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What is the origin of the famous interstellar object ‘Oumuamua? How did it form and where did it come from? An article published April 13 in Nature Astronomy by ZHANG Yun of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) and Douglas NC Lin of the University of California, Santa Cruz, offers a comprehensive first answer to this mystery, which it involves tidal forces like those felt by Earth’s oceans and explains all the unusual features of this interstellar object.
‘Oumuamua was discovered on October 19, 2017 by the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1) located in Hawaii. As the first known interstellar object to visit our Solar System, ‘Oumuamua bears no resemblance to anything else in the Solar System. Its dry surface, unusually elongated shape, and puzzling movement even led some scientists to wonder if it was an alien probe.
“It really is a mystery,” said ZHANG Yun, the study’s first author, “but some signs, such as its colors and the absence of radio emission, point to ‘Oumuamua as a natural object.”
“Our goal is to come up with a comprehensive scenario, based on well-understood physical principles, to put all the tantalizing clues together,” said Douglas Lin, co-author of the study.
In general, the first interstellar object discovered was supposed to be an icy body, like comets. In effect, frozen objects are constantly ejected from their host systems. They are also much more visible due to their apparent coma. However, the dry appearance of ‘Oumuamua, similar to rocky bodies, such as asteroids in the Solar System, indicates a different ejection scenario.
“The discovery of ‘Oumuamua implies that the population of rocky interstellar objects is much larger than we previously thought. On average, each planetary system should in total eject around one hundred billion objects like’ Oumuamua. We need to build a very efficient scenario. “ZHANG said.
“In space, some objects occasionally get very close to a larger one. Tidal forces from the largest can disturb these little ones, as happened with Comet Shoemaker-Levy 9 when it passed near Jupiter.”
ZHANG and Lin performed high-resolution computer simulations to model the dynamics of an object that flies close to a star. They discovered that the star can dramatically divide the object, if it gets close enough to the star, into extremely elongated fragments, and then eject them into interstellar space.
“The elongated shape is more compelling when we consider the phase transition of the material during the stellar encounter. The long axis to short ratio can be even greater than ten.” ZHANG said. Due to intense stellar radiation, the surfaces of the fragments melt at a very short distance from the star and re-condense at greater distances. Like melting chocolate grains, the surface materials come together to keep the shape elongated.
“Heat diffusion also consumes large amounts of volatiles. These fragments dry out and have a surface similar to that of Oumuamua.” ZHANG added. “However, some water ice buried below the surface may be conserved. These waste water ices could be activated during their passage through the Solar System to cause their non-gravitational movement.”
“The tidal fragmentation scenario not only provides a way to form a single ‘Oumuamua, but it also represents the vast population of rocky interstellar objects.” ZHANG said.
Their calculations demonstrate the efficiency of stellar tides in the production of this type of object. Prospective parents, including long-lived comets, debris disks, and even planets, can transform into ‘Oumuamua-sized pieces during stellar encounters. The inferred numerical density of interstellar objects is consistent with the occurrence rate of ‘Oumuamua.
This work highlights the prolificity of the population of interstellar Oumuamua-like objects among the stars. Since these objects pass through the domains of habitable zones, the possibility of transport of matter capable of generating life by these objects cannot be ruled out.
“This work provides a plausible narrative linking its strange properties to the planet formation process that is everywhere in the Milky Way,” said Gregory Laughlin, professor of astronomy at Yale University.
“‘Oumuamua is just the tip of the iceberg. We anticipate that many more interstellar visitors with similar traits will be discovered by future observation with the upcoming Vera C. Rubin Observatory,” Lin said.
“This is a very new field. These interstellar objects could provide critical clues to how planetary systems form and evolve, and how life on Earth began.” ZHANG said.
“This work does a remarkable job of explaining a variety of ‘Oumuamua’s unusual properties with a single consistent model.” Astronomer Matthew Knight of the US Naval Academy. The US, co-leader of the ‘International Institute for Space Science Oumuamua’ team, “As future interstellar objects are discovered in the coming years, it will be very interesting to see if any exhibit properties similar to Oumuamua.” , may indicate that the processes described in this study are very widespread “.
Research work
related links
Headquarters of the Chinese Academy of Sciences
Lands Beyond Beyond – additional solar planets – news and science
Life beyond earth
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NASA selects early-stage technology concepts for new ongoing study
Washington DC (SPX) April 08, 2020
Future technologies that could generate images of Exo planets, allow faster trips to Mars, and send robots to explore ocean worlds may have started as NASA’s Innovative Advanced Concepts (NIAC). Investing in early-stage technology ideas from NASA, industry, and academic researchers across the country, the program has selected 23 potentially revolutionary concepts with a total value of $ 7 million.
Among the selections are 16 new concepts and seven studies that previously received at least one NIA … read more
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