Paris Observatory

About: Paris Observatory is a facility organization based out in Paris, Île-de-France, France. It is known for research contribution in the topics: Galaxy & Stars. The organization has 786 authors who have published 966 publications receiving 14742 citations. The organization is also known as: Observatoire de Paris.

A strong magnetic field around the supermassive black hole at the centre of the Galaxy

Abstract: Earth's nearest candidate supermassive black hole lies at the centre of the Milky Way Its electromagnetic emission is thought to be powered by radiatively inefficient accretion of gas from its environment, which is a standard mode of energy supply for most galactic nuclei X-ray measurements have already resolved a tenuous hot gas component from which the black hole can be fed The magnetization of the gas, however, which is a crucial parameter determining the structure of the accretion flow, remains unknown Strong magnetic fields can influence the dynamics of accretion, remove angular momentum from the infalling gas, expel matter through relativistic jets and lead to synchrotron emission such as that previously observed Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre and show that the pulsar's unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission-from radio to X-ray wavelengths-from the black hole

OSIRIS – The Scientific Camera System Onboard Rosetta

Abstract: The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm px−1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma. OSIRIS comprises a high resolution Narrow Angle Camera (NAC) unit and a Wide Angle Camera (WAC) unit accompanied by three electronics boxes. The NAC is designed to obtain high resolution images of the surface of comet 67P/Churyumov-Gerasimenko through 12 discrete filters over the wavelength range 250–1000 nm at an angular resolution of 18.6 μrad px−1. The WAC is optimised to provide images of the near-nucleus environment in 14 discrete filters at an angular resolution of 101 μrad px−1. The two units use identical shutter, filter wheel, front door, and detector systems. They are operated by a common Data Processing Unit. The OSIRIS instrument has a total mass of 35 kg and is provided by institutes from six European countries.

A kinetic model of the solar wind with Kappa distribution functions in the corona.

Abstract: A kinetic model of the solar wind based on Kappa velocity distribution functions for the electrons and protons es- capingoutofthecoronaispresented.Thehighvelocityparticles formingthetailofthesedistributionfunctionshaveanenhanced phase space density compared to a Maxwellian. The existence of such velocity distribution functions have been introduced in the pioneering work of Scudder (1992a,b) to explain the high temperature of the coronal plasma. The first results obtained with this new kinetic model of the solar wind are very encour- aging, indeed they fit better many major features observed in the solar wind than earlier models: e.g. the large bulk velocities observed in high speed streams emitted out of coronal regions where the plasma temperature is smaller, and the low speed so- lar wind originating in the hotter equatorial regions of the solar corona. This new kinetic model is also able to predict the high speed solar wind streams without unreasonably large coronal temperatures and without additional heating of the outer region ofthecorona,asitisneededinhydrodynamicmodelstoachieve the same solar wind speed.

Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006

Abstract: Every three years the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements revises tables giving the directions of the poles of rotation and the prime meridians of the planets, satellites, minor planets, and comets. This report introduces improved values for the pole and rotation rate of Pluto, Charon, and Phoebe, the pole of Jupiter, the sizes and shapes of Saturn satellites and Charon, and the poles, rotation rates, and sizes of some minor planets and comets. A high precision realization for the pole and rotation rate of the Moon is provided. The expression for the Sun’s rotation has been changed to be consistent with the planets and to account for light travel time