'Oumuamua is a large, cigar-shaped object that was first identified in October 2017, exiting our solar system at nearly 57,000 mph (92,000 km/h), indicating it could not have originated in our solar system.
Since then, scientists have tried to explain its origin and composition, with two papers published in March by Arizona State University astrophysicists suggesting it was made of nitrogen ice. However, a new paper has been published by Harvard astrophysicists in opposition to this suggestion. Astronomers have been unable to explain the source of its speed, as it shows no signs of propellant gases leaving it. The gravitational pull of the Sun is also insufficient to have accelerated it to the speeds that have slingshotted 'Oumuamua in and out of the solar system.
Alan Jackson and Steven Desch of the Arizona State University suggested that 'Oumuamua was likely a large chunk of nitrogen ice, having broken off of a planet similar to Pluto outside of our solar system. Given Pluto is 98% solid nitrogen, there likely are many similar planets, exo-Plutos, outside of our solar system from which 'Oumuamua may have broken off.
They proposed that evaporating nitrogen gas could propel the object, and these gases would be invisible to observers telescopes, explaining why the source of its speed was not readily identifiable.
Amir Siraj and Avi Loeb of Harvard University published a paper on November 5th, 2021, disputing this suggestion.
[Suggesting] 'Oumuamua is a nitrogen iceberg is flawed because there isn't enough nitrogen in the universe to make an object like 'Oumuamua, which is somewhere between 1,300 and 2,600 feet (400 and 800 meters) long and between 115 and 548 feet (35 and 167 m) wide.
They estimated that the mass of exo-Plutos necessary to explain the creation of 'Oumuamua would be more than 60 times the mass per star needed to create all of the planets in our solar system. When factoring in cosmic rays that would slow down and degrade 'Oumuamua, their calculation states that 1,000 times the mass of stars in the galaxy would be needed to create enough exo-Plutos to lead to 'Oumuamua's creation.
Jackson and Desch dispute these claims, stating their calculations align with previous research on the number of nitrogen-based masses flying around space.
"They are attempting to manufacture controversy when none exists," Desch said.
Siraj and Loeb's paper can be read here.