The Chicken-Egg Question Goes Galactic
Jan 12 at 6:06pm by Aileen
Hi-res infrared composite of galactic core
Atronomers and astrophysicists determined some years ago – after that strange beastie known as a “black hole” was accepted to probably be a real physical phenomenon, that there are gigantic black holes at the center of galaxies. Moreover, they found they could determine the mass of these galactic black holes via a fairly simple ratio between the mass of the central bulge of stars and the hole they surround (about 1:10,000). It has been presumed that the hole at the galactic center got there by the joining of stellar mass black holes, which then continued to grow by accretion of mass from the stars drawn into the gravity well.
More recently, however, scientists examining galaxies much farther away in space and time found a different pattern. The farther back into the history of the universe they looked, the ratio between galactic black holes and the mass of the stars surrounding them did not follow the 1:10,000 ‘rule’ – the holes account for much more of the mass, meaning they were huge even way back in the early days of the universe.
As quoted in Wired’s article Yo Galaxy’s Mama Is a Black Hole, astronomer Chris Carilli of the National Radio Astronomy Observatory said during a briefing at the American Astronomical Society’s annual meeting that “The simplest conclusion is that the black holes come first and they somehow grow the galaxy around them.”
Uh, Oh. “Copernican Principle” Might Be Wrong
Sep 29 at 6:06pm by Aileen
Most of us have never heard of this “Copernican Principle” that is apparently so popular in astrophysics. According to Wikipedia The Copernican principle insists that Earth is not in a central, specially favored position in the universe (or solar system). New York Times science blogger John Tierney examines the principle as part of the Doomsday argument.
Physicists at Oxford University, however, have released a paper that reaches the conclusion that we just might inhabit a ’special’ region of the universe after all.
In the article Dark Energy: Is It Merely An Illusion?, the Oxford scientists theorize that we might instead inhabit a “huge void” in the universe where the density of matter is particularly low. This would tend to account for increasing expansion, which simply cannot be explained by the gravitational realities factored on the density of matter, on the assumption that the density is uniform throughout the universe.
The Oxford mavericks conclude that forthcoming tests of the Copernican principle should help sort the reality from the theories in the next few years.
News Flash: Higgs Remains Missing
Sep 9 at 5:05pm by Aileen
As the LHC accelerator at CERN prepares to complete final whole-torus testing and “shoot the moon” with particles colliding at ~5TeV per beam, the report from the DZero experiment at Fermilab’s Tevatron is in – “Wiggly Higgly” (the so-called “God Particle” that imparts mass to matter) remains missing in action at 170GeV/c2.
The prediction that the Higgs boson would appear at 114GeV/c2 was ruled out in 2000, this experiment rules out the next best guess of mass for the exchange particle. This finding will tend to put more importance on findings expected from the higher energy levels at LHC over the next few years, though experimenters have long believed Higgs would be discovered at the lower Tevatron energies. That appears to have been ruled out too.
Higgs is probably the most famous component of the ‘Standard Model’ of physics to remain MIA after so much expense over so many years of seeking answers about the nature of nature. The Tevatron experiment did succeed in producing Z boson pairs, so researchers had maintained hope for Higgs at this level.
It took 600 physicists from 90 institutions in 18 countries to determine that Higgs is not present at 170GeV. Perhaps the LHC physicists will have better luck while they’re busy producing quark-gluon plasmas, mini black holes and other odd sub-sub-particles of interest. It’s scheduled to be fully up and running by October, so some answers should come soon!
Link:
Hunt for Elusive Higgs Boson Gets Boost
Our Universe: Missing, Found, Then Missing Again
Nov 8 at 10:10pm by Aileen
Keeping Up With Astronomy’s Game of Hide-and-Seek
Big astrophysics science news this week that a Big Chunk of the Universe Is Missing – Again. This requires a little background for understanding how it is our universe can be so adept at playing hide-and-seek.
As much as 96% of the mass necessary to account for how our universe is observed to be has been missing for a long time. The mass is necessary to explain the gravity that holds galaxies together, but all the atomic matter we can see in planets, comets, asteroids, assorted space junk, stars and galaxies accounts for just 4% of it. In 1974 astronomer Vera Rubin discovered that instead of following a Newtonian scheme where Mercury travels faster around the sun than Neptune does, almost all stars rotating around a galaxy’s center – at any distance – all travel at the same speed.
There had to be some ‘extra’ source of gravity working in galaxies, but there wasn’t nearly enough mass to account for this anomaly. The choice was between gravity being variable (unthinkable!) or the existence of a great deal of extra mass that we couldn’t see. Scientists jumped on that answer in defense of Newtonian/Einsteinian gravity and gifted us with “Dark Matter.”
RECENT COMMENTS