Planets Around Giant Stars: Life on a Short Leash express
A star nine times heavier than the Sun ignites a zone around it where liquid water could slosh on a planet's surface. But this zone is like a narrow strip of beach at low tide: it will vanish in 30 million years. Such stars live bright and die young, leaving life no time for the long journey from microbes to complex beings.
Astronomers traced the fate of Earth-like planets around stars of various masses — from light ones like our Sun to giants 120 times heavier. They accounted for how the star spins, how its wind blows, and how ultraviolet radiation strips the planet's atmosphere. It turns out that around a star of 9 solar masses, a planet can retain air and water at distances of 70–130 astronomical units — two to three times farther than Pluto is from the Sun. But already around a star of 12 solar masses, the habitable zone narrows to a thin thread, and at 15 solar masses, it disappears altogether.
After the star burns hydrogen in its core, it expands into a red giant, and the habitable zone briefly opens up again, but now at distances of hundreds of astronomical units. For a star of 25–30 solar masses, this window lasts from thirty thousand to one and a half million years. Less than the time humanity has existed as a species.
Such planets are like fireflies in a night forest: they flash for a moment and then fade. Searching for life on them is like catching a fleeting instant, but that is exactly where the most unexpected biosignatures might hide.
The habitable zone around a star of 9 solar masses lies farther out than Pluto's orbit — at a distance of 70–130 astronomical units. A year on such a planet would last several centuries.
In Stanislaw Lem's novel 'Solaris', the planet orbits two stars, a red and a blue one, and its ocean lives its own mysterious life. Massive blue stars are exactly the kind that give planets only a brief chance at habitability.