Register for updates

 
 

Astronomy & Astrophysics
RSS Feed
A New Spin on Saturn’s Peculiar Rotation
Wednesday, March 25, 2015 11:47:00 AM

TAU researcher's new system to measure Saturn's rotation can be applied to other planets as well

Tracking the rotation speed of solid planets, like the Earth and Mars, is a relatively simple task: Just measure the time it takes for a surface feature to roll into view again. But giant gas planets Jupiter and Saturn are more problematic for planetary scientists, as they both lack measureable solid surfaces and are covered by thick layers of clouds, foiling direct visual measurements by space probes. Saturn has presented an even greater challenge to scientists, as different parts of this sweltering ball of hydrogen and helium are known to rotate at different speeds, whereas its rotation axis and magnetic pole are aligned.

A new method devised by Tel Aviv University researcher Dr. Ravit Helled, published recently in Nature, proposes a new determination of Saturn's rotation period and offers insight into the internal structure of the planet, its weather patterns, and the way it formed. The method, by Dr. Helled of the Department of Geosciences at TAU's Raymond and Beverly Sackler Faculty of Exact Sciences and Drs. Eli Galanti and Yohai Kaspi of the Department of Earth and Planetary Sciences at the Weizmann Institute of Science, is based on Saturn's measured gravitational field and the unique fact that its east-west axis is shorter than its north-south axis.

According to the new method, Saturn's day is 10 hours, 32 minutes and 44 seconds long. When the researchers applied their method to Jupiter, whose rotation period is already well known, the results were identical to the conventional measurement, reflecting the consistency and accuracy of the method.

Between sunup and sundown on Saturn

For years, scientists have had difficulty coming up with a precise measurement of Saturn's rotation. "In the last two decades, the standard rotation period of Saturn was accepted as that measured by Voyager 2 in the 1980s: 10 hours, 39 minutes, and 22 seconds," said Dr. Helled. "But when the Cassini spacecraft arrived at Saturn 30 years later, the rotation period was measured as eight minutes longer. It was then understood that Saturn's rotation period could not be inferred from the fluctuations in radio radiation measurements linked to Saturn's magnetic field, and was in fact still unknown." The Cassini spacecraft had measured a signal linked to Saturn's magnetic field with a periodicity of 10 hours, 47 minutes and 6 seconds long — slower than previous recordings.

"Since then, there has been this big open question concerning Saturn's rotation period," said Dr. Helled. "In the last few years, there have been different theoretical attempts to pin down an answer. We came up with an answer based on the shape and gravitational field of the planet. We were able to look at the big picture, and harness the physical properties of the planet to determine its rotational period."

Helled's method is based on a statistical optimization method that involved several solutions. First, the solutions had to reproduce Saturn's observed properties (within their uncertainties): its mass and gravitational field. Then the researchers harnessed this information to search for the rotation period on which the most solutions converged.

Narrowing the margin of error

The derived mass of the planet's core and the mass of the heavy elements that make up its composition, such as rocks and water, are affected by the rotation period of the planet.

"We cannot fully understand Saturn's internal structure without an accurate determination of its rotation period," said Dr. Helled. Knowledge of Saturn's composition provides information on giant planet formation in general and on the physical and chemical properties of the solar nebula from which the solar system was formed.

"The rotation period of a giant planet is a fundamental physical property, and its value affects many aspects of the physics of these planets, including their interior structure and atmospheric dynamics," said Dr. Helled. "We were determined to make as few assumptions as possible to get the rotational period. If you improve your measurement of Saturn's gravitational field, you narrow the error margin."

The researchers hope to apply their method to other gaseous planets in the solar system such as Uranus and Neptune. Their new technique could also be applied in the future to study gaseous planets orbiting other stars.




Latest News

New Yeast Model of Metabolic Disorders May Lead to Life-saving Therapies

Unicellular organism mimics pathology and symptoms of congenital diseases, TAU researchers say.

TAU-Led International Team Discovers New Way Supermassive Black Holes Are "Fed"

These "giant monsters" were observed suddenly devouring gas in their surroundings.

New Biomarker Links Cancer Progression to Genome Instability

High level of specific protein in tumors indicates prognosis as well as optimal treatments, TAU researchers say.

Microplastics and Plastic Additives Discovered in Ascidians All Along Israel's Coastline

TAU report is first to assess presence of plastic additives in Eastern Mediterranean and Red Sea marine life.

Heart Cell Defect Identified as Possible Cause of Heart Failure in Pregnancy

TAU research has diagnostic and therapeutic implications.

Sustainable "Plastics" Are on the Horizon

New sustainable biopolymer technology developed by TAU researchers may one day free the world of its worst pollutant.

Drivers Who Can "Bid" for Parking Spaces May Improve Parking Options Around the World

Parking algorithm can relieve pressure on lucrative parking areas, TAU researchers say.

Breast Cancer Recruits Bone Marrow Cells to Increase Cancer Cell Proliferation

Cancer-associated fibroblasts are derived from bone marrow cells called mesenchymal stromal cells, TAU researchers say.

Epigenetic Map May Pave Way for New Therapeutic Solutions to Hearing Loss

Understanding the expression of and controlling the genes involved in hearing are milestone discoveries, TAU researchers say.

Gas Clouds Whirling Around Black Hole Form Heart of Extremely Distant Luminous Astronomical Object

Discovery is the first detailed observation of the environs of a massive black hole outside the Milky Way.

contentSecondary
c

© 2019 American Friends of Tel Aviv University
39 Broadway, Suite 1510 | New York, NY 10006 | 212.742.9070 | info@aftau.org
Privacy policy | Tel Aviv University