Dynamical constraints on the origin of hot and warm Jupiters with close friends

Image: Artist's concept of a "hot Jupiter" - Credit: NASA/JPL-Caltech

Gas giants orbiting their host star within the ice line are thought to have migrated to their current locations from farther out.

In a recent paper (Antonini et al 2016) the authors consider the origin and dynamical evolution of observed Jupiters, focusing on hot and warm Jupiters with outer friends. They show that the majority of the observed Jupiter pairs (twenty out of twenty-four) will be dynamically unstable if the inner planet was placed at >~1AU distance from the stellar host.

This finding is at odds with formation theories that invoke the migration of such planets from semi-major axes >~1AU due to secular dynamical processes (e.g., secular chaos, Lidov-Kozai oscillations) coupled with tidal dissipation. In fact, the results of N-body integrations show that the evolution of dynamically unstable systems does not lead to tidal migration but rather to planet ejections and collisions with the host star.

This and other arguments lead the authors to suggest that most of the observed planets with a companion could not have been transported from further out through secular migration processes. More generally, by using a combination of numerical and analytic techniques they show that the high-e Lidov-Kozai migration scenario can only account for less than 10% of all gas giants observed between 0.1-1 AU.

Simulations of multi-planet systems support this result. Their study indicates that rather than starting on highly eccentric orbits with orbital periods above one year, these "warm" Jupiters are more likely to have reached the region where they are observed today without having experienced significant tidal dissipation.

Antonini et al 2016 (preprint) - Dynamical constraints on the origin of hot and warm Jupiters with close friends - (arXiv)

Comments

A SIGNIFICATIVE FRACTION OF BARYONS RESIDE IN THE FILAMENTS OF THE COSMIC WEB

(Credit: NASA, ESA, and E. Hallman (University of Colorado, Boulder) Observations of the cosmic microwave background indicate that baryons (protons, neutrons, etc., - the ordinary matter just to understand) occupies only 5% of the total energy content of the Universe (95% is dark matter and dark energy). However in the local universe approximately half of this "ordinary" matter it has never been observed.

A UNIVERSE WITHOUT A CENTER?

Image Credit: Eugenio Bianchi, Carlo Rovelli & Rocky Kolb. According to the standard theories of cosmology, there is no center of the universe. In a conventional explosion, material expand out from a central point and the instinct suggests that with the Big Bang happened something similar. But the Big Bang was not an explosion like that at all: it was an explosion of space, not an explosion in space . The Big Bang happened everywhere in the Universe.

A Sapphire Super-Earth

Twenty-one light years away, in the constellation Cassiopeia, a planet by the name of HD219134 b orbits its star with a year that is just three days long. With a mass almost five times that of Earth, it is what is known as a super-Earth. Unlike our planet, however, these super-Earths were formed at high temperatures close to their host star and contain high quantities of calcium, aluminum and their oxides – including sapphire and ruby. HD219134 b is one of three candidates likely to belong to a new, exotic class of exoplanets. These objects are completely different from the majority of Earth-like planets. They have 10 to 20 percent lower densities than Earth. Researchers looked at different scenarios to explain the observed densities. For example, a thick atmosphere could lead to a lower overall density. But two of the exoplanets studied, 55 Cancri e and WASP-47 e, orbit their star so closely that their surface temperature is almost 3,000 degrees and they would have lost this ...

SpaceTime

Search This Blog