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.

Recommended by us: Boson

“  Bosons All particles fall into one of two classes, bosons or fermions. Two bosons with identical properties can be in the same place at the same time, but two fermions cannot.           By Sean Carroll, California Institute of Technology There are two kinds of elementary particles in the universe: bosons and fermions. Bosons don’t mind sitting on top of each other, sharing the same space. In principle, you could pile an infinite number of bosons into the tiniest bucket. Fermions, on the other hand, don’t share space: only a limited number of fermions would fit into the bucket. Matter, as you might guess, is made of fermions, which stack to form three-dimensional structures. The force fields that bind fermions to each other are made of bosons. Bosons are the glue holding matter together. Bosons and fermions act like two different kinds of spinning tops. Even when a boson or fermion is by itself, it always has an intrinsic angular momentum, which scientists call spin. Bosons always have an integer amount of spin (0, 1, 2...), while fermions have half-integer spin (1/2, 3/2, 5/2...).  Before July 2012, every fundamental particle that physicists had discovered had non-zero spin. But the theory behind the Higgs boson predicts that it should have no spin. If the early indications hold up and the new particle discovered at the Large Hadron Collider really is the Higgs boson, it will be the first known example of an elementary particle that knows no direction and no polarization—a truly revolutionary discovery.                                                                                                                                                                                                                          (From: http://www.symmetrymagazine.org)                   ”

Higgs o non Higgs questo è il dilemma!!

In questo articolo uscito il 2 Agosto, sul sito Arxiv.org nella sezione hep-ph, gli autori Jhon Ellis e Dae Sung Hwang si domandano se l'eccesso che è stato recentemente riportato dagli esperimenti ATLAS e CMS, con una massa di circa 125 GeV e con caratteristiche simili a quelle attese per il bosone di Higgs, possa avere o meno spin zero così come richiesto dal Modello Standard.