For all we know, Earth is the only place in the universe that hosts life.
Every living thing here depends on liquid water, which provides the perfect environment for chemical reactions.
Life began billions of years ago with simple single-celled organisms, but it took nearly three billion years for complex, multicellular life to emerge.
Human beings, capable of looking at the stars and asking whether we are alone, have only been around for a tiny fraction of Earth’s history.
This raises a fascinating possibility: planets with liquid water may be common, but intelligent life might be rare.
If we want to meet extraterrestrial life, we may have to go out and find it ourselves.
The problem, of course, is the scale of the universe. Even the nearest stars are many light-years away, and with current technology we could only hope to visit the very closest ones within a human lifetime.
That means the best places to look are sun-like stars near Earth—about 60 stars within 30 light-years.
If any Earth-sized planets orbiting these stars also have the right temperatures for liquid water, they could be strong candidates for hosting life.
Finding such planets, however, is like looking for a firefly next to a spotlight. A star is a million times brighter than its orbiting planet, so separating their light is one of astronomy’s hardest challenges.
The sharper the image a telescope can capture, the better its chance of spotting the faint glow of a planet.
The sharpness depends on both the size of the telescope and the wavelength of light being observed.
Planets with liquid water shine brightest in infrared light, with wavelengths around 10 microns—twenty times longer than visible light. To separate an Earth-like planet from its star at 30 light-years away, a telescope would need to collect light across at least 20 meters.
And it would need to be in space, above Earth’s atmosphere, which otherwise blurs the image.
For comparison, the James Webb Space Telescope (JWST) is only 6.5 meters wide, and it was extremely difficult and expensive to launch. Building and launching a circular 20-meter telescope seems nearly impossible with current technology.
Scientists have suggested alternatives, like flying multiple smaller telescopes in formation, or using shorter wavelengths of light. But these methods face enormous technical challenges. Another idea is to launch a “starshade” spacecraft to block starlight before it reaches the telescope.
Yet this would require not only two spacecraft, but also enormous amounts of fuel to keep moving the starshade into position for different targets.
A new study published in Frontiers in Astronomy and Space Sciences offers a simpler solution: change the shape of the telescope mirror. Instead of a massive circular mirror, researchers propose a rectangular one, measuring one by 20 meters.
With this design, the telescope could separate a planet from its star along the mirror’s long axis. By slowly rotating the mirror, astronomers could search for planets at different positions around a star.
The study suggests such a telescope—similar in overall size to JWST, but with a different mirror shape—could discover half of all Earth-like planets around nearby sun-like stars in under three years.
If there really is about one Earth-like planet per sun-like star, this means roughly 30 promising candidates within 30 light-years. Some of these could reveal atmospheric signatures of life, such as oxygen created by photosynthesis.
In the long run, the most promising targets could even be visited by space probes, sending back pictures of alien landscapes. The rectangular telescope may not just be a clever piece of design—it could be our best chance of finding Earth 2.0.
Source: Frontiers.
