For the first time, astronomers used supermassive black holes only after the Great Bang for measuring the rate of expansion of the Universe. Now, we have a greater mystery of our hands than the response that gives this effort.
It turns out that the universe is growing faster than expected. This could mean that the dark energy that is believed to promote the acceleration of this expansion, sometimes interpreted as the cosmological constant described by Albert Einstein, is not so cosmologically constant after all.
Instead, it could grow stronger.
The rate of expansion of the universe is called Hubble Constant, and it is incredibly difficult to determine. Each test seems to have a different result; Recently, Planck satellite data, measuring the cosmic microwave background, was set at 67.4 kilometers per second per megaparse, with uncertainty of less than 1 percent.
Other methods usually include the use of "standard candles", objects of known light such as cepheid variable stars or type Ia supernova, from which distance can be calculated on the basis of their absolute size.
Last year, the calculation of the cepheid variable of the star Hubble Constant resulted in a score of 73.5 kilometers (45.6 miles) per second per megaparsec. So, you can see why astronomers are continually tormenting this strange cosmic bear.
But a few years ago, astronomers realized that the distance to another object can be calculated accurately. Enter quasars, along with their black holes.
Quasars are among the brightest objects in the universe. Each of them is a galaxy that orbits the supermassive black hole actively feeding the material. Its light and radio shows are caused by a material around a black hole, called a accretion disk, which emits intense light and friction heat, as it spins like circulating water in brains.
They also emit X-rays and ultraviolet light; and, as the astronomers of Guido Rizaliti of the Università di Firenze, Italy and Elizabeta Luso from the University of Durham, Great Britain discovered, the ratio of these two wavelengths produced by a quasar varies depending on ultraviolet luminosity.
Once this known light is known, as calculated from this relationship, the quasar can be used like any other standard candle.
And that means we can measure it farther back in the history of the universe.
"The use of quasars as standard candles has great potential because we can observe them at far greater distances than us from a type Ia supernova and so use them to explore much earlier eras in the history of the cosmos," Luso said.
The researchers compiled UV data for 1,598 quasars from just 1.1 billion to 2.3 billion years after the Big Bang and used their distances to calculate the rate of expansion of the early Universe.
They also crossed their results against the results of Ia-type supernatants covering the last 9 billion years, and found similar results when they overlap. But in the early Universe, where only the quasars offer measurements, there was a discrepancy between what they noticed and what was predicted on the basis of the standard cosmological model.
"We monitored the quasars back in just one billion years after the Big Bang, and we found that the rate of expansion of the universe to date is faster than we expected," Rizaliti said.
"This could mean that dark energy becomes stronger, because the cosmos becomes older."
We really do not know what the dark energy is – we can not see it or find it. It's just the name we give to an unknown repulsive force that seems to accelerate the expansion of the Universe over time.
(Based on that expansion rate, astrophysicists calculated that dark energy represents about 70 percent of the universe – so more precise expansion will give us a more precise calculation of dark energy.)
If the density of dark energy increases over time, scientists believe it would mean that this is not Einstein's cosmic constant after all. But it will explain strange numbers – and perhaps even the difference between Hubble Constant's previous results.
For now, there is still a lot of work to be done to test this result and see if there is a hard work.
"This model is quite interesting because it can solve two puzzles at once, but the jury is definitely not out and we will need to look at many more models in detail before we can solve this cosmic puzzle," Rizaliti said.
"Some scientists have suggested that new physics may be needed to explain this discrepancy, including the possibility that dark energy is growing with strength. Our new results agree with this proposal."
The team's research is published in the journal Nature Astronomy, and can be read in full on the arXiv printing resource.