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Niku, Drac and L91 Perturbed by Planet Nine…or Something Else?

Dr Konstantin Batygin and Dr Mike Brown argue in their latest paper that the retrograde Kuiper Belt Objects Niku and Drac could have once been extended scattered disk objects (1).  If you have been following these blogs during 2016, it will come as no surprise to you to hear that the influence which perturbed them into their anomalous current orbits was Planet Nine, the 10+Earth-mass planet lurking several hundred-plus Astronomical Units away, whose gravitational influence seems to be influencing the objects in and beyond the Kuiper Belt beyond Neptune (2):

“Adopting the same parameters for Planet Nine as those previously invoked to explain the clustering of distant Kuiper belt orbits in physical space, we carry out a series of numerical experiments which elucidate the physical process though which highly inclined Kuiper belt objects with semi-major axes smaller than a < 100 AU are generated. The identified dynamical pathway demonstrates that enigmatic members of the Kuiper belt such as Drac and Niku are derived from the extended scattered disk of the solar system.” (1) Read More…

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Sub-Brown Dwarfs Hiding in Plain Sight

Not so long ago, brown dwarfs (failed stars caught in an awkward in-betweener zone between stars and planets) were hypothetical bodies.  Their low stellar masses allow for only a very short period of light-emission in their early years, after which they cool and darken considerably.

[A] brown dwarf has too little mass to ignite the thermonuclear reactions by which ordinary stars shine.  However, it emits heat released by its slow gravitational contraction and shines with a reddish colour, albeit much less brightly than a star.” (1)

It was recognised early on that if they existed at all, they would be very difficult to spot – and so it proved.  In recent years, the ability to detect these objects has improved considerably, including more effective infra-red sky surveys.  As they have become more common, the frontier of sub-stellar bodies has dropped in mass into the ultra-cool stellar bodies known as sub-brown dwarfs – many of which would equally properly be designated as rogue gas giant planets.  These objects tend to have masses below 13 times that of Jupiter (13Mj) (2).  These objects have always interested me greatly, and very early on in my own research efforts I was advocating the potential importance of sub-brown dwarfs in the hunt for additional planets orbiting our own Sun at great distances (3).  I used the term ‘Dark Star’ to describe these ultra-cool objects; a term suggested by a friend of mine.  Some can be found orbiting stars (usually beyond 50AU) while others are free-floating entities in their own right.

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