GIANT PLANETS IN PROTOPLANETARY DISKS WITH SPIRAL ARMS?

There are many theories about the formation of the planets but the direct observational evidences are quite a few. Recently, the ground-based telescopes photographed two large spiral arms around two young stars. The mechanisms that have generated these structures are not very clear.

Recent studies based on computer simulations suggest that such structures may indicate the presence of giant planets "invisible" (too faint to be seen with existing tools). A comparison between simulations and direct observations may be able to obtain not only the position of the planet but also its mass.
The method proposed in addition to opening a new avenue for detecting extrasolar planets also offers a new look at the mechanisms that act in the early stages of planet formation.

To know more:
http://arxiv.org/abs/1507.03596
http://arxiv.org/abs/1507.03599
http://arxiv.org/abs/1511.01178
http://arxiv.org/abs/1412.3412
http://hubblesite.org/newscenter/archive/releases/2015/40/full/

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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 ).

A METHOD TO TEST THE EXISTENCE OF REGULAR BLACK HOLES

Illustration of a black hole. Image Credit & Copyright: Alain Riazuelo The existence of the singularity is an intrinsic problem of the General Relativity (GR). At the fundamentally level, the resolution of the problem of the singularity lies with the expectation that under situations where quantum effects become strong, the behavior of gravity could possibly greatly deviate from that predicted by the classical theory of GR. Regular black hole solution are proposed with the same spacetime geometry outside the horizon as the traditional black hole, but bears no singularity inside. Whether or not black hole singularities should exist, they would be covered by the black hole horizon. The black hole horizon serves as an information curtain hindering outside observers from directly observing the interior structure of the black hole, and determining that whether or not the black hole singularity does really exist. A method is needed to check the correctness of the new constructions ...

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).

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