Nov 16, 2021 08:35 AM
(This post was last modified: Nov 16, 2021 08:37 AM by C C.)
https://phys.org/news/2021-11-aliens-oum...eberg.html
EXCERPTS: . . . In the paper where he broached the possibility, Loeb indicated that "Oumuamua's unusual character and behavior were consistent with a solar sail. This included the highly-reflective nature of the object and its profile, which appeared to be either cigar-shaped or pancake-like. More importantly, its sudden acceleration and deviation from its expected orbit appeared to be the result of radiation pressure, which is precisely how solar sails achieve propulsion.
There was also the way it entered our solar system, which allowed it to make a flyby of Earth after passing closest to our sun (perihelion). In other words, its orbital dynamics allowed it to get a close look at the only habitable planet in our solar system, which is precisely what one might expect of an interstellar probe. These arguments were detailed further in Loeb's book, "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth."
At the time of the book's writing, all attempts to explain "Oumuamua in terms of natural phenomena fell short. Basically, there was no single explanation that could account for its brightness, profile and acceleration while acknowledging that there was no evidence of outgassing. In addition, the sudden acceleration could not be attributed to gravitational forces since these should have been slowing "Oumuamua down at the time.
In March of 2021, two researchers from the School of Earth and Space Exploration (SESE) at Arizona State University (ASU) offered a new hypothesis. [...] In their first paper, Jackson and Desch addressed the size and compositional constraints of "Oumuamua and showed that "Oumuamua's albedo was similar to the nitrogen ices on the surfaces of Triton and Pluto. In their second paper, they showed how these types of nitrogen ice fragments could be generated by the collision of extrasolar objects similar in composition to Pluto and Kuiper Belt Object (KBOs).
[...] Siraj and Loeb took the nitrogen iceberg model and examined what amount of stellar material is required to make it work. ... What they found was that even under the most optimistic assumptions possible, the model fails by several orders of magnitude. In short, a star system would not have enough nitrogen ice to allow for such a robust population of exo-Plutos, which means that statistically, there simply cannot be enough ISOs composed of N2 to account for the fortuitous detection of "Oumuamua.
The model becomes even more unlikely when one considers how cosmic rays naturally erode ISOs. [...] In addition, Siraj and Loeb cite research that appeared shortly after their study appeared on the arXiv that casts doubt on the prevalence of nitrogen icebergs in our galaxy.
[...] What does this mean for "Oumuamua and the more "exotic" explanation of its origin—i.e., that it might have been an ET solar sail? For starters, it does not mean "it was aliens," nor is anyone in the astronomical community making that assertion. But it does mean that this latest attempt to explain "Oumuamua in terms of natural phenomena does not fit all of the requirements—contrary to what many suspected previously.
"The nitrogen model is now off the table," said Siraj. "This means that the "Oumuamua mystery remains wide open, motivating even more strongly the study of objects like "Oumuamua in the future. This is the goal of the interstellar object branch of the Galileo Project, which I have the privilege of leading—to discover and characterize objects like "Oumuamua, and ultimately to understand their nature." (MORE - missing details)
EXCERPTS: . . . In the paper where he broached the possibility, Loeb indicated that "Oumuamua's unusual character and behavior were consistent with a solar sail. This included the highly-reflective nature of the object and its profile, which appeared to be either cigar-shaped or pancake-like. More importantly, its sudden acceleration and deviation from its expected orbit appeared to be the result of radiation pressure, which is precisely how solar sails achieve propulsion.
There was also the way it entered our solar system, which allowed it to make a flyby of Earth after passing closest to our sun (perihelion). In other words, its orbital dynamics allowed it to get a close look at the only habitable planet in our solar system, which is precisely what one might expect of an interstellar probe. These arguments were detailed further in Loeb's book, "Extraterrestrial: The First Sign of Intelligent Life Beyond Earth."
At the time of the book's writing, all attempts to explain "Oumuamua in terms of natural phenomena fell short. Basically, there was no single explanation that could account for its brightness, profile and acceleration while acknowledging that there was no evidence of outgassing. In addition, the sudden acceleration could not be attributed to gravitational forces since these should have been slowing "Oumuamua down at the time.
In March of 2021, two researchers from the School of Earth and Space Exploration (SESE) at Arizona State University (ASU) offered a new hypothesis. [...] In their first paper, Jackson and Desch addressed the size and compositional constraints of "Oumuamua and showed that "Oumuamua's albedo was similar to the nitrogen ices on the surfaces of Triton and Pluto. In their second paper, they showed how these types of nitrogen ice fragments could be generated by the collision of extrasolar objects similar in composition to Pluto and Kuiper Belt Object (KBOs).
[...] Siraj and Loeb took the nitrogen iceberg model and examined what amount of stellar material is required to make it work. ... What they found was that even under the most optimistic assumptions possible, the model fails by several orders of magnitude. In short, a star system would not have enough nitrogen ice to allow for such a robust population of exo-Plutos, which means that statistically, there simply cannot be enough ISOs composed of N2 to account for the fortuitous detection of "Oumuamua.
The model becomes even more unlikely when one considers how cosmic rays naturally erode ISOs. [...] In addition, Siraj and Loeb cite research that appeared shortly after their study appeared on the arXiv that casts doubt on the prevalence of nitrogen icebergs in our galaxy.
[...] What does this mean for "Oumuamua and the more "exotic" explanation of its origin—i.e., that it might have been an ET solar sail? For starters, it does not mean "it was aliens," nor is anyone in the astronomical community making that assertion. But it does mean that this latest attempt to explain "Oumuamua in terms of natural phenomena does not fit all of the requirements—contrary to what many suspected previously.
"The nitrogen model is now off the table," said Siraj. "This means that the "Oumuamua mystery remains wide open, motivating even more strongly the study of objects like "Oumuamua in the future. This is the goal of the interstellar object branch of the Galileo Project, which I have the privilege of leading—to discover and characterize objects like "Oumuamua, and ultimately to understand their nature." (MORE - missing details)