Astronomers think they know how Uranus got flipped onto its side. According to detailed computer simulations, a body about twice the size of Earth slammed into Uranus between 3 to 4 billion years ago. The impact created an oddity in our Solar System: the only planet that rotates on its side.

A study explaining these findings was presented at the American Geophysical Union’s (AGU) Fall Meeting in Washington DC held between December 10th to 14th. It’s led by Jacob Kegerreis, a researcher at Durham University. It builds on previous studies pointing to an impact as the cause of Uranus’ unique orientation. Taken altogether, we’re getting a clearer picture of why Uranus rotates on its side compared to the other planets in our Solar System. The impact also explains why Uranus is unique in other ways.

When the Solar System formed, it all started with a massive cloud of gas and dust. The cloud swirled as it became more dense, and eventually the Sun formed in the center, with the rest of the gas and dust swirling around it. The Sun contains about 99.8% of the mass in the Solar System, and as the remaining 0.2% swirled around it, clumps began to form into the planets we know today. As they formed, the rotation of the gas cloud was imparted to the planets. So, all of the planets rotate the same way, except for Uranus, (and Venus, which was likely struck by an asteroid.)

The planets aren’t all exactly alike; Earth is tilted on its axis a little, giving us seasons, and so are Jupiter, Neptune, and Saturn, to varying degrees. But they’re still oriented more or less the same as the rest of the planets and moons. But Uranus isn’t. It’s tilted on its side relative to its fellow planets, by about 98 degrees.

Between 3 to 4 billion years ago, a body twice the size of Earth impacted Uranus, knocking the ice giant onto its side. Image Credit: Jacob A. Kegerreis/Durham University

Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which it is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.

“Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today.” – Jacob Kegerreis, Durham University.

Mid-collision snapshots from the simulation. Image Credit: Kegerreis et. al., 2018, Durham University.

For years, evidence has been building that supports a collision between Uranus and a body about twice the size of Earth. This most recent study builds on that evidence, and comes from a group of scientists led by Jacob Kegerreis from Durham University. According to an abstract from their presentation at the AGU, they “performed a suite of smoothed particle hydrodynamics (SPH) simulations to investigate in detail the results of a giant impact on the young Uranus.” SPH is a computational method developed in the 1970s to study astrophysical problems. It’s also used in ballistics, volcanology, and oceanography.

“We ran more than 50 different impact scenarios using a high-powered super computer to see if we could recreate the conditions that shaped the planet’s evolution. Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today,” said Kegerreis.

The results of their simulations explain not only Uranus’ obliquity, but also some of its other properties:

Not only does Uranus rotate on its side, but so do its five largest moons.
It’s magnetic field is also lopsided, and doesn’t go out the poles.
It’s the only planet where the interior heat doesn’t escape from its core.

The collision that made Uranus what it is today happened two or three billion years ago, but according to the simulation it was over in a matter of hours.

The simulation shows that a body about twice the size of Earth slammed into Uranus, tilting it to about 98 degrees. The object that slammed into it was made of rock and ice, and some of that material fell into Uranus’ core. According to the abstract, not all of it did, and that explains why Uranus doesn’t shed heat from its core: “Furthermore, most of the impactor’s ice and energy is deposited in a hot, high-entropy shell at a radius of 3 R. This could explain Uranus’ observed lack of heat flow from the interior…”

Diagram of the interior of Uranus. Credit: Public Domain

Diagram of the interior of Uranus. Credit: Public Domain

The abstract also says that this could help explain the planet’s weird magnetic field. While Earth’s magnetic field is tilted from its geographic poles by 11 degrees, Uranus’ field is tilted by 59 degrees.

Uranian Magnetic Field. Image: Public Domain, https://commons.wikimedia.org/w/index.php?curid=3059141

The simulation also suggests that the moons of Uranus formed after the collision. There was likely a ring of debris as the result of the impact, and the moons formed from that debris. That’s why the five largest moons rotate on the same axis as the planet.

Uranus, and the Solar System’s other ice giant, Neptune, are the least studied planets in our system. There’ve been no dedicated missions to either planet, though Voyager 2 did visit them briefly in the late 1980s. Scientists rely on observation and computer simulation to understand them both. This latest study builds on other evidence pointing to impacts as the cause of Uranus’ tilt. Once such study suggested multiple impacts were responsible, but that line of evidence hasn’t persisted.

It shouldn’t be a surprise to anyone that an impact is responsible for Uranus’ predicament. The history of the Solar System is full of impacts. The so-called ‘Late Heavy Bombardment‘ about 4 billion years ago pelted Earth and the inner Solar System with asteroids. Earth’s Moon may have been created from a collision between Earth and a doomed planet called “Theia”. On the Moon, Venus, and other bodies we can see the abundant craters caused by impacts. And, of course, a massive asteroid strike here at home brought on the demise of the dinosaurs and changed the history of our planet forever.

Many missions to Uranus have been proposed, but so far none have been approved. But space scientists are nothing if not patient. Eventually, a dedicated mission to this far-flung neighbour will be launched, and some of this ice-giant’s secrets will be unlocked.

Sources:

Research Paper: Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion
Press Release: Cataclysmic Collision Shaped Uranus’ Evolution
AGU Conference Abstract: How Uranus Fell Over: Consequences of Giant Impacts with High Resolution Simulations
Wikipedia: Uranus

As a follow-up to my 2-part article on Shadow People and the Philadelphia Experiment – which is very much driven by the words and controversial claims of a whistleblower – I thought I would share with you over the next few days a number of additional whistleblower-based accounts that have come my way. We’ll begin with one which concerns the controversial Roswell affair of 1947. Back in 1998, I wrote a book titled The FBI Files. It told the story of the Bureau’s involvement in the UFO phenomenon, contactee cases, the alleged Aztec, New Mexico UFO crash of 1948, the cattle mutilation mystery, and even FBI records on the sinister Men in Black. Chapter Four of the book was titled “The Oak Ridge Invasion.” As so often happens when I write a book, people who personally know something of its contents or subject-matter will contact me and share the relevant information. And that is precisely what happened with regard to that specific chapter. It was a study of FBI files that had been declassified under the terms of the Freedom of Information Act and which described various UFO encounters at the Oak Ridge National Laboratory, Tennessee, from the late 1940s to the early 1950s.

One of the people who contacted me – by letter, via the London, England-based publisher of The FBI Files, Simon & Schuster – was an elderly woman who worked at Oak Ridge in 1947, and who had read my book. She added she had some information that I was sure to find of interest, but which she preferred to tell me about specifically in person. Well, as I was living in the U.K. at that time, there wasn’t much of a chance of me meeting up with her at any time soon – which is exactly what I told her. I couldn’t persuade her to put her revelations onto paper. Nor would she share them with me over the telephone. And, she wasn’t on email – not a massive number of old folks were online in 1998, I am guessing. So, for a couple of years it was a case of her story not just stalling, but coming to a complete halt. That is, until the summer of 2001.

I moved to the United States to live in early 2001, and, in the summer, I traveled around much of the west coast – chiefly to do a series of lectures for various UFO groups in California. I put out a feeler to that same old lady, explaining my new circumstances and asking if we could now, finally, talk. Well, that would be just fine, she said. On July 28, 2001 I hung out with the then-seventy-nine-year-old woman: we had lunch in a Los Angeles restaurant and chatted extensively. She was driven to the restaurant by a family member, a much younger man who seemed to be equally as worried as she was. Nevertheless, she agreed to share what she knew, providing her name was never published (although, she was required to provide Simon & Schuster’s legal people with a release-form, as were each and all of the other whistleblowers when I wrote my 2005 book on all this: Body Snatchers in the Desert). So, I sat back and listened.

I referred to her in the book as the Black Widow. There was a relevant reason for this; a reason which was not mentioned in Body Snatchers in the Desert: her husband, who she married in 1972, was African-American. She, however, was not. They were both just into their very early fifties when they married and had twenty-four happy years together, despite some unforgivable racist comments from her ignorant family. It was in 1996 that her husband passed away, hence the title I gave her. When we met, and knowing that she had read The FBI Files, my natural assumption was that she wanted to tell me something about UFO encounters at the Oak Ridge facility. Makes sense, right? No. I was wrong: what she actually wanted to share with me was certain information that, if provable, would radically alter the face of Ufology and blow the Roswell case right out of the water. As we ate, I wondered, with a fair degree of excitement: what the hell have I got myself into? It wasn’t long before I had the answer to that loaded question.

The Black Widow, born in 1922, had been in the employ of Oak Ridge – in a medical capacity – from the mid-1940s to the early 1950s. While there, and on three occasions between May and July 1947, she saw a number of unusual-looking bodies brought to the facility – and under stringent security. They looked like regular Japanese people, she said. Others, however, displayed the signs of certain medical conditions: dwarfism, oversized heads, and bulging eyes. A few of the bodies were extensively damaged – as if they had been in violent accidents. In all, fifteen such bodies were brought to Oak Ridge under great secrecy; all of them reportedly used in certain high-altitude, balloon-based experiments in New Mexico, one of which led to the Roswell legend. Or, became a part of the legend is probably more correct. The Black Widow said: “Those bodies – the Roswell bodies – they weren’t aliens. The government could care less about those stories about alien bodies found at Roswell – except to hide the truth.”

She added: “I don’t know anything at all about how these people were brought [to the United States], but I heard at Oak Ridge that some of them were in the States in late 1945 and brought over with Japanese doctors and Nazi doctors who had been doing similar experiments. That’s when some of this began.” The story continued that at least some of the people used in the tests were American prisoners given the opportunity to cut the lengths of their sentences – if, that is, they were willing to take a chance and take part in the dicey experiments. Reportedly, a number did take the bait, but failed to survive the flights. Some of the handicapped people did not come from Japan, but from “hospitals and “asylums” in the United States.

All of the material evidence was said to have been eventually destroyed – chiefly because the operations didn’t provide much in the way of results, and because of the outright illegality of the experiments. Everything, the Black Widow said, was hidden beneath a mass of fabricated tales of flying saucers and little men from the stars. She doubted that anything of any significance still existed – certainly not the bodies or the balloons, and probably not even the old records, which she believed were burned to oblivion. Unless, however, some of them were preserved for secret, historical purposes, which is not impossible. I hope they were. If not, it may be nigh on impossible to conclusively prove anything about Roswell – ever.

There was one final aspect of the Black Widow’s story that needs to be addressed: her overwhelming fear. It was ever-present throughout our 2001 meeting. She tried to disguise that fear with smiles and laughter, but she was certainly no Oscar-winning Hollywood actor. That’s for sure. Seeing through her facade was like seeing through freshly polished glass. In Body Snatchers in the Desert I said that she “…possessed the sad and somewhat sunken eyes of a person with the weight of the world on her shoulders. She was clearly looking for someone to speak with; but, equally, she was very concerned about the ramifications of doing so, ‘if the government finds out.’”