Zeroing in on the Mystery of Dark Matter --"We are on the Verge of Detecting a N
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These are amazing times we live in.
Sent: 2/18/2013 6:14:46 P.M. Eastern Standard Time
Subj: The Daily Galaxy: News from Planet Earth & Beyond
_The Daily Galaxy: News from Planet Earth & Beyond_
_Zeroing in on the Mystery of Dark Matter --"We are on the Verge of
Detecting a New Particle of Nature"_
Posted: 18 Feb 2013 08:37 AM PST
The galaxies and other structures we see in the universe are made
predominantly of undected dark matter. "We are so excited because we believe we are
on the threshold of a major discovery," said Michael Turner, director of
the Kavli Institute for Cosmological Physics at the University of Chicago,
at a conference of the American Association for the Advancement of Science
(AAAS). The existence of Dark matter presents a serious threat to the
so-called Standard Model of physics mainly because it does not explain gravity.
"On the cosmology side we now understand that this mysterious dark matter
holds together our galaxy and the rest of the Universe," said Turner. "And
the tantalizing thing on the cosmology side is that we have an airtight
case that the dark matter is made of something new... there is no particle in
the Standard Model that can account for dark matter."
"The real question is why dark matter has six times the energy that is in
ordinary matter," said Lisa Randall of _Harvard University_
1.1169444444 (Harvard%20University)&t=h) . "It could be 10 trillions times
bigger... This is an intriguing sign that there is maybe some other
interaction we can detect."
The ultimate dark-matter sleuth is the new _Alpha Magnetic Spectrometer_
(http://en.wikipedia.org/wiki/Alpha_Magnetic_Spectrometer) , also designated
AMS-02, a particle physics experiment module aboard the _International Space
Station (ISS)_ (http://en.wikipedia.org/wiki/International_Space_Station) ,
which captures gamma rays coming from collisions of dark matter particles.
AMS functions by sampling these high-energy particles from deep space. The
sensitivity of the AMS is more than 100 to 1,000 times more sensitive than
previous instruments. The first results will be published in two to three
weeks, according to _Samuel Ting_
(http://web.mit.edu/physics/facultyandstaff/faculty/samuel_ting.html) , a Nobel laureate and professor at the
_Massachusetts Institute of Technology (MIT)_
(Massachusetts%20Institute%20of%20Technology)&t=h) who is the mastermind of the two-billion-dollar
project. Its experiments will help researchers study the formation of the
universe and search for evidence of dark matter and antimatter.
The device is equipped with over 300,000 data channels that require
compression with an on-board supercomputer before the information can be
transmitted to Earth. “The space station [AMS device] can detect particles of
practically unlimited energy,” Ting says, which means that it can also hunt for
proposed galaxies made of the elusive dark matter.
Ting oversees a 500 member global team of scientist to work on this 1.5
billion dollar project, made possible because US President Barack Obama who
proposed to extend the space station for a minimum of 5 years beyond 2015,
with an additional budget of 3 billion dollars per year.
In an interview with BBC News Ting stated: “This really is the very first
very, very precise particle physics detector. You enter into a totally new
domain. It's very hard to predict what you'll find."
Space-based spectrometers are not something new, but this instrument is
particularly important because it represents the first one of its type to
take a superconducting magnet to low-Earth orbit. The international physics
community hopes that, through measurements collected with the AMS, they will
be able to answer at least a small portion of yet-unanswered,
Universe-related questions that deal with the origins and the future of the cosmos.
Its observations will probably build up on those obtained by the Italian
satellite PAMELA, a high-energy particle observer launched in 2006. This
observatory has already gathered some interesting leads on pinpointing the
first clear pieces of evidence on dark matter, and the AMS will have the
ability to either permanently confirm or deny these findings, and the dark
matter/dark energy theory as a whole.*
Dark matter makes up about 23 percent of the mass-energy content of the
universe, even though we don’t know what it is or have yet to directly see it
(which is why it’s called “dark”).
The image above is one of the most detailed maps of dark matter in our
universe ever created. The location of the dark matter (tinted blue) was
inferred through observations of magnified and distorted distant galaxies seen
in this picture.
"Figuring out what is dark matter has become a problem that
astrophysicists, cosmologists and particle physicists all want to solve, because dark
matter is central to our understanding of the universe," says _Michael S.
Turner_ (http://en.wikipedia.org/wiki/Michael_Turner_(cosmologist)) – Rauner
Distinguished Service Professor and Director of the Kavli Institute for
Cosmological Physics at the University of Chicago.
"We now have a compelling hypothesis, namely that dark matter is comprised
of WIMPs (_Weakly Interacting Massive Particle_
(http://en.wikipedia.org/wiki/Weakly_interacting_massive_particles) ), particles that don’t radiate
light and interact rarely with ordinary matter. After decades of trying to
figure out how to test the idea that dark matter is made up of WIMPs, we have
three ways to test this hypothesis. Best of all, all three methods are
closing in on being able to either confirm or falsify the WIMP. So the stars
have truly aligned."
A theoretical cosmologist trained in both particle physics and
astrophysics, Michael Turner coined the term “dark energy” and helped establish the
interdisciplinary field that combines cosmology and elementary particle
"Ten years ago," Turner says, "I don't think you would've found
astronomers, cosmologists, and particle physicists all agreeing that dark matter was
really important. And now, they do. And all of them believe we can solve
the problem soon. It's wonderful listening to particle physicists explain the
evidence for dark matter, and vice versa –astronomers explaining WIMPs as
dark matter. "
"As cosmologists," said _Rocky Kolb_
(http://en.wikipedia.org/wiki/Edward_Kolb) , who studies the application of elementary-particle physics to the
_very early Universe_ (http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang)
, and is the co-author with Michael Turner of The Early Universe, the
standard textbook on particle physics and cosmology, "one of our jobs is to
understand what the universe is made of. To a good approximation, the galaxies
and other structures we see in the universe are made predominantly of dark
matter. We have concluded this from a tremendous body of evidence, and now
we need to discover what exactly is dark matter. The excitement now is
that we are closing in on an answer, and only once in the history of humans
will someone discover it. "
"Nothing in cosmology makes sense without dark matter, says Turner. "We
needed it to form galaxies, stars and other structures in the Universe. And
so it's absolutely central to cosmology. We also know that none of the
particles known to exist can be the dark matter particle. So it has to be a new
particle of nature. Remarkably, our most conservative hypothesis right now
is that the dark matter is a new form of matter – out there to be
discovered and to teach us about particle physics."
"Dark matter is absolutely central to cosmology, said Turner, "and the
evidence for it comes from many different measurements: the amount of
deuterium produced in the big bang, the cosmic microwave background, the formation
of structure in the Universe, galaxy rotation curves, gravitational
lensing, and on and on."
"There is five times more dark matter than ordinary matter, and its
existence allows us to understand the history of the universe beginning from a
formless particle soup until where we are today," said Turner. "If you said,
'You no longer have dark matter,' our current cosmological model would
collapse. We would be back to square one."
"Dark matter particles, or WIMPs," said Turner, "don’t interact with
ordinary matter often. It's taken 25 years to improve the sensitivity of our
detectors by a factor of a million, and now they have a good shot at detecting
the dark matter particles. Because of the technological developments, we
think we are on the cusp of a direct detection. Likewise for indirect
detection. We now have instruments like the Fermi satellite (the Fermi Gamma-ray
Space Telescope) and the IceCube detector (the IceCube Neutrino Observatory
at the South Pole) that can detect the ordinary particles (positrons,
gamma rays or neutrinos) that are produced when dark matter particles
annihilate, indirectly allowing dark matter to be detected. IceCube is big enough to
detect neutrinos that are produced by dark matter annihilations in the
Answering the observation that the dark matter particle might not be
detectable, Turner said that for 20 to 30 years, this idea that dark matter is
part of a unified theory has been our Holy Grail and has led to the WIMP
hypothesis and the belief that the dark matter particle is detectable. "But
there’s a new generation of physicists that is saying, 'Well, there's an
alternative view. Dark matter is actually just the tip of an iceberg of another
world that is unrelated to our world. And I cannot even tell you about
that world. There are no rules for that other world, at least that we know of
Sadly, this point of view could be correct and might mean the solution to
the dark matter problem is still very far away, that discovering what dark
matter actually is could be 100 years away.
The Daily Galaxy via _http://www.kavlifoundation.org_
(http://www.kavlifoundation.org/) and AFP 2013
Image Credit: NASA/JPL-Caltech/ESA/Institute of Astrophysics of Andalusia,
University of Basque Country/JHU
(http://www.dailygalaxy.com/my_weblog/2013/01/gravitinos-will-they-unlock-the-mystery-of-dark-matter-in-the-universe.html) _"Gravitinos" --Will They
Unlock the Mystery of Dark Matter in the Universe?_
(http://www.bbc.co.uk/news/science-environment-21495800) _'Space LHC' to
release first results_
(http://www.dailygalaxy.com/my_weblog/2013/01/dark-matter-did-it-play-a-role-in-creating-life-in-the-universe-2012-most-popular.html) _Dark Matter
--Could It Play a Role in Creating Life in the Universe? (2012 Most Popular)_
(http://www.dailygalaxy.com/my_weblog/2012/12/cern-newest-research-confirms-existence-of-higgs-boson.html) _CERN's Research Confirms Existence of
Higgs Boson --Will It Lead to a "New Physics"?_
_Image of the Day: The Largest Galaxy in the Observable Universe?_
Posted: 18 Feb 2013 08:59 AM PST
The spectacular _barred spiral galaxy_
(http://en.wikipedia.org/wiki/Barred_spiral_galaxy) NGC 6872 has ranked among the biggest stellar systems for
decades. A eam of astronomers from the United States, Chile and Brazil have
crowned it the largest-known spiral, based on archival data from NASA's
_Galaxy Evolution Explorer_ (http://www.galex.caltech.edu/) (GALEX) mission,
which has since been loaned to the _California Institute of Technology_
-118.125494 (California%20Institute%20of%20Technology)&t=h) . Measuring
tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than
522,000 light-years, making it more than five times the size of our Milky Way.
"Without GALEX's ability to detect the ultraviolet light of the youngest,
hottest stars, we would never have recognized the full extent of this
intriguing system," said lead scientist Rafael Eufrasio, a research assistant at
NASA's _Goddard Space Flight Center_
d%20Space%20Flight%20Center)&t=h) in Greenbelt, Md., and a doctoral
student at _Catholic University of America_
University%20of%20America)&t=h) in Washington.
The galaxy's unusual size and appearance stem from its interaction with a
much smaller disk galaxy named IC 4970, which has only about one-fifth the
mass of NGC 6872. The odd couple is located 212 million light-years from
Earth in the southern constellation Pavo. Astronomers think large galaxies,
including our own, grew through mergers and acquisitions -- assembling over
billions of years by absorbing numerous smaller systems. Intriguingly, the
gravitational interaction of _NGC 6872 and IC 4970_
(http://en.wikipedia.org/wiki/NGC_6872_and_IC_4970) may have done the opposite, spawning what may
develop into a new small galaxy.
"The northeastern arm of NGC 6872 is the most disturbed and is rippling
with star formation, but at its far end, visible only in the ultraviolet, is
an object that appears to be a tidal dwarf galaxy similar to those seen in
other interacting systems," said team member Duilia de Mello, a professor
of astronomy at Catholic University.
Computer simulations of the collision between NGC 6872 and IC 4970
reproduce the basic features of the galaxies as we see them today. They indicate
that IC 4970's closest encounter occurred 130 million years ago and that the
smaller galaxy followed a path (dashed curve) close to the plane of the
spiral's disk and in the same direction it rotates. The tidal dwarf candidate
is brighter in the ultraviolet than other regions of the galaxy, a sign it
bears a rich supply of hot young stars less than 200 million years old.
The researchers studied the galaxy across the spectrum using archival data
from the European Southern Observatory's Very Large Telescope, the Two
Micron All Sky Survey, and NASA's _Spitzer Space Telescope_
(http://www.spitzer.caltech.edu/) , as well as GALEX. By analyzing the distribution of energy
by wavelength, the team uncovered a distinct pattern of stellar age along
the galaxy's two prominent spiral arms. The youngest stars appear in the far
end of the northwestern arm, within the tidal dwarf candidate, and stellar
ages skew progressively older toward the galaxy's center. The southwestern
arm displays the same pattern, which is likely connected to waves of star
formation triggered by the galactic encounter.
A 2007 study by Cathy Horellou at _Onsala Space Observatory_
1.9177777778 (Onsala%20Space%20Observatory)&t=h) in Sweden and Baerbel
Koribalski of the Australia National Telescope Facility developed computer
simulations of the collision that reproduced the overall appearance of the
system as we see it today. According to the closest match, IC 4970 made its
closest approach about 130 million years ago and followed a path that took
it nearly along the plane of the spiral's disk in the same direction it
rotates. The current study is consistent with this picture.
As in all barred spirals, NGC 6872 contains a stellar bar component that
transitions between the spiral arms and the galaxy's central regions.
Measuring about 26,000 light-years in radius, or about twice the average length
found in nearby barred spirals, it is a bar that befits a giant galaxy. The
team found no sign of recent star formation along the bar, which indicates
it formed at least a few billion years ago. Its aged stars provide a fossil
record of the galaxy's stellar population before the encounter with IC
4970 stirred things up.
"Understanding the structure and dynamics of nearby interacting systems
like this one brings us a step closer to placing these events into their
proper cosmological context, paving the way to decoding what we find in
younger, more distant systems," said team member and Goddard astrophysicist Eli
The Daily Galaxy via
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