Chapter 1: Understanding Moonmoons

The term "moonmoon" is a whimsical way to describe a moon that orbits another moon. Alternatively known as "submoon," or the less common "subsatellite," these terms evoke curiosity, even though they diverge from the definition of satellites, which can include artificial constructs.

In the grand tapestry of the cosmos, it's not unusual for fragments of space debris to orbit larger celestial bodies like planets or stars. A moon, however, is typically an object large enough to maintain a spherical shape, possessing its own distinct surface characteristics—akin to a mini-planet.

While our solar system lacks genuine moonmoons, ongoing research in extrasolar planetary systems continues to reveal surprises. Although a confirmed "exomoonmoon" has yet to be identified, at least one substantial exomoon has been observed. The variations seen in distant planetary systems suggest the feasibility of sizable moonmoons orbiting unusually large moons of gigantic planets—phenomena we do not have in our immediate neighborhood.

One notable candidate for discussion is a hypothetical moon, potentially orbiting the gas giant Kepler-1625b, which is roughly 12 times the mass of Jupiter.

This massive "superjovian" orbits its star approximately every four days, categorizing it as a "hot superjovian." Kepler-1625 itself resembles our sun but is slightly cooler, placing Kepler-1625b at the inner edge of what we consider the "Habitable Zone." Though these circumstances hint at a dynamic environment, it does not reach the extreme conditions associated with brown dwarfs.

Interestingly, the parent star is likely a "yellow giant," indicating it has gone through substantial changes in luminosity and temperature. This means Kepler-1625b may have dwelled within a habitable zone for a significant portion of its existence.

While the potential existence of the "neptmoon," or Neptunian moon, has been challenged by recent observations, the concept of moonmoons remains intriguing. Speculation about their formation isn't far-fetched—larger moonmoons could form in specific scenarios, even if they're rare.

If you've read about Hycean worlds—sub-Neptunian pseudo-Super-Earths—you might recognize that some large, anomalously habitable Hycean worlds could resemble Neptunian environments. Neptune itself is notorious for its extreme conditions, with a cryogenic climate that could be described as one of the most meteorologically violent in the solar system, featuring permanent supersonic winds and even diamond rain.

Section 1.1: The Harsh Reality of Neptune

Neptune's atmosphere doesn't exhibit a clear transition between gaseous and liquid states, and while it doesn’t have a typical ocean surface, it could potentially harbor stunningly alien mixtures of water and ammonia. This conjecture illustrates the diverse possibilities that exist throughout the universe.

Let us imagine a scenario where a superjovian resides within its parent star's habitable zone, accompanied by a Neptunian moon. Tidal heating from their interactions could generate warmth, supported by potential radiative heating from the host star. Neptune, home to Triton—a moon larger than Pluto—exhibits cryovolcanism, hinting at a hidden ocean beneath its icy surface.

Chapter 2: The Cosmic Connection

In contemplating the relationship between our hypothetical superjovian and its moons, we envision a landscape ripe for life. The unique proximity of these celestial bodies raises intriguing questions about panspermia—the transfer of life across planets.

Life could potentially evolve on multiple celestial bodies within this system, each developing in distinct ways. The exploration of these worlds may reveal life forms that could radically reshape their understanding of existence and their place in the cosmos.

The dynamics of life emerging independently on these worlds could lead to transformative cultural exchanges, much like humanity's evolutionary journey. As we ponder the vast universe, we confront the possibility that our isolation may hinder our ability to progress as a species.

This article serves as the first part of a broader exploration into the biological, civilizational, and technological dynamics of our theoretical celestial trio, inspired by the real-world Kepler-165b and its tenuous moonmoon.