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]
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…]
“Dark energy” is one of the more unfortunate names in science. You’d think it has something to do with dark matter (itself a misnomer), but it has the opposite effect: while dark matter drives the clumping-up of material that makes galaxies, dark energy pushes the expansion of the Universe to greater and greater rates. Though we should hate on the term “dark energy”, we should respect Michael Turner, the excellent cosmologist who coined the phrase. He is also my academic “grand-advisor”: he supervised Arthur Kosowsky’s PhD, and Arthur in turn supervised mine.
And of course, I worked on dark energy as a major part of my PhD research. In my latest piece for Slate, I describe a bit of my dysfunctional relationship with cosmic acceleration, and why after 16 years dark energy is still a matter of frustration for many of us.
Because dark energy doesn’t correspond easily to anything in the standard toolkit of physics, researchers have been free to be creative. The result is a wealth of ideas, some that are potentially interesting and others that are frankly nuts. Some string theorists propose that our observable universe is the result of a vast set of parallel universes, each with a different, random amount of dark energy. Other physicists think our cosmos is interacting with a parallel universe, and the force between the two drives cosmic acceleration. Still others suspect that dark energy is a sign that our currently accepted theory of gravity—Einstein’s general theory of relativity—is incomplete for the largest distances. [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!
The idea isn’t as crazy as it sounds. A pair of philosophers recently argued that if we accept the eventual complexity of computer hardware, it’s quite probable we’re already part of an ‘ancestor simulation’, a virtual recreation of humanity’s past. Meanwhile, a trio of nuclear physicists has proposed a way to test this hypothesis, based on the notion that every scientific programme makes simplifying assumptions. If we live in a simulation, the thinking goes, we might be able to use experiments to detect these assumptions.
However, both of these perspectives, logical and empirical, leave open the possibility that we could be living in a simulation without being able to tell the difference. [read more….]
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….]