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Something is producing weird orbits in the Kuiper belt — is it 'Planet X' or something else?

Some have suggested that there is no hidden giant out there.

Photo credit: Daniel Olah on Unsplash
  • Some objects at the edge of our solar system have unusual orbits — they cluster together suggesting a large celestial body is pushing them close together.
  • Instead of a massive unfound planet, it may be the gravitational pull from an equally massive disc of small, icy objects.
  • Researchers created a model of such a disc that explained everything.

It's clear that something is warping the orbits of objects out at the edge of our solar system, but what that might be remains a matter of conjecture. Probably the most exciting theory is that it's a thus-unseen massive object popularly dubbed "Planet 9" or "Planet X," probably a better name as long as there's some debate about the status of the original Planet 9 — Pluto — and since "X" suggests the unknown at the same time as it's the Roman numeral for 10.

In any event, some have suggested that there is no hidden giant out there, but that the orbital distortions we're seeing are due to the pull of combined gravitational forces from a group of smaller trans-Neptunian objects (TNOs) in the icy Kuiper belt. This idea just got a strong boost from Antranik Sefilian, University of Cambridge, and Jihad Touma of the American University of Beirut in Lebanon.

They have, for the first time, developed a model that demonstrates how such a combination field could generate precisely the mysterious orbits that have been observed.

The problem Planet X solved and the problem with Planet X

Image source: Vadim Sadovski / Junk Peter / Shuterstock

Out at the edge of our solar system is an area of dwarf planets and icy rocks, the Kuiper belt. By and large, the orbits of these bodies, Kuiper belt objects (KBOs) , are influenced by our system's giant planets — Saturn, Jupiter, Uranus, and Neptune. However, a few years ago, five KBOs caught astronomers' attention by having orbits that cluster together, suggesting that some single thing is pushing them into close proximity to each other. (As of this writing, about 30 of these outliers have been spotted.)

Crunching the math to figure out what could be doing this led Caltech astronomers Konstantin Batygin and Mike Brown to propose the existence of a perturber, a massive planet that's 10 times the size of Earth and has an orbit extending some 20 times farther away from the Sun than Neptune. A full circuit would take Planet X between 10,000 and 20,000 years. By comparison, Neptune only requires 165 years to orbit the sun.

The main problem with Planet X is obvious. Astronomers' best efforts to see it, thus confirming its existence, have come up short so far.

KBOs for the TKO?

Image source: Mopic / Shutterstock

"The Planet Nine hypothesis is a fascinating one, but if the hypothesized ninth planet exists, it has so far avoided detection," says Sefilian. "We wanted to see whether there could be another, less dramatic and perhaps more natural, cause for the unusual orbits we see in some TNOs. We thought, rather than allowing for a ninth planet, and then worry about its formation and unusual orbit, why not simply account for the gravity of small objects constituting a disc beyond the orbit of Neptune and see what it does for us?"

So Sefilian and Touma began modeling behavior of the TNOs in the presence of the known solar system planets plus a disc of small icy bodies, out beyond Saturn, that together had a mass roughly that of the proposed Planet X. Their initial virtual disc explained the orbits of some of the observed TNOs, though not all. When they started playing with the composition of the disc, however, the remaining TNO orbits could be accounted for.

One potential gotcha with the disc hypothesis is that in order for a disc of sufficient mass to exist, the mass of the entire Kuiper Belt would have to be somewhere between a few times and 10 times Earth's mass.

Of course, Sefilian's and Touma's disc is thus far as unseen as Planet X. "The problem," explains Sefilian, "is when you're observing the disc from inside the system, it's almost impossible to see the whole thing at once. While we don't have direct observational evidence for the disc, neither do we have it for Planet 9, which is why we're investigating other possibilities. Nevertheless, it is interesting to note that observations of Kuiper belt analogs around other stars, as well as planet formation models, reveal massive remnant populations of debris."

So, Planet X or the newly proposed disc? Not need to choose yet, Sefilian says. "It's also possible that both things could be true — there could be a massive disc and a ninth planet. With the discovery of each new TNO, we gather more evidence that might help explain their behavior."

Hulu's original movie "Palm Springs" is the comedy we needed this summer

Andy Samberg and Cristin Milioti get stuck in an infinite wedding time loop.

Gear
  • Two wedding guests discover they're trapped in an infinite time loop, waking up in Palm Springs over and over and over.
  • As the reality of their situation sets in, Nyles and Sarah decide to enjoy the repetitive awakenings.
  • The film is perfectly timed for a world sheltering at home during a pandemic.
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Two MIT students just solved Richard Feynman’s famed physics puzzle

Richard Feynman once asked a silly question. Two MIT students just answered it.

Surprising Science

Here's a fun experiment to try. Go to your pantry and see if you have a box of spaghetti. If you do, take out a noodle. Grab both ends of it and bend it until it breaks in half. How many pieces did it break into? If you got two large pieces and at least one small piece you're not alone.

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Our ‘little brain’ turns out to be pretty big

The multifaceted cerebellum is large — it's just tightly folded.

Image source: Sereno, et al
Mind & Brain
  • A powerful MRI combined with modeling software results in a totally new view of the human cerebellum.
  • The so-called 'little brain' is nearly 80% the size of the cerebral cortex when it's unfolded.
  • This part of the brain is associated with a lot of things, and a new virtual map is suitably chaotic and complex.

Just under our brain's cortex and close to our brain stem sits the cerebellum, also known as the "little brain." It's an organ many animals have, and we're still learning what it does in humans. It's long been thought to be involved in sensory input and motor control, but recent studies suggests it also plays a role in a lot of other things, including emotion, thought, and pain. After all, about half of the brain's neurons reside there. But it's so small. Except it's not, according to a new study from San Diego State University (SDSU) published in PNAS (Proceedings of the National Academy of Sciences).

A neural crêpe

A new imaging study led by psychology professor and cognitive neuroscientist Martin Sereno of the SDSU MRI Imaging Center reveals that the cerebellum is actually an intricately folded organ that has a surface area equal in size to 78 percent of the cerebral cortex. Sereno, a pioneer in MRI brain imaging, collaborated with other experts from the U.K., Canada, and the Netherlands.

So what does it look like? Unfolded, the cerebellum is reminiscent of a crêpe, according to Sereno, about four inches wide and three feet long.

The team didn't physically unfold a cerebellum in their research. Instead, they worked with brain scans from a 9.4 Tesla MRI machine, and virtually unfolded and mapped the organ. Custom software was developed for the project, based on the open-source FreeSurfer app developed by Sereno and others. Their model allowed the scientists to unpack the virtual cerebellum down to each individual fold, or "folia."

Study's cross-sections of a folded cerebellum

Image source: Sereno, et al.

A complicated map

Sereno tells SDSU NewsCenter that "Until now we only had crude models of what it looked like. We now have a complete map or surface representation of the cerebellum, much like cities, counties, and states."

That map is a bit surprising, too, in that regions associated with different functions are scattered across the organ in peculiar ways, unlike the cortex where it's all pretty orderly. "You get a little chunk of the lip, next to a chunk of the shoulder or face, like jumbled puzzle pieces," says Sereno. This may have to do with the fact that when the cerebellum is folded, its elements line up differently than they do when the organ is unfolded.

It seems the folded structure of the cerebellum is a configuration that facilitates access to information coming from places all over the body. Sereno says, "Now that we have the first high resolution base map of the human cerebellum, there are many possibilities for researchers to start filling in what is certain to be a complex quilt of inputs, from many different parts of the cerebral cortex in more detail than ever before."

This makes sense if the cerebellum is involved in highly complex, advanced cognitive functions, such as handling language or performing abstract reasoning as scientists suspect. "When you think of the cognition required to write a scientific paper or explain a concept," says Sereno, "you have to pull in information from many different sources. And that's just how the cerebellum is set up."

Bigger and bigger

The study also suggests that the large size of their virtual human cerebellum is likely to be related to the sheer number of tasks with which the organ is involved in the complex human brain. The macaque cerebellum that the team analyzed, for example, amounts to just 30 percent the size of the animal's cortex.

"The fact that [the cerebellum] has such a large surface area speaks to the evolution of distinctively human behaviors and cognition," says Sereno. "It has expanded so much that the folding patterns are very complex."

As the study says, "Rather than coordinating sensory signals to execute expert physical movements, parts of the cerebellum may have been extended in humans to help coordinate fictive 'conceptual movements,' such as rapidly mentally rearranging a movement plan — or, in the fullness of time, perhaps even a mathematical equation."

Sereno concludes, "The 'little brain' is quite the jack of all trades. Mapping the cerebellum will be an interesting new frontier for the next decade."

Economists show how welfare programs can turn a "profit"

What happens if we consider welfare programs as investments?

A homeless man faces Wall Street

Spencer Platt/Getty Images
Politics & Current Affairs
  • A recently published study suggests that some welfare programs more than pay for themselves.
  • It is one of the first major reviews of welfare programs to measure so many by a single metric.
  • The findings will likely inform future welfare reform and encourage debate on how to grade success.
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