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September 11, 2021 Archives

Saturday, September 11, 2021

CONTINUITY: Railroad Car Ferry

Posted at 13:39 Permalink

TRACKING WITH CLOSEUPS: Narrowing the Search for Planet Nine


The existence of a giant planet beyond Neptune — referred to as Planet Nine (P9) — has been inferred from the clustering of longitude of perihelion and pole position of distant eccentric Kuiper belt objects (KBOs). After updating calculations of observational biases, we find that the clustering remains significant at the 99.6% confidence level. We thus use these observations to determine orbital elements of P9. A suite of numerical simulations shows that the orbital distribution of the distant KBOs is strongly influenced by the mass and orbital elements of P9 and thus can be used to infer these parameters. Combining the biases with these numerical simulations, we calculate likelihood values for discrete set of P9 parameters, which we then use as input into a Gaussian Process emulator that allows a likelihood computation for arbitrary values of all parameters. We use this emulator in a Markov Chain Monte Carlo analysis to estimate parameters of P9. We find a P9 mass of 6.2[+2.2−1.3] Earth masses, semimajor axis of 380[+140−80] AU, inclination of 16±5∘ and perihelion of 300[+85−60] AU. Using samples of the orbital elements and estimates of the radius and albedo of such a planet, we calculate the probability distribution function of the on-sky position of Planet Nine and of its brightness. For many reasonable assumptions, Planet Nine is closer and brighter than initially expected, though the probability distribution includes a long tail to larger distances, and uncertainties in the radius and albedo of Planet Nine could yield fainter objects.

Posted at 12:54 Permalink

THE HAPPENING WORLD: Tour of the Chinese Space Station Tianhe Core Module

Dialogue is in Chinese, with scrolling English subtitles.

Posted at 12:14 Permalink

CONTEXT: Thallium—Colour, Compounds, and Murder

Posted at 11:12 Permalink