Cosmologists in Search of Planet Nine: the Case for CMB Experiments

Abstract

Cosmology experiments at mm-wavelengths can detect Planet Nine if it is the size of Neptune, has an effective temperature of 40 K, and is 700 AU from the Sun. It would appear as a ~30 mJy source at 1 mm with an annual parallax of ~5 arcmin. The challenge is to distinguish it from the approximately 4000 foreground asteroids brighter than 30 mJy. Fortunately, these asteroids are known to the Minor Planet Center and can be identified because they move across a resolution element in a matter of hours, orders of magnitude faster than Planet Nine. If Planet Nine is smaller, colder, and/or more distant than expected, then it could be as faint as 1 mJy at 1 mm. There are roughly $10^6$ asteroids this bright and many are unknown, making current cosmology experiments confusion limited for moving sources. Nonetheless, it may still be possible to find the proverbial needle in the haystack using a matched filter. This would require mm telescopes with high angular resolution and high sensitivity in order to alleviate confusion and to enable the identification of moving sources with relatively short time baselines. Regardless of its mm flux density, searching for Planet Nine would require frequent radio measurements for large swaths of the sky, including the ecliptic and Galactic plane. Even if Planet Nine had already been detected by other means, measuring its mm-flux would constrain its internal energy budget, and therefore help resolve the mystery of Uranus and Neptune, which have vastly different internal heat.

5 pages, 1 figure, ApJL accepted

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Cited by in corpus (20)

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• Orbital clustering of distant Kuiper Belt Objects by hypothetical Planet 9. Secular or resonant ?
• The fates of Solar system analogues with one additional distant planet
• The Hunt for Planet Nine: Atmosphere, Spectra, Evolution, and Detectability
• Making Planet Nine: A Scattered Giant in the Outer Solar System
• The Atacama Cosmology Telescope: A search for Planet 9
• Searching for Planet Nine with Coadded WISE and NEOWISE-Reactivation Images
• Preliminary constraints on the location of the recently hypothesized new planet of the Solar System from planetary orbital dynamics
• Finding Planet Nine: apsidal anti-alignment Monte Carlo results
• Probing Oort clouds around Milky Way stars with CMB surveys
• A 3pi Search for Planet Nine at 3.4 microns with WISE and NEOWISE
• Towards an explanation of orbits in the extreme trans-Neptunian region: The effect of Milgromian dynamics
• On the origin of extreme trans-Neptunian objects within Modified Newtonian Dynamics
• The Case for a Large-Scale Occultation Network
• A new approach to distant solar system object detection in large survey data sets
• A Search for Planet Nine with IRAS and AKARI Data
• A Far-Infrared Search for Planet Nine Using AKARI All-Sky Survey