(ORDO NEWS) — Black holes could explain the mysterious form of energy that astronomers believe makes up much of the universe.
The existence of “dark energy” has been made based on observations of stars and galaxies, but it has not been possible to explain what it is and where it comes from.
The substance or matter that makes up the familiar world around us is only 5 percent of everything that is in the universe.
Another 27 percent is dark matter, the shadow counterpart of ordinary matter that does not emit, reflect, or absorb light. However, most of the cosmos – about 68 percent – is made up of dark energy.
The study is being conducted by 17 astronomers from nine countries and led by the University of Hawaii.
The collaboration involved UK researchers based at STFC RAL Space, The Open University and Imperial College London.
By examining data spanning nine billion years of cosmic history, astronomers have found the first evidence of a “cosmological connection,” which would mean that the growth of black holes over time is linked to the expansion of the universe itself.
The idea that black holes might contain something called vacuum energy (a manifestation of dark energy) is not particularly new and was actually discussed theoretically as early as the 1960s.
But this latest work assumes that this energy (and thus the mass of black holes) will increase with time as the universe expands as a result of cosmological coupling.
The team calculated how much of the dark energy in the universe could be associated with this process. They found that black holes could potentially explain the total amount of dark energy we measure in the universe today.
The result could solve one of the most fundamental problems of modern cosmology.
Fast expansion
Our universe began with the Big Bang about 13.7 billion years ago. The energy of this explosion of space and time caused the universe to expand rapidly, and all the galaxies flew apart from each other.
However, we expect this expansion to gradually slow down due to gravity. about everything in space.
This is the version of the universe we thought we were living in until the late 1990s, when the Hubble Space Telescope discovered something strange.
Observations of distant exploding stars have shown that the universe actually expanded more slowly in the past than it does today.
Thus, the expansion of the universe was not slowed down due to gravity, as everyone thought, but instead accelerated. It was very unexpected, and astronomers struggled to explain it.
To explain this, it has been suggested that “dark energy” is responsible for pushing things apart more than gravity pulls them together.
The concept of dark energy was very similar to the mathematical construct proposed by Einstein but later rejected, the “cosmological constant” that opposes gravity and keeps the universe from collapsing.
Star explosions
But what is dark energy? The solution seems to lie in another cosmic mystery: black holes. Black holes are usually born when massive stars explode and die at the end of their lives.
The gravity and pressure from these strong explosions compress a huge amount of material into a small space.
For example, a star of about the same mass as our Sun would be crushed in a space of only a few tens of kilometers.
The attraction of a black hole is so strong that even light cannot escape it – everything is sucked in. At the center of a black hole is a place called a singularity, where matter is crushed into a point of infinite density.
The problem is that singularities are a mathematical construct that should not exist.
Black holes located at the centers of galaxies are much heavier than those that are born when stars die violently.
These galactic “supermassive” black holes can weigh millions and billions of times the mass of our Sun.
All black holes grow in size by accumulating matter, swallowing stars that come too close, or by merging with other black holes. So we expect them to get bigger as the universe ages.
In the latest paper, the team examined supermassive black holes at the centers of galaxies and found that these black holes gain mass over billions of years.
Radical rethinking
The team compared past and present observations of elliptical galaxies lacking star formation.
These dead galaxies have used up all their fuel, so any increase in the mass of their black holes during this time cannot be attributed to the usual processes by which black holes grow by accumulating matter.
Instead, the team hypothesized that these black holes actually contain a vacuum of energy and that they are “linked” to the expansion of the universe, such that their mass increases as the universe expands.
This model neatly provides a possible origin for dark energy in the universe. It also circumvents the mathematical problems that affect some black hole studies because it avoids the need for a singularity at the center.
The team also calculated how much dark energy in the universe could be associated with this pairing process. They concluded that black holes could provide the necessary amount of vacuum energy to explain all the dark energy we measure in the universe today.
This not only explains the origin of dark energy in the universe, but also forces us to radically rethink our understanding of black holes and their role in space.
Much more work needs to be done to test and confirm this idea, both from observations of the sky and from theory. But perhaps we will finally see a new way to solve the problem of dark energy.
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