2 research outputs found
Spin state and moment of inertia of Venus
Fundamental properties of the planet Venus, such as its internal mass
distribution and variations in length of day, have remained unknown. We used
Earth-based observations of radar speckles tied to the rotation of Venus
obtained in 2006-2020 to measure its spin axis orientation, spin precession
rate, moment of inertia, and length-of-day variations. Venus is tilted by
2.6392 0.0008 degrees () with respect to its orbital plane. The
spin axis precesses at a rate of 44.58 3.3 arcseconds per year
(), which gives a normalized moment of inertia of 0.337 0.024
and yields a rough estimate of the size of the core. The average sidereal day
on Venus in the 2006-2020 interval is 243.0226 0.0013 Earth days
(). The spin period of the solid planet exhibits variations of 61 ppm
(20 minutes) with a possible diurnal or semidiurnal forcing. The
length-of-day variations imply that changes in atmospheric angular momentum of
at least 4% are transferred to the solid planet.Comment: 20 pages, 7 figures, supplementary information. Submitted to Nature
Astronomy on October 14, 202
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Spin state and moment of inertia of Venus
Fundamental properties of the planet Venus, such as its internal mass
distribution and variations in length of day, have remained unknown. We used
Earth-based observations of radar speckles tied to the rotation of Venus
obtained in 2006-2020 to measure its spin axis orientation, spin precession
rate, moment of inertia, and length-of-day variations. Venus is tilted by
2.6392 0.0008 degrees () with respect to its orbital plane. The
spin axis precesses at a rate of 44.58 3.3 arcseconds per year
(), which gives a normalized moment of inertia of 0.337 0.024
and yields a rough estimate of the size of the core. The average sidereal day
on Venus in the 2006-2020 interval is 243.0226 0.0013 Earth days
(). The spin period of the solid planet exhibits variations of 61 ppm
(20 minutes) with a possible diurnal or semidiurnal forcing. The
length-of-day variations imply that changes in atmospheric angular momentum of
at least 4% are transferred to the solid planet