Scientists determine the origin of the extra-solar object ‘Oumuamua’

In 2017, the first interstellar object from outside our Solar System was discovered at the Pan-STARRS Astronomical Observatory in Hawaii. It was called ‘Oumuamua, which means “scout” or “messenger” in Hawaiian. The object was like a comet, but with features strangely enough to defy classification.

Two astrophysicists from Arizona State University, Steven Desch and Alan Jackson of the School of Earth and Space Exploration, wanted to explain the strange features of ‘Oumuamua and determined that it is likely a slice of Pluto-like planet from another solar system. Their findings were recently published in a few articles in the AGU Journal of Geophysical Research: Planets

“Oumuamua was in many ways like a comet, but it was curious enough in several ways that mystery surrounded its nature, and speculation about what it was,” said Desch, a professor at the School of Earth and Space Exploration.

Based on observations of the object, Desch and Jackson determined several features of the object that differed from what would be expected of a comet.

In terms of speed, the object entered the solar system at a speed slightly slower than expected, indicating that it has not traveled in interstellar space for over a billion years or so. In terms of size, the pancake shape was also more flattened than any other known object in the solar system.

They also noted that although the object received a slight push from the sun (a “rocket effect” common in comets as sunlight evaporates the ice they are made of), the pressure was stronger than could be explained. Finally, the object lacked a detectable escaping gas, which is usually visible through the tail of a comet. In all, the object looked a lot like a comet, but unlike any comet ever seen in the solar system.

Desch and Jackson then hypothesized that the object was made of different types of ice and calculated how quickly these ice creams would sublimate (from a solid to a gas) if ‘Oumuamua passed the sun. From there they calculated the rocket effect, the mass and shape of the object and the reflectivity of the ice creams.

“That was an exciting moment for us,” said Desch. “We realized that a patch of ice would be much more reflective than people thought, which meant it could be smaller.

Desch and Jackson found one ice in particular – solid nitrogen – that exactly matched all of the object’s features at once. And since solid nitrogen ice can be seen on Pluto’s surface, it is possible that a comet-like object was made of the same material.

“We knew we had come up with the right idea when we completed the calculation for what albedo (how reflective the body is) would make the movement of ‘Oumuamua match the observations,'” said Jackson, a researcher and researcher at ASU. “That value turned out to be the same as we observe on the surface of Pluto or Triton, bodies covered with nitrogen ice.”

They then calculated the rate at which chunks of solid nitrogen ice would have struck from Pluto’s surfaces and similar bodies early in our solar system’s history. And they calculated the probability that chunks of solid nitrogen ice from other solar systems would reach ours.

“It was probably knocked off the surface by an impact about half a billion years ago and thrown out of its mother system,” Jackson said. Made from frozen nitrogen also explains the unusual shape of ‘Oumuamua. As the outer layers of nitrogen ice evaporated, the body’s shape would have gradually become more flattened, much like a bar of soap does when the outer layers are rubbed off. . “

Could ‘Oumuamua have been alien technology?

Although ‘Oumuamua’s comet-like nature was quickly recognized, its inability to immediately explain it in detail led to speculation that it is a piece of alien technology, as in the recently published book’ Extraterrestrial: The First Signs of Intelligent Life Beyond Earth ‘by Avi Loeb from Harvard University.

This has led to a public debate about the scientific method and the responsibility of scientists not to come to unfounded conclusions too quickly.

“Everyone is interested in aliens, and it was inevitable that this first object outside the solar system would make people think of aliens,” Desch said. “But it’s important in science not to jump to conclusions. It took two or three years to come up with a natural explanation – a chunk of nitrogen ice – that matches everything we know about ‘Oumuamua. long in science, and too soon to say we exhausted all natural explanations. “

While there is no evidence that it is alien technology, as a fragment of a Pluto-like planet, “Oumuamua has provided scientists with a special opportunity to look at extrasolar systems in a way they could not before.” As more objects such as’ Oumuamua are found and studied, scientists can continue to expand our understanding of what other planetary systems are like and the ways they resemble or differ from our own solar system.

“This research is exciting because we have probably solved the mystery of what ‘Oumuamua is and we can reasonably identify it as a chunk of an’ exo-Pluto, ‘a Pluto-like planet in another solar system,” said Desch. “Until now, we had no way of knowing if other solar systems have Pluto-like planets, but now we’ve seen a piece of one go beyond Earth.”

Desch and Jackson hope that future telescopes, such as those at the Vera Rubin Observatory / Large Synoptic Survey Telescope in Chile, which can regularly survey the entire southern sky, will be able to find even more interstellar objects than they can and other scientists can. further testing ideas.

“It is hoped that in a decade or so we can get statistics on what kinds of objects pass through the solar system and whether chunks of nitrogen ice are rare or as common as we have calculated,” Jackson said. “Either way, we should be able to learn a lot about other solar systems and whether they have gone through the same kind of collision histories as ours.”