De devulgationi eloquentia

Our gravity group in Lisbon have just published a series of short movies where many group members describe some general aspect of Einstein's theory and beyond.

Have a look at Videoteca do Gravitão, muito boa!

Check out all cool resources at our group's outreach webpage

NuSTAR on the spin of supermassive BHs

Some month ago, in this post, we reported about the launch of the Nuclear Spectroscopic Timing Array (NuSTAR).

Today NASA scheduled a media teleconference to announce one of the first scientific achievements of this mission: the first precise measurement of the spin of a supermassive black hole. 

The discovery will appear in this week Nature's issue.

It turns out that NGC 1365 hosts a rapidly spinning supermassive black hole at its center, and this black hole rotates very close to its theoretical limit imposed by Einstein's General Relativity.

Curiosity: 

one usually refers to these black holes as "extremal" because their spin is close to its maximum value. In "God-given" natural units, the angular momentum of an extremal black hole is J=M^2. 

Indeed, what is usually called the "Kerr limit" is J/M^2 = 1.  This is by no means an "extremal" value!! [For example, Earth also spins around its axis and it has J/M^2~ 10^9 in natural units!]

This doesn't mean that these black monsters in the sky don't spin fast, quite the opposite: because their mass is HUGE, the angular momentum of an extremal black hole of about 10^6 solar masses [roughly the mass of the black hole at the center of the NGC 1365 galaxy]  is as large as 10^13 times that of Earth... a pretty huge and fast spinning top!

PS:

The first author of the paper, Guido Risaliti is an Italian astrophysicists who works here at the Harvard-Smithsonian CfA and at Italian Institute for Astrophysics in Arcetri.

Harvard Stories #1

My personal excuse not to post on the blog.
We are literally submerged in snow, I spent my few spare time in shoveling snow and enjoy the storm.

Good news: 1) I survived Nemo blizzard; 2) i'm more or less settled in Cambridge (moving to the "definitive" apartment in two weeks); 3) I can do nothing but work; 4) eventually i'll have time/willing to post again here. 5) You can fetch good food in Boston. 6) Finally, I live in a bike-friendly city (this is not completely true, but it's way better than Rome, Lisbon and Cagliari).

Bad news: 1) You can fetch good *expensive* food in Boston. 2) My flatemates have an interaction cross section which is a substantial fraction of that of neutrinos. 3) My spouse is still in Italy, still experiencing some problems with the VISA. She was supposed to come here before me, unfortunately she will arrive in March (hopefully). Bad news #2+#3 are main responsible for Good News #3.

Anyway, I wanted to tell another story (nonetheless related to my life here).

Causarum investigatio

I'm in Vienna for the 13th Vienna conference on Instrumentation.
If you are interested in particle detectors either for physics research or for other applications you probably want to have a look at the massive number of talks and posters presented here.
Slides are freely accessible from the timetable of the conference.
Since I am more interested on the scientific application of these instruments... I was also delighted by the painting you can see in this (poor quality) picture. It represents various scientists, or if you want natural philosophers, investigating about the causes; of what? Of everything.
This is a side of the ceiling of the "Festsaal" of the Osterreichischen Akademie der Wissenschaften, ("Academy of sciencies") here in Vienna.
What is even more inspiring is that most of the depicted scientists are using various instruments, such as a telescopes for example, to investigate. Very well linked to the topic of the conference, where the link between science and technology appears so evidently bidirectional...

Enjoy the talks and the picture!

A.A.A. nome per le lune di Plutone cercasi!!

Notizia interessante per tutti gli appassionati di astronomia e non solo!
Si tratta dei due nuovi satelliti di Plutone che sono stati scoperti dal telescopio spaziale Hubble tra il 2011 e il 2012. Per il momento sono stati battezzati temporaneamente come P4 e P5, ma il SETI (Search for Extra-Terrestrial Intelligence) Institute ha chiesto aiuto a tutti gli appassionati lanciando un concorso online, come riportato anche qui dal notiziario dell'istituto nazionale di astrofisica.
Potrete votare fino a mezzogiorno del 25 Febbraio su questo sito: http://www.plutorocks.com/.

Recommended by us: CERN and Sterile Neutrinos

CERN Set to Study Sterile Neutrinos

by Edwin Cartlidge on 5 February 2013

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A new experimental facility to detect a hypothetical particle that many physicists think probably doesn't exist could be up and running at the CERN laboratory near Geneva, Switzerland, within 3 years, assuming that the lab's member states approve spending roughly $110 million to build it.

The sterile neutrino, if it exists, would be an obscure variety of an already otherworldly subatomic particle. Ordinary neutrinos, which have no charge and almost no mass, come in three varieties: electron, muon, and tau. They are very hard to detect because their interaction with ordinary matter is extremely feeble, but over the years physicists have detected enough of them to observe that as they travel through space they can "oscillate" from one flavour to another.

This oscillation phenomenon, which means that neutrinos cannot be entirely massless, has been confirmed by many different experiments. But one such experiment produced results at odds with the rest. That was the Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos National Laboratory in New Mexico, which in data acquired between 1993 and 1998 showed muon antineutrinos to be oscillating into electron antineutrinos far more readily than expected.

(Continue to read on news.sciencemag.org)

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