Astronomers reveal the first ever image of the black hole at the core of our galaxy.
Category: cosmology – Page 223
Measuring a Black Hole Shadow
Posted in cosmology, robotics/AI
A new technique for measuring the shadows cast by a black hole binary could enable astronomers to glean details about these massive systems.
During its first keynote at Google I/O 2022, Google detailed its latest language model, LaMDA 2, and an app called AI Test Kitchen.
The above video approximates noise from the black hole at the center of the Perseus galaxy cluster, which experts discovered had a pitch over a “million billion times deeper” than the limits of human hearing, making it too deep to be heard.
Leonard Susskind (Stanford University)
https://simons.berkeley.edu/events/quantum-colloquium-black-…ing-thesis.
Quantum Colloquium.
A few years ago three computer scientists named Adam Bouland, Bill Fefferman, and Umesh Vazirani, wrote a paper that promises to radically change the way we think about the interiors of black holes. Inspired by their paper I will explain how black holes threaten the QECTT, and how the properties of horizons rescue the thesis, and eventually make predictions for the complexity of extracting information from behind the black hole horizon. I’ll try my best to explain enough about black holes to keep the lecture self contained.
Panel featuring Scott Aaronson (UT Austin), Geoffrey Penington (UC Berkeley), and Edward Witten (IAS); Umesh Vazirani (UC Berkeley; moderator). 1:27:30.
The swirling spiral of the elegant galaxy M99 is on display in this week’s image from the Hubble Space Telescope. As a prototypical spiral galaxy, like our Milky Way, M99 has the classical rotating disk of stars, gas, and dust, which is concentrated and bright in the center and reaches out into space with spiral arms. But his particular galaxy isn’t just any spiral galaxy — it is a “grand design” spiral galaxy, a classification given to the neatest and most orderly spiral galaxies whose arms are particularly prominent and well-defined.
The galaxy M99 is located in the constellation of Coma Berenices and is around 42 million light-years from Earth. As well as being visually stunning, this galaxy is an interesting target of research and has been imaged by Hubble’s Wide Field Camera 3 instrument twice, for two different research projects.
The first project M99 was observed for is one which looked at the difference between two types of explosions that can occur at the end of a star’s life: Novae and supernovae. Supernovae are the more dramatic, famous events, in which massive stars run out of fuel and explode in huge, bright events which can send out shockwaves and leave behind distinctive remnants. The less famous novae are dimmer events that happen when white dwarfs in a binary system with a larger star suck off layers of matter from that star’s outer shell.
Sanctions imposed on Russia over its invasion of Ukraine are forcing lenders and businesses to pull out of the country.
This visualization shows 22 X-ray binaries in our Milky Way galaxy and its nearest neighbor, the Large Magellanic Cloud, that host confirmed stellar-mass black holes. The systems are depicted at the same physical scale, and their orbital motion is sped up by nearly 22,000 times. The view of each bin.
This visualization shows 22 X-ray binaries in our Milky Way.
The Milky Way is the galaxy that contains the Earth, and is named for its appearance from Earth. It is a barred spiral galaxy that contains an estimated 100–400 billion stars and has a diameter between 150,000 and 200,000 light-years.
An international group of astronomers led by Benjamin Thomas of The University of Texas at Austin has used observations from the Hobby-Eberly Telescope (HET) at the university’s McDonald Observatory to unlock a puzzling mystery about a stellar explosion discovered several years ago and evolving even now. The results, published in today’s issue of The Astrophysical Journal, will help astronomers better understand the process of how massive stars live and die.
When an exploding star is first detected, astronomers around the world begin to follow it with telescopes as the light it gives off changes rapidly over time. They see the light from a supernova get brighter, eventually peak, and then start to dim. By noting the times of these peaks and valleys in the light’s brightness, called a “light curve,” as well as the characteristic wavelengths of light emitted at different times, they can deduce the physical characteristics of the system.
“I think what’s really cool about this kind of science is that we’re looking at the emission that’s coming from matter that’s been cast off from the progenitor system before it exploded as a supernova,” Thomas said. “And so this makes a sort of time machine.”
Circa 2014 o.o!
When someone mentions “different dimensions,” we tend to think of things like parallel universes – alternate realities that exist parallel to our own, but where things work or happened differently. However, the reality of dimensions and how they play a role in the ordering of our Universe is really quite different from this popular characterization.
To break it down, dimensions are simply the different facets of what we perceive to be reality. We are immediately aware of the three dimensions that surround us on a daily basis – those that define the length, width, and depth of all objects in our universes (the x, y, and z axes, respectively).
Beyond these three visible dimensions, scientists believe that there may be many more. In fact, the theoretical framework of Superstring Theory posits that the universe exists in ten different dimensions. These different aspects are what govern the universe, the fundamental forces of nature, and all the elementary particles contained within.
On gravitational preheating
Posted in cosmology, particle physics
We consider dark matter production during the inflaton oscillation epoch. It is conceivable that renormalizable interactions between dark matter and inflaton may be negligible. In this case, the leading role is played by higher dimensional operators generated by gravity and thus suppressed by the Planck scale. We focus on dim-6 operators and study the corresponding particle production in perturbative and non-perturbative regimes. We find that the dark matter production rate is dominated by non-derivative operators involving higher powers of the inflaton field. Even if they appear with small Wilson coefficients, such operators can readily account for the correct dark matter abundance.