Asteroids

Artist's concept of the interstellar asteroid 'Oumuamua (Image courtesy The international Gemini Observatory/NOIRLab/NSF/AURA artwork by J. Pollard)

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An article published in “The Astrophysical Journal Letters” reports a study on the interstellar asteroid 1I/2017 U1, known as ‘Oumuamua, that offers evidence that it’s not some sort of hydrogen iceberg. Abraham Loeb of the Center for Astrophysics | Harvard & Smithsonian (CfA) and Thiem Hoang of the Korea Astronomy and Space Science Institute (KASI) examined the premise of the study that proposed that possibility, that an object composed mostly of molecular hydrogen could form within a giant molecular cloud and be pushed in interstellar space. The researchers concluded that various processes would cause the sublimation of molecular hydrogen, so an iceberg probably couldn’t be formed or would be destroyed by the stars that formed in the same molecular cloud before it could even end up in interstellar space.

IIE iron meteorite sample (Photo courtesy Carl Agee, Institute of Meteoritics, University of New Mexico)

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An article published in the journal “Science Advances” reports the results of sophisticated analyzes indicating that IIE iron meteorites are fragments of a planetesimal that had a differentiated structure. A team of researchers conducted various types of tests that gave these results about meteorites called achondrites, composed of materials that were subjected to melting, differentiation, and crystallization. The difference compared to chondrites, meteorites composed of undifferentiated materials, shows that the objects they come from formed and evolved in different ways in space and time.

The disaggregation (top row) and linear fractures (bottom row) in rocks on asteroid Bennu

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An article published in the journal “Nature Communications” reports the evidence of thermal fractures on asteroid Bennu caused by the temperature difference between day and night. A team of researchers led by Jamie Molaro of the Planetary Science Institute in Tucson, Arizona, examined images of Bennu’s surface captured by NASA’s OSIRIS-REx space probe, and found examples of this phenomenon. It’s the first detection of this phenomenon on an object without an atmosphere, and this offers new information to understand the evolution of Bennu and in general of asteroids over time. That includes the progressive disaggregation of rocks through the particular effect of thermal fracturing called exfoliation.

A diagram of the evolution of the interstellar asteroid 'Oumuamua's size and shape

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An article accepted for publication in the “Astrophysical Journal Letters” reports a study on the interstellar asteroid 1I/2017 U1 / ‘Oumuamua that offers an explanation for its strange properties. Professor Gregory Laughlin of the University of Yale and Dr. Darryl Seligman of the University of Chicago examined the data collected during the various observations of ‘Oumuamua concluding that it could contain a significant percentage of hydrogen ice and could have originated in the heart of a molecular cloud.

The possible orbit of an interstellar centaur asteroid

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An article published in the journal “Monthly Notices of the Royal Astronomical Society” reports evidence of the interstellar origin of some asteroids of the centaur family and two transneptunian objects. Astronomer Fathi Namouni of the University of the Côte d’Azur in Nice, France, and his colleague Helena Morais of the Universidade Estadual Paulista, Brazil, used computer simulations to reconstruct the orbits of those asteroids backwards, concluding that they’re likely interstellar asteroids captured from another system that could have been much closer when the Sun and the stars born with it had just formed.