Home » Technology » Near star passage could explain the origin of the interstellar “cigar” How Oumuamua got its shape – scinexx

Near star passage could explain the origin of the interstellar “cigar” How Oumuamua got its shape – scinexx

Quiz solved? Researchers may have figured out how the interstellar object Oumumua got its exceptionally elongated shape – and why it resembles an asteroid rather than a comet. Accordingly, the “mother lump” of Oumuamua flew so close to a strange star that its tidal forces tore it into elongated fragments. At the same time, this also created the solid, low-ice crust of the rock, as the scientists report in the journal “Nature Astronomy”.

On October 19, 2017 discovered Astronomers created a cigar-shaped object that raced through the solar system at extremely high speed. The ‘Oumuamua chunk quickly turned out to be of interstellar origin. However, its cigar-shaped appearance and firm, asteroid-like crust were surprising. Because typically comets – icy chunks from the outer areas of a planetary system – are catapulted out and become interstellar objects.

Created at Sternpassage?

Now researchers may have solved the riddle of Oumuamua. “It’s a really mysterious object, but some features, such as its color and lack of radio emissions, suggest that Oumuamua is of natural origin,” said Yun Zhang of the Chinese Academy of Sciences. “Our goal was therefore to develop a scenario that can explain all of these fascinating peculiarities.”

Tearing an object through the tidal forces and forming elongated fragments.© NAOC / Y. Zhang

Together with his colleague Douglas Lin from the University of California in Santa Cruz, Zhang developed a model simulation that reconstructs a possible path of origin for the interstellar “cigar”. According to this, Oumuamua could have originated when a larger, comet-like object flew too close to its home star. With such a passage, the star’s gravitational influence creates strong tidal forces that can tear up even larger chunks.

Fragment of a torn comet

But can such an extremely shaped structure as Oumuamua arise? As the simulation showed, this is actually possible. Because when an object is torn apart by stellar tidal forces, many of its debris evaporate and melt. Under the influence of the tidal forces, however, they then condense into new, sometimes extremely elongated structures. “The ratio of the long to the short axis can even be greater than ten to one for these objects,” says Zhang.

Oumuamua could therefore be the fragment of a comet that once orbited an alien star. “We have shown that Oumuamua-like interstellar objects can be generated by tidal force-related fragmentation during close encounters with their central stars,” Lin says. The simulation also showed that the kinetic energy of these fragments is sufficient to be thrown out of their home system.

Explanation for asteroid-like crust

And yet another peculiarity of Oumuamua could explain this scenario: its solid, rock-like crust and the lack of a visible tail. Because in contrast to the interstellar comet 2l / Borisov At first glance, Oumumua looks more like an asteroid. Nevertheless, slight outgassings seem to influence its trajectory, as astronomical observations suggest.

The simulations now confirm this. They show that while the fragment is formed, volatile substances outgas from the surface of the fragment, but water ice and other such components remain inside. “This process explains not only the surface colors of ‘Oumuamua and the absence of a visible coma, but also the dryness of such interstellar objects,” says Zhang.

According to the researchers, there could still be tons of such “masked” interstellar comets in space. “Oumuamua is just the tip of the iceberg,” says Lin. (Nature Astronomy, 2020; doi: 10.1038 / s41550-020-1065-8)

Source: University of California-Santa Cruz

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