Elusive Planet Nine could be an alternative form of gravity masquerading as a planet, study claims

[admin]

Astronomers suggest that an alternative concept of gravity, known as modified Newtonian dynamics, could explain orbital inconsistencies that have previously pointed to the existence of a ninth planet in the solar system.

Elusive Planet Nine could be an alternative form of gravity masquerading as a planet, study claims : Read more

 

[Bruce Mardle]

"Isaac Newton's second law states that gravity tugging on an object is inversely proportional to the distance between the object and the object that is pulling it, meaning that gravity gets weaker as the distance between the two objects increases. But MOND tweaks this and suggests that past a certain distance, the gravitational pull is directly proportional to the distance..."
The second law states that the force of gravity is inversely proportional to the square of the distance. I guess MOND suggests that it's more like inversely proportional to the distance. If it were proportional to the distance it'd grow stronger the further apart things were, which would give a very different Universe!

 

[Hartmann352]

A theory developed to replace dark matter may mean bad news for Planet Nine, a hypothetical as-yet-unseen world in the outer solar system. The odd orbital alignments of icy objects in this region that were initially considered a smoking-gun signature for the putative planet’s gravitational influence could instead be caused by gravity itself behaving against expectations, some researchers say.

In 2016 astronomers proposed Planet Nine’s existence as a way of explaining a strange sort of clustering observed in several small bodies found in and beyond the Kuiper Belt, a distant region of the solar system containing Pluto and many other objects. But fervent searches for the planet have so far proved fruitless, leading some scientists to doubt Planet Nine’s existence.

So what else might explain the curious orbital patterns? One suggestion is modified Newtonian dynamics, or MOND. Originally developed to explain the surprisingly speedy rotations of galaxies without resorting to dark matter, today MOND is a collective term given to theories that assume the force of gravity does not always (as Isaac Newton and Albert Einstein insisted) follow the inverse square law. Variations of this law pop up everywhere in physics; for gravity, it would dictate that the gravitational force between two objects is inversely proportional to the square of the distance between them. MOND’s success as a dark matter alternative has been limited, however, because most astrophysicists remain convinced that the universe we see around us is better accounted for by theories that incorporate the mysterious invisible substance.

MOND has typically been used to explain wide-scale galactic phenomena. But when theoretical physicists Katherine Brown of Hamilton College and Harsh Mathur of Case Western Reserve University realized that its effects should be measurable at the outskirts of the solar system, they decided to see how it could affect the proposed Planet Nine. Their new study was published on September 22 in the Astronomical Journal.

“We thought we would probably disrupt Planet Nine’s predictions a little bit through MOND,” Mathur says. “It took us completely by surprise when we found that, in fact, we could explain the whole alignment that is seen by MOND, and so it becomes an alternative to Planet Nine.”

OCTOBER 25, 2023
6 MIN READ

‘Modified’ Gravity May Make Planet Nine Disappear​

Strange patterns in the orbits of small objects in the outer solar system could be explained by gaps in our understanding of gravity rather than an as-yet-unseen new world

BY NOLA TAYLOR TILLMAN

See: https://www.scientificamerican.com/article/modified-gravity-may-make-planet-nine-disappear/

A new class of Kuiper Belt objects (KBOs) that lie beyond Neptune with semimajor axes greater than 250 astronomical units show orbital anomalies that have been interpreted as evidence for an undiscovered ninth planet. We show that a modified gravity theory known as modified Newtonian dynamics (MOND) provides an alternative explanation for the anomalies using the well-established secular approximation. We predict that the major axes of the orbits will be aligned with the direction toward the Galactic center and that the orbits cluster in phase space, in agreement with observations of KBOs from the new class. Thus, MOND, which can explain galactic rotation without invoking dark matter, might also be observable in the outer solar system.

See: https://iopscience.iop.org/article/10.3847/1538-3881/acef1e

There is the very real possibility that the ninth planet's just not there. Or it might not be a single planet at all, but a batch of rocks. Or, according to new research conducted by physicists Katherine Brown of Hamilton College and Harsh Mathur of Case Western Reserve University, what we have interpreted as evidence of a planet could instead be a sign that something is missing from our current model of gravity as described under general relativity. According to their recent study, the subtle abnormalities in the orbits of various objects some attribute to a hidden planet are also consistent with a different kind of gravitational model – one called Modified Newtonian Dynamics (MOND). MOND is an alternative paradigm of dynamics, seeking to replace Newtonian dynamics and general relativity. It aims to account for the ubiquitous mass discrepancies in the Universe, without invoking the dark matter that is required if one adheres to standard dynamics. I'm betting, as I always have, on Einstein.
Hartmann352