Scientists Determine ‘Oumuamua Isn’t Made From Molecular Hydrogen Ice After All
The argument over the origins and molecular structure of ‘Oumuamua continued with an announcement in The Astrophysical Journal Letters that in spite of earlier promising claims, the interstellar things is not made of molecular hydrogen ice after all.
The earlier study, released by Seligman & Laughlin in 2020– after observations by the Spitzer Space Telescope set tight limitations on the outgassing of carbon-based molecules– suggested that if ‘Oumuamua were a hydrogen iceberg, then the pure hydrogen gas that provides it its rocket-like push would have left detection. Researchers at the Center for Astrophysics Harvard & Smithsonian ( CfA) and the Korea Astronomy and Area Science Institute (KASI) were curious whether a hydrogen-based item could in fact have made the journey from interstellar area to our planetary system.
” The proposition by Seligman and Laughlin appeared appealing since it may explain the severe extended shape of ‘Oumuamua as well as the non-gravitational acceleration. Nevertheless, their theory is based upon an assumption that H2 ice might form in thick molecular clouds. If this holds true, H2 ice things might be abundant in the universe, and thus would have significant ramifications. H2 ice was also proposed to discuss dark matter, a mystery of contemporary astrophysics,” said Dr. Thiem Hoang, senior scientist in the theoretical astrophysics group at KASI and lead author on the paper. “We wanted to not only test the presumptions in the theory but likewise the dark matter proposition.” Dr. Avi Loeb, Frank B. Baird Teacher of Science at Harvard and co-author on the paper, included, “We were suspicious that hydrogen icebergs could not endure the journey– which is most likely to take numerous countless years– since they evaporate too rapidly, and as to whether they might form in molecular clouds.”
Traveling at a blistering speed of 196,000 miles per hour in 2017, ‘Oumuamua was first classified as an asteroid, and when it later accelerated, was found to have homes more comparable to comets. The 0.2 km radius interstellar object didn’t fit that category, either, and its point of origin has actually stayed a secret. Researchers concentrated on the huge molecular cloud (GMC) W51– one of the closest GMCs to Earth at just 17,000 light years away– as a potential point of origin for ‘Oumuamua, but hypothesize that it just could not have made the journey intact. “The most likely place to make hydrogen icebergs remains in the densest environments of the interstellar medium. These are giant molecular clouds,” stated Loeb, verifying that these environments are both too far away and are not conducive to the development of hydrogen icebergs.
An accepted astrophysical origin for strong things is development by sticky crashes of dust, however in the case of a hydrogen iceberg, this theory might not hold together. “An accepted path to form a km-sized object is first to form grains of micron-size, then such grains grow by sticky crashes,” stated Hoang.
Although the research study explored damage of H2 ice by multiple systems including interstellar radiation, cosmic rays, and interstellar gas, sublimation due to heating by starlight has the most damaging effect, and according to Loeb, “Thermal sublimation by collisional heating in GMCs might damage molecular hydrogen icebergs of ‘Oumuamua-size before their escape into the interstellar medium.” This conclusion prevents the theory that ‘Oumuamua journeyed to our planetary system from a GMC, and further precludes the proposal of primitive snowballs as dark matter. Evaporative cooling in these circumstances does not decrease the role of thermal sublimation by starlight in the destruction of H2 ice items.
‘ Oumuamua first gained notoriety in 2017 when it was found shouting through space by observers at Haleakalā Observatory, and has since been the topic of ongoing studies. “This object is mystical and tough to comprehend due to the fact that it displays peculiar homes we have never ever seen from comets and asteroids in our solar system,” said Hoang.
While the nature of the interstellar tourist is currently an unsolved mystery, Loeb recommends it won’t remain so for much longer, specifically if it’s not alone. “If ‘Oumuamua belongs to a population of similar items on random trajectories, then the Vera C. Rubin Observatory (VRO), which is scheduled to have its very first light next year, ought to find roughly one ‘Oumuamua-like object each month. We will all wait with anticipation to see what it will find.”
Recommendation: “Destruction of Molecular Hydrogen Ice and Ramifications for 1I/2017 U1 (‘ Oumuamua)” by Thiem Hoang and Abraham Loeb, 17 August 2020, The Astrophysical Journal Letters
DOI: 10.3847/2041-8213/ abab0c