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‘Oumuamua – Outer Space’s Short Visit to Our Solar System

In 2017, ‘Oumuamua became the first recorded object from interstellar space to pass through our solar system. It immediately triggered considerable speculation due to its extraordinary characteristics: was it more like an asteroid or a comet? Some scientists even suggested it was a spaceship. In a study recently published in Nature Astronomy (DOI 10.1038/s41550-019-0816-x), an interna-tional team of scientists from Europe and the USA, including Susanne Pfalzner from JSC, analysed the collected data on ʻOumuamua. What is particularly baffling is that while ʻOumuamua appears to accelerate along its trajectory – which is typical of comets – the astronomers were unable to detect the gas emissions that are usually associated with this acceleration. The authors assume that the physical processes observed here are universal, but that they have simply not yet seen anything like ʻOumuamua in our solar system. However, this study showed that ʻOumuamua is of completely natural origin.

It is estimated that billions of trillions of objects like ‘Oumuamua are present in any cubic parsec (about 35 cubic light years) of the Milky Way. Susanne Pfalzner and Michele Bannister (Queens University Belfast, UK) showed in a second study (DOI 10.3847/2041-8213/ab0fa0) that the number of ‘Oumuamuas incorporated into a protoplanetary disk and participating in planet formation might be relatively high. One possible consequence of the abundance of these objects is that they might occasionally jump-start planet formation. Although much more work needs to be done, including many simulations, one thing is clear: the importance of interstellar objects in the planet formation process can no longer be ignored.

Contact: Prof. Susanne Pfalzner,

from JSC News No. 267, 27 September 2019