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Why might visiting interstellar objects disappear in space before we see them?

A new research message shows that cosmic ray erosion limits the lifespan of icy interstellar (ISO) objects, and although there may be many of them, they simply do not last as long as thought, and if this is true, it is possible That the 'Oumuamua' interstellar object was much larger when it began its journey, wherever it may be. The team of researchers studied four different types of ice: nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4).

They then studied cosmic rays in the interstellar medium (ISM) and the effect of erosion on the ice. They also considered the erosion that collisions between glacial ISOs and surrounding gas in the ISM might cause on the ISOs. The research takes into account many variables, as the erosion time of a given glacial ISO can vary according to the strength of the cosmic rays. The same is true of confrontations with gas in the ISM. Different types of ice erode at different rates.

Previous research suggested that 'Oumuamua could be an N2 icy part of an object similar to Pluto in another solar system. In this scenario, the initial size of 'Oumuamua' was between 10-50 km, and the actual size within this range will be determined mainly by the strength of the cosmic rays to which it was exposed.

The researchers looked at it another way, too, and if the formation mechanisms of different ISOs tell us about an object's initial radius, they can set the distance limits to its origin based on the object's velocity. The higher the ISO, the greater the impact of gas collision corrosion within the ISM. On the other hand, the slower the ISO moves, the more time it spends in exposure to cosmic rays, which means it must erode more quickly.

This kind of research is in its infancy, and the researchers say we need to learn more about the changing strength of cosmic rays in the Milky Way to make further progress. They wrote: "It is also clear from this example that a more detailed study of the spatial profile of galactic CRs may help shed light on the origin of ISOs passing through the Solar System.

As advanced monitoring facilities such as the Vera Rubin Observatory will become available online in the next few years, we are bound to discover more and more of them. We hope to discover them at greater distances and have more time to study them. There is even talk of a mission that could visit ISO as it makes its way through our solar system. The European Space Agency plans to launch the Comet Interceptor mission in 2029.

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