David Jewitt et al 2020 ApJL 896 L39

Hubble observations of interstellar comet 2I/Borisov reveal an outburst and splitting of the comet’s nucleus, likely ejecting one or more meter-sized boulders that nonetheless made up a small fraction of the comet’s mass.

Thomas M. Esposito et al 2020 AJ 160 24

A ~4-year direct imaging survey of 104 stars resulted in 26 debris disks and 3 protoplanetary/transitional disks being resolved in scattered light — 7 for the first time — and characterized.

V. A. Acciari et al 2020 ApJS 248 29

Observations of the TeV blazar Mrk 421 during flaring activity show energy-dependent variability on multi-hour timescales and energy-independent variability on sub-hour timescales, favoring a multi-zone scenario.

Yong Zheng et al 2020 ApJ 896 143

Synthetic observations of simulated Milky Way analogs demonstrate and quantify multiple observational biases that are at play when we study the Milky Way’s circumgalactic medium.

Matija Ćuk et al 2020 Planet. Sci. J. 1 22

Simulations of the past tidal evolution of the Uranian system suggest that the most recent major mean–motion resonance between two large moons, Ariel and Umbriel, greatly influenced the system’s current confirguration.

Noé Brucy et al 2020 ApJL 896 L34

Models show that stellar feedback is not sufficient to regulate star formation in gas-rich high-redshift galaxies, but external driving of turbulence could further reduce the star formation rate to that observed.