Followup on the star torn apart by a black hole: Hubble picture

IIRC it depends on the black hole. Right now there isn't a precise formula for it.

The breakup of the star would form an accretion disc, the jets would form at the axis of rotation. The formation of the jets are classically mechanical (conservation of angular momentum by various means) and so the focus of the jet depends on the speed of the matter being ejected, the amount of matter being ejected and the mass of the black hole.

Moreover, the matter falling into the black hole is heated to plasma level and so there is very strong magnetic activity. As the accretion disc spins, the magnetic field lines twist along the axis of rotation - the same axis as the ejected matter. This has the upshot of focusing the jets very tightly.

http://en.wikipedia.org/wiki/Black_hole#Accretion_of_matter

I'm not sure about these beams, but at least GRBs from collapsing stars come from a relativistic shock wave with gamma of ~1000, IIRC. Such high gamma gives a very collimated beam of radiation, of order 1/gamma, due to relativistic beaming. So taking 1/1000 radians as a ballpark value, 1mrad is about the divergence of a typical laser. (Laser pointers have slightly higher divergence due to the short cavity, but things like He-Ne lasers are typically 1mrad.)

Somebody on one of the blogs mentioned about 5 degrees, make that 3.6 degrees, which is a hundredth of the full circle or 0.06 rad, and since for such values x is approximately tan(x), it would be about 4 billion times 0.06 or 240 million lightyears narrow at our distance.

Only visible because the ripped apart star particles created "the light of a trillion suns"!!

I don't see why, its a perfectly cromulent word.

[ http://en.wikipedia.org/wiki/Cromulent#Embiggen_and_cromulen... ]

A GRB plays an important part in the novel Diaspora by Greg Egan. I'd recommend it if you're interested in learning what would actually happen were we to be closer. (Without being a trained astrophysicist, the events in the novel seemed plausible, so I assume Mr. Egan did his homework).

These planets were torn apart long time ago - when that black hole was formed. Before forming that black hole stars were exploding, so all ~nearby planets were most likely blown away.