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| Could there finally be tangible evidence for the existence of dark matter in the Universe? After sifting through reams of X-ray data, scientists in EPFL's Laboratory of Particle Physics and Cosmology (LPPC) and Leiden University believe they could have identified the signal of a particle of dark matter. |
Could there finally be tangible evidence for the existence of dark
matter in the Universe? After sifting through reams of X-ray data,
scientists in EPFL's Laboratory of Particle Physics and Cosmology (LPPC)
and Leiden University believe they could have identified the signal of a
particle of dark matter. This substance, which up to now has been
purely hypothetical, is run by none of the standard models of physics
other than through the gravitational force. Their research will be
published next week in Physical Review Letters.
When physicists study the dynamics of galaxies and the movement of
stars, they are confronted with a mystery. If they only take visible
matter into account, their equations simply don't add up: the elements
that can be observed are not sufficient to explain the rotation of
objects and the existing gravitational forces. There is something
missing. From this they deduced that there must be an invisible kind of
matter that does not interact with light, but does, as a whole, interact
by means of the gravitational force. Called "dark matter," this
substance appears to make up at least 80% of the Universe.
Andromeda and Perseus revisited
Two groups have recently announced that they have detected the much
sought after signal. One of them, led by EPFL scientists Oleg Ruchayskiy
and Alexey Boyarsky, also a professor at Leiden University in the
Netherlands, found it by analyzing X-rays emitted by two celestial
objects -- the Perseus galaxy cluster and the Andromeda galaxy. After
having collected thousands of signals from the ESA's XMM-Newton
telescope and eliminated all those coming from known particles and
atoms, they detected an anomaly that, even considering the possibility
of instrument or measurement error, caught their attention.
The signal appears in the X-ray spectrum as a weak, atypical photon
emission that could not be attributed to any known form of matter. Above
all, "the signal's distribution within the galaxy corresponds exactly
to what we were expecting with dark matter, that is, concentrated and
intense in the center of objects and weaker and diffuse on the edges,"
explains Ruchayskiy. "With the goal of verifying our findings, we then
looked at data from our own galaxy, the Milky Way, and made the same
observations," says Boyarsky.
A new era
The signal comes from a very rare event in the Universe: a photon
emitted due to the destruction of a hypothetical particle, possibly a
"sterile neutrino." If the discovery is confirmed, it will open up new
avenues of research in particle physics. Apart from that, "It could
usher in a new era in astronomy," says Ruchayskiy. "Confirmation of this
discovery may lead to construction of new telescopes specially designed
for studying the signals from dark matter particles," adds Boyarsky.
"We will know where to look in order to trace dark structures in space
and will be able to reconstruct how the Universe has formed."
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