Witten proposes planet 9 is small black hole

[Lawrence Crowell]

This is entertaining. He also coauthored a paper below on using photon sails to perform this probing.

LC

https://arxiv.org/abs/2004.14192  

Searching for a Black Hole in the Outer Solar System

Edward Witten

There are hints of a novel object ("Planet 9") with a mass 5−10 M⊕ in the outer Solar System, at a distance of order 500 AU. If it is a relatively conventional planet, it can be found in telescopic searches. Alternatively, it has been suggested that this body might be a primordial black hole (PBH). In that case, conventional searches will fail. A possible alternative is to probe the gravitational field of this object using small, laser-launched spacecraft, like the ones envisioned in the Breakthrough Starshot project. With a velocity of order .001 c, such spacecraft can reach Planet 9 roughly a decade after launch and can discover it if they can report timing measurements accurate to 10−5 seconds back to Earth.

Comments:	4 pp, additional references
Subjects:	Earth and Planetary Astrophysics (astro-ph.EP); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
Cite as:	arXiv:2004.14192 [astro-ph.EP]
	(or arXiv:2004.14192v2 [astro-ph.EP] for this version)

https://arxiv.org/abs/2005.12336  

Exploration of the outer solar system with fast and small sailcraft

Slava G. Turyshev, Peter Klupar, Abraham Loeb, Zachary Manchester, Kevin Parkin, Edward Witten, S. Pete Worden

Two new interplanetary technologies have advanced in the past decade to the point where they may enable exciting, affordable missions that reach further and faster deep into the outer regions of our solar system: (i) small and capable interplanetary spacecraft and (ii) light-driven sails. Combination of these two technologies could drastically reduce travel times within the solar system. We discuss a new paradigm that involves small and fast moving sailcraft that could enable exploration of distant regions of the solar system much sooner and faster than previously considered. We present some of the exciting science objectives for these miniaturized intelligent space systems that could lead to transformational advancements in the space sciences.

Comments:	A White Paper to the National Academy of Sciences Planetary Science and Astrobiology Decadal Survey 2023-2032. 13 pages, 5 figures and 2 tables
Subjects:	Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)
Cite as:	arXiv:2005.12336 [astro-ph.IM]
	(or arXiv:2005.12336v1 [astro-ph.IM] for this version)

[ronaldheld]

Not certain those flyby micro craft will determine whether it exists.

     Ronald

[Lawrence Crowell]

On Saturday, May 30, 2020 at 1:49:23 PM UTC-5, ronaldheld wrote:

Not certain those flyby micro craft will determine whether it exists.

     Ronald

It requires some prior information on possible location. It is a radar or laser ranging process. It occurred to me that maybe a better approach would be to direct radar microwaves into the Kuiper belt. Return signals would come from reflecting off of Kuiper belt objects. This could establish a geodetic map out there. Also if there is an invisible gravitating body out there the small timing difference could be measured.

The problem I do see with actually sending spacecrafts out there is this involves a lot of spatial volume. If one's initial estimate on where this gravitating body is wrong by a few steradian angle measure you can easily miss it.

LC