If true, this could mark an astronomy breakthrough.
Category: cosmology – Page 118
In today’s paper, a unique gravitational wave event is re-examined as the possible origin of an AGN flare. What are the odds?
Over ten years ago, the Dark Energy Survey (DES) began mapping the universe to find evidence that could help us understand the nature of the mysterious phenomenon known as dark energy. I’m one of more than 100 contributing scientists that have helped produce the final DES measurement, which has just been released at the 243rd American Astronomical Society meeting in New Orleans.
Dark energy is estimated to make up nearly 70% of the observable universe, yet we still don’t understand what it is. While its nature remains mysterious, the impact of dark energy is felt on grand scales. Its primary effect is to drive the accelerating expansion of the universe.
The announcement in New Orleans may take us closer to a better understanding of this form of energy. Among other things, it gives us the opportunity to test our observations against an idea called the cosmological constant that was introduced by Albert Einstein in 1917 as a way of counteracting the effects of gravity in his equations to achieve a universe that was neither expanding nor contracting. Einstein later removed it from his calculations.
This week’s image from the Hubble Space Telescope shows the aftermath of an epic explosion in space caused by the death of a massive star.
Some of the most dramatic events in the cosmos are supernovas, when a massive star runs out of fuel to fuse — first running out of hydrogen, then helium, then burning through heavier elements — and eventually can no longer sustain the outward pressure from heat caused by this fusion. When that happens, the star collapses suddenly into a dense core, and its outer layers are thrown off in a tremendous explosion called a Type II supernova.
The space between streams of stars may be influenced by the presence of the universe’s most mysterious form of matter.
Perhaps the greatest and most frustrating mystery in cosmology is the Hubble tension problem. Put simply, all the observational evidence we have points to a universe that began in a hot, dense state, and then expanded at an ever-increasing rate to become the universe we see today. Every measurement of that expansion agrees with this, but where they don’t agree is on what that rate exactly is.
We can measure expansion in lots of different ways, and while they are in the same general ballpark, their uncertainties are so small now that they don’t overlap. There is no value for the Hubble parameter that falls within the uncertainty of all measurements, hence the problem.
Of course, most of the results depend on a long chain of observational results. When we measure cosmic expansion using distant supernovae, for example, the result depends on the derived distances of these supernovae as found through the cosmic distance ladder, where ever greater distances are determined based on the distance of closer things.
The End of the Multiverse
Posted in cosmology
Audiences are falling out of love with dizzying multiverse sagas. Can the concept still be a useful lens on the psychology of regret, or is it dead on arrival?
Astronomers spot periodic lights coming from near the black hole at the center of our galaxy.
The supermassive structure dates to about 400 million years after the Big Bang, and it’s particularly large for its age.
Structure of Space-Time Video
Posted in cosmology
A Visual Model of Space and Time linking Gravity, Dark Energy, Black Holes, and Inertia.