measured that even slight dis- man, and Olin J. Eggen. Many of them were in the midst of turbances from active regions can be registered and dubbed active astronomical careers, and their papers are cited else- ““ seismic holography of solar activity ÏÏ (Braun et al. 1998; where in these pages. Chen et al. 1998b). Even more dramatic is the Ðrst detection of a ““ Sun quake ÏÏ caused by a solar Ñare (Kosovichev & Zharkova 1998). It was compared with the ““ energy that would be released if the earthÏs continents were covered 2.
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