HD 45364's Milankovich

Last couple years I missed this one: the HD 45364 system. 34.35 ±0.04 parsecs from here, in the southern "Bigger Dog" constellation, its star shines 0.637 L_⊙. In 2009 its two known planets were seen to orbit at 3:2 resonance like Neptune and its plutini. (It was actually the first resonance raised to publication.) Zhexing Li, Stephen Kane and three others were curious what another decade of study might offer.

They went with a dynamical model, which is of course better than Kepler (meant for a two-body system only) and feasible for these narrow bounds. Their equations echo more Laplace:

φb = 3λc - 2λb + ϖb
φc = 3λc - 2λb + ϖc

... but integrated numerically. They say the resonance is impermanent; the planets librate. It looks like 3:2 now but will shift, then shift back. That is the stability here. Eccentricity changes too, b 0-0.07 and c 0-0.03. Ah! Milankovitch. Which is about the limit of interplanetary interreactions, compare lately Gliese 1153 = HD 104067.

All this constrains the planets' mutual ratio of mass. It actually cuts the mass of c, which is unusual given that radial mass when not transiting is always given in M sini. They are considered 0.19 and 0.55 M_j. The angles i are such that sini approaches 1. That is: each planet orbit wobbles into edge-on to us some of the time.

As to how these giants got to the inner system: they were thought to be migrates from further-out. Two models allow for arrival into the quasiresonance here. Keeping in mind we still own no constraints on radius therefore density / composition.

The authors see space for exomoons; as migrates, these planets had space to accrete Jupiter-like menageries of rock and ice, before rolling inbound. At 0.9 AU, c's maximum eccentricity is 0.03; this half-Jovian cuts into the inner sector of the HZ where our Earth would be. Such moons as exist might include Iolikes, a rocky Ganymede around b, and an ice Ganymede around c which becomes a watermoon.

Li et al. suggest we keep watching this space for when b and maybe also c transit/s, as at least b should soon. With any moons.

If c does own a moon free of its planet's tides, that brings up habitability; although, I don't hold hopes for its internal magnet, being certainly tidally-locked and small. But: more HZ stretches beyond 0.9 AU. The authors think planets could survive here too. Nothing here has budged the Milankovitch dance; so if anything is out to 5 AU / 10 year period, it's not Jovian. But most likely is that even small planets will be migrates - therefore, I think, little Neptunes. Hycean.

Interplanetary fission pulse engine

h/t Stephen "Vodka" Green and Gizmodo, Howe Industries promises fission-driven pulsed plasma. Harry Wolper in Green's comments informs us that this is no Orion rocket; this one is smaller-scale, "only" delivering 100kN thrust with its 5000 N/N s specific-impulse. So if nothing else NASA might actually get permission to torch it up, as with FireStar, like from TLL2.

RocketStar did their boast when at SBIR phase 2. Howe has completed the NIAC phase 1. Why the different acronyms? - because RocketStar are working with the military. Although they did get to test it on a NASA Artemis mission.

Howe's promise meanwhile is to get a manned mission to Deimos ("Mars") in two months, rather than the Hohmann six - or the Aldrin five. Unlike with Hohmann or Aldrin: here the transport must take the engine, and use it, to accelerate and to decelerate.

Even with those longer-duration missions, someone's got to bring some kind of engine to dock with Deimos which presently lacks a spaceport. Howe's engine looks ... let's say, competitive with RocketStar's. It helps that Howe supplied some numbers which RocketStar didn't.

Forgeworld

55 Cancri e is a hot planet with a molten rock and metal surface, with compressed solid rock beneath that. We were just wanting confirmation on the conductivity (convectivity rather) and composition of its atmosphere.

NASA delivers, from two of the Webb's instruments. Dayside is 1810 K, which must be convecting from some (violent) wind; carrying said wind, is carbon monoxide and dioxide.

CO is a reducing-agent. If there was any iron-oxide to smelt, on this surface, it would be quite smelted. I suspect it just sinks. Rising up rather, they say: are these carbon gasses themselves; there's no way a planet this hot keeps its gas unless it is being replenished. It's not a stiff dead Black Planet, however much it acts like one on the surface.

Inflatable modules are closets

Sierra Space and Max Space are competing in the inflatable-module, er, space. The pioneering work was done by Bigelow, with the Expandable Activity Module (BEAM) on the ISS. … but Bigelow haven’t updated their “news” since 2019.

It all seems a bit dangerous for LEO with all those Kessler shards flying about, even with better space-tugs. Luckily, buried in this EVA story, is coming an experiment to molniya out to 1400 km before pulling back to LEO.

For LEO I rate inflatable mods as best for nonhuman activity. The air should be low-pressure and no-oxygen. I can think of electronics and perishable storage. If the seal breaks, no-one gets hurt and the air we actually breathe isn't lost; if there's an electric short, no fires start. It's a bit of a pest to get over there and tweak something, but it won't need full EVA and, again, if there's a breach the mechanic can get reeled in quickly and won't, like, lose an eye.

Remote aeroponics are coming, also. Since this process gives off oxygen, I don't want it for electronics or storage. Here too, I don't rate as human-breathable; this is whither we dump as much CO₂ as we can. We'll need, instead, circulation between this and the main station.

Persians on the moon

Reynolds links the wall of death. The "millennial" generation might rather consider Prince of Persia - in its 2000s form (not to be confused with our 2D version, fellow X'ers).

Imagine if the Islamic Republic could lob rockets to the Moon instead of at Jews all the time, sigh. But anyway.

I expect this is transportable to Mars' and Mercury's gravity. Maybe not for spinwheel space habitats, because of Coriolis; luckily those are already arbitrarily-imbued with gravity.

Running around slightly-angled walls for that extra bit of G does sound fun. But it may be hard on the ankles. Special gear for those?

The Guardian, bless it, took the time to look up alternatives - up in Northumbria University, where they found Nick Caplan. He points out that once we're talking special gear, we may as well go all the way with inflatable cuffs.

Hussey 918

The most wonderful person on Youtube reports on the currently-offline TOI/TESS project: it has pinned down a G system at 95 parsecs.

This tiny spot on the late-nineteenth-century photo-plates avoided the consideration of Flamsteed and Draper. William Joseph Hussey at the Lick Observatory notched "1905.17" as a "double star", publishing it March 1905 in his ninth catalogue: HU 918. It was subsequently ignored, basically; until it became TESS's "Transit Of Interest 4633". Those... ugh... "citizen scientists" precovered the data to dig into the binary's deep(er) history.

With the additional attention the binary's orbit is resolved: period 231 +32/-24 years. This is not as constrained as it could be, but in all fairness our observations pre-TESS aren't great for some tiny 95pc dotpair in a disused catalogue.

These astronomers for their part avoid the name "Hussey 918". This blog's juvenilia aside: they're unsure which star in it is the transit-of-interest. They do know which is A: it's a ~1.1 sol mass; B is 0.05 masses less. Unfortunately they are eccentric (0.91!) so they are interfering with each other's light, currently. So I will call whichever star owns the planets, "TOI 4633".

There's a Saturn(?)like b but it does not transit, so of poorly constrained mass and even volume; it remains a "candidate" pending more observation. Anton Petrov is excited about TOI 4633 c - the actual transit. This planet is 47.8 Earth mass +23.8/-27.6, which again will get better constrained dependent on stellar and "b" finetuning. Radius is better-constrained: ~2.4 Earth; contrast Neptune 3.85. Whether you call it subNeptune or superNeptune depends on whether you're talking volume or mass. Eccentricity is 0.12 a bit more than Mars'.

At this mass in its location, which rounds to 1.6 Earth flux even without that other Hussey companion: expect a large gas envelope. This will settle into a wholly obscurant clouddeck like Venus': Sudarsky II. These clouds likewise will be low on pH; although a magnetic field will keep in the water, at least. Petrov already knows no-one's living on this planet. I add: the planet's own tides will disrupt any "Doppler" world at 0.85 AU's L4/L5.

Petrov waxes more hyper about the possibility of Galilean moons. The Hill Radius would fit one; "b" is far inbound of the place. Um. Well. There's no impactor on this thing as can offer a moon like ours, of a decent proportion of this planet's mass. Titan's mass is 0.0225 Earth and that's including its shell of ice, ice which these moons won't have.

Whether these warm moons have water... there we really must speculate. How far out is the planet's magnetic shield? Are any moons Ganymedean, themselves? One can imagine a small interior moon by itself without Io-like tectonics. Or a larger moon anywhere also not being squashed, with its own dynamo. Otherwise (and most-likely) they're tiny irradiated rocks: think, Titania and Oberon.

For those who consider HU 918 important, and however good it be to constrain parameters: it might not be a candidate for Webb time - yet. Petrov considers prime time for a few more decades hence, when A and B separate sufficiently we can at least see which star is the T.-o'-I.

What this system buys us, rather: is a model of a binary system which can support a Neptunelike at Earthlike irradiance, allowing for those short hot summers of perihelion. It even offers a "hot Jupiter" inbound. Skiffy worldbuilders rejoice.

TESS 5/8: Back in business, as of yesterday.

Intelligent design, by genehacking

I don't trust "Vox Day" so a fair start-assumption wherever monsignor Beale hits a hot-button issue in drive-by snark, is: he's not on the level. On whatever has caused species evolution on this planet Earth, he hasn't restrained himself. Lately though, he has been... arguing the point: mostly from a 1966 conference. Now he's got Frank Tipler on board. Tipler endorses the alien gene-meddling theory.

The alien cannot have launched from this planet. It must have come from some other ... region. We are running short of regions as can host a sufficiently-advanced technology - and we'd need to ask, why, did that technology deem this place worth the visit. If it breached Einstein's speedlimit then - perhaps - we should fall at Its feet, in homage. Note: the Baghestan has already restricted "god" to any entity with transcosmic access.

Beale still engages in more snark than he needs to, in mocking the modern biologic synthesis as "epicycles". Well... yeah. But what's wrong with epicycles? Any study of a dynamic process must pile on additional factors. The "epicycle" which corrected Uranus' orbit was Neptune, in its own orbit. Likewise in medicine: organs must play in concert, or we call the failure "nonfunctional" even "cancerous". Medicine flows down the stream from biology.

For those who care to explore the genehacking FTL-alien hypothesis: here's "Mittens", 1966, 1966, more 1966 and some maths. That's not an endorsement... unless you're already worldbuilding a "Jackaroo" universe where those benevolent aliens have started doling out marginal planets, in which case - have at it. You can even put those humanoid Klingons and/or catgirls in there. Who's to judge.

SOLAR SYSTEMS 5/10: Suppose TRAPPIST-1 was constructed?