A new study suggests that the elusive Planet Nine, thought to be lurking somewhere in the outer reaches of the solar system, may not be a planet at all. Instead, what we assumed to be a massive object could be evidence of this gravity It doesn’t work like we thought it worked. But the new theory does not suit everyone.
the Planet Nine hypothesis, It was first proposed in 2016He argues that the unusual orbits of objects in the Kuiper Belt go beyond it Neptunewhich appears to have been pulled away the sunThis can be explained by the existence of an undiscovered ninth planet whose size is 10 times the mass of Earth. Astronomers have been searching for Planet Nine ever since. in spite of Searching nearly half of the night skySo far, they have come up empty-handed.
In the new study, published on September 22 Astronomical magazineResearchers have proposed another explanation for the gravitational anomalies observed in the outer solar system: the absence of any anomalies. Instead, the team showed that the discrepancies disappear completely when applying an alternative concept of gravity known as modified Newtonian dynamics (MOND).
Isaac Newton’s second law It states that the gravity pulling on an object is inversely proportional to the distance between the object and the object pulling it, which means that gravity becomes weaker as the distance between the two objects increases. But MOND modifies this and suggests that after a certain distance, the pull of gravity is directly proportional to the distance, meaning that the force of gravity does not decrease as quickly at greater distances. This suggests that objects orbiting a larger body at great distances, such as stars on the outskirts of spiral galaxies like the Milky Way, would experience a greater gravitational force than the second law suggests.
According to MOND, Kuiper belt objects are actually being pulled in by the rest of our galaxy, not by an undiscovered planet.
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The researchers were surprised by their findings. The initial goal of their study was to “rule out” MOND as a possible explanation for Planet Nine. However, when they applied it to the problem, it seemed to solve the problem completely.
“MOND is really good at explaining galaxy-scale observations,” said the study’s author Mathur is cruelA theoretical physicist at Case Western Reserve University in Ohio said: statement. “But I didn’t expect that it would have such noticeable effects on the outer solar system.”
It was mond It was first proposed in 1983 As an alternative to Dark matter — Invisible particles of unknown origin that supposedly make up 27% of the total matter in the universe, according to NASA. Dark matter has been proposed to explain the “missing mass problem”, which arose when astronomers realized that stars and planets alone could not explain the observed gravitational force of galaxies. But MOND suggests that if distant objects are experiencing greater gravity, there may not be as much mass lost as we initially thought.
However, MOND cannot explain all the missing mass in the universe, and therefore cannot completely rule out the idea of dark matter. Other studies have suggested this Reconciling MOND with quantum mechanics and relativity, “unconventional” things must be added to existing theoriesSome of these additions present a problem.
Related: The elusive Planet Nine could be surrounded by hot moons, and that’s how we’ll find it
Not everyone is convinced by the latest Planet Nine theory.
“I would be happy with the idea that what we thought was Planet Nine was really new physics.” Michael Brown, an astronomer at Caltech who co-proposed the Planet Nine hypothesis, told Live Science in an email. “But I think the chances are [of this being true] “It’s probably just a regular planet instead,” he added.
MOND is not the only alternative explanation for Planet Nine to emerge in recent years. Some experts have It has been suggested that the hypothetical planet is actually a small black hole Which pulls surrounding things inward.
But whether or not MOND is the answer to the mystery of Planet Nine, the study team believes the concept has a role to play in increasing understanding of our cosmic neighborhood.
“Whatever the outcome, this work highlights the potential for the outer solar system to serve as a laboratory for testing gravity and studying fundamental problems of physics,” said the study’s author. Catherine BrownThe theoretical physicist at Hamilton College in New York State said in the statement.
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