Ravit Helled

Research

Planetary formation Helled's research deals with the formation and evolution of planets in the Solar System and beyond. Her studies examine the relationship between the formation of planets and their internal structure, for the gas giants Jupiter and Saturn, and the ice giants Neptune and Uranus. The processes that lead to the formation of planets in the Solar System are compared to the formation of exoplanets. She also examines whether a uniform mechanism can be found predicting the formation of planets, and the differences among different planetary systems and the physical processes that influence the formation of planets in a particular system.

Internal structure of planets and time of internal rotation Helled's research group also examines the internal structure of planets and their composition. Computational models are developed to predict the dynamic behaviour of a planet and compare it with existing observations. The team is investigating the velocities of the gas giants' internal rotation and whether their structures can be related to the atmospheric movement of these planets.

Calculating the rotation periods of Saturn, Uranus and Neptune In 2010, Helled and collaborators suggested that the rotation periods of both Uranus and Neptune are in fact unknown. They suggested that the lengths of day on the ice giants are ≈16.58 hr (Uranus) and 17.46 (Neptune). In 2015, Helled and collaborators accurately calculated Saturn's rotation time (10 hours, 32 minutes, 45 seconds). The previous calculation was based on measurements of the Voyager 2 probe in 1981. However, calculations from the Cassini probe showed that there is a discrepancy in numbers and a gap in the understanding and calculating of Saturn's rotation time. The problem is that the components of Saturn's atmosphere, especially hydrogen and helium, travel at different speeds and do not attest to Saturn's own rotation. Helled's research determined the speed of rotation by measuring Saturn's gravitational field and calculating its density and oblateness (the fact that its polar diameter is smaller than its equatorial diameter).

Obstacles to the movement of winds in Uranus and Neptune Together with Yohai Kaspi and Oded Aaronson of the Weizmann Institute of Science, Adam Schumann, and Bill Hubbard of the University of Arizona, Helled succeeded in calculating that the strong winds blowing over Neptune and Uranus are limited to an atmospheric layer whose depth is not more than 1,000 km. On Neptune, these winds blow at speeds of about 2,000 km/h, with storms and strong jet currents. Since the discovery of these winds by the Voyager 2 probe, researchers have been trying to find out the extent of the phenomenon of wind, in order to better understand the composition of these ice giants. The team modelled the influence of the winds on the gravitational field of the planets to show that the jet currents constitute only a small percentage of the planet's mass. The movement of the winds changes the momentary mass of the planet and thus causes a fluctuation in its gravitational field. By calculating the relationship between pressure and density for the wind pattern and measuring the torque, they proved that the wind layer is limited to 1,000 km thick and constitutes only a few percent of the planet's mass. The researchers were able to create a map of the gravitational field of the planets based on wind data.

Selected publications

Awards and recognition Selected among the 50 most influential women of Forbes Israel (2015) Selected among the 50 influential women of Globes (2016) Selected in the list of the 40 most promising young people of the year by Globes (2016) The Mako site selected her as one of its most influential people in Israel (2016) The 2024 Farinella Prize for her outstanding contributions to research into ‘the internal structure of planetary bodies: clues on formation processes of the Solar System’.