September 8th, 1966 was a Thursday. Not a fresh-start-Monday or an exciting Saturday. A regular old Thursday; except that this one catalysed a cultural phenomenon. This was the Thursday that “Star Trek” was first broadcast, drawing viewers across the United States into a space-age world that revolutionised television.
The thing is, in 1966 no exoplanets (planets beyond our Solar System) had actually been discovered. Yet the franchise gave audiences a galaxy brimming with desert planets, ocean worlds, binary sunsets, and countless versions of Earth. Sixty years later, astronomers have confirmed more than 6,000 planets beyond the Solar System, known as exoplanets.
But how well do “Star Trek”’s fictional worlds compare with those astronomers have actually discovered?
When many of us think “Star Trek”, the first planet that comes to mind is the dry, hot, and rocky Vulcan. Canonically, it orbits 40 Eridani A, a real star around 16 light-years from Earth. Real stars invite real observations, which led to astronomers announcing a possible planet in orbit in 2018. Of course, this was nicknamed Vulcan. However, later work has shown that this apparent signal was likely caused by stellar activity, rather than a planet in orbit.
This is, unfortunately, a common issue. Stellar activity, such as starspots, convection, and other magnetic activity, is very good at producing signals that look incredibly planetary.
Although the candidate planet was ultimately discredited, genuine hot, rocky planets do exist around other stars. Many of them orbit extremely close, completing an orbit in less than an Earth day. Some may have molten surfaces, atmospheres poisoned with vapourised rock, or even permanent day and night sides. While Vulcan itself may not be real, nature has produced rocky worlds considerably more hostile than Spock’s birthplace.
In contrast to Vulcan, “Star Trek” also gave us planets almost entirely covered with water. One particularly intriguing case is The Waters, from Voyager’s Thirty Days episode. The Waters is a sphere of water, with no solid core, kept together by a containment field. This is a little different to what an astronomer would refer to as a water world, but a planet-sized mass of water could theoretically be held together by its own gravity, without the need for a containment field.
However, the immense pressure deep inside this would transform much of the water into high-pressure ice rather than leaving it as one enormous liquid ocean. While no exoplanet has been definitively proven to have a global ocean, there are candidates like TOI-1452 b — a super-Earth orbiting a red dwarf star — that could contain a much larger proportion of water than Earth. It’s important to keep in mind, however, that a water-rich planet doesn’t necessarily make a good home. Water could exist beneath a chokingly thick atmosphere, as high-pressure ice, or sitting above an inhospitable interior.
Something “Star Trek” got very right is planets with two or more suns, such as Risa under its twin stars. The first confirmed planet orbiting two stars — known as a circumbinary planet — was Kepler-16 b. As it orbits a binary star system, it would experience a double sunset from the surface…if a surface existed.
Unlike many of the fictional planets in “Star Trek”, Kepler-16b is a cold, gas giant; not somewhere we could sit and admire the view. In 1966, not only had exoplanets not yet been discovered, but astronomers had no observational evidence that planets could form and remain stable in dynamically complicated multiple star systems.
There are, however, many circumstances where reality goes far beyond what was imagined in “Star Trek”.
Take WASP-76 b, an ultra-hot gas giant around 640 light-years away. The planet has a dayside so hot that iron vaporises, and it could be re-condensing into iron-rain on the cooler nightside. KELT-9 b is similarly hot, with molecules torn apart by the heat and metals existing in the atmosphere. 55 Cancri e is a super-Earth that orbits its host star every 18 hours, and could be covered by a magma ocean. There are also rogue planets, wandering through space with no host star.
“Star Trek” frequently invented strange planets by changing one familiar feature, but nature stared at the rulebook and ripped it to shreds. We’ve observed planets that have combinations of temperature, gravity, chemistry, and orbital architecture that writers in 1966 never could have anticipated.
The greatest scientific accuracy in “Star Trek” wasn’t the description of any given planet. Instead, it beautifully predicted that we live in a galaxy in which planets are abundant, gorgeously varied, found around a huge range of stars, and worth investigating even when they are nothing like Earth.
The necessity of a large population of conveniently habitable, human-safe worlds for “Star Trek”’s storytelling definitely set a limitation on the types of planets explored throughout the franchise. Our discoveries so far show that finding planets with Earth-like conditions is incredibly difficult, but not that they aren’t out there, somewhere.
“Star Trek” gave us a galaxy teeming with strange new worlds. Sixty years later, the surprise isn’t that these worlds exist, but that the real ones are even stranger than writers dared to imagine.
