Interstellar visitor’s Oumuamua could be the shattered remnant of a Pluto-like object

Four years ago, astronomers detected “Oumuamua”, the first interstellar object known to pass through our solar system. The object exhibited an array of weird and inexplicable characteristics, some of which are consistent with a shard of ice ripped from a Pluto-like object, new research shows.

“We suggest that Oumuamua was probably thrown from a young star system about half a billion years ago,” say the authors of two new research papers published in the Journal of Geophysical Research: Planets. Because the object exhibits features seen on the moon of Pluto and Neptune, Triton, the authors, planetary Alan Jackson and astrophysicist Steven Desch, both of Arizona State University, say, “Maybe Oumuamua is to be the first piece of exoplanet that was brought to us.

Of course what they mean is that it is the first known piece of exoplanet that was brought to us; and by exoplanet, they mean an exo-dwarf planet, because Pluto is technically not a planet (if these fixes aren’t what they wanted to say, then I say they should be).

In their papers, Jackson and Desch classify ‘Oumuamua as an “ex-Pluto”, which I find pretty cool. Indeed, astronomers often compare exoplanets and other astronomical phenomena to those orbiting our Sun, referring to hot Jupiters, super-Earths and sub-Neptunes, for example. We can now add “ex-Pluto” to the list of known astronomical objects, and by virtue of that, “Pluto” in general – small icy worlds located in the Kuiper Belts (another analogous term borrowed from our solar system) of distant star systems.

Until this traveler from afar visited us, “we had no way of knowing if other solar systems had Pluto-like planets, but now we have seen a piece of a passage through Earth,” Desch said in a commentary. AGU declaration. Well, that assumes that this interpretation is correct, which if it is, means “ Oumuamua would be the first evidence that Pluto-like objects exist elsewhere in the galaxy.

“ Oumuamua did not stay long when he visited our neighborhood in 2017, as he was driving at speeds of up to 196,000 miles per hour (315,430 km / h). It’s hard to fathom that kind of speed, but saying it was doing 54 miles per second (87 km / s) helps a bit.

The interstellar object was fast, but it was also weird. “Oumuamua is quite small – about half the size of a block – but exceptionally thin, with a depth of around 115 feet (35 meters). This form is so strange and unprecedented that at least one scientist said ‘Oumuamua may not be natural at all and instead some kind of probe sent by aliens. The object is also very bright (i.e. it has a high albedo), it has a weak comet-shaped coma, and it has a slight rate of acceleration apparently not caused by gravity.

For the first of the two studies, Jackson and Desch considered several different types of ice that could exist on such an object. They did that to determine how the evaporation of ice might contribute to the observed non-gravitational acceleration of the object. Scientists made calculations on how quickly these various ice creams sublimated (when a solid turns directly into gas) when ‘Oumuamua has passed through our Sun. Factors such as mass, shape and reflectivity have also been taken into account to explain the propulsive effect produced by sublimating ice.

Solid nitrogen turned out to be the best match. This is a very interesting result, as Pluto and Triton are known for their nitrogen-rich solid surfaces. and for albedos similar to that described for ‘Oumuamua.

Nitrogen could also explain the unusual shape of the object. “Oumuamua had only recently taken on his crepe appearance, a consequence of flying close to the sun, according to the study. The resulting melting caused the object to lose more than 95% of its total mass, and as the ice evaporated, “the shape of the body would have become progressively more flattened, just like a loaf of bread does. soap when the outer layers are rubbed. through use, ”Jackson said.

In the second paper, the authors estimated the rate at which Pluto-like objects might have large chunks of ice ripped from their surface during their youth. They also estimated how fast these pieces would become interstellar and make the long trip to our solar system.

“A similar fragment, generated in another solar system, after traveling for about half a billion years in interstellar space, would correspond to the size, shape, luminosity and dynamics of [‘Oumuamua]The authors wrote in the second article. “The chances of detecting such an object, as well as other comet-like objects like the 2I / Borisov interstellar object, are consistent with the number of such objects we would expect in interstellar space if most star systems ejected comets and [nitrogen] fragments of ice with the same efficiency as our solar system.

The 2I / Borisov object, in case you were wondering, was detected in 2019, and it is the second known interstellar object to cross our solar system.

Matthew Knight, astrophysicist at the US Naval Academy and expert on ‘Oumuamua, was impressed with the comprehensiveness of the two studies.

“The authors did an excellent job of meeting various observational and theoretical constraints with a simple and consistent model,” said Knight, who was not involved in the new research. in an email. “Their key idea, that ‘Oumuamua was mostly composed of highly reflective nitrogenous ice, is both creative and plausible, as we have ample evidence that nitrogenous ice is common on the surface of Pluto and other large objects in the system. external solar.

Knight said these ideas had “a good chance of eventually being accepted as the best explanation for ‘Oumuamua”.

As it stands, we only know of two interstellar objects, “ Oumuamua and 2I / Borisov, but that could change soon thanks to the upcoming Vera C. Rubin observatory and the 10-year Legacy Survey of Space and Time. project.

“It is predicted that the LSST should find about one per year, so when we have 10 or 20 known objects, we’ll be in a much better position to do a statistical assessment, ”Knight said. “It will be very exciting to see how these results change our understanding of how our solar system works and reveal how similar or unlike our solar system is to other solar systems.”