A NEW EVOLUTIVE SCENARIO FOR THE JUPITER'S CORE?

Image: This artist's conception shows a Jupiter-sized planet forming from a disk of dust and gas surrounding a young, massive star. - NASA

Astronomers have discovered nearly 500 planetary systems each with multiple planets, and typically these systems include a few planets with masses several times greater than Earth's (super-Earths), orbiting closer to their star than Mercury is to the Sun, and Jupiter-like gas giants are also often found close to their star. [2]

In a recent paper (Raymond et al. 2016) the authors suggest an alternative scenario for the formation of the Jupiter's core: it may have formed in the innermost of the protoplanetary disk and it would later be migrated to the outer region via planet-disk interactions.

The migration of the Jupiter's core may have removed solids from the inner disk by resonance and it may thus explain the absence of terrestrial planets closer than Mercury. Finally it may also have influenced the formation of the Saturn's core.

[1] Raymond et al 2016 (accepted to MNRAS) - Did Jupiter's core form in the innermost parts of the Sun's protoplanetary disk? (arXiv)
[2] Jupiter - (Wikipedia)

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ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).

CONSTRAINTS ON THE LOCATION OF A POSSIBLE 9TH PLANET

Image: The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Such an orbital alignment can only be maintained by some outside force, Batygin and Brown say. Their paper argues that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech The astronomers have noticed some of the dwarf planets and other small, icy objects tend to follow orbits that cluster together. To explain the unusual distribution of these Kuiper Belt objects, several authors have advocated the existence of a superEarth planet in the outer solar system ( planet Nine or planet X ).

RADIATIVE CLEARING OF PROTOPLANETARY DISCS

Image: protoplanetary disc surrounding the young star HL Tauri, a very young T Tauri star in the constellation Taurus, approximately 450 light-years (140 pc) from Earth in the Taurus Molecular Cloud. These new ALMA observations reveal substructures within the disc that have never been seen before and even show the possible positions of planets forming in the dark patches within the system. Credit: ALMA (ESO/NAOJ/NRAO) T Tauri stars are pre-main-sequence stars in the process of contracting to the main sequence. Their central temperatures are too low for hydrogen fusion. Instead, they are powered by gravitational energy released as the stars contract, while moving towards the main sequence, which they reach after about 100 million years. Roughly half of T Tauri stars have circumstellar disks, which in this case are called protoplanetary discs because they are probably the progenitors of planetary systems like the Solar System.

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