A team of astrophysicists has made an unusual discovery that they say appears to challenge our current understanding of gravity based on Newton’s law of universal gravitation, according to a newly published paper.
The controversial claim, published on Monthly Notices of the Royal Astronomical Society, appears to be consistent with alternative interpretations of one of the most mysterious fundamental interactions in physics.
In their new study, an international team of astrophysicists say they made the discovery while surveying open star clusters. These formations are created as a cloud of gas emerges after the birth of thousands of stars in a relatively short period of time, the remnants of which are ejected as these star clusters ignite and begin to expand, which can result in the formation of anywhere from several tens, to many thousands of new stars.
The role of gravity in this process includes how weak gravitational forces essentially serve as the glue that contains these star clusters and holds them together. Able to survive for hundreds of millions of years, these clusters eventually begin to lose stars over time, resulting in the formation of a pair of “tidal tails,” one of which is dragged behind the open star cluster as it is propelled into space. while the other protrudes in front of the formation.
Based on Newton’s law of universal gravitation, we would expect the process of how various stars in the cluster are allocated to any of these tidal tails to be completely random. However, this was not the case according to the team involved in the recent study, which found that one of the two tails was clearly capable of outstripping its star-grabbing counterpart.
“In the clusters we studied, the front tail always contains significantly more stars close to the cluster than the back tail,” according to Dr. Jan Pflamm-Altenburg, Helmholtz Institute for Radiation and Nuclear Physics.
“The asymmetry between the number of stars in the main and trailing tail tests the theory of gravity,” the authors wrote in their paper.
Dr Tereza Jerabkova, one of the paper’s co-authors, says the research team was the first to develop the method they used to estimate the number of stars distributed in the pair of tidal tails in star clusters.
“When we analyzed all the data, we met [a] contradicting current theory,” Jerabkova said in a statement, adding that the level of data precision the team had in survey data from ESA’s pioneering Gaia mission was “necessary” to make their observations.
If not the traditionally accepted Newtonian concept of gravity, then what do these new, contradictory data seem to show about the weakest of the four fundamental forces?
The research team believes that a theory of gravity involving what is appropriately known as Modified Newtonian Dynamics (MOND) may provide the answer. Proponents of MOND argue that observations of galaxies and their properties indicate the need for modifications to Newton’s law of universal gravitation. Importantly, such ideas could potentially solve problems such as the dark matter question, offering alternative models to explain the behavior of galaxies, which in many cases do not seem to obey the laws of physics as we understand them today.
“Simply put, according to MOND, stars can leave a cluster through two different doors,” says Pavel Krupa, lead author of the study, who added that where one “door” leads to the tidal tail that facing forward and the other to the one behind the cluster.
However, as Krupa notes, “the former is much narrower than the latter — so a star is less likely to escape the cluster through it.”
“Newtonian theory of gravity, on the other hand, predicts that both doors should be the same width,” says Krupa.
Although team members express that the current tools available to physicists that might help them analyze possible modifications required for Newtonian dynamics are limited, simulation-based calculations nevertheless appear to be able to accurately predict the lifetimes of open star clusters.
This, according to the research team, is much smaller than what Newton’s laws seem to allow, and for Kroupa and her team, this may even explain the mystery of why star clusters in galaxies near our own they have been observed to disappear faster than astronomers expect.
Of course, theories that require major changes to our existing models of how the universe works are generally slow to gain favor with scientists. Modifications to Newton’s theory of gravity, while useful in resolving such observations as those in the team’s recent study, will also have broader implications that could potentially extend to almost all areas of physics. But for Kroupa and her team, accepting and incorporating such ideas into our knowledge of the universe would be more useful overall than anything else.
“[I]it solves many of the problems that cosmology faces today,” says Krupa.
The team’s paper, “Asymmetric tidal tails of open star clusters: cluster-crossing stars induce Newtonian gravity,” was published in Monthly Notices of the Royal Astronomical Society.
Micah Hanks is editor-in-chief and co-founder of The Debrief. Watch his work at micahhanks.com and on Twitter: @MicahHanks.
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