Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Wednesday, May 1, 2019

Spins, jets, and wobbles

In the last couple of weeks, I've written about the discovery of colliding neutron stars six billion light years away, the incredible achievement of generating the first-ever photograph of a black hole, and a team that found a white dwarf star which amazingly still had a planet orbiting around it, even though you'd think the process of becoming a white dwarf would obliterate anything nearby.

So the achievements of the astrophysicists have been coming hard and fast lately.  But this week, a team led by James Miller-Jones of the International Centre for Radio Astronomy Research at Curtin University (Perth, Australia) has found something that might be the weirdest yet: a spinning black hole that is precessing like a top, wobbling so quickly that it actually drags spacetime along with it.

The object is called V404 Cygni, and was first sighted in 2015 when it suddenly began to emit a jet of plasma.  The explanation was thought to be that it had encountered a cloud of matter (or possibly had captured another star) which was slowing being devoured.  It's been known for some times that as matter spirals toward a black hole, it spins faster and faster -- rather like water going down a drain -- and in the process emits particles that are funneled along the magnetic field lines of the black hole and emerge as jets from each pole -- in the case of V404 Cygni, traveling at 60% of the speed of light.

So far, this is impressive, but still very much in line with the predictions of the current model.  But  Miller-Jones and his team found out that V404 Cygni had another feature; the jets of plasma it was emitting were exhibiting such rapid precession that they were flailing around with a period of only a few minutes.

"This is one of the most extraordinary black hole systems I've ever come across," Miller-Jones said, in an interview with Science Alert.  "We think the disc of material and the black hole are misaligned.  This appears to be causing the inner part of the disc to wobble like a spinning top and fire jets out in different directions as it changes orientation."

Here's an image that Miller-Jones's team generated of what this might look like from closer up:

(The Science Alert page I linked above has a very cool animation of what this system in motion -- you should all check it out.)

The strangest part is that the mass and rapid spin of the black hole have generated an effect called frame dragging, wherein spacetime near a massive rotating object becomes distorted, with nearer regions experiencing a drag analogous to what happens if you rapidly stir a glass full of honey.  (It's not truly fluid drag -- it's a relativistic effect that wouldn't be observed at slow rotational speeds -- but has a similar effect.)

"We were gobsmacked by what we saw in this system - it was completely unexpected," said astrophysicist Greg Sivakoff of the University of Alberta, a member of the team who discovered the phenomenon.

So once again, what's out there in deep space has shown itself to be wonderfully weird.  It seems fitting to end with the quote from biologist J. B. S. Haldane -- "The universe is not only stranger than we imagine, it is stranger than we can imagine."


This week's Skeptophilia book recommendation is for any of my readers who, like me, grew up on Star Trek in any of its iterations -- The Physics of Star Trek by Lawrence Krauss.  In this delightful book, Krauss, a physicist at Arizona State University, looks into the feasibility of the canonical Star Trek technology, from the possible (the holodeck, phasers, cloaking devices) to the much less feasible (photon torpedoes, tricorders) to the probably impossible (transporters, replicators, and -- sadly -- warp drive).

Along the way you'll learn some physics, and have a lot of fun revisiting some of your favorite tropes from one of the most successful science fiction franchises ever invented, one that went far beyond the dreams of its creator, Gene Roddenberry -- one that truly went places where no one had gone before.

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