synopsis of a raven

BLACK HOLES WITH RAVENOUS APPETITES DEFINE TYPE I ACTIVE GALAXIES

** Synopsis: New research suggests that the central black holes in Type I and Type II active galaxies consume matter at different rates, upending popular theory. **

For decades, astronomers have tried to pin down why two of the most common types of active galaxies, known as Type I and Type II galaxies, appear different when observed from Earth. Although both galaxy types host voracious supermassive black holes known as active galactic nuclei, which actively swallow matter and emit massive amounts of radiation, Type I galaxies appear brighter to astronomers’ telescopes.

New research from an international team of astronomers, with contributions from the University of Maryland, makes a major modification to a popular theory called the unified model. According to this model, the active nuclei of Type I and Type II galaxies have the same fundamental structure and energetic profile, but appear different solely because the galaxies point toward Earth at different angles. Specifically, Type II galaxies are tilted such that they are obscured by their own rings of dust, making Type I galaxies appear brighter by comparison.

The new results, published September 28, 2017, in the journal Nature, suggest that Type I and Type II galaxies do not just appear different – they are, in fact, very different from each other, both structurally and energetically. The key factor that distinguishes Type I and Type II galaxies is the rate at which their central black holes consume matter and spit out energy, according to the researchers.

“The unified model has been the prevailing wisdom for years. However, this idea does not fully explain the differences we observe in galaxies’ spectral fingerprints, and many have searched for an additional parameter that fills in the gaps,” said Richard Mushotzky, a professor of astronomy at UMD and a co-author of the study. “Our new analysis of X-ray data from NASA’s Swift Burst Alert Telescope suggests that Type I galaxies are much more efficient at emitting energy.”

To conduct the study, Mushotzky and his colleagues re-examined data from 836 active galaxies detected by NASA’s Swift Burst Alert Telescope that strongly emit high-energy, or “hard,” X-rays – the same X-rays that medical technicians use to visualize the human skeleton.

To measure the mass and growth rate of these galaxies’ active nuclei – the supermassive black holes at the galaxies’ centers – the researchers used data from 12 different ground-based telescopes spread across the globe to complement the data from the Swift satellite.

“This project began in 2009, as part of my doctoral work at UMD, and has radically grown with the help of more than 40 researchers across the globe,” said Michael Koss (M.S. ‘07, Ph.D. ‘11, astronomy), a research scientist at Eureka Scientific, Inc. and a co-author of the paper. “When I started out, I spent a month of lonely nights by myself at the Kitt Peak National Observatory observing a few dozen galaxies. I never dreamed we would eventually expand to such a large sample, enabling us to answer many amazing scientific questions for the first time.”

By comparing differences in the X-ray spectra between Type I and Type II galaxies, the researchers concluded that, regardless of which way the galaxy faces Earth, the central black holes in Type I galaxies consume matter and emit energy much faster compared with the black holes at the center of Type II galaxies.

“Our results suggest this has a lot to do with the amount of dust that sits close to the central black hole,” said Mushotzky, who is also a fellow of the Joint Space-Science Institute. “Type II galaxies have a lot more dust close to the black hole, and this dust pushes against the gas as it enters the black hole.”

For decades, astronomers preferentially studied Type II galaxies, largely because the active nuclei of Type I galaxies are very bright, making it difficult to see the stars and gas clouds that constitute the rest of the galaxy. Because the unified model suggested that all active galaxies were fundamentally the same, astronomers focused their efforts on the galaxies that host Type II active nuclei because they are easier to observe.

“But now, because our results suggest that the two types of galaxies are indeed fundamentally different, it is likely that a lot of researchers will re-evaluate their data and take another look at Type I galaxies,” Mushotzky said. “By putting us on a path to better understand the differences between the galaxies that host Type I and Type II active nuclei, this work will help us better understand how supermassive black holes influence the evolution of their host galaxies.”


IMAGE….Many active galactic nuclei are surrounded by large, dark, donut-shaped clouds of gas and dust, as seen in this artist’s rendering. A popular theory known as the “unified theory” suggests that differences in the brightness of active galactic nuclei, as seen from here on Earth, are due to the placement of this donut of obscuring dust relative to our angle of observation. However, new research suggests that two of the most common types of active galactic nuclei do, in fact, exhibit fundamental physical differences in the way they consume matter and spit out energy. Credit: NASA/JPL-Caltech

The Raven King (Review)

Synopsis: locked behind a magical door, there was a third sleeper that shouldn’t be woken, a demon, the Unmaker. It has been freed, and now it is feeding on the ley line, causing strange things to happen and destroying everything around itself. Cabeswater is being unmade, Ronan’s dreams are under attack, Henrietta is in danger, and Gansey’s gang has to find Glendower as soon as possible, if they want this to stop.

Book 4 of The Raven Cycle.

It feels so odd when you get to the end of a good story. I loved the plot of the Raven Cycle, with its legendary kings, dream woods and magic-archeological findings. I loved the world of the Raven Cycle: it feels like deep, dark ocean waters, all mysteries that you can’t even begin to unravel and magic that you can barely dip your toes in. I loved the characters of the Raven Cycle, too, because it’s impossible not to love them, they almost look alive from how tenderly wrought they look in all their little quirks, qualities and flaws, when they are presented to you. And I loved Maggie Stiefvater’s writing, it’s such a lush thing.

           After three books of this, I was so engrossed in the story that I’d probably have wolfed down anything that you put in front of me without even caring about what I was reading, and I intend that as compliment, not a complaint. The Raven King was a nice resolution for the series, but it’s not that perfect last book. The plot ended up too big when the search for Glendower, plus the demon, plus Ronan’s dreams, plus all the preexisting psychic or magical powers and some new ones, plus the artifact hunters, plus the ley line’s non-linear time, plus each character’s specific personal struggles were all meshed together. There is a lot more happening in The Raven King than in the first three books of the Raven Cycle, but they are all about the same size, so The Raven King’s story looks a bit rushed and squeezed in to fit a smaller space than what it needed. Sometimes it’s hard to follow what is happening, and there were many subplots for the secondary characters, but they get dropped in the middle of the book, their characters are cut out of the story, and in the end you don’t know what happens to anyone except Gansey, Blue, Ronan, Adam and Henry Cheng. So, lots of potential issues, but they don’t bother you when you are reading because the way this story is told is so compelling. I just noticed that there was something with which I wasn’t quite happy about this book after I’d finished it, because I stopped to think about it to write this review.  

The Raven Cycle was really such a wonderful story. I think I’ll miss it.

Raven helps Bellamy navigate Mount Weather.
— 

synopsis for 2x12, Rubicon.

My only comfort that will get me through next episode is knowing that despite being tortured and strung up for his blood, Bellamy will be in good enough shape to navigate MW in the episode after. 

This won’t take away the pain from seeing my baby hurt though oooohmygod no it will not.