Tuesday, May 7, 2013

Dark Matter and Dark Energy

Dark matter...comes from the observation that galaxies should not be able to rotate at the speed they seem to rotate at based on their visible mass alone (and this is a huge effect - approximately 84% of the mass required for our observations seems to be invisible). It's 23% of the mass-energy total in the universe. If dark energy is 73% and dark matter is 23%, then there's only 4% left for the visible mass and energy in the universe, which is amazing. (Alex Kritchevsky on Quora)
Seeing the invisible (observing the dark side of the universe): It seems that most of the universe is made up of mysterious ingredients which we cannot see directly. I will describe in pictures "gravitational lensing", the bending of light by gravity, which is predicted by Einstein's General Relativity.  The dark components of the universe do not emit or absorb light, but do exert a gravitational attraction, and it turns out that gravitational lensing is one of the most promising methods for finding out more about them.(sarah bridle from royalsociety.org)
Importance: "Because the amount of matter and energy in the universe determines the rate of expansion," Dr. Michio Kaku tells us. "We now know there is a lot more dark energy than we previously thought. Therefore, the universe is undergoing an inflationary exponential expansion.  It is in a runaway mode, but here is the catch: we don't know how long that runaway mode is going to last."(brightthink.com)
A whiff of dark matter on the  ISS :
On April 3rd, researchers led by Nobel Laureate Samuel Ting of MIT announced that the Alpha Magnetic Spectrometer, a particle detector operating on board the International Space Station since 2011, has counted more than 400,000 positrons, the antimatter equivalent of electrons.  There’s no danger of an explosion, but the discovery is sending shock waves through the scientific community.
The Alpha Magnetic Spectrometer
mounted outside the
International Space Station.
"These data show the existence of a new physical phenomenon," wrote Ting and colleagues in an article published in the Physical Review Letters. "It could be a sign of dark matter." 
 But where do the positrons come from?  The Universe is almost completely devoid of antimatter,
 One idea is dark matter. Astronomers know that the vast majority of the material Universe is actually made of dark matter rather than ordinary matter. They just don't know what dark matter is.  It exerts gravity, but emits no light, which makes it devilishly difficult to study.
 A leading theory holds that dark matter is made of a particle called the neutralino. Collisions between neutralinos should produce a large number of high-energy positrons, which the AMS should be able to detect with unprecedented sensitivity. (science.nasa.gov) (April 15, 2013)


# for Dark Matter formation fundamental facts, go through the google search ..
amateur  astronomy series
nucleosynthesis
star > white dwarf > black dwarf
neutron star >  black hole> supernova > dark matter

No comments:

Post a Comment