Tag Archives: news

Welcome to IAG, Henrique

Let’s give a warm welcome to Henrique Gubolin, my new graduate student. Let’s hear from Henrique himself:

Hi! I’m Henrique Gubolin Torres, and I’m starting my masters degree under the supervision of Rodrigo Nemmen; I just graduated in physics at IF-USP and I already worked with galaxy clusters and simulations before.

In this new project, I’ll be doing black hole simulations with the help of some well known magnetohydrodynamic codes, of course. We will simulate gas around a non-spinning black hole (Schwarzschild) using a semi-Newtonian approach and Magnetohydrodynamic (MHD). I’m looking forward to this project and to my new graduate student life, so… here we go!

Nearby radio galaxies host incredibly “green” black holes: Paper accepted to MNRAS

I recently got a paper accepted to MNRAS with my collaborator Sasha Tchekhovskoy at UC Berkeley. Here are a couple of quick points about the paper:

  • Basic idea: take observed black hole systems and treat them as engines. Measure what flows in (fuel) and what comes out (exhaust). Dividing the energy of what comes out by the amount of energy that flows in, we get an energy efficiency.
  • We measured this efficiency for 27 nearby supermassive black holes which produce jets (radio galaxies). Our analysis is based on recent Chandra observations and current ideas on accretion disks.
  • The results imply that black hole engines are producing more energy than flows in: efficiencies > 100%. This is completely opposite to the general idea that everything disappears inside black holes. Black holes are actually quite “green” (energy-efficient).
  • Does this violate energy conservation? No. The extra energy that comes out would be extracted from the spin energy of the black hole.
  • What constraints do these results put on black holes physics? In order to explain the data, black holes need to: (i) be rapidly rotating, (ii) be surrounded by strong magnetic fields (see footnote below). Such “dynamically-important” magnetic fields act as catalysts of the energy extraction.

The paper got some coverage in the brazilian press here and here.

ps. The technical name for “strong magnetic fields” is “magnetically arrested disk” (abbreviated as MAD). This is a fashionable idea among theorists that are simulating black hole accretion flows. My collaborator (Tchekhovskoy) is one of the theorists doing such fantastic GRMHD simulations.

Buracos negros na Folha de SP

Neste Domingo foi publicado no jornal Folha de São Paulo uma reportagem sobre o meu trabalho de divulgação científica sobre buracos negros: veja seis maneiras de morrer com um buraco negro.

A reportagem é muito divertida e gostei especialmente das ilustrações: tragédia no espaço.

Para os curiosos que lerem esta postagem e a reportagem da Folha, seguem esclarecimentos sobre alguns ponto do texto:

  • As maneiras 1 e 2 de morrer no artigo são uma consequência do mesmo fenômeno físico, chamado de forças de maré e causado pelo comportamento da atração gravitacional a objetos astronômicos. Este tipo de fenômeno causa as marés na Terra.
  • Sobre a maneira 3: não se preocupem, o nosso Sol jamais se tornará um buraco negro porque ele é muito “magrinho”.
  • O telescópio de raios gama lançado pela NASA em 2008 chama-se Fermi, e não Glast. Glast era o nome da missão antes do lançamento. Eu estou envolvido com esta missão desde 2011.
  • Na reportagem: “analisando os diferentes espectros de radiação emitidos pelos buracos negros […]”. Na verdade, os buracos negros não emitem radiação em si, o que brilha é o turbilhão de gás caindo neles ou o gás que é expulso antes de cair.
  • A reportagem menciona que os buracos negros “ejetam mais energia do que absorvem — estão na verdade consumindo sua massa”. Nem todos os buracos negros se comportam desta maneira, mas uma pequena fração deles parece ter este comportamento bizarro, conforme eu e um colaborador temos pesquisado. Os artigos científicos relatando esta descoberta estão aqui e aqui.

Divirtam-se com estas tragédias espaciais!

Academia Brasileira de Ciências

I learned today that I was appointed as one of the new junior members of the Academia Brasileira de Ciências (ABC) [the Brazilian Academy of Sciences] for the period of 2015-2019! I am thrilled and feeling very honored with this opportunity!

Junior members of the ABC are scientists younger than 40 years old which are selected among the many thousands of Brazilian scientists due to their academic promise and outstanding productivity. I was appointed as one of the five junior members for the region of São Paulo.

The junior membership of ABC (membro afiliado da ABC) was created on 2007. As far as I can tell, I am the first astrophysicist ever appointed to this position.


See also: Docentes da USP são eleitos membros titulares da Academia Brasileira de Ciências.

No Programa Fantástico, Rede Globo

Neste Domingo, dia 16 de Novembro, fui entrevistado no Programa Fantástico da Rede Globo, falando novamente sobre o pouso do Philae no cometa 67P. O vídeo da reportagem — muito bem feita — consta neste link.

Penso que o programa fez um ótimo papel em educar o povo sobre a missão Rosetta e os cometas. Parabéns, Rede Globo!

Um esclarecimento: Não tive envolvimento com a missão Rosetta e a minha área de pesquisa não são os cometas.

If you do not understand portuguese and need a little background about brazilian TV

I was featured last Sunday evening in the weekly brazilian TV show Fantástico.  If you are wondering: yes, Fantástico means “fantastic”. This is a prime time TV show which is watched by around 10 million people in Brasil and abroad (this is my rough estimate of the number of viewers). It is one of the most watched tv spots in Brasil, besides the telenovelas. Overall, I think they did a great job in educating the public about the Rosetta mission and comets, and it was quite informative! Well done, Rede Globo.

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By the way, I am not involved in any way with the Rosetta mission and my field of research is not comets.

Entrevista no Jornal Record News, sobre a Sonda Rosetta e o pouso do robô Philae no cometa 67P

Na Quarta-feira da semana passada, 12 de Novembro, fui entrevistado no Jornal da Record News do Canal Record News, pelo apresentador Heródoto Barbeiro. Falei sobre o feito histórico da Sonda Rosetta, e do pouso do robô Philae no cometa 67P.

O vídeo da entrevista, em duas partes consta nos links abaixo:

Gostei da maneira como o Heródoto conduziu a entrevista.

JOSÉ EDUARDO CAVALCANTI - PRESIDENTE DO GRUPO AMBIENTAL, MEMBRO DO CONSELHO SUPERIOR DE MEIO AMBIENTE DA FIESP E CONSELHEIRO DO INSTITUTO DE ENGENHARIA - CRISE DE ABASTECIMENTO DE ÁGUA

Inauguration of ASTRI SST-2M telescope, Cherenkov Telescope Array

I had the pleasure this week to attend the inauguration of the ASTRI SST-2M telescope at Serra La Nave, Catania. This telescope is a prototype for the mini-array telescopes that will be part of the Cherenkov Telescope Array (CTA). CTA is the future of ground-based gamma-ray astronomy. The mini-array in particular will observe the universe at energies >10 TeV. For comparison, a 10 TeV photon has 1013 times more energy than an optical photon. CTA will observe the high-energy universe in a complementary energy range to the amazing Fermi LAT.

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