HIP 29724 might have an Earth someday

Telescope-designers talk Hill-Radius. Worldbuilders, faced with a Jovian or brown-dwarf, should look instead to the Kirkwood Gaps. Between 3:1 and SJL1, only asteroids form. Note that Ceres is a capture, therefore unnaturally large for the Belt.

We'll start with the Hadean systems recently identified. Of these, HD 43976 = HIP 29724's B has the tightest orbit at 6.3 AU. This star is a now-G2V 1.04 M_⊙; its presumed-main companion is, at 0.063 M_⊙, a brown-dwarf.

The paper didn't tell us a year so we'll ask Kepler: (a*a*a) /(y*y) = 1.04+0.063 for this system's barycentre. 15.056 Earth years; compare ol' Jove, 11.862. The main (canonical) Kirkwood will be a third that, 5.019 years; Kepler says this is 3.029 AU (compare our gap 2.5 AU / 3.95 years). Note: well inside the 4.59 AU orbit of this sucker's 1.71 AU L1.

I find in 4:1 and 5:1 no safe-space, either; betwixt 4:1 and 5:1 lies the Hungaria. That's <2.06 AU here; HIP 29724's corresponding Hungaria runs 2.15-2.5 AU. Mars makes difficult to figure what might exist in the Hungaria; if Mars weren't actually, like, here. Maybe instead a Magyar planet could exist at a high inclination. It's metastable so best if resonant, also, with an Earthlike say at 3:2.

HIP 29724's habitable-zone is trickier inasmuch as my immediate source the Universe Guide is wrong about the star's age. This error, I suspect, comes from that the star is hot like an old star even though it is very young. I just have to trust 1.08 luminosity and the 5000s K. These will grow over time in any case. According to the calculator, expect (at 6000 K, which seems reasonable once it all gets Archaean and beyond) a habitable-zone from maybe 0.95 AU out to 1.7 AU.

All assumes a general lack of eccentricity which seems unconstrained so far. I will say that as the ratio gets longer (closer to the main star), the distances between the gaps shorten - therefore, the available mass to form a planet shortens. On the other hand also lengthening is the epoch against n-body chaos; such that Mars does exist in our System, and so much more the Earth-Venus resonance.

As necessarily-small Mars hasn't hurt us down in the 0.7-1.0 AU range, neither would (I think) a super-Earth "Planet Budapest". So I'm not (yet) seeing a problem with HIP 29724 spawning planets in habitability.

SEEING IT NOW 6/25: I did some dynamic sketches. HIP 29724 is a long shot. These guys thought HIP 21152 was more interesting anyway.