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Tom Mazanec
2019-Mar-26, 10:57 AM
Imagine an Earth mass planet with a lunar mass BH orbiting 5000 miles away (1000 miles above the surface).
Will the two tidal bulges be symmetrical, or will the one below the BH be "pointy"?

Hornblower
2019-Mar-26, 11:44 AM
Imagine an Earth mass planet with a lunar mass BH orbiting 5000 miles away (1000 miles above the surface).
Will the two tidal bulges be symmetrical, or will the one below the BH be "pointy"?

If I am not mistaken the primary will be shaped sort of like an egg with the small end toward the secondary. At larger separations the shape becomes more nearly symmetrical.

Roger E. Moore
2019-Mar-27, 02:32 AM
There is some talk about lunar-mass black holes existing.

https://arxiv.org/abs/1706.03868

Lunar Mass Black Holes from QCD Axion Cosmology

Tanmay Vachaspati (Submitted on 12 Jun 2017 (v1), last revised 18 Jun 2018 (this version, v2))

In the QCD axion scenario, a network of domain walls bounded by cosmic strings fragments into pieces. As these fragments collapse, some of them will form black holes. With standard QCD axion parameters, the black holes will have lunar masses (Mbh∼10^−8M⊙). Even though their number density is difficult to estimate, arguments suggest that they can constitute a reasonable fraction of the critical cosmological density.