Scientists have discovered the dark matter which had been lost since the birth of the universe. For the first time ever, about 5 per cent of the elusive dark matter in the universe has been discovered. This dark matter has been lost since Big Bang.
“The discrepancy between the cosmological parameters in the modern Universe and the Universe shortly after the Big Bang can be explained by the fact that the proportion of dark matter has decreased,” said Igor Tkachev, from the Institute for Nuclear Research (INR) of the Russian Academy of Sciences.
“We have now, for the first time, been able to calculate how much dark matter could have been lost and what the corresponding size of the unstable component would be,” said Tkachev.
In 1930s, it was believed that a large proportion of ‘hidden mass’ was there in the universe. Scientists had then discovered “peculiarities” in a cluster of galaxies which moved as if they were under the effect of gravity from an unseen source.
The proportion of dark matter in the universe is 26.8 per cent, while the rest is ordinary matter (4.9 per cent) and dark energy (68.3 per cent), the data from the European Space Agency (ESA)’s Planck space telescope suggests.
A problem that arose after studying observations from the Planck telescope could now be solved using the properties of dark matter.
The fluctuations in the temperature of the cosmic microwave background radiation - the “echo” of the Big Bang was measured by this device.
Measuring these fluctuations enabled the researchers to calculate key cosmological parameters using observations of the universe in the - about 300,000 years after the Big Bang.
Parameters which describe the rate of expansion of the universe and those associated with the number of galaxies in clusters vary significantly with data obtained from observations of the modern universe, said Tkachev.
The discrepancy can be explained by the decaying dark matter (DDM) hypothesis, which states that in the early universe there was more dark matter, but then part of it decayed.
Researchers analysed Planck data and compared them with the DDM model and the standard Lambda-Cold Dark Matter model with stable dark matter. The comparison showed that the DDM model is more consistent with the observational data.
However, the researchers found that the effect of gravitational lensing greatly limits the proportion of decaying dark matter in the DDM model.
The data from observations of various cosmological effects allowed the researchers to give an estimate of the relative concentration of the decaying components of dark matter in the region of 2% to 5%.
“This means that in today’s universe there is 5 per cent less dark matter than in the recombination era,” said Tkachev.
The study appears in the journal Physical Review D.
(With inputs from PTI)