Andy Lloyd's

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Blog 64   (July 2018)

Currently being written

  News, links, videos and comment   relating to the Dark Star Theory 

 

 

Ultra-Cool Brown Dwarf Wearing Shades

A very young binary star system in the constellation Chameleon has a tiny companion - an ultra low mass brown dwarf.  The existence of this very young brown dwarf/sub-brown dwarf has been confirmed by checking back through previous images of the CS Cha binary, and it is clearly part of this star system.  Its mass is uncertain, making it uncertain whether this is a planetary mass object or a young dwarf star.  The binary system has its own protoplanetary disk, perhaps some 55AU across.   This disk seems to be playing tricks with the light from the companion object, which is located some 210AU from the central binary star system (1).

This light is polarised to a highly unusual extent, which is making a calculation of the mass of the object difficult.  The dusty protoplanetary disk itself has a large cavity within it, perhaps as large as 15AU across.  This arrangement strongly implies that planetary formation is an ongoing process:

"From unresolved mid- to far-infrared photometry it is predicted that CS Cha hosts a disk with a large cavity. In addition, SED modeling suggests significant dust settling, pointing towards an evolved disk that may show signs of ongoing or completed planet formation." (2)

Whatever its mass turns out to be, the companion object also seems to have its own "unresolved disk and dust envelope" (2).

 

Written by Andy Lloyd,  9th July 2018

References:

1) Netherlands Research School for Astronomy "Dutch astronomers photograph possible toddler planet by chance" 8 May 2018 https://phys.org/news/2018-05-dutch-astronomers-toddler-planet-chance.html

2) C. Ginski et al. "First direct detection of a polarized companion outside of a resolved circumbinary disk around CS Cha" accepted for publication in A&A, 6 May 2018

 

 

 

 

 Image Credit: C. Ginski & SPHERE

 

 

Planetary Collision Jolted Uranus

It's often been thought likely that an early planetary collision was the reason for Uranus being knocked onto its side.  Recent scientific work using computer simulations has helped to confirm this, and nailed the culprit down to a planet of at least 2 Earth masses (1).  It may have been a grazing blow by the impactor, capable of reconfiguring/building the rings and moons, but insufficiently catastrophic to rip away more than about 10% of its atmosphere. 

Additionally, there's reason to suspect that at least some of the impactor has had a long-term effect upon the planetary properties of the injured ice giant.  The research team wonder whether materials embedded into Uranus (careful...) may have created an insulating layer which holds in the heat of the interior of the planet. 

"Most of the material from the impactor's rocky core falls in to the core of the target. However, for higher angular momentum impacts, significant amounts become embedded anisotropically as lumps in the ice layer. Furthermore, most of the impactor's ice and energy is deposited in a hot, high-entropy shell at a radius of ~3 Earth radii. This could explain Uranus' observed lack of heat flow from the interior and be relevant for understanding its asymmetric magnetic field." (2)

This might then explain why Uranus is so cold compared with its peers.  What I'm particularly interested in here is when this took place.  Was it during the planetary accretion stage, when the protoplanetary disk was being knotted into so many competing planetessimals, jostling for supremacy?  Or was it later, during the period known as the Late, Heavy Bombardment?  According to the Nice model (which I'm somewhat sceptical about), there was a period of migration of the great planets, bringing about chaos and disruption.  Was Uranus hit during this migratory phase?  This seems to be an open question.

 

Written by Andy Lloyd,  11th July 2018

References:

1)  Durham University press release "Cataclysmic collision shaped Uranus' evolution" 3rd July 2018 https://www.dur.ac.uk/news/newsitem/?itemno=35167 with thanks to John

2)  Kegerreis, J. et al. (2018). Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion. The Astrophysical Journal, 861(1)

 

 

 

 

 

   

 

 

 

 

 

 

 

     

 

 

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