For the first time, astronomers used supermassive black holes immediately after the Big Bang to measure the rate of expansion of the Universe. Now we have a big mystery than the answer given by these efforts.
It turns out that the Universe is growing faster than expected. This may mean that the dark energy, which is thought to drive the acceleration of this expansion, also sometimes interpreted as the cosmological constant described by Albert Einstein, is not so cosmologically constant after all.
Instead, it can become stronger.
The rate of expansion of the universe is called the Hubble constant, and it was incredibly difficult to determine. It seems that each test gives its result; Recently, data from Planck's satellite, which measured the cosmic microwave background, set it at 67.4 kilometers (41.9 miles) per second per megaparsec with an uncertainty of less than 1 percent.
Other methods typically include the use of “standard candles”, objects with known luminosities, such as Cepheid variable stars or Type Ia supernovae, from which distances can be calculated based on their absolute value.
Last year, the calculation of the variable cepheid star for Hubble's constant gave a result of 73.5 kilometers (45.6 miles) per second per megaparsec. So you can understand why astronomers continue to poke at this strange space bear.
But a few years ago, astronomers realized that the distance to another object could also be calculated accurately. Enter the quasars along with your black holes.
Quasars are among the brightest objects in the universe. Each of them is a galaxy that revolves around a supermassive black hole, actively feeding on material. Its light and radio emission is caused by material around a black hole, called an accretion disk, which emits intense light and heat from friction, because it circulates like water circulating in a sewer.
They also emit x-ray and ultraviolet radiation; and, as astronomers Guido Figsaly of the University of Florence, Italy, and Elizabeth Lussau of the University of Durham, UK, discovered, the ratio of these two wavelengths produced by the quasar varies with the UV luminosity.
Once this brightness is known, as calculated from this relationship, the quasar can be used just like any other standard candle.
This means that we can continue to measure the history of the universe.
“The use of quasars as standard candles has great potential, since we can observe them at a much greater distance from us than type Ia supernovae, and thus use them to study much earlier epochs in the history of space,” said Lusso.
The researchers collected ultraviolet radiation data on 1,598 quasars for just 1.1–2.3 billion years after the Big Bang and used their distances to calculate the expansion rate of the early Universe.
They also compared their results with the results of type Ia supernovae, which span the last 9 billion years, and found similar results where they overlap. But in the early Universe, where only quasars provide measurements, there was a mismatch between what they observed and what was predicted based on the standard cosmological model.
“We observed quasars just a billion years after the Big Bang and found that the rate of expansion of the Universe until today was faster than we expected,” said Risaly.
"This may mean that dark energy becomes stronger with the age of the cosmos."
We really do not know what dark energy is – we cannot see or detect it. It’s just a name that we give to an unknown repulsive force that seems to accelerate the expansion of the Universe over time.
(Based on this expansion rate, astrophysicists estimate that dark energy is about 70 percent of the Universe, so a more accurate expansion rate will also give us a more accurate calculation of the amount of dark energy.)
If the density of dark energy increases with time, scientists believe that this means that it is not Einstein’s cosmological constant. But that would explain strange numbers — and perhaps even a mismatch between the previous results of the Hubble constants.
At the moment, there is still a lot of work to check this result and see how stable it is.
“This model is quite interesting, because it can solve two puzzles at the same time, but the jury has definitely not been announced yet, and we will have to consider many more models before we can solve this space puzzle,” said Drawaly.
“Some scientists have suggested that new physics may be required to explain this inconsistency, including the likelihood that dark energy is growing in strength. Our new results are consistent with this assumption. ”
Team research was published in the journal Astronomy of nature, and can be read completely on the arXiv preprint resource.