Archives de la catégorie : Nouvelles et annonces

Grâce au puissant spectromètre imageur SITELLE installé au télescope Canada-France-Hawaï (CFHT), des astronomes ont cartographié la célèbre nébuleuse du Crabe avec une finesse sans précédent, leur permettant de produire une toute première représentation tridimensionnelle réaliste des débris de cette explosion de supernova. Cette analyse révèle une structure filamentaire complexe dont la morphologie globale fait penser à un cœur.

La nébuleuse du Crabe (Messier 1) est l’un des objets astronomiques les plus étudiés, tant par les astronomes amateurs que par les chercheurs professionnels. Depuis qu’un lien a clairement été établi entre cette nébuleuse et « l’étoile invitée » découverte par les astronomes chinois le 4 juillet 1054, des milliers d’articles ont été écrits à son sujet, couvrant divers domaines de la physique et de l’astronomie. Toutefois, de nombreuses questions demeurent quant à la nature de l’étoile qui a explosé et aux mécanismes qui ont façonné son explosion.

Le chercheur du Centre de recherche en astrophysique du Québec (CRAQ), Thomas Martin, qui a dirigé cette étude à l’Université Laval, espère répondre à ces questions en utilisant cette nouvelle reconstruction tridimensionnelle. « Les astronomes pourront dorénavant se promener autour, et même à l’intérieur de la nébuleuse du Crabe afin d’étudier les filaments un par un. », décrit Martin, « À la manière d’une escouade d’enquêteurs étudiant la distribution et la composition chimique des débris laissés par l’explosion d’une bombe ». Le professeur à l’Université Purdue (Indiana) et co-auteur de cette publication, Dan Milisavljevic, un expert des supernovæ, conclut que « la morphologie fascinante de filaments gazeux révélée par ces nouvelles données semble contredire l’explication la plus communément admise sur la façon dont l’explosion s’est produite ».

Full release for links to video and paper: https://www.cfht.hawaii.edu/en/news/HeartofTheCrab/

We received with great sadness the news that Paul Felenbok passed away  on Tuesday 22 December 2020, at the age of 84.

Paul was born in Warsaw shortly before WWII and lived as a child in  the ghetto, from which he fled through the sewers with his family in  1943, just before the tragic uprising. He was only 7 at the time, and  lost both his parents during this escape.

He arrived in France in 1946, at the age of 10, and was raised in an  orphanage. He obtained his baccalaureate, then a scholarship to join  the Sorbonne. After a degree in physics and a certificate in fluid  mechanics, he joined Paris Observatory in Meudon. He then spent a year  at the University of Berkeley, after which, on his return to Meudon in  1963, he defended his thesis in theoretical and experimental molecular  physics applied to astronomy. He was then appointed as an astronomer  at Paris Observatory, where he remained until his retirement in 2004.

Paul Felenbok, an expert in spectroscopy, was above all a brilliant  and immensely inventive instrumentalist. Among his many achievements,  we owe him several major advances in spectroscopy and astronomy:

– The visionary development of vacuum UV spectroscopy in the  laboratory in the 1970s, providing data that would become  indispensable for future space missions.

– A new and totally innovative version of Lallemand’s electronographic  camera, the so-called « valve camera », allowing the replacement of  nuclear plates without breaking the vacuum in the cell compartment.  This was an essential development that should have secured a long life  for the electronographic camera, had it not been quickly overriden by  CCD detectors.

– The introduction in France of fibre optics spectroscopy, with in  particular the development in the 1980s of the prototypical mobile  ISIS spectrograph, and in the 90s of the MEFOS fibre positioner and  FUEGOS project at ESO.

He also largely inspired and supported the development of the MUSICOS  multi-site spectroscopy network and participated in the development of  the CFHT, in particular with the MOS-SIS spectrograph.

Always keen to pass on his knowledge and experience, as witnessed by  the many students he has trained and for whom he has worked  tirelessly, he also attached great importance to the contact with the  public, as he demonstrated on many occasions, e.g. by running the  public relation unit (UNICOM) of Paris Observatory at the beginning of  the 2000s.

The development of astronomy in the French Alps village of St-Véran is  yet another of his great achievements. In the late 1960s, he spotted  the remarkable astronomical qualities of the Château-Renard site above  St-Véran, considered for a time to host the planned 3.60m telescope.  He managed to build there a small observatory housing a solar  coronagraph, which was operated for half a dozen years. Paul then  obtained that this observatory be made available to amateur  astronomers who have now been using it for nearly 30 years, and then  to have it completely renovated. He then developed « la Maison du  Soleil (House of the Sun) », in the village of St-Véran, a public  centre which houses, among other experiments, the very high-resolution  spectrograph Sharmor on loan from Paris Observatory.

With Paul, the astronomical community is losing a great astronomer. He  was an extraordinary man, with a sparkling intelligence, swarming with  ideas. He was also a leader, a go-getter, solid, pragmatic, quick and  direct. His passion and enthusiasm for astronomy and instrumentation  were communicative. He was at the same time a profoundly good man,  humane, generous, always ready to listen, always dedicated to others.

Paul had managed to overcome his tragic childhood, which he almost  never spoke of, to build himself an extraordinarily human and  endearing personality. Only a few years ago, convinced by his daughter  Véronique, had he finally agreed to entrust his memories to a writer  and director, David Lescot. This resulted in a deeply moving play,  « Ceux qui restent (Those who remain) ».

All our saddened thoughts go out to his wife Betty and their two  daughters Véronique and Isabelle and their families.