Colliding Galaxies, X-rays and Dark Matter
Dark Matter is Theorized to Have Long Life
Earlier in 2007, scientists mapped the shape of the collected groupings of dark matter using Hubble technology. The universe, made up of visible celestial bodies, stars, planets and galaxies, is mostly comprised of large quantities of invisible--and as yet unidentified--dark matter.
Dark matter is invisible because it does not reflect light. There are theories as to what it might be, including that it might be made up of axions, which are hypothetical elementary particles that are predicted to have no electric charge and a very small mass and that interact minimally with ordinary visible matter.
Dark matter, first discovered in the 1970s, has mass and therefore has gravitation. This gravity can be measured according to Newton's principal of the proportionality of mass and distance. Further, galaxies can be analyzed and weighed to derive mass. From this measurement it is clear that the greatest component of mass in galaxies is invisible dark matter.
Additionally, these galaxies, which can yield revealing measurements, gather into clusters with each cluster containing up to several thousand galaxies. Just as galaxies can collide, galaxy clusters can also collide. Astrophysicist Signe Riemer-Sorensen, a Ph. D. student at the Niels Bohr Institute, has added to the understanding of dark matter through his analysis of two clusters of galaxies that are colliding.
When galaxies collide, it is not the galaxies nor the dark matter of the galaxies that meet in the collision. What meets is the huge clouds of gas and dust which comprise about 12 percent of the mass of galaxy clusters.
These crashing gas and dust clouds in the colliding galaxies are hot and they emit x-ray that can be observed and measured. It is therefore possible to see how the clouds are actually forcibly pushed out of the galaxies while the galaxy clusters collide. Furthermore, when these hot, x-ray emitting clouds collide with each other, they become even hotter and emit even more x-ray. The result is that a large and intense front of gas is generated.
This is significant to the search for the characteristics of dark matter. Theories on dark matter suggest that it may be comprised of a new and still undetected type of particle. Among the suggestions for these new particles are types of particles that emit x-ray when they decay. The theorized axion is such a particle: as yet undetected and hypothesized to decay and emit x-ray (interestingly, the axion is also integral to theories involving extra dimensions).
Thus, in order to search for x-ray from decaying particles in dark matter, researchers need to look in places where there is an exceptionally high concentration of dark matter but no hot, x-ray emitting gas. Such a place is found in two colliding clusters of galaxies: as much as 85 percent of the mass can be dark matter and the hot gas clouds that themselves emit x-ray have been pushed out of the galaxies. That leaves available dark matter and an unobstructed search for x-ray from decaying particles can therein be conducted.
In the two colliding galaxies that Riemer-Sorensen has analyzed, whose gravitational measurements show that up to 85 percent of the mass is dark matter, no x-ray of any significance has been measured.
The result of this significantly zero measurement is that it can be concluded that if axions are the particle comprising the stuff of dark matter, then not much dark matter has aged enough to decay and emit x-ray. When insignificant x-ray is emitted from dark matter, it is possible to calculate an upper limit to how soon the hypothesized axions would begin decay and thus determine the lifetime of the investigated dark matter.
The results Riemer-Sorensen obtained indicate that, if dark matter is comprised of axions, dark matter has a very, very long lifetime. The theorized lifetime for axions is 3,000,000 billion years and the calculated age of the galactic dark matter is 13,700 billion years. The conclusion therefore is that, if axions are to be the stuff of dark matter, dark matter has a very, very long lifetime.
"The dark matter of the universe has a long lifetime," University of Copenhagen.
Published by K.L. Hartwig
A retired stockbroker, I am in e-education, tutoring in English Literature and Language and studying for an M.A. in English Linguistics. View profile
Dark Matter Particles May Be Fewer Due to Effect of "Dilaton"Research shows that theories of the properties of dark matter may be generating models that overestimate the role of supersymmetry neutralinos by neglecting the influence of dil...- Dark MatterA brief overview of the current state of our understanding of Dark Matter, and how we arrived scientifically at this point.
- Dark Matter May Have Helped Stars DevelopDark matter is a word that those who follow science may hear about, but what you will not hear defined is exactly what dark matter is. It is not because scientists and the intellectuals who follow them are trying to c...
- An Overview of the Theories on Dark MatterIt was always known that there was matter in the sky that we couldn't see. Dark matter makes up 90% of the universe. It cannot emit, absorb or reflect light, which makes it truly black.
- A New Theory of the Universe: Cosmic Web and Dark MatterMany scientists believe that dark matter makes up most of the universe. Then what really is dark matter?
- A Brief Overview of the Motions of Galaxies Within Our Universe
- Galaxy Cluster Collision Proves Existence of Dark Matter
- Proof of Dark Matter in the Universe
- Dark Matter: Have Its Particles Been Detected?
- The Gravity Theory Dispenses with Dark Matter
- NASA's GLAST is Launched into Earth Orbit
- Universe Might Weigh Much Less than We Think
4 Comments
Post a Comment...fascinating history of physics as well.
Um... yeah big mistake here though guys - dark matter was not discovered in 1970 because it has NEVER been discovered. it was invented - not discoverd- as a bandaid/solution to a problem contained in Einstein's gravity theory. Billions of dollars in scientific research and thousands of very smart brains have yet to produce one tiny eentsy weensy bit of dark matter. problemo to be sure.
So, at this point in time, dark matter is still fiction which raises all kinds of questions about Einstein-Newtonian Gravity Theories and their validity.
There are other theories of gravity that don't need to rely on the concept of dark matter - the most sturdy and interesting one being MOG or Modified Gravity Theory by John W. Moffat. His book (just released last month) is called Reinventing Gravity: a Physicist goes beyond Einstein. I highly recommend picking this up as it explains his theory in detail, along with the whole problem of dark matter much better than I can, and is really a fascinati
Seems like you are on a particle physics run as of late. That's good- it gives me a chance to catch up on all the latest developments in that field. Nice article here, again.
Thanks for this informative article. It contains some very interesting information for those of us who enjoy learning about the many wonders of the universe.