The dark matter of the universe has a long lifetime

Oct 01, 2007
Bullet Cluster
The two clusters of galaxies, called Bullet Cluster, are in the process of moving through each other. The red curves show gravitational measurements of the combined mass that consists of partly the visible matter of the galaxies and partly the invisible dark matter. X-ray measurements of the two clusters of galaxies show that the clouds of gas have been pushed out at the collision between the two clusters of galaxies. In the cluster of galaxies to the right there is a lot of dark matter, but very little x-ray, so the dark matter decays very slowly and thus has a very, very long lifetime. Credit: Photo: Chandra x-ray telescope

New research from the Niels Bohr Institute presents new information that adds another piece of knowledge to the jigsaw puzzle of the dark mystery of the universe – dark matter. The research has just been published in the scientific journal Physical Review Letters.

The universe consists not just of visible celestial bodies, stars, planets and galaxies. It also has a mystical fellow player – dark matter. The astronomers can measure that the dark matter exists in big quantities but no one knows what it is, nobody has seen it. It does not emit light and it does not reflect light. It is invisible. It is a mystery and the researchers have many theories.

The dark matter has caused the researchers headaches for decades since it was detected in the 1970s, and there is intense research into the phenomena. It is invisible but it has got mass, and thus it has got gravitation that can be measured. By analysing the galaxies it is possible to weigh them, and it turns out that by far the greatest matter of the collective mass of the galaxy is dark matter.

Just like stars get together in galaxies, the galaxies get together in clusters of galaxies of up to several thousand galaxies. The astrophysicist Signe Riemer-Sørensen, PhD student at the Niels Bohr Institute, has analysed two clusters of galaxies that collide.

Colliding clusters of galaxies are analysed

When the two clusters of galaxies meet neither the galaxies nor the dark matter collide. However, about 12 per cent of the mass of the cluster of galaxies consists of huge clouds of gas and dust and these clouds collide. The gas clouds are hot and emit x-ray that can be observed, and it is possible to see how the clouds are actually pushed out of the two clusters of galaxies at the collision. When the clouds of gas collide they become even hotter and emit more x-ray so that a whole chock front of warn gas is generated.

Observations indicate that the dark matter can be a new and still undetected type of particle. Among the suggestions for the dark matter, are particles that when they decay they emit x-ray. One is the so called axions that are particles which is explained in theories with extra dimensions. So to be able to look for x-ray from dark matter the researchers are looking in places where there is a big concentration of dark matter, but no gas. Such places are found in the two colliding clusters of galaxies where the gas clouds have been pushed out at the collision.

Signe Riemer-Sørensen has analysed the one of the two clusters of galaxies that are in the process of colliding. The analyses show that it is a very heavy cluster with many galaxies, and measurement of the gravitation show that there is a very big amount of dark matter, up to 85 per cent of the collective mass. However, no x-ray of any consequence was measured.

When the dark matter does not emit significant x-ray it is possible to calculate an upper limit to how quickly the particles decay and thus calculate their lifetime. The result is that if axions are to be the dark matter they must have a life span that is longer that 3.000.000 billion years. In that case there is not very much dark matter that has decayed yet if it was formed 13.7 billion years ago. The conclusion is that dark matter has a very, very long lifetime.

Source: University of Copenhagen

Explore further: What is Nothing?

add to favorites email to friend print save as pdf

Related Stories

A spectacular landscape of star formation

6 hours ago

This image, captured by the Wide Field Imager at ESO's La Silla Observatory in Chile, shows two dramatic star formation regions in the Milky Way. The first, on the left, is dominated by the star cluster NGC ...

New survey begins mapping nearby galaxies

Aug 18, 2014

A new survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) has been launched that will greatly expand our understanding of galaxies, including the Milky Way, by charting the internal ...

A possible signal from dark matter?

Aug 12, 2014

(Phys.org) —Galaxies are often found in groups or clusters, the largest known aggregations of matter and dark matter. The Milky Way, for example, is a member of the "Local Group" of about three dozen galaxies, ...

Recommended for you

What is Nothing?

5 hours ago

Is there any place in the Universe where there's truly nothing? Consider the gaps between stars and galaxies? Or the gaps between atoms? What are the properties of nothing?

On the hunt for dark matter

8 hours ago

New University of Adelaide Future Fellow Dr Martin White is starting a research project that has the potential to redirect the experiments of thousands of physicists around the world who are trying to identify the nature ...

Water window imaging opportunity

Aug 21, 2014

Ever heard of the water window? It consists of radiations in the 3.3 to 4.4 nanometre range, which are not absorbed by the water in biological tissues. New theoretical findings show that it is possible to ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

gongii
not rated yet Oct 02, 2007
Why can't the dark matter decay into other than X-rays. Can the gamma ray bursts mean something?
s0cratus
not rated yet Apr 23, 2009
Matter and %u2018dark matter.%u2018
Fact and Speculation.
=========.
1.
Fact.
The detected material mass of the matter in the Universe is so small
(the average density of all substance in the Universe is approximately
p=10^-30 g/sm^3) that it cannot %u201C close %u201C the Universe and therefore
our Universe as whole is %u201C open%u201D, endless.
But what to do with the infinite Universe the physicists don't know.
The concept of infinite/ eternal means nothing
to a scientists. They do not understand how they could
draw any real, concrete conclusions from this characteristic.
A notions of "more", "less", "equally, "similar" could not
be conformed to a word infinity or eternity.
The Infinity/Eternity is something, that has no borders,
has no discontinuity; it could not be compared to anything.
Considering so, scientists came to conclusion that the
infinity/eternity defies to a physical and mathematical definition
and cannot be considered in real processes.
Therefore they have proclaimed the strict requirement
(on a level of censor of the law):
« If we want that the theory would be correct,
the infinity/eternity should be eliminated ».
Thus they direct all their mathematical abilities,
all intellectual energy to the elimination of infinity.
Therefore they invented an abstract "dark matter" and " dark energy".
They say: " 90% or more of the matter in the Universe is unseen.
And nobody knows what it is.
2.
Speculation.
Unknown %u201Cdark matter %u201C it is matter which makes up the difference
between observed mass of a galaxies and calculated mass%u2026%u2026
which%u2026.will %u2026%u201D close %u201C %u2026.the Universe, as %u2026%u2026.
as%u2026%u2026the astrophysicists want.
#.
The Dark Matter is another official dogma of our astronomy.
/ V. H. Vergon. /
#
"Dark energy, this mysterious stuff in the vacuum of space
which makes the universe want to accelerate, is the basis
for standard cosmology today because it explains much
of what we see,"
/ Research by Dr David Wiltshire, from
New Zealand's University of Canterbury /.
#
Dark Energy may be Vacuum
http://www.eureka...1607.php
============= . .
My opinion.

The Dark Energy is the Vacuum.
Vacuum is not a dead space as the Classic Physics says.
Vacuum is some kind of Energetic Space as the
Quantum Theory says.
The Energetic Vacuum itself is %u2018 The Dark Energy %u2018.
The physicists only invent new word %u2018Dark Energy %u2018 instead of
to say %u2018 ENERGETIC VACUUM %u2019.
========== . .
Everything began from Infinite Energetic Vacuum: T=0K.
Somehow, the energy is extracted from the Vacuum
(the Energetic Dirac Soup) and turned into particles.
The Materialistic World gets its finite being
from an Infinite Energetic Being %u2013 Vacuum: T=0K.

To understand this %u2018speculation%u2019 we must know:
1. What is Vacuum: T=0K ?
2. Which virtual particles can exist in Vacuum?
3. How can virtual particles turn into real particles?
======== .
Until now the physicists ignore the Vacuum Energy T=0K
because it is the Zero Point Energy for our measuring devices.
Because the Absolute Zero Point Energy is border for our
measuring devices.
Can this fact be enough reason to stop our investigation?
==========..
#
When the next revolution rocks physics,
chances are it will be about nothing%u2014the vacuum, that endless
infinite void.
http://discoverma...cs/space
http://discoverma...erything
================ . .
Please, have patience and wait %u201Cwhen the next revolution rocks physics.%u201D
===============. .
Best wishes.
Israel Sadovnik. / Socratus.
http://www.physfo...pic=2548
http://www.wbabin...vnik.htm
http://www.socratus.com