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The interstellar comet 2I/Borisov bears a strong resemblance to Oort Cloud comets, judging from its appearance in images taken over the first six weeks of observation. To test the proposed affinity in more diagnostic terms, 2I is compared to Oort Cloud comets of similar perihelion distance, near 2 AU. Eight such objects are identified among the cataloged comets whose orbits have been determined with high accuracy. This work focuses on three particular characteristics: the light curve, the geometry of the dust tail, and the dust parameter Afrho. Unlike Oort Cloud comets with perihelia beyond the snow line, Oort Cloud comets with perihelia near 2 AU show strong evidence of the original halo of slowly accelerating, millimeter-sized and larger icy-dust grains only in early tail observations. The dust tail in later images is primarily the product of subsequent, water-sublimation driven activity nearer perihelion but not of activity just preceding observation, which suggests the absence of microscopic-dust ejecta. Comet 2I fits, in broad terms, the properties of the Oort Cloud comets with perihelia near 2 AU and of fairly low activity. Future tests of the preliminary conclusions are proposed.
We processed images taken with the Hubble Space Telescope (HST) to investigate any morphological features in the inner coma suggestive of a peculiar activity on the nucleus of the interstellar comet 2I/Borisov. The coma shows an evident elongation, i
The composition of comets in the Solar System come in multiple groups thought to encode information about their formation in different regions of the outer protosolar disk. The recent discovery of the second interstellar object, 2I/Borisov, allows fo
We present Hubble Space Telescope observations of a photometric outburst and splitting event in interstellar comet 2I/Borisov. The outburst, first reported with the comet outbound at 2.8 AU (Drahus et al.~2020), was caused by the expulsion of solid p
2I/Borisov is the second interstellar object (ISO) after Oumuamua (Meech et al. 2017), but differs from Oumuamua drastically with its extensive cometary activity. A key ingredient to understand the nature of this comet is its size. However, due to it
We present high resolution imaging observations of interstellar comet 2I/Borisov (formerly C/2019 Q4) obtained using the Hubble Space Telescope. Scattering from the comet is dominated by a coma of large particles (characteristic size 0.1 mm) ejected