Is Unknown Force In Universe Acting On Dark Matter?

http://www.sciencedaily.com/releases/2009/10/091022154644.htmScience News


Is Unknown Force In Universe Acting On Dark Matter?


ScienceDaily (Oct. 23, 2009)
— An international team of astronomers have found an unexpected link
between mysterious 'dark matter' and the visible stars and gas in
galaxies that could revolutionise our current understanding of gravity.



See also:
Space & Time

• Dark Matter
  
• Astrophysics
  
• Astronomy
  
• Galaxies
  
• Cosmology
  
• Sun
  

Reference

• Galaxy formation and evolution
  
• Star cluster
  
• Supergiant
  
• Dark matter
  

One of the astronomers, Dr Hongsheng Zhao of the SUPA Centre of
Gravity, University of St. Andrews, suggests that an unknown force is
acting on dark matter. The findings are published this week in the
scientific journal Nature.
Only 4% of the universe is made of known material. Stars and gas in
galaxies move so fast that astronomers have speculated that the gravity
from a hypothetical invisible halo of dark matter is needed to keep
galaxies together. However, a solid understanding of dark matter as
well as direct evidence of its existence has remained elusive.
Now the team believes that the interactions between dark and
ordinary matter could be more important and more complex than
previously thought, and even speculate that dark matter might not exist
and that the anomalous motions of stars in galaxies are due to a
modification of gravity on extragalactic scales.
Dr. Benoit Famaey (Universities of Bonn and Strasbourg) explains:
"The dark matter seems to 'know' how the visible matter is distributed.
They seem to conspire with each other such that the gravity of the
visible matter at the characteristic radius of the dark halo is always
the same. This is extremely surprising since one would rather expect
the balance between visible and dark matter to strongly depend on the
individual history of each galaxy."
Dr. Zhao at the SUPA Centre of Gravity notes, "The pattern that the
data reveal is extremely odd. It's like finding a zoo of animals of all
ages and sizes miraculously having identical, say, weight in their
backbones or something. It is possible that a non-gravitational fifth
force is ruling the dark matter with an invisible hand, leaving the
same fingerprints on all galaxies, irrespective of their ages, shapes
and sizes."
Such a force might solve an even bigger mystery, known as 'dark
energy', which is ruling the accelerated expansion of the Universe. A
more radical solution is a revision of the laws of gravity first
developed by Isaac Newton in 1687 and refined by Albert Einstein's
theory of General Relativity in 1916. Einstein never fully decided
whether his equation should add an omnipresent constant source, now
called dark energy.
Dr Famaey added, "If we account for our observations with a modified
law of gravity, it makes perfect sense to replace the effective action
of hypothetical dark matter with a force closely related to the
distribution of visible matter."
The implications of the new research could change some of the most
widely held scientific theories about the history and expansion of the
universe.
Lead researcher Dr. Gianfranco Gentile at the University of Ghent
concludes, "Understanding this puzzling conspiracy is probably the key
to unlock the formation of galaxies and their structures."



Journal reference:

நந்திதா அக்கா இதனை தமிழில் தந்தால் நன்ராக இருக்கும். தர முடியுமா பிலீஸ்....