Vilović and colleagues (International Journal of Astrobiology, 2024) grew garden cress and a cyanobacterium for up to 14 days under three conditions, simulated sunlight, simulated light from a 4,300 Kelvin K dwarf at the distance where a planet would stay temperate, and darkness. Cress under the K-dwarf lamp often sprouted a day or two earlier and looked taller. Dry mass, water uptake and photosynthetic efficiency, the things the study actually measured, were comparable to cress under sunlight.

The measured result is parity. Photosynthesis works about as well in orange light, which is the useful finding. The stronger result belonged to the cyanobacteria, which showed higher photosynthetic activity and faster culture growth under K-dwarf light. The Times kept the plant and dropped the bacteria.

Heller and Armstrong put the best range at up to two or three Earth masses, large enough to keep a thicker atmosphere and a longer running geology, not so large that plate tectonics stalls. The 2020 follow up by Schulze-Makuch, Heller and Guinan (Astrobiology) narrowed it to about 1.5 Earth masses and about 10 percent wider than Earth.

There is no single definition. The Times figure sits between the two papers and is presented as settled.

This is the 2014 paper's picture. Stronger gravity flattens topography, which spreads water into shallow seas, and shallow seas are among the most productive habitats on Earth. A bigger iron core should make a stronger magnetic field. The article frames the passage as imagination, which is fair.

The same physics cuts the other way. Flatter topography with a little more water gives a world with no land at all, and models predict many super-Earths should be completely ocean covered. Cowan and Abbot (2014) argue a deep water cycle can pull enough water into the mantle to prevent that. Others find that stresses inside planets only slightly bigger than Earth can stop plates from moving. None of these traits (land fraction, tectonics, magnetic field) can be measured on any exoplanet with current instruments.

The number traces to Kopparapu and colleagues (2013), who moved the inner edge of the sun's habitable zone from 0.95 to 0.99 astronomical units. Their own paper says the real edge is probably closer to the sun, because the model left out clouds. A follow up the same year moved it to 0.97. One climate modeler told Physics World he could put a planet at 0.9 AU and it would be perfectly habitable.

The mechanism at that edge is a moist greenhouse, where water reaches the upper atmosphere and hydrogen leaks to space. That is a slow leak over long periods, with no boiling involved. And the article applies a present day boundary to an Earth four billion years ago, when the young sun was roughly 30 percent dimmer. On that Earth, two percent closer would have been warmer and still wet.

Zircon crystals suggest liquid water by roughly 4.4 billion years ago. The oldest widely accepted evidence of life is around 3.5 billion years old. Older claims, near 3.7 and 4.1 billion years, exist and are disputed.

Almost as soon is one reading of a gap of several hundred million years. Reasonable, and presented as consensus.

The best known calculation, Schröder and Smith (2008), puts the sun's maximum size about 7.6 billion years out and concludes Earth is swallowed, because tides drag it inward even as the sun's mass loss pushes it outward.

Earth's fate at that stage is still argued, and the conclusion has flipped several times since the 1920s. The expansion is also gradual on human scales. None of this matters to life, which ends long before. It does matter to a sentence written as settled.

K dwarfs live tens of billions of years, and their habitable zones sit closer in, so planets there transit more often and are easier to study. ESA lists Plato's launch for early 2027. The Extremely Large Telescope in Chile is 39 meters across and under construction. NASA's Habitable Worlds Observatory is a concept for the 2040s. Most rocky planets Webb has examined around small red M dwarfs have looked airless, though in July 2026 a team reported evidence that one of them, LHS 1140 b, has kept an atmosphere.

K dwarfs stay magnetically active longer than the sun does, and the 2014 paper treats them as a compromise on radiation. The article describes their light as steady.

The 2020 paper, which is the hypothesis's most concrete test against real data, screened more than 4,000 known exoplanets and found 24 candidates. None met every criterion, and all are more than 100 light years away. The 2014 paper named Alpha Centauri B as the ideal place to look, because an Earth mass planet had been reported there in 2012. That planet was later shown to be an artifact of the data.

No skeptic appears. When the idea was new in 2014, the astrophysicist Steven Desch told National Geographic that calling a planet superhabitable "is comparable to calling someone only a little bit pregnant." His point was that we cannot yet measure habitability in degrees on any planet but this one.