Virgin Galactic

Résumé

Virgin Galactic est une société aérospatiale lancée en 2004 par l’entrepreneur britannique, fondateur du groupe Virgin, Sir Richard Branson. La firme propose de fournir des vols suborbitaux à des fins touristiques et de recherches. Toujours en phase de test, l’offre touristique est annoncée opérationnelle à l´horizon 2022. Le prix du ticket est compris entre

US et

US. Plus de 600 personnes se sont inscrites sur liste d’attente avec paiement d’une avance. But Virgin Galactic planifie d'envoyer des passagers dans l'espace à une altitude dépassant , pour un prix compris entre et . Le vol comprend plusieurs phases, culminant par quelques minutes dans l'espace avant de redescendre sur Terre. L'objectif annoncé est celui de lancer l'industrie du tourisme spatial. Elle prévoit de lancer à terme 400 vols par an depuis sa base aérospatiale le Spaceport America, située au Nouveau-Mexique . Dans l'histoire de la conquête spatiale, au , seulement 514 astronautes différents ont dé

Source officielle

https://fr.wikipedia.org/wiki/Virgin_Galactic

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This course is a "concepts" course. It introduces a variety of concepts in use in the design of a space mission, manned or unmanned, and in space operations. it is at least partly based on the practical space experience of the lecturer.

The objective of the course is to present with different viewpoints, the lessons learned which lead to the decisions in the space exploration and their consequences today and for the decades to come. A semester continuous evaluation is done through a project (see below).

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The Sdss-Iv Extended Baryon Oscillation Spectroscopic Survey: Quasar Target Selection

Johan Comparat, Jean-Paul Richard Kneib, Pierre Laurent, David Schlegel

As part of the Sloan Digital Sky Survey (SDSS) IV the extended Baryon Oscillation Spectroscopic Survey (eBOSS) will improve measurements of the cosmological distance scale by applying the Baryon Acoustic Oscillation (BAO) method to quasar samples. eBOSS will adopt two approaches to target quasars over 7500 deg(2). First, a "CORE" quasar sample will combine the optical selection in ugriz using a likelihood-based routine called XDQSOz, with a mid-IR-optical color cut. eBOSS CORE selection (to g < 22 or r < 22) should return similar to 70 deg(-2) quasars at redshifts 0.9 < z < 2.2 and similar to 7 deg(-2)z > 2.1 quasars. Second, a selection based on variability in multi-epoch imaging from the Palomar Transient Factory should recover an additional similar to 3-4 deg(-2)z > 2.1 quasars to g < 22.5 A linear model of how imaging systematics affect target density recovers the angular distribution of eBOSS CORE quasars over 96.7% (76.7%) of the SDSS north (south) Galactic Cap area. The eBOSS CORE quasar sample should thus be sufficiently dense and homogeneous over 0.9. 500,000 new quasars and >500,000 uniformly selected spectroscopically confirmed 0.9 < z < 2.2 quasars. At the conclusion of eBOSS, the SDSS will have provided unique spectra for more than 800,000 quasars.

Iop Publishing Ltd2015

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Chromosome maps of young LMC clusters: an additional case of coeval multiple populations

Carmela Lardo

Recent studies have revealed that the multiple populations (MPs) phenomenon does not occur only in ancient and massive Galactic globular clusters (GCs), but it is also observed in external galaxies, where GCs sample a wide age range with respect to the Milky Way. However, for a long time, it was unclear whether we were looking at the same phenomenon in different environments or not. The first evidence that the MPs phenomenon is the same regardless of cluster age and host galaxy came out recently, when an intermediate-age cluster from the Small Magellanic Cloud, Lindsay 1, and a Galactic GC have been directly compared. By complementing those data with new images from the Hubble Space Telescope (HST), we extend the comparison to two clusters of different ages: NGC 2121 (similar to 2.5 Gyr) and NGC 1783 (similar to 1.5 Gyr), from the Large Magellanic Cloud. We find a clear correlation between the RGB (red giant branch) width in the pseudo-colour C-F275W,C- (F343N,) (F438W) and the age of the cluster itself, with the older cluster having larger sigma(C-F275W,C- F343N,C- F438W)(RGB) and vice versa. Unfortunately, the sigma values cannot be directly linked to the N-abundance variations within the clusters before properly taking account the effect of the first dredge-up. Such HST data also allow us to explore whether multiple star formation episodes occurred within NGC 2121. The two populations are indistinguishable, with an age difference of only 6 +/- 12 Myr and an initial helium spread of 0.02 or lower. This confirms our previous results, putting serious constraints on any model proposed to explain the origin of the chemical anomalies in GCs.

OXFORD UNIV PRESS2020

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