118 research outputs found
Cerere Ferdinandea. La scoperta del primo asteroide (ora pianeta nano) nelle collezioni storiche dell'Osservatorio di Palermo
No full textCatalogo della mostra "Cerere Ferdinandea", con saggio iniziale sulla scoperta di Cerere e schede descrittive dei materiali in mostra.
Indice: Prefazione di Giusi Micela; Cerere Ferdinandea; Giuseppe Piazzi e l’Osservatorio di Palermo; Il contesto della scoperta; La “nuova stella” osservata da Piazzi; La “caccia” internazionale al nuovo astro; La scelta del nome; Il ritrovamento di Cerere; Pianeta o asteroide?; Conclusioni; Catalogo della mostra: Quadri e ritratti; Strumenti; Libri e carte; Bibliografi
Ceres Ferdinandea. The discovery of the first asteroid (now dwarf planet) in the historical collections of the Palermo Observatory
No full textCatalogue of the exhibition "Ceres Ferdinandea", with an introductory essay on the discovery of Ceres and description cards of the items on display. Contents:
Preface by Giusi Micela and Maria Cristina De Sanctis ;
Ceres Ferdinandea ;
Giuseppe Piazzi and the Palermo Observatory ;
The background of the discovery ;
The “new star” observed by Piazzi ;
The international “hunt” of the new star ;
The choice of name ;
The new finding of Ceres ;
Planet or asteroid? ;
Conclusions ;
Exhibition catalogue ;
Paintings and portraits ;
Instruments ;
Books and papers ;
Bibliograph
Modelling the hidden magnetic field of low-mass stars
No full textPL acknowledges support from a Science and Technology Facilities Council studentship. JM, AAV and RF acknowledge support from fellowships of the Alexander von Humboldt foundation, the Royal Astronomical Society and Science and Technology Facilities Council, respectively.Zeeman-Doppler imaging is a spectropolarimetric technique that is used to map the large-scale surface magnetic fields of stars. These maps in turn are used to study the structure of the stars' coronae and winds. This method, however, misses any small-scale magnetic flux whose polarization signatures cancel out. Measurements of Zeeman broadening show that a large percentage of the surface magnetic flux may be neglected in this way. In this paper we assess the impact of this 'missing flux' on the predicted coronal structure and the possible rates of spin-down due to the stellar wind. To do this we create a model for the small-scale field and add this to the Zeeman-Doppler maps of the magnetic fields of a sample of 12 M dwarfs. We extrapolate this combined field and determine the structure of a hydrostatic, isothermal corona. The addition of small-scale surface field produces a carpet of low-lying magnetic loops that covers most of the surface, including the stellar equivalent of solar 'coronal holes' where the large-scale field is opened up by the stellar wind and hence would be X-ray dark. We show that the trend of the X-ray emission measure with rotation rate (the so-called 'activity-rotation relation') is unaffected by the addition of small-scale field, when scaled with respect to the large-scale field of each star. The addition of small-scale field increases the surface flux; however, the large-scale open flux that governs the loss of mass and angular momentum in the wind remains unaffected. We conclude that spin-down times and mass-loss rates calculated from surface magnetograms are unlikely to be significantly influenced by the neglect of small-scale field.Peer reviewe
The mass of Kepler-93b and the composition of terrestrial planets
No full textKepler-93b is a 1.478 ± 0.019 R ⊕ planet with a 4.7 day period around a bright (V = 10.2), astroseismically characterized host star with a mass of 0.911 ± 0.033 M ☉ and a radius of 0.919 ± 0.011 R ☉. Based on 86 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 32 archival Keck/HIRES observations, we present a precise mass estimate of 4.02 ± 0.68 M ⊕. The corresponding high density of 6.88 ± 1.18 g cm–3 is consistent with a rocky composition of primarily iron and magnesium silicate. We compare Kepler-93b to other dense planets with well-constrained parameters and find that between 1 and 6 M ⊕, all dense planets including the Earth and Venus are well-described by the same fixed ratio of iron to magnesium silicate. There are as of yet no examples of such planets with masses >6 M ⊕. All known planets in this mass regime have lower densities requiring significant fractions of volatiles or H/He gas. We also constrain the mass and period of the outer companion in the Kepler-93 system from the long-term radial velocity trend and archival adaptive optics images. As the sample of dense planets with well-constrained masses and radii continues to grow, we will be able to test whether the fixed compositional model found for the seven dense planets considered in this paper extends to the full population of 1-6 M ⊕ planets.Peer reviewe
Radio sources in the Chandra Galactic Bulge Survey
No full textWe discuss radio sources in the Chandra Galactic Bulge Survey region. By cross-matching the X-ray sources in this field with the NRAO VLA Sky Survey archival data, we find 12 candidate matches. We present a classification scheme for radio/X-ray matches in surveys taken in or near the Galactic plane, taking into account other multiwavelength data. We show that none of the matches found here is likely to be due to coronal activity from normal stars because the radio to X-ray flux ratios are systematically too high. We show that one of the source could be a radio pulsar, and that one could be a planetary nebula, but that the bulk of the sources are likely to be background active galactic nuclei (AGN), with many confirmed through a variety of approaches. Several of the AGN are bright enough in the near-infrared (and presumably in the optical) to use as probes of the interstellar medium in the inner Galaxy
Italian Report to the 43rd COSPAR Scientific Assembly
No full textLorenzo Amati,Giovanni Ambrosi, Angela Bazzano, Tomaso Belloni, Valentina Braito, John Robert Brucato, Patrizia Caraveo, Elisabetta Cavazzuti, Ignazio Ciufolini, Alessandro Coletta, Marino Crisconio, Paolo de Bernardis, Maria Cristina De Sanctis, Roberto Della Ceca, Vincenzo Della Corte, Piero Diego, Elisabetta Dotto, Silvano Fineschi, Mario G. Lattanzi, Monica Lazzarin, Ettore Lopinto, Maria Federica Marcucci, Silvia Masi, Gabriele Mascetti, Giusi Micela, Alessandro Mura, Lorenzo Natalucci, Roberto Orosei, Isabella Pagano, Giuseppe Piccioni, Piergiorgio Picozza, Giampaolo Piotto, Luigi Piro, Roberto Ragazzoni, Sofia Randich, Fabio Reale, Paolo Soffitta, Daniele Spadaro, Luigi Spinoglio, Gianpiero Tagliaferri, Marco Tavani, Elisabetta Tommasi, Monica Tosi, Ginevra Trinchieri, Diego Turrini, Valerio Vagelli, Giovanni Valentini, Luca Valenziano, Barbara Vetere, Stefano Vitale, Angela VolpeThis document summarizes the last two years of space science activity in Italy and is the Italian Report to the 43rd COSPAR General Assembly. It is edited by INAF, the formal Italian national body that by the law supports the COSPAR activities, with the collaboration of ASI and the other
stakeholders playing a major role in the Italian scientific space programs (INFN, CNR, INGV, etc.).
In view of the appreciation received for the former editions, this year the Report has been formulated in a similar condensed form to give the relevant information in a snapshot, though providing a fully updated overview of the Italian research programs carried out from space. We apologize for any omission or misunderstanding. The Report is organized with the description of the scientific goals, technical requirements and actual realization of the space missions, enumerated following the COSPAR Scientific Commissions scheme:
https://cosparhq.cnes.fr/scientific-structure/scientific-commissions/
Italy is today deeply involved in space science with a multifaceted activity. A remarkable sequence of scientific results over the past years and a considerable number of projects driven by
Italian scientists, engineers and technologists position Italy as a frontrunner in space astrophysicsand space physics
The Kepler-454 system : A small, not-rocky inner planet, a Jovian world, and a distant companion
No full textKepler-454 (KOI-273) is a relatively bright (V = 11.69 mag), Sun-like starthat hosts a transiting planet candidate in a 10.6 d orbit. From spectroscopy, we estimate the stellar temperature to be 5687 +/- 50 K, its metallicity to be [m/H] = 0.32 +/- 0.08, and the projected rotational velocity to be v sin i 10 years and mass >12.1M_J . The twelve exoplanets with radii <2.7 R_Earth and precise mass measurements appear to fall into two populations, with those <1.6 R_Earth following an Earth-like composition curve and larger planets requiring a significant fraction of volatiles. With a density of 2.76 +/- 0.73 g cm-3, Kepler-454b lies near the mass transition between these two populations and requires the presence of volatiles and/or H/He gas.Peer reviewe
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