That mystery was ultimately explained by a recalculation of Neptune’s mass in the 1990s, but then a new theory of a potential planet nine was put forward in 2016 by astronomers Konstantin Batygin and Mike Brown at Caltech (the California Institute of Technology).

Their theory relates to the Kuiper Belt, a giant belt of dwarf planets, asteroids and other matter that lies beyond Neptune (and includes Pluto). Many Kuiper Belt objects – also referred to as trans-Neptunian objects – have been discovered orbiting the Sun, but like Uranus they don’t do so in a continuous expected direction. Batygin and Brown argued that something with a large gravitational pull must be affecting their orbit, and proposed planet nine as a potential explanation.

This would be comparable to what happens with our own Moon. It orbits the Sun every 365.25 days, in line with what you would expect in view of their distance apart. However, the Earth’s gravitational pull is such that the Moon also orbits the planet every 27 days. From the point of view of an outside observer, the Moon moves in a spiraling motion as a result. Similarly, many objects in the Kuiper Belt show signs of their orbits being affected by more than just the Sun’s gravity.

While astronomers and space scientists were initially skeptical about the planet nine theory, there has been mounting evidence thanks to increasingly powerful observations that the orbits of trans-Neptunian objects are indeed erratic. As Brown said in 2024:

“I think it is very unlikely that P9 does not exist. There are currently no other explanations for the effects that we see, nor for the myriad other P9-induced effects we see on the Solar System.”

In 2018, for example, it was announced that there was a new candidate for a dwarf planet orbiting the Sun, known as 2017 OF201. This object measures around 700km across (Earth is roughly 18x bigger) and has a highly elliptical orbit. This lack of a roughly circular orbit around the Sun suggested either an impact early in its lifetime that put it on this path, or gravitational influence from planet nine.

Problems with the theory

On the other hand, if planet nine exists, why hasn’t anyone found it yet? Some astronomers question whether there’s enough orbital data from Kuiper objects to justify any conclusions about its existence, while alternative explanations get put forward for their motion, such as the effect of a ring of debris or the more fantastical idea of a small black hole.

The biggest issue, however, is that the outer Solar System just hasn’t been observed for long enough. For example, object 2017 OF201 has an orbital period of about 24,000 years. While an object’s orbital path around the Sun can be found in a short number of years, any gravitational effects probably need four to five orbits to notice any subtle changes.

New discoveries of objects in the Kuiper Belt have also presented challenges for the planet nine theory. The latest is known as 2023 KQ14, an object discovered by the Subaru telescope in Hawaii.

It is known as a “sednoid,” meaning it spends most of its time far away from the Sun, though within the vast area in which the Sun has a gravitational pull (this area lies some 5,000AU or astronomical units away, where 1AU is the distance from the Earth to the Sun). The object’s classification as a sednoid also means the gravitational influence of Neptune has little to no effect on it.

2023 KQ14’s closest approach to the Sun is around 71AU away, while its furthest point is about 433AU. By comparison, Neptune is about 30AU away from the Sun. This new object is another with a very elliptical orbit, but it is stabler than 2017 OF201, which suggests that no large planet, including a hypothetical planet nine, is significantly affecting its path. If planet nine exists, it would therefore perhaps have to be farther than 500AU away from the Sun.

To make matters worse for the planet nine theory, this is the fourth sednoid to be discovered. The other three also exhibit stable orbits, similarly suggesting that any planet nine would have to be very far away indeed.

Nonetheless, the possibility remains there could still be a massive planet affecting the orbits of bodies within the Kuiper Belt. But astronomers’ ability to find any such planet remains somewhat limited by the restrictions of even unmanned space travel. It would take 118 years for a spacecraft to travel far enough away to find it, based on estimates from the speed of Nasa’s New Horizons explorer.

This means we’ll have to continue to rely on ground- and space-based telescopes to detect anything. New asteroids and distant objects are being discovered all the time as our observing capabilities become more detailed, which should gradually shed more light on what might be out there. So watch this (very big) space, and let’s see what emerges in the coming years.

The affected area is known as the PrK transfer tunnel. NASA and Roscosmos have been monitoring the leak for years while working to understand its root cause and reduce the loss of air. Roscosmos has used both temporary and permanent sealants as part of its leak mitigation efforts.

Leak Rate Rises During Progress 95 Operations

According to NASA’s latest update, Roscosmos detected a higher leak rate during cargo operations involving the Progress 95 spacecraft during the week of June 1. The leak rate increased to about two pounds per day, and engineers identified new suspected leak areas inside the PrK.

Following those findings, Roscosmos decided on Friday morning to prepare for a more extensive inspection and structural repair effort. The revised plan included cutting a bracket to improve access to an area that may have been contributing to the leak. NASA noted that this method could have increased the risk to the surrounding structure.

Astronauts Enter Safe Haven as Precaution

Because of the potential structural risk, NASA directed the four SpaceX Crew-12 members and NASA astronaut Chris Williams to take a heightened safety posture known as a safe haven. Williams traveled to the station aboard the Soyuz MS-28 spacecraft.

As a precaution, the astronauts sheltered inside the SpaceX Dragon spacecraft while the repair procedure was being evaluated.

Roscosmos Pauses Repair Work for More Data

Later Friday morning, Roscosmos chose not to proceed with the structural repair work. Instead, teams paused the operation to gather more measurements and review additional data.

The follow-up work included inspecting suspected areas of interest and reviewing places where sealant had already been applied. NASA strongly supported the decision to collect more information before moving ahead.

After Roscosmos paused the repair effort, Crew-12 and Williams ended their safe haven activities and returned to normal operations aboard the orbiting laboratory.

NASA said it will continue working with Roscosmos and the space station’s other international partners to assess the situation and ensure the leak issue is resolved.

The compound, known by researchers as “Compound 10,” is the result of nearly two decades of work led by Ursula Quitterer, Professor of Molecular Pharmacology at ETH Zurich.

A Long Search for New Alzheimer’s Clues

The research began almost 20 years ago when Quitterer received brain tissue samples from a colleague at Ain Shams University Hospital in Cairo. The samples were collected during tumor surgeries and came from both people with dementia and individuals without the condition.

Those samples helped launch an investigation into a protein called GRK2, which has been the focus of Quitterer’s research for many years.

GRK2 plays an important role throughout the body. As a regulatory protein, it helps cells respond to signals and adapt to stress. It is active in several organs, including the heart and the brain, where it supports healthy nerve cell function.

Using both human brain tissue and mouse models of Alzheimer’s disease, the ETH Zurich team uncovered evidence that GRK2 may be a major contributor to dementia. Their findings were recently published in the journal Cell Reports Medicine.

When a Protective Protein Turns Harmful

GRK2 exists in two forms inside cells. One form functions normally, while the other becomes inactive through cellular processes.

The researchers found that the inactive version accumulates in large amounts in the brains of people with dementia. Similar patterns were also observed in mice that develop Alzheimer’s-like symptoms.

Further experiments revealed that inactive GRK2 molecules clump together inside nerve cells. These clusters attach to mitochondria, the structures often referred to as the “powerhouses” of cells, and interfere with their function.

“The GRK2 aggregates block the pores of the mitochondria, reducing the amount of energy they can supply and leading to a situation of stress inside the cells,” Quitterer explains.

The team also found that inactive GRK2 appears to increase the production of amyloid beta, a protein fragment widely associated with Alzheimer’s disease.

This creates a damaging cycle. Amyloid beta places additional stress on nerve cells, which leads to the formation of even more inactive GRK2. As more GRK2 accumulates and forms aggregates, the disease process continues to accelerate.

Compound 10 Breaks the Cycle

To interrupt this cycle, the researchers designed and tested several experimental compounds in cell cultures and mice.

Among them, Compound 10 delivered the strongest results. The compound prevented GRK2 molecules from forming harmful aggregates, allowing mitochondria to function more effectively. As a result, amyloid beta deposits were reduced, nerve cells remained healthier, and cell death was slowed.

The benefits extended beyond the brain.

In mice, Compound 10 also appeared to improve heart function and influence aging-related changes. The researchers observed that treated animals developed fewer gray hairs as they grew older.

Why the Research Took Nearly Two Decades

The team has completed the basic research phase and filed a patent application for Compound 10.

According to Quitterer, one reason the work took so long is the nature of Alzheimer’s research itself.

“It took so long simply because everything takes so long in Alzheimer’s research,” explains Quitterer.

Because Alzheimer’s is an age-related disease, the researchers worked with older mice. These animals were typically between one and a half and two years old. Each experiment required a similar amount of time before meaningful conclusions could be drawn and the next stage of research could begin.

“It’s all a great deal slower than in cancer research, for example.”

A New Target for Future Alzheimer’s Treatments

ETH Zurich and the researchers are now seeking a company interested in advancing Compound 10 toward drug development.

“Alzheimer’s is a very complex disease,” says Quitterer. Current medications do not cure the disease, but rather — at most — delay its progression by several months.

“That’s why it’s so important that we’ve now identified a new target protein in the form of GRK2, as well as an active ingredient that operates via GRK2 and therefore via a different mechanism than existing Alzheimer’s drugs.”

While much more research is needed before the compound could be tested in people, the discovery opens the door to a new treatment strategy. Researchers believe that combining Compound 10 with existing Alzheimer’s medications could eventually provide greater benefits and improve quality of life for patients.