C. A. Higgins and D. SolusDepartment of Physics & Astronomy Middle Tennessee State Univ., Murfreesboro, TN

F. Reyes and the late T. D. Carr (Emeritus)Department of AstronomyUniversity of Florida, Gainesville, FL

History of Rotation History of Rotation Period measurementsPeriod measurements Galileo (1610) Schroeter (1787) Surface features Marth (1875, 1885) Jupiter ephemeris, Sys I and Sys II defined Williams (1896) nine zones of latitude Shain (1956) Radio Rotation Period Gallet (1957), Gardener and Shain (1958) Carr et al. (1958) - - - System III (1957) IAU (1962) --- first defined System III (1957) period 1960s and 70s many measurements: DAM and DIM Riddle & Warwick (1976) + 25 scientists agreed to the System III (1965) - - - 9h 55m 29.71s

Duncan (1971) decimetric measurement Carr (1972) decametric measurement Kaiser & Alexander 1972) decametric & power spectrum Berge (1974) decimetric measurement

IAU (1977) System III (1965) Sandel & Dessler (1988) System IV

System IV

18TL

1

8TR

20TL

2

0TR

22TL

2

2TR

• 5° bins Jupiter CML• Ephemeris SysIII (1965)

nObservatio

Activity

tt

PO .. Source A

Source B

Source C

• Peaks are Source A Occurrence Probability• 12-yr Declination Effect (DE)

DE

Multiple 12-yr dataCML shift < 0Period < SysIII(1965)

CML shift > 0 Period > SysIII(1965)

• P’ – new rotation period (in decimal hours)• P – old rotation period (9.92492 h = 9h 55m 29.71s)• Δt – time between observation epochs in years (this

example t = 24.017 y or 210533 h)• 360 – number of degrees per rotation• - degrees shift in longitude of the second histogram

with respect to the first that maximizes the correlation coefficient (this example -6.8°)

• Example = -6.8° → 9.92491 h ( = 9h 55m 29.68s)

tPP

360

1'1

0

Weighted Mean Period 9h 55m 29.689 ± 0.004s

SysIII (1965)NewPeriod

Weighted Mean Period 9h 55m 29.689 ± 0.004s Max Possible Drift ≈ 4 ms/yr (from Higgins et al., JGR 1997)

SysIII (1965)NewPeriod

Jupiter’s Internal Rotation PeriodJupiter’s Internal Rotation Period

Rotation Periods 1σ

Rotation Period Measurements

00.10.20.30.40.50.60.70.80.9

1

0.60 0.62 0.64 0.66 0.68 0.70 0.72 0.74 0.76 0.78 0.80

Rotation Period (in excess of 9h 55m 29s)

Sys III (1965)

Yu & Russell(2009)

Higgins et al.(1997)

Higgins et al.(MOP 2011)

ConclusionsConclusions Jupiter’s DAM Rotation Period

Weighted Mean Period 9h 55m 29.689s ± 0.004s Max Possible Drift ~ 4 ms/yr

No conclusive secular variation Radio sources are stable over long term observations

Discussion Differential rotation Other calculations IAU has returned the period back to Sys III (1965) IAU would like a response from the MOP community

Thank you!

Entered UF at 16; M.S. in 1940 WWII (physicist at Aberdeen, MD) Worked with A-bomb tests at Bikini First PhD in Astrophysics at UF (1958) Co-founder of UFRO, Radio program Univ. of Chile Involved with creation of Arecibo radio telescope Designed and build a 26 MHz array of (640 dipoles) 2 Books and many book chapters (Jupiter, Physics of the Jovian Magnetosphere, Radio Astronomy) Co-investigator of PRA group for Voyager missions Jupiter radio emissions (rotation and S-bursts) ASTEROID #96288 named and dedicated for Tom Advised over 25 PhD and MS theses Pioneer in VLBI > 30 years UF Professor; Retired in 1995 Loved Florida’s natural habitat and itsconservation

Dr. Thomas D. CarrDr. Thomas D. Carr1917 - 20111917 - 2011