Hello Space Fans and welcome to another edition
of Space Fan News.
Dark News Everyone!
It appears we're getting closer to understanding
BOTH dark energy and dark matter.
First, dark energy.
According to a team of astronomers at the
University of Portsmouth and LMU University
Munich, dark energy, whatever it is, is real.
After conducting a two-year study, the scientists
concluded that the likelihood of the existence
of dark energy stands at 99.996 per cent.
Now for those of you who don't know, the universe
is accelerating as it expands, this was discovered
a while back by carefully measuring redshifts
of Type 1a supernovae, this was such a huge
discovery that the guys who made it got the
Nobel Prize for it last year.
This was a really surprising discovery, everyone
assumed the universe would be gradually slowing
down after the Big Bang, but that's not what
we found.
The universe is accelerating.
Now, for this to be happening, one of two
things is going on: either something is pushing
everything apart, there must be a force causing
everything to not just expand, but to go faster
over time…
Or there's something about our current theories
of gravity we don't understand on large scales
and we need to go back to the drawing board.
Now since the discovery of the acceleration
of the expansion of the universe, there has
been a lot of controversy over what's going
on.
Many astronomers disput the idea of a dark
energy pushing everything apart.
Well this week, this group of astronomers
claim to have settled it.
They are 99.996 percent sure that dark energy
exists, that's the same level of certainty
CERN scientists claimed for the discovery
of the Higgs Boson earlier this year.
They still don't know what it is, but they
are as sure it's there as we are of the Higgs
Boson.
So what makes them so sure dark energy is
real?
There are many other techniques that have
been used to confirm the reality of dark energy
but they are indirect measurements of the
accelerating Universe, not direct observations.
This research says that you can see dark energy
through something called the Integrated Sachs
Wolfe effect in the CMB.
The Cosmic Microwave Background is the radiation
of the residual heat of the Big Bang and is
seen all over the sky.
In 1967 Sachs and Wolfe proposed that light
from this radiation would become slightly
bluer as it passed through the gravitational
fields of lumps of matter, an effect known
as gravitational redshift.
In 1996, this idea was taken to the next level
and it was suggested that astronomers could
look for these small changes in the energy
of the light by comparing the temperature
of the radiation in the CMB with maps of nearby
galaxies.
If dark energy didn't exist, then there would
be no correspondence between these the distant
cosmic microwave background and relatively
closer distribution of galaxies.
But if dark energy did exist, then we would
see a strange, counter-intuitive effect where
the cosmic microwave background photons would
gain energy as they travelled through large
lumps of mass.
I know, it's weird, but as the CMB radiation
travels through material, it gains energy
under this effect.
So to test this, you look at photons from
the CMB while they travel through nearby galaxies
on their way to us and look for this effect.
If dark energy is out there, we would see
the CMB photons blue shifted as they gained
energy through the Sachs Wolfe Effect.
Here's a diagram that shows what I'm talking
about.
Here are the maps they used in the comparison,
they are in increasing order of distance from
the Earth.
On the left are are six shells containing
maps of the millions of distant galaxies used
in the study - these are galaxies in between
us and the background CMB.
These maps are produced using different telescopes
in different wavelengths and are colour-coded
to show denser clumps of galaxies as red and
under-dense regions as blue.
The last, largest shell shows the temperature
of the cosmic microwave background from the
WMAP satellite (red is hot, blue is cold)
Comparing the hot and cold temperatures of
the CMB with the clumps of galaxies in the
foreground, they found (at 99.996% significance)
very small correlations between them.
So there you go, dark energy is real and backed
up by observations, it appears we have a direct
method for finding out that it's there.
Everyone is hoping for more confirmation with
future measurements of the CMB and in the
new galaxy surveys that are taking place now.
I'll keep you posted.
Next, as if that wasn't enough, this week
astronomers announced a technique for finding
dark matter, and once again, to find it, we
look at the CMB.
Astronomers looking at the all-sky CMB survey
taken by the Planck Space telescope have observed
a very unique emission of radio radiation
from the center of our galaxy.
Using different methods to separate the signal
for very broad range of wavelengths, the Planck
team determined that the radiation has a spectrum
which has the same form as that of synchrotron
emission, which is created when electrons
and positrons circulate at high energies around
the lines of the Magnetic Field in the center
of the galaxy.
This radiation, they believe, could come from
dark matter,
Here's why:
Early in the 20th Century, Niels Bohr and
others have predicted that dark matter may
consist of very heavy particles that are around
10 times as heavy as the Higgs particle, or
1,000 times heavier than a proton.
Of course as we all know, they have very irritating
property that they do not interact with ‘normal’
matter particles, they don't even interact
with each other.
Most theories predict that there should be
a very high concentration of dark matter at
the center of galaxies and even though they
don't interact with anything, there's no reason
to think that they they can't become so concentrated
such that every once in a while, they will
collide.
These collisions would produce electrons and
positrons (particles that we can see) and
because they are charged, will start to rotate
around the magnetic field at the center of
our galaxy and when they do this, they produce
this signature synchrotron radiation.
Up until now, It has simply not been possible
to observe this radiation in much detail before,
previous instruments have just not been sensitive
enough.
But with Planck, this unusual radiation is
seen very clearly.
According to Pavel Naselsky, professor of
cosmology at the Discovery Center at the Niels
Bohr Institute at the University of Copenhagen,
“The radiation cannot be explained by the
structural mechanisms in the galaxy and it
cannot be radiation from supernova explosions.
I believe that this could be proof of dark
matter.
Otherwise, we have discovered absolutely new
(and unknown for physics) mechanism of acceleration
of particles in the Galactic centre”
He also says he is expecting more exciting
results in the next few months.
I'll keep you posted on that too.
Well, that's it for this dark edition of Space
Fan News, thank you for watching and as always,
Keep Looking Up.
