A FEW years ago, in a Berlin laboratory, astrobiologist Iva Vilovic was thrilled to see garden cress sprouting under a light designed to mimic a “K-dwarf” star – an orange-hued star cooler and slower-burning than our yellow sun.
To her surprise, the cress grew even faster and taller than it did under simulated sunlight.
The results suggested that photosynthesis, the process that supplies energy for Earth’s entire food web, could also occur on planets orbiting these orange stars.
“K-dwarf light is a very interesting light source, and it should be considered, if not prioritised, for any type of search for extraterrestrial life, in my opinion,” said Vilovic, now at the Leibniz Institute for Astrophysics in Potsdam, Germany.
In particular, alien life might thrive on planets slightly larger than Earth, known as super-Earths, orbiting these stars.
Some scientists believe such planets could be among the liveliest places in the galaxy, perhaps even more suitable for life than our own world.
They call them “superhabitable worlds” – planets where carbon-based life could persist longer and evolve into more complex and diverse forms.
As imagined by scientists, a superhabitable world would be about 20% to 30% wider and twice as massive as Earth, orbiting at just the right distance from its star for liquid water to exist on the surface.
Its stronger gravity would help retain a thicker atmosphere, creating a warmer, more stable climate.
A larger iron core could also generate a stronger magnetic field, offering better protection against cosmic radiation.
The surface might resemble a paradise of shallow seas and archipelagos.
Stronger gravity would make the planet rounder and smoother, with shallower ocean basins and fewer extreme variations in terrain.
On Earth, tropical islands and shallow seas are among the most biodiverse habitats.
Imagine an entire planet covered in such environments, where isolated islands and varied landscapes encourage the evolution of distinct species.
Clear, shallow waters would allow light to reach the seabed, sustaining abundant alien algae and plant life, and in turn a thriving marine ecosystem.
The light could come from the orange glow of a K-dwarf star.
The idea of looking beyond Earth-like planets gained traction in the 2010s.
Astronomers had long concentrated on finding rocky, watery planets roughly the size of Earth, orbiting stars similar to our sun.
But should Earth really be the benchmark?
The question was raised by John Armstrong, a professor at Weber State University in Utah, in the comments section of an online astrobiology seminar: “Shouldn’t there be planets more habitable than Earth?”
It got astronomer Rene Heller, now at the Max Planck Institute for Solar System Research in Germany, thinking.
In the search for chemical signs of life on distant worlds, he argued, scientists had been looking for Earth twins when our planet might not be the ideal model for habitability.
“Currently, humanity is looking for Earth-like planets with the same anthropocentric bias,” Heller said. “Of course, Earth is special to us. But from a universal perspective, why should Earth be a reference?”
After all, Earth is only marginally habitable.
Most astrobiologists believe liquid water on a planet’s surface is essential for life to emerge.
On Earth, the first bacteria appeared almost as soon as water accumulated on its cooling surface roughly four billion years ago.
But if Earth were just 2% closer to the sun, that water might never have pooled. Instead, it would have boiled away.
We got lucky, but our luck will not last.
The sun is gradually expanding and brightening, and scientists estimate that Earth will become too hot to sustain complex life such as plants and animals in roughly half a billion years.
For Heller, the search for more habitable worlds is about answering some of humanity’s biggest questions.
It is about “finding out if we are alone, if we could have been found, if there’s someone to talk to”, he said.
“Although I am not, at least in my everyday life, a very spiritual person,” he added, “it’s nevertheless something that at least drives me – this question, Could there be someone?”
Heller approached Armstrong, and together they published a 2014 paper introducing the concept of superhabitable worlds, which they envisaged as archipelago-covered super-Earths.
They argued that cool, relatively small K-dwarf stars would make better hosts for such planets than sun-like stars.
These stars burn their hydrogen fuel more slowly and brighten far more gradually.
Our sun has about five billion years of hydrogen fuel remaining before it expands into a red giant, eventually engulfing Earth.
K-dwarfs, by contrast, can shine steadily for tens of billions of years.
Life on a planet orbiting one would therefore have much longer to evolve, potentially producing increasingly complex organisms.
What those life forms might look like is anyone’s guess.
Earth’s inhabitants have grown increasingly complex over the past four billion years, eventually producing human-level intelligence.
Whether evolution elsewhere could go further remains an open question.
For Vilovic, the search for superhabitable planets is partly “an idealistic dream of a world that has beautiful conditions that are not being influenced by humans in a negative way”.
She also sees it as a “drive to find extremes” – the most favourable conditions for the kind of life scientists already understand.
And she is optimistic that such worlds exist.
“I like to believe that statistically speaking, in the realm of the universe, it is likely that life exists – especially on superhabitable planets,” she said. — ©2026 The New York Times Company
This article originally appeared in The New York Times
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