Astrophysical and Planetary Sciences Colloquium

Monday, October 26, 2020 at 12:40

https://cuboulder.zoom.us/j/96981439846

Veerle Sterken, ETH Zurich

"Interstellar visitors in the Solar System"

A Pretty Image from the Talk

Abstract:

In 1993, the Ulysses dust detector registered interstellar dust particles from the local interstellar cloud on their way through the Solar System. These were the very first in situ detections of interstellar dust moving through the Solar System. Ever since, such particle fluxes have been further measured by Ulysses and other spacecraft, including measurements of dust composition by the Cassini Cosmic Dust Analyzer. In 2006, the Stardust sample return mission brought back samples of cometary dust, but also three interstellar dust candidates whose compositions were analysed in the laboratory. Also about two decades ago, first radar detections of (presumed) interstellar meteors were reported, and optical detections have followed. Finally, in 2017, a first very large interstellar visitor, the asteroid 1I/’Oumuamua, was detected in the Solar System during its journey outward toward interstellar voids. Two years later, the first interstellar comet 2I/Borisov was observed, this time before it reached its perihelion.

These observations of interstellar objects, from tiny to very large, have opened up a new and exciting area of science. These interstellar visitors provide ground truth information on what is usually observed in the dust phase by more classical astronomical means. However, the detection of such interstellar visitors is not straightforward. The smallest interstellar dust particles are filtered by electromagnetic forces, while interstellar dust larger than a micrometer is challenging to detect due to the limited surface areas of the in situ dust instruments. Atmospheric meteor observations are known to be prone to measurement errors in velocity, uncertainties in reducing meteor data, and ultimately in orbital determination.

In this talk we review the observations of these interstellar visitors. We explain the significance of the observations, the challenges for detection, and we give an outlook for the future.

 

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