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| The changing phases of extrasolar planet CoRoT-1b |
| Hot Jupiters are a class of extrasolar planet that orbit their parent stars at very short distances. They are expected to be tidally locked, which can lead to a large temperature difference between their daysides and nightsides. Infrared observations of eclipsing systems have yielded dayside temperatures for a number of transiting planets. The day-night contrast of the transiting extrasolar planet HD 189733b was 'mapped' using infrared observations. It is expected that the contrast between the daysides and nightsides of hot Jupiters is much higher at visual wavelengths, shorter than that of the peak emission, and could be further enhanced by reflected stellar light. Here we report the analysis of optical photometric data obtained over 36 planetary orbits of the transiting hot Jupiter CoRoT-1b. The data are consistent with the nightside hemisphere of the planet being entirely black, with the dayside flux dominating the optical phase curve. This means that at optical wavelengths the planet's phase variation is just as we see it for the interior planets in the Solar System. The data allow for only a small fraction of reflected light, corresponding to a geometric albedo of <0.20. |
| Publication date: 28 May 2009 |
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| The detection of Broad Iron K and L line emission in the Narrow-Line Seyfert 1 Galaxy 1H 0707-495 using XMM-Newton |
| Since the discovery of the first broad iron-K line in 1995 from the Seyfert Galaxy MCG 6-30-15, broad iron-K lines have been found in several other Seyfert galaxies, from accreting stellar mass black holes and even from accreting neutron stars.
The iron-K line is prominent in the reflection spectrum created by the hard X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron-L line emission should be detectable when the iron abundance is high.
Here we report the first discovery of both iron-K and L emission, using XMM-Newton observations of the Narrow-Line Seyfert 1 Galaxy 1H 0707-495. The bright Fe-L emission has enabled us,
for the first time, to detect a reverberation lag of 30 s between the direct X-ray continuum and its reflection from matter falling into the hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole.
The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light-minute, from the event horizon of a rapidly-spinning, massive black hole. |
| Publication date: 28 May 2009 |
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| Solar System Observations with MIRI, The Mid InfraRed Instrument on the James Webb Space Telescope |
| MIRI is the Mid InfraRed Instrument for the James Webb Space Telescope (JWST) and will provide imaging, coronography and integral field spectroscopy in the range between 4.9 and 28.6 micron. We summarise solar system observations which may be possible with this instrument, drawing on examples of observations made with previous space missions such as IRAS, ISO and Spitzer. Presented at the conference "Future Ground Based Solar System Research, Isola d'Elba, 8-12 September 2008" |
| Publication date: 26 May 2009 |
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| Non-radial oscillation modes with long lifetimes in giant stars |
| Towards the end of their lives, stars like the Sun greatly expand to become red giant stars. Such evolved stars could provide stringent tests of stellar theory, as many uncertainties of the internal stellar structure accumulate with age. Important examples are convective overshooting and rotational mixing during the central hydrogen-burning phase, which determine the mass of the helium core, but which are not well understood. In principle, analysis of radial and non-radial stellar oscillations can be used to constrain the mass of the helium core. Although all giants are expected to oscillate, it has hitherto been unclear whether non-radial modes are observable at all in red giants, or whether the oscillation modes have a short or a long mode lifetime, which determines the observational precision of the frequencies. Here we report the presence of radial and non-radial oscillations in more than 300 giant stars. For at least some of the giants, the mode lifetimes are of the order of a month. We observe giant stars with equally spaced frequency peaks in the Fourier spectrum of the time series, as well as giants for which the spectrum seems to be more complex. No satisfactory theoretical explanation currently exists for our observations. |
| Publication date: 21 May 2009 |
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| Climate evolution of Venus |
| The processes in the atmosphere, interior, surface, and near-space environment that together maintain the climate on Venus are examined from the specific point of view of the advances that are possible with new data from Venus Express and improved evolutionary climate models. Particular difficulties, opportunities, and prospects for the next generation of missions to Venus are also discussed. |
| Publication date: 20 May 2009 |
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| Science Requirements Document for Marco Polo |
| This document describes the detailed scientific requirements for the Marco Polo mission. These
requirements are derived from discussions by the Science Study Team (SST) of the Marco Polo
study and is based on the scientific objectives as described in the Marco Polo Proposal to
ESA's Cosmic Vision programme (RD 01).
[This is an abbreviated version of the original document abstract.]
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| Publication date: 20 May 2009 |
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| Cluster and Image: new ways to study the Earth's plasmasphere |
| Ground-based instruments and a number of space missions have contributed to our knowledge of the plasmasphere since its discovery half a century ago, but it is fair to say that many questions have remained unanswered. Recently, NASA's Image and ESA's Cluster probes have introduced new observational concepts, thereby providing a non-local view of the plasmasphere. Image carried an extreme ultraviolet imager producing global pictures of the plasmasphere. Its instrumentation also included a radio sounder for remotely sensing the spacecraft environment. The Cluster mission provides observations at four nearby points as the four-spacecraft configuration crosses the outer plasmasphere on every perigee pass, thereby giving an idea of field and plasma gradients and of electric current density. This paper starts with a historical overview of classical single-spacecraft data interpretation, discusses the non-local nature of the Image and Cluster measurements, and emphasizes the importance of the new data interpretation tools that have been developed to extract non-local information from these observations. The paper reviews these innovative techniques and highlights some of them to give an idea of the flavor of these methods. In doing so, it is shown how the non-local perspective opens new avenues for plasmaspheric research. |
| Publication date: 15 May 2009 |
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| Size and Shape of Saturn's Moon Titan |
| Cassini observations show that Saturn's moon Titan is slightly oblate. A fourth-order spherical harmonic expansion yields north polar, south polar, and mean equatorial radii of 2574.32 +- 0.05 kilometers (km), 2574.36 +- 0.03 km, and 2574.91 +- 0.11 km, respectively; its mean radius is 2574.73 +- 0.09 km. Titan's shape approximates a hydrostatic, synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to Saturn than Titan presently does. Titan's lack of high relief implies that most-but not all-of the surface features observed with the Cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation. Titan's depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes. |
| Publication date: 15 May 2009 |
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| LISA Pathfinder: the experiment and the route to LISA |
| LISA Pathfinder (LPF) is a science and technology demonstrator planned by the European Space Agency in view of the LISA mission. As a scientific payload, the LISA Technology Package on board LPF will be the most precise geodesics explorer flown as of today, both in terms of displacement and acceleration sensitivity. The challenges embodied by LPF make it a unique mission, paving the way towards the space-borne detection of gravitational waves with LISA. This paper summarizes the basics of LPF, and the progress made in preparing its effective implementation in flight. We hereby give an overview of the experiment philosophy and assumptions to carry on the measurement. We report on the mission plan and hardware design advances and on the progress on detailing measurements and operations. Some light will be shed on the related data processing algorithms. In particular, we show how to single out the acceleration noise from the spacecraft motion perturbations, how to account for dynamical deformation parameters distorting the measurement reference and how to decouple the actuation noise via parabolic free flight. |
| Publication date: 07 May 2009 |
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| Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades in Magnetized Weakly Collisional Plasmas |
| This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulent motions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. -- Remainder of abstract is truncated -- |
| Publication date: 06 May 2009 |
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| A global study of hot flow anomalies using Cluster multi-spacecraft measurements |
| Hot flow anomalies (HFAs) are studied using observations of the magnetometer and the plasma instrument aboard the four Cluster spacecraft. We study several specific features of tangential discontinuities on the basis of Cluster measurements from the time periods of February-April 2003, December 2005-April 2006 and January-April 2007, when the separation distance of spacecraft was large. The previously discovered condition (Facskó et al., 2008) for forming HFAs is confirmed, i.e. that the solar wind speed and fast magnetosonic Mach number values are higher than average. Furthermore, this constraint is independent of the Schwartz et al. (2000)'s condition for HFA formation. The existence of this new condition is confirmed by simultaneous ACE magnetic field and solar wind plasma observations at the L1 point, at 1.4 million km distance from the Earth. The temperature, particle density and pressure parameters observed at the time of HFA formation are also studied and compared to average values of the solar wind plasma. The size of the region affected by the HFA was estimated by using two different methods. We found that the size is mainly influenced by the magnetic shear and the angle between the discontinuity normal and the Sun-Earth direction. The size grows with the shear and (up to a certain point) with the angle as well. After that point it starts decreasing. The results are compared with the outcome of recent hybrid simulations. |
| Publication date: 05 May 2009 |
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| Estimating the magnetic energy inside traveling compression regions |
| We investigate a series of six TCRs (traveling compression regions), appearing in the course of a small substorm on 19 September 2001. Except for two of these TCRs, all Cluster spacecraft were located in the lobe and detected the typical signatures of TCRs, i.e., compressions in |B| and bipolar Bz variations. We use these perturbations in Bz for calculations on the magnetic energy inside the TCR and compare the amount of magnetic field energy with the kinetic energy inside the underlying plasma bulge. According to results obtained from theory, the amount of magnetic energy inside TCRs is about two times higher than the kinetic plasma energy inside the accompanied plasma bulge. We verify this theoretical result by first investigations of the magnetic field energy inside TCRs. The calculations lead to a magnetic energy in the order of 1010 Joule per RE for each of the TCRs. |
| Publication date: 04 May 2009 |
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| ...While Planck dusts the skies for the fingerprints of inflation |
| The big bang: The universe bursts into existence, an infinitely dense and hot soup of subatomic particles and radiation. In a fraction of a nanosecond, it doubles its size again and again, in a faster-than-light growth spurt known as inflation. That bizarre, hypothetical stretching evens out the universe but also sets off ripples in space and time called gravitational waves, which 13.7 billion years later should have left traces in the afterglow of the big bang, the cosmic microwave background (CMB). The 400 researchers working with the European Space Agency's (ESA's) Planck satellite hope to spot those traces - subtle patterns in the polarization of the microwaves called "B modes" -before anyone else does. |
| Publication date: 01 May 2009 |
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| ESA Bulletin 138: Looking back to the dawn of time - The science behind ESA's Planck observatory |
| Only a few decades ago, the origin of the Universe
was a scientific topic lacking reliable data. However,
scientists now know where to look for answers, and
they are steadily gaining the means to do so. ESA' s
ambitious Planck mission is the next step in solving
many of cosmology's biggest questions. |
| Publication date: 01 May 2009 |
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| Herschel will open a new vista on infant stars and galaxies... |
| With the biggest mirror yet flown in space, Europe's new Herschel Space Observatory will peer through a new wavelength window at the cool regions of the universe. It will be launched together with Planck, a mission to map the cosmic microwave background radiation in unprecedented detail. In addition to studying the formation of galaxies and stars, astronomers hope to use Herschel to study comets, asteroids, and planetary atmospheres in our solar system and how debris disks around stars form into planets. |
| Publication date: 01 May 2009 |
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