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So far, we only know of two interstellar objects (ISO) to visit our solar system. They are ‘Oumuamua and 2I / Borisov. There is a possible third ISO named CNEOS 2014-01-08, and research suggests there should be many more.
But a new research letter shows that cosmic ray erosion limits the lifespan of icy ISOs, and while there may be many more, they just don’t last as long as you think.
If that’s true, then ‘Oumuamua was probably much taller when he started his journey, wherever he is.
The title of the research letter is “Erosion of Icy Interstellar Objects by Cosmic Rays and Implications for ‘Oumuamua”. It is available on the arxiv.org preprint site and has not yet been peer reviewed. The main author is Vo Hong Minh Phan from the University of Aachen in Germany.
The team of researchers looked at four different types of ice: nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4).
Next, they considered cosmic rays in the interstellar medium (ISM) and their erosion effect on ice. They also took into account the erosion that collisions between the frozen ISOs and the ambient gas in the ISM would have on the ISOs.
The research takes into account many variables. The CR flux can vary widely, and the erosion time for a given icy ISO can vary depending on the strength of the cosmic rays. The same is true for encounters with gas in the ISM. And different types of ice also erode at different rates.
There is a lot that we don’t know about ‘Oumuamua. In fact, we hardly know anything about it.
We don’t know what it’s made of, we only have range estimates for its size, and we don’t really know where it came from. There is little evidence to prove much about this conclusively.
But all the same, there are some interesting possibilities.
Previous research has suggested that ‘Oumuamua could be a fragment of N2 ice from a body similar to Pluto in another solar system. This scenario has ‘Oumuamua originated from somewhere in Perseus’ arm about 0.5 Gyr ago.
In this scenario, the initial size of Oumuamua would have been between 10 and 50 km (6-31 miles). The actual size in this range would be determined primarily by the strength of the cosmic rays to which it was subjected.
The researchers also looked at it in another way. If the formation mechanisms of the different ISOs tell us the initial radius of the object, then they can set distance limits for its origin depending on the speed of the object.
The higher the speed of an ISO, the greater the erosion effect of collisions with the gas inside the ISM. And on the other hand, the slower an ISO moves, the more time it spends exposed to cosmic rays, which means it should erode faster.
This type of research is still in its infancy. The authors point out that we need to know more about the varying strength of cosmic rays in the Milky Way to make further progress.
“It is also clear from this example that a more detailed study of the spatial profile of galactic CRs could help shed light on the origin of ISOs passing through the solar system,” they write.
We have only known ‘Oumuamua for four years. The study of ISOs is in its infancy. With only two ISOs known to date, there isn’t a lot of hard data to go on.
As advanced observing facilities such as the Vera Rubin Observatory come online in the next few years, we will discover more and more of them.
Hopefully we will discover them at a greater distance and have more time to study them. There’s even talk of a mission that can visit an ISO as it makes its way through our solar system.
ESA plans to launch the Comet Interceptor mission in 2029. The interceptor would park at Sun-Earth point L2 and wait. It can stay there for three years and wait for the arrival of a long-lived comet accessible.
Then he could be sent to study the comet. If no suitable comet arrives, it is understood that the interceptor could be used to investigate an ISO if a suitable one arrives.
And the Initiative for Interstellar Studies has launched its own potential ISO mission called Project Lyra. Lyra is a spacecraft that could be sent to visit ISOs by passing a slingshot past Jupiter, or using advanced systems like nuclear propulsion.
But missions take a long time to plan and implement. And a lot of things must be going well.
In the meantime, the authors believe the best way to expand our knowledge is to deepen our understanding of the strength of cosmic rays throughout the Milky Way. With this, we could at least better understand the origins of ISO. Who knows what we will learn?
The researchers end their letter with the following: “It would be interesting to integrate a detailed modeling of the CR distribution in the galactic disk to define more stringent constraints on the birth site of known ISOs and this could help to better clarify their origin.”
This article was originally published by Universe Today. Read the original article.
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