A new wave of researchers is setting out to help shed light on the unseen forces shaping the universe, and keep Europe at the forefront of experimental cosmology.
The XENON Dark Matter Project buried in a mountain in Italy is looking for a hypothetical type of particle that could make up dark matter. © XENON Dark Matter Project
Earlier this year, Dr Alexey Boyarsky at Leiden Observatory in the Netherlands discovered what could be indirect evidence of dark matter, while researchers at the European Space Agency (ESA) are now developing a probe that will try to measure dark energy, the unseen force believed to be driving the accelerated expansion of the universe.
They are using Europe’s Planck satellite to map cosmic microwave background radiation. ‘The Planck satellite has been the best tool on offer for these broad scales,’ said physicist René Laureijs of the ESA, who believes Europe has become the global home of experimental cosmology.
To cement Europe’s position, the EU-funded Invisibles project is training over 200 scientists to hunt neutrinos, dark matter and dark energy, which constitute the mysterious ‘dark sector’ of the universe and are essential to its cosmological evolution.
‘Our aim is to lift the curtain on this dark sector, while providing training for the next generation of scientists who will lead this quest in the future,’ said project coordinator Professor Belén Gavela.
The idea of dark matter came about some 80 years ago when researchers realised that galaxies were spinning so fast that centrifugal force should have torn them apart based on the amount of gravitating matter visible inside them.
‘The scientific questions we’re trying to answer go to the core of that human quest to find out what nature’s made of.’
Swiss astronomer Fritz Zwicky postulated in 1933 that the galaxies must contain some sort of additional ‘dunkle Materie’, or dark matter, to bind them together. Researchers now believe there is more than five times as much dark matter in the universe as normal matter, yet they still do not know what it is.
Using XMM-Newton, an orbiting observatory run by the ESA, Dr Boyarsky and his team recorded a signal of X-ray photons that have about the right energy – 3.5 kiloelectron-volts – to have been produced when ‘sterile neutrinos’ decay somewhere in the distant cosmos.
This is significant because some researchers believe that so-called sterile neutrinos could be components of dark matter.
Dark energy
However, dark matter is not the biggest mystery facing cosmology. Dark energy makes up two-thirds of all mass–energy, researchers believe, and by using the Planck satellite to study the microwave background, cosmologists can test their leading theory of the universe’s evolution, known as the lambda-CDM (cold dark matter) model, where the ‘lambda constant’ refers to dark energy.