No need for Planet Nine? Small items of gravity could explain weird jobs

An artist’s image of Sedna, which started to be the extremely distant orbit by the collective gravity of many small objects.


DENVER — a Small but noisy space rocks push and push each other to have made the unusual jobs some astronomers refer to as the signature of the hypothetical Planet Nine,” a new study suggests.

To date, researchers have discovered more than 2,300 bodies in the cold, isolated area, outside the orbit of Neptune. The huge number of these trans-Neptunian objects (TNOs) makes it computationally intensive models of the evolution of their jobs. However, the new study suggests that the complex gravity dancing under the TNOs can be enough to send some, such as the dwarf planet Sedna, strange and intriguing paths.

“The picture we have in our head is a lot of small moons floating around the solar system, the interaction with comets,” Ann-Marie Madigan, an assistant professor in the Department of Astrophysical and Planetary Sciences at the University of Colorado in Boulder (CU-Boulder), said during a press conference today (4 June). [The Search for Planet Nine, in Photos]

Madigan and CU-Boulder student Jacob Fleisig presented the results here at the 232nd meeting of the American Astronomical Society in Denver.

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No need for Planet Nine?

The Kuiper Belt, the region immediately beyond Neptune, ports TNOs of many sizes. The largest of these is Pluto, which was discovered more than 60 years for one of the others.

Some TNOs are “free-standing objects, which orbit far from the sun that they are not significantly influenced by the gravity of Neptune or any other known planet. Perhaps the most famous of these is Sedna, which is 11,400 years to make one orbit and never comes closer to the sun than 20 times farther than Pluto.

In 2016, astronomers Konstantin Batygin and Mike Brown is known that a distant undiscovered planet might have made of the unusual signatures of some of the TNO orbits in the Kuiper Belt, and sent to Sedna and other free-standing objects to even more remote areas. Batygin and Brown calculated that, in this world, called Planet Nine, 10 times more mass than the Earth and the orbit of the sun about 20 times farther away than Neptune does.

But not everyone is on board with the Planet Nine hypothesis. The skeptics are Madigan and Fleisig, who, together with the study co-author Alexander Zderic, a UC Boulder student, think they have found an alternative solution for the strange orbital signatures.

According to the researchers’ simulations, the TNOs move, like the hands of a clock, with the most massive objects slowly, like the hour hand, and the smaller tap quickly, like the minute hand. The result is that smaller bodies are piling up fast — and their accumulated force of gravity is strong enough to reshape the paths of larger TNOs that are in your area.

Eventually, the bigger pieces of wind in extreme jobs, just like Sedna.

“They are what is the cause of this detachment, and not an unseen ninth planet,” Fleisig said during the press conference. [Our solar system: A Photo Tour of the Planets]

The severity of the situation

If this is the answer to the TNO-puzzle, why has no one else noticed? Madigan and Fleisig said, the problem is one of scale. It is computationally expensive to a mass for each of the thousands of TNOs, so most simulations let them massless, who denies how they handle gravity. [Trans-Neptunian Objects in the Extreme Outer solar system (Infographic)]

“The crucial difference is their mass in the simulation,” said Madigan

The researchers do not add mass to all of the TNOs, only up to about 400. But that was enough to the most massive objects in bizarre jobs.

The collective-gravity hypothesis is not a silver bullet, however. For example, there is still “clustering in pomega,” that Madigan described as the odd fact that the orbits of the detached objects, all tilt the same way.

“Planet Nine explains this very well, and we’re not doing it,” Madigan said.

Ironically, while the new research discounts the need for an undiscovered planet, it requires the presence of thousands of smaller invisible objects.

“The handful we’ve seen is not enough,” Fleisig said.

Madigan told that the early solar system was filled with enough debris to build dozens of Earths, but in much smaller pieces. Because most of the objects are modeled massless most of the studies dispose of the mass of the solar system. Adding mass means that there is more of that material might have to hang around, their smaller size to keep is detected.

“The objects that we have seen so far, are just the tip of the iceberg,” Fleisig said.

While the small size of most TNOs makes it a challenge to detect their movement and makes it even harder. Usually, the bigger an object is, the easier it is to discover. But because the largest objects are hurled into the most eccentric orbits, they are harder to find, the researchers said.

In addition, the presence of the tiny hand already spotted suggests a larger population, Madigan said.

“If there are only 10 out there, and we detected a 10, it’s bizarre, a lot of luck,” she said.

The death of the dinosaurs

The gravitational interaction between the TNOs can also explain the other strange event: the extinction of the nonavian dinosaurs about 65 million years ago.

Previous studies have suggested that the mass extinction can occur with regularity, and some researchers have linked this observed frequency of pulses from comet or asteroid impacts. What could lead to a cyclical rain of death? Other researchers have cited dark matter or of the sun hypothesis unseen companion star, Nemesis, and candidates. (Nemesis has never been exhibited and is dismissed by most scientists.)

Madigan called this impact-extinction cycle idea “geology of the Planet Nine” — an unknown connection, she said, is under discussion in geological circles.

If the small gravitational interactions between the TNOs are hurling objects like Sedna to beyond, they were also some of the rocks in the inner solar system. Fleisig said the team of the model makes periodic comet showers for the rocky planets, including the Earth. While the researchers could not directly connect their comments to the collision that wiped out the dinosaurs and most life on Earth, Fleisig called the possibility “exciting.”

“It is exciting and evocative,” Madigan said.

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