by The universe may be younger than we think, based on the movements of satellite galaxies that show how far they have collapsed into a group of galaxies.
According to the measurement of the Cosmic microwave background radiation (CMB) at the European Space Agencyplanck mission, the universe is about 13.8 billion years old. This calculation is based on what is known as the Standard Model cosmologywhich describes a flat dominated universe dark energy and dark dark and is expanding at an accelerating rate.
The IS Standard Model is then used as a basis for supercomputer simulations that can demonstrate the growth of large-scale structures i the universe — galaxies, galaxy clusters and giant chains and galactic walls.
However, these models have now deteriorated in relation to new measurements of pairs of movements galaxies which is not consistent with what the simulations are telling us.
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In a new study, astronomers led by Guo Qi from the National Astronomical Observatories of the Chinese Academy of Sciences studied pairs of satellites in galaxy groups.
Galaxy groups, such as our own Local Group, are small collections of galaxies in which several large galaxies are connected to a cluster of smaller ones. Like larger galaxy clusters, these galaxy groups form where there are filaments in the cosmic web of material that travels across the universe together, with smaller galaxies moving along the filaments before collapsing into a group.
Using observations made by the Sloan Digital Sky Survey (SDSS) of 813 galaxy groups within about 600 million light year from WorldQi’s team focused on the most massive galaxy in each group and measured how it pairs satellites on the other side of that galaxy moved.
They found that the fraction of satellite galaxies that were counter-rotating with respect to each other – in other words, the giant galaxy orbits in opposite directions – is higher than predicted by computer simulations of large-scale structure , such as the Millennium Simulation and the Illustris TNG300 model, both of which are based on the Standard Model as described by the Planck mission.
This is a natural situation if the satellites have just fallen into orbit around the group’s largest galaxy. But above time, galaxy groups and clusters should reach a relaxed dynamical state, with most of the satellites rotating. If groups of galaxies and clusters came together when the Standard Model suggests they should, the fraction of counter-rotating satellites should be smaller. A problem for the Standard Model is that they are a larger fraction of satellites.
“We found in the SDSS data that satellite galaxies are accreting/collapsing into the massive groups, with a stronger signal of ongoing assembly compared to simulations with Planck parameters,” Qi told Space.com in an email .
In other words, the satellite galaxies appear to have only recently fallen into their respective groups.
“This suggests that the universe is younger than Planck’s observations of the CMB suggested,” Qi said. “Unfortunately, this work cannot estimate the age of the universe in a quantitative way.”
This is because the movements of the satellite pairs and models of how groups form still have too much freedom to be able to put a firm figure on how much younger than 13.8 billion years these results suggest know that the universe.
If correct, the new results suggest that something is wrong with the Standard Model, and that some of our assumptions about the universe must be wrong. In fact, one cosmic paradox that scientists are currently investigating may be the answer.
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The expansion rate of the universe is defined by a number called the the Hubble constant. Planck measured the Hubble constant as 67.8 kilometers per second per megaparsec — in other words, every megaparsec volume of space increasing 67.8 kilometers (42.1 miles) every second. (One megaparsec is about (3.26 million light years.) Based on this expansion rate, cosmologists are able to calculate the age of the universe as 13.8 billion years by rewinding the clock.
However, observations of the redshift of Type Ia supernovawhich is exploding white dwarf, give the value of the Hubble constant as 73.2 kilometers (45.5 miles) per second per megaparsec. At this rate of expansion, rewinding the clock would give a younger age of 12.6 billion years.
Both measurements of the Hubble constant are considered incontrovertible, and yet they differ greatly. This paradox is called “Hubble tension.”
“This could be related to the Hubble tension problem of course,” Qi said when asked if the younger age suggested by satellite pairs in galaxy groups supports the faster accretion rate from the supernova measurements.
However, there are other obstacles to overcome. If we lower the age of the universe too much, then astronomers will be in a difficult position stars is known to be older than the universe itself.
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Perhaps the explanation lies with other aspects of the Standard Model. For example, the model relies heavily on dark matter, but so far scientists don’t know what dark matter is. Other researchers argue that dark matter does not exist at all, and that its gravitational effects can be explained by a modification of the laws of gravity at low accelerations, such as those of longer orbiting satellite galaxies. Qi’s team found that pairs of satellites at larger orbital radii are more likely to rotate against each other.
For now, more details would be welcome. The same phenomenon should exist for larger galaxy clusters, Qi said, but clusters tend to be further away and due to the limited sample size and poorer data quality currently there is no definitive measurement.
The universe is ancient, whatever the correct age value, but these new results suggest that it may be able to pull back some of its youth.
The new results were published on 22 January in the journal Natural Astronomy.
