“Consideration of particle emission from black holes would seem to suggest that God not only plays dice, but also sometimes throws them where they cannot be seen.” –Stephen Hawking
Last week, I wrote about how high-energy cosmic rays strike Earth’s atmosphere and wind up bombarding everything on Earth’s surface with super-fast moving particles, some of which are even unstable!
In passing, I mentioned that these cosmic rays (mostly protons) come from a variety of sources, such as the Sun, neutron stars, supernova remnants, the centers of galaxies, and (everyone’s favorite) black holes.
(Above is a starburst galaxy, with light from cosmic rays colliding with the interstellar/intergalactic medium shown in false color.)
As always, there were some very good comments on the post, including one that took me to task for the black holes statement:
How does anything ‘come from’ a black hole?
Aaah, black holes, quite possibly the suckiest objects in the Universe.
So, how about it? Everyone knows that the definition of a black hole is that it’s something so dense and so massive that nothing — not matter, not anti-matter, not even light — can escape from behind the event horizon of a black hole. And this is true!
But near a black hole, just outside the event horizon, there’s some incredible stuff going on. First off, the matter. Every black hole has a flat disc of matter orbiting it at an incredibly high speed. Due to forces like friction and gravitational tides, the matter gets ripped apart into individual molecules, atoms, and subatomic particles, and eventually spirals in towards the center.
So we wind up with — somewhat close to the event horizon — a bunch of small, fast-moving, and charged particles. But the black hole, like all star-type objects, has a magnetic field. Unlike the Earth, which has a magnetic field of about 0.6 Gauss at the surface, or the Sun, which can reach a field strength of up to 4,000 Gauss on a Sunspot, a black hole can have magnetic fields in excess of 1,000,000,000,000 Gauss!!
And while these charged, fast moving particles spiral in toward the black hole’s center, they feel the effects of the magnetic field. What effects are those?
It turns out that a basic law of physics is that, if you hold your right hand in an “L” shape (fingers together, thumb out), and point your fingers in the direction of the magnetic field and thumb in the direction the particle is moving, your palm “pushes” the particle perpendicular to both directions!
This causes black holes to suck these particles up and down, perpendicular to the disk, and shoot them out at ultra-high speeds in two jets!
And if one of those jets happens to be pointed towards you, are you ever in for a treat!
It’s a cosmic ray feast! Courtesy of your friendly neighborhood black hole, of course.
And that’s how a whole slew of ultra-high energy particles can come, without any problems at all, from a black hole! So enjoy the cosmic ray showers, and I hope this takes you into a great weekend!