April 16, 2021

it could be the rest of an exocometa that disintegrated

it could be the rest of an exocometa that disintegrated

A synthesis of the data collected from asteroid 'Oumuamua has determined that it is about remnant of an interstellar comet shattered before its perihelion or closest passage from the Sun.

The study comes from Zdenek Sekanina, from NASA's Jet Propulsion Laboratory, specialized for almost 40 years in the study of meteors, comets and interstellar dust.

Sekanina discusses the possibility that the observations that began in October 2017 by the Pan-STARRS 1 Telescope were actuallyn fragment of the original object that entered our system at the beginning of 2017.

To begin with, Sekanina refers to a previous investigation by another famous astronomer, John E. Bortle, which indicates how weak comets in near-parabolic orbits that bring them closer to more than 1 AU from the Sun will probably suddenly disintegrate shortly before they arrive. to perihelion. Subsequent investigations, according to Sekanina, also indicate that, in some cases, a considerable fragment could be left behind.

As he states in his study, this fragment would resemble "a devolatilized aggregate of loose dust grains that may have an exotic shape, peculiar rotational properties and extremely high porosity, all acquired in the course of the disintegration event." If this sounds familiar, it is because the description fits perfectly with 'Oumuamua.

For example, one of the first things that astronomers determined about 'Oumuamua (apart from the fact that it was not likely to be a comet) was that it had a rather strange shape. Based on the readings acquired from the Very Large Telescope (VLT), a team of researchers determined that 'Oumuamua was an elongated object, probably composed of rocky material, reports Universe Today.

This was followed by a study done in 2018 by Wesley C. Fraser (and others), who found that, unlike the small asteroids and planetesimals in the Solar System (which have periodic turns), the turn of Oumuamua was chaotic. At that time, the team concluded that this was an indication of past collisions. But, according to Sekanina's assessment, this could be the result of the disintegration of the original object.

Sekanina then made comparisons with C / 2017 S3 and C / 2010 X1 (Elenin), two comets that experienced disintegration when they reached perihelion. In both cases, the disintegration of these comets involved an explosive event and the release of a "monstrous spongy aggregate powder". From this, Sekanina deduced that 'Oumuamua would not experience degassing and would be subject to the effects of solar radiation pressure.

Again, this is completely consistent with the observations made of 'Oumuamua. As pointed out by Avi Loeb, from Harvard University and the Harvard-Smithsonian Center for Astrophysics (CfA), in one of several research papers on the subject, the acceleration of 'Oumuamua upon leaving the Solar System it could not be attributed to degassing (as indicated above suggested).

In short, if the composition of 'Oumuamua included volatile materials (ie, water, carbon dioxide, methane, ammonia, etc.) as a comet, it would have experienced degassing when it approached our Sun, which would have been visible when it was detected after perihelion. However, this was not the case, which raised the question of how radiation pressure could be responsible for its acceleration.

At that time, Loeb suggested that a possible explanation for this could be that "Oumuamua was an artificial object, similar to the concept of 'Lightsail' currently developed by Breakthrough Starshot, but as Sekanina argues, this behavior could be the result of Oumuamua being of a class of previously unstudied object that is subject to radiation pressure.


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