Four years ago, astronomers discovered ‘Oumuamua – the first interstellar object known to pass through our solar system. The object had a series of strange and inexplicable features, some of which are consistent with an icy shard ripped from a Pluto-like object, according to new research.
“We suggest that ‘Oumuamua was probably thrown out of a young galaxy about half a billion years ago,’ explain the authors of two new research papers published in the Journal of Geophysical Research: Planets. Because the object exhibits features seen on Pluto and Neptune’s moon Triton, say the authors, planetary scientist Alan Jackson and astrophysicist Steven Desch, both of Arizona State University, “‘Oumuamua may be the first piece of an exoplanet. that is brought to us. “
What they mean of course is that it is the first known piece of an exoplanet brought to us; and by exoplanet they mean an exo dwarf planet since Pluto is not technically a planet (if these corrections are not what they intended to say, then I say they should be).
In their papers, Jackson and Desch classify ‘Oumuamua as an “ex-Pluto,” which I think is pretty cool. Indeed, astronomers often compare exoplanets and other astronomical phenomena to those orbiting our sun, referring, for example, to hot Jupiters, super-Earths, and sub-Neptunes. We can now add “ex-Plutos” to the list of known astronomical objects, and based on this “Plutos” in general – small icy worlds in the Kuiper Belts (another analogous term taken from our solar system) of distant star systems.
To this traveler from afar brought us a visit, “we had no way of knowing if other solar systems have Pluto-like planets, but now we’ve seen a piece of one going beyond Earth,” Desch said in an AGU pronunciationWell, that assumes that this interpretation is correct, which if it does, means’ Oumuamua would be the first evidence that Pluto-like objects exist elsewhere in the galaxy.
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Oumuamua didn’t stay long when it visited our neighborhood in 2017, as it was traveling at speeds of 196,000 miles per hour (315,430 km / h). It’s hard to comprehend that kind of speed, but saying it traveled 54 miles per second (87 km / s) helps somewhat.
The interstellar object was fast, but also weird. Oumuamua is pretty small – about half the size of a city block – but exceptionally thin, with a depth of about 115 feet (35 meters). This form is so strange and unprecedented that there is at least one scientist said ‘Oumuamua may not be natural at all and instead some sort of probe sent by aliens. The object is also very shiny (i.e. it has a high albedo), it has a faint comet-like coma and apparently shows a slight acceleration not caused by gravity.
For the first Of the two studies, Jackson and Desch considered different types of ice that could be found on such an object. They did this to determine how the evaporation of ice might contribute to the observed non-gravitational acceleration of the object. The scientists have calculated how quickly these different types of ice are sublimated (when a solid instantly turns to gas) when ‘Oumuamua passed our sun. Factors such as mass, shape and reflectivity were also taken into account to explain the propulsion-like effect of the sublimating ice.
Solid nitrogen turned out to be the best match. That’s a very interesting result, as Pluto and Triton are known for their solid nitrogen-rich surfaces and for albedos similar to those described for ‘Oumuamua.
Nitrogen could also explain the object’s unusual shape. Oumuamua had only recently acquired its pancake-like appearance, according to the study, a result of flying close to the sun. The resulting melt 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 more and more flattened, much like a bar of soap does when the outer layers are rubbed off.” by use, ”Jackson said.
In the second paper, the authors estimate the speed at which Pluto-like objects can tear large chunks of ice from their surfaces during childhood. They also estimated the speed at which these stretches would become interstellar and make the long journey to our solar system.
A similar fragment, generated in another solar system, after traveling through interstellar space for about half a billion years, would correspond to the size, shape, brightness and dynamics of [‘Oumuamua], ”Wrote the authors in the second article. The probability of detecting such an object, as well as more comet-like objects such as the interstellar object 2I / Borisov, is consistent with the number of such objects that we expect in interstellar space as most galaxies have comets and [nitrogen] ice fragments with the same efficiency as our solar system. “
Object 2I / Borisov, in case you’re wondering, was detected in 2019, and it’s the second known interstellar object to pass through our solar system.
Matthew Knight, an astrophysicist at the US Naval Academy and an expert on ‘Oumuamua, was impressed with the completeness of the two studies.
“The authors did an excellent job satisfying several observational and theoretical limitations with a simple and self-consistent model,” said Knight, who was not involved in the new study. in an email. “Their main idea, that ‘Oumuamua consisted mainly of highly reflective nitrogen ice, is both creative and satisfyingly plausible, given that we have sufficient evidence that nitrogen ice is common on the surface of Pluto and other large objects in the outer solar system.”
Knight said these ideas “have a good chance of eventually being accepted as the best explanation for ‘Oumuamua.”
As it stands, we only know 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 expected that LSST should find about one per year, so if we have 10 or 20 known objects, we will be in a much better position to make a statistical assessment, ”said Knight. “It will be very exciting to see how these results change our understanding of how our solar system works and show how similar – or not – our solar system is to other solar systems.”