Astronomers have now used gravitational magnification to measure the rotation rate of a supermassive black hole in a very distant galaxy. From four separate images of the same black hole, R.C. Reis, M.T. Reynolds, J.M. Miller, and D.J. Walton found it was spinning nearly as fast as possible. That likely means it was spun up by a small number of mergers with other black holes rather than a gradual increase from eating smaller amounts of mass.
This marks the first measurement of black hole rotation outside the local Universe…. [Read more]
(OK, it doesn’t scan. So sue me.) Quantum entanglement is a challenging topic, and one which has tripped up a lot of people (including many physicists!) over the decades. In brief, entanglement involves two (or more) particles constituting a single system: measurement on one particle instantly determines the result of similar measurements on the second, no matter how far they are separated in space. While no information is transferred in this process, it’s still at odds with our everyday experience with how the world should work. I updated my earlier explanation of entanglement, which hopefully can help clear up some of the confusion.
Recent work either assumes entanglement is real and probes some of the more interesting implications, or tests some mathematical relations known as Bell’s inequalities. The latter are aimed at quantifying the difference between the predictions of quantum physics and certain alternative models. In that spirit, a group of researchers proposed using light from quasars to randomize the measurement apparatus in entanglement experiments, to eliminate the tiny possibility of a weird loophole in quantum theory.
If a detector has some correlation with the hidden variables of the particles being measured, then the two detectors don’t act independently. That’s true even if only a very tiny amount of information is exchanged less than a millisecond before measurements take place. The interaction would create the illusion that the particles are entangled in a quantum sense, when in fact they are influencing the detectors, which in turn dictate what measurements are being taken. This is known as the “detector settings independence” loophole—or somewhat facetiously as the “free will” loophole, since it implies the human experimenter has little or no choice over the detector settings. [Read more…]
Final note: this is probably the first paper I’ve covered that involves both my undergraduate research focus (quantum measurement) and my PhD work (cosmology), albeit in a much different way than both.
Cassiopeia A (abbreviated Cas A) is a historical oddity. The supernova was relatively close to Earth—a mere 11,000 light-years distant—and should have been visible around CE 1671, yet no astronomers of any culture recorded it. That’s in stark contrast to famous earlier explosions: Tycho’s supernova, Kepler’s supernova, and of course the supernova that made the Crab Nebula. This mysterious absence has led some astronomers to speculate that some unknown mechanism diffused the energy from the explosion, making the supernova far less bright than expected. [Read more…]
One new model, proposed by Anastasia Fialkov, Rennan Barkana, and Eli Visbal, suggests that energetic X-rays could have heated the primoridal gas to the point that reionization happened relatively rapidly. That’s in contrast with other hypotheses, which predict a more gradual reionization process. The X-rays in the new model were emitted by systems that include neutron stars or black holes. The nicest feature of the new proposal is that it predicts a unique pattern in light emission from the primordial gas, which could conceivably be measured by current radio telescopes. [Read more….]
Magnetic monopoles are hypothetical objects that act like the isolated north or south pole of a magnet. Ordinarily when you break a magnet in half, you end up with two smaller magnets, but some theories predict independent existence for monopoles — though they obviously must be rare in nature, because we haven’t seen one yet.
When detectors fail, sometimes ingenuity can provide another way. As Richard Feynman realized, quantum systems can be used to simulate each other if the structure of their quantum states is the same. A group of researchers used a Bose-Einstein condensate — a collection of very cold atoms that behave like a single quantum system — to emulate the behavior of a magnetic monopole.
Thus, in lieu of hunting for particles that are monopolar, M. W. Ray, E. Ruokokoski, S. Kandel, M. Möttönen, and D. S. Hall emulated the behavior of a north magnetic charge using ultracold atoms. The result was behavior described as a Dirac magnetic monopole, something never before seen. This experiment relied on the quantum character of monopoles and might provide hope that isolated magnetic charges could exist in nature.
Quantum simulations work like simulations run on an analog computer: researchers construct electric circuits that obey the same basic mathematical equations as a more complicated physical phenomenon, which allows them to emulate the complicated system without trying to solve the (possibly unsolvable) equations that describe it. A quantum simulation lets physicists substitute a controllable physical system for one that might be too challenging to ever construct in the lab. [Read more….]
Rydberg atoms have the electrons in their outer layers excited until the electrons are only weakly bound to the nucleus, making the atoms physically very large. The increased size allows light to scatter off the outermost electrons without much interference from the nucleus or from the inner core of electrons. In other words, it’s a way to isolate the electron dynamics from other messy phenomena. Noble gases like argon are particularly useful for this, since they are largely non-reactive chemically and relatively easy to model theoretically. [Read more….]
Ball lightning is weird: a spherical glowing object that zooms horizontally at a fast rate before vanishing. (I wonder how many UFO sightings are ball lightning.) It’s a rare phenomenon — far more so than ordinary lightning — so nobody had been able to measure its properties with scientific equipment until now. As it happened, a group of scientists in China who were studying regular lightning serendipitously spotted a ball lightning event, and measured its chemical signature. The verdict?
Now, a team of researchers serendipitously observed ball lightning at a time when they had the right equipment to study it. Jianyong Cen, Ping Yuan, and Simin Xue were in the field measuring the properties of ordinary lightning when they happened to catch ball lightning with both their high-speed cameras and their spectrographs. They found the chemical composition of the event matched that of soil. That strongly supports the hypothesis (proposed nearly fifteen years ago) that ball lightning is basically a dirt clod dislodged and heated to incandescence by a cloud-to-ground lightning strike. [Read more…]
Type Ia supernovae are triggered either by the explosion of white dwarfs that accrete too much matter and exceed their maximum stable mass, or by the collision of two white dwarfs. (That’s as opposed to core-collapse supernovae, which are the explosions of stars much more massive than the Sun.) Because they all explode in very similar ways, Type Ia supernovas are “standard candles”: objects that can be used to measure distances to very distant galaxies. The use of them to track the expansion of the Universe was recognized by the 2011 Nobel Prize. [read more…]
What’s cool is that various astronomers, including a number of amateur astronomers, spotted the supernova before it was identified as such. M82 is a popular observing target because it’s distinctive and (yes) not far away. My colleagues at Universe Today and CosmoQuest actually highlighted the galaxy during their Virtual Star Party on Sunday evening, meaning they saw the supernova before we knew what a big deal it was going to be!
Astronomers have identified a filament in the cosmic web, which is the pattern formed by dark matter. That web in turn dictates the distribution of galaxies, since the dark matter attracts ordinary matter — atoms — through its gravity. However, it’s hard to spot the filaments connecting the different halos of dark matter, because they are far less massive and contain less gas than galaxies. The trick in this new study was to spot the faint glow of gas as it was lit up by a quasar: a bright energetic black hole in a nearby galaxy.
Sebastiano Cantapulo and colleagues observed the light emitted by the filament’s gas as it glowed under bombardment from a quasar, a powerful jet of particles propelled from a massive black hole. However, the researchers also found at least ten times more gas than expected from cosmological simulations, which suggests that there may be more gas between galaxies than models predict. [Read more….]
Evidently I forgot to post one of these roundups last week, so here’s two weeks’ worth of writing all at once! Also, I have a new sticker design you can order, for those of you (like me) who don’t willingly run for exercise, but want to feel you’ve accomplished something anyway. At least in a cosmological sense, we all run this marathon we call existence.
- Drown your town, drown the world (Galileo’s Pendulum): My colleague Andrew David Thaler asked how much water would be required to flood the whole world to the height of Mount Everest, so I took up the challenge.
- Hellish exoplanet has Earth-like density and composition (Ars Technica): It’s difficult to measure both the mass and the size of exoplanets (planets orbiting other stars), because discovery methods are complementary to each other. A new pair of papers described the first exoplanet with a density similar to Earth’s, meaning it probably has a similar composition. However, the planet is hot enough to melt most rocks. Don’t plan your vacation there.
- New LUX experiment: No dark matter in this corner (Ars Technica): Researchers operating the Large Underground Xenon (LUX) dark matter detector announced the results of the first three months of operation. They found: nothing. Well, specifically they found nothing where some other detectors might have found a possible dark matter signature.
- Ghosts in the detector: why null results are part of science too (Galileo’s Pendulum): To follow up that previous article, here’s why the LUX detector wasn’t a failure, and definitely why we shouldn’t think dark matter doesn’t exist.
- A comment on comments, with cats (Galileo’s Pendulum): Comments on websites have always been a point of some debate. Do we have them? How do we moderate them? What constitutes reasonable commenting, and who makes that decision? Because of an ongoing “debate” between a few vocal people about pterosaur flight (of all things) on an old post about gravity, which I simply don’t have time or willingness to moderate, I decided to close down comment threads on older posts. That riled some people up.
- So close, yet so far (Galileo’s Pendulum): The closest star to the Solar System is invisible to the unaided eye, but in many ways it’s a more typical star than the Sun — much less the other stars we see in the night sky.
- The census of alien worlds (Galileo’s Pendulum): The Kepler observatory’s primary mission is over, but its legacy lives on. Based on Kepler data, scientists have estimated the possible number of Earth-class planets orbiting at habitable distances from Sun-like stars. Here’s my take on that study.
- I don’t believe in science (Galileo’s Pendulum): Oftentimes, big ideas in science — the Big Bang model, evolution, climate change — are regarded as optional, matters of belief. Here are some of my musings about science, belief, and what it means to trust science in the face of bad behavior, fraud, and controversy.
- Weekly Space Hangout (Universe Today): Yesterday, I participated in the weekly round-up of space and astronomy news, in conversation with other science writers. Much fun was had!