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Although planets are thought to usually<\/a> form around stars, they don’t always stay put. The early years of a planetary system can become gravitationally chaotic, and simulations suggest that a significant percentage of worlds get jostled out into interstellar space<\/a>.<\/p>\n These rogue planets are very difficult to detect, but scientists think there are a lot of them out there<\/a>. If there are 17 to 21 rogue planets for every star, as per a 2023 estimate<\/a>, that puts the number of these wandering worlds in the trillions<\/a>.<\/p>\n According to a 2025 paper<\/a>, these rogue planets \u2013 at least the larger ones \u2013 can form their own systems of moons<\/a>. It’s also possible for a world ejected from a star’s orbit to hang onto its moon<\/a>, according to modeling<\/a>.<\/p>\n Rogue planets themselves are not thought to be good places to look for life. One of the most critical ingredients for life on Earth is liquid water; there’s no form of life that we know of<\/a> that can exist without it.<\/p>\n To search for life, we must first search for the conditions suitable for liquid water. A world drifting through space with no star to warm it is unlikely to host those conditions \u2013 it’s far, far too cold.<\/p>\n However, a star isn’t the only thing that can generate warmth \u2013 and a rogue planet that has retained its exomoon might be able to warm that moon. During the process of ejection from a star, an exomoon’s orbit around a rogue planet is likely to be shifted towards a more oval shape.<\/p>\n This means its proximity to the planet changes over the course of its orbit, which generates a push-pull of stresses deep in the exomoon’s innards that heats it from within.<\/p>\n That, on its own, is not enough for habitability. There needs to be another ingredient that keeps the internal heat from radiating out into space. Previous models have solved this problem with a thick atmosphere of carbon dioxide<\/a> that acts like a blanket, trapping heat inside.<\/p>\n However, in extremely cold environments, carbon dioxide condenses, allowing heat to escape relatively rapidly. A 2023 study found that a carbon dioxide atmosphere could maintain exomoon habitability for up to around 1.6 billion years<\/a>.<\/p>\n This might be sufficient time for life to emerge, but insufficient for further development; it took until Earth was nearly 3 billion years old<\/a> for life to evolve multicellularity.<\/p>\n So Dahlb\u00fcdding and his colleagues turned to an alternative model; what if, they asked, the atmosphere was not carbon dioxide, but hydrogen? Hydrogen stays gaseous even in extremely cold conditions and can trap heat effectively.<\/p>\n This is because, although infrared radiation mostly penetrates hydrogen without stopping, under high-pressure conditions, hydrogen molecules can collide with each other, creating complexes that absorb and trap thermal radiation.<\/p>\n When the team modeled exomoons with hydrogen atmospheres, conditions conducive to liquid water remained stable for up to 4.3 billion years in some cases.<\/p>\n Related: A Distant Spacecraft Has Confirmed That Earth Is Habitable<\/a><\/p>\n Of course, other conditions<\/a> would need to be met for life to emerge and thrive, but as a starting point, this work shows that exomoon habitability is indeed plausible \u2013 that stars are not a requirement for conditions that could support life.<\/p>\n We don’t currently have any instruments capable of probing the atmospheres of these moons, if we find any, but there are ways to test the idea further in the realm of theory.<\/p>\n “In future work, we will explore habitable configurations beyond a hydrogen-dominated atmosphere and test whether they are stable and can trap sufficient heat,” the researchers write<\/a>. “Increasing the complexity of the model \u2026 will allow us to better assess the habitability of these unseen worlds.”<\/p>\n![\"Subscribe](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2026\/01\/1767449653_841_Generic-Health-Promo-Final-642x273.jpg\")
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