One day, the futuristic telescope could provide detailed images of planets hundreds of light-years away.

Astronomers have already discovered more than 5,000 planets orbiting other stars. And while that’s an outstanding achievement, we actually learn quite little about these distant worlds. We know they exist, but the rest is a mystery. However, researchers have devised a way to characterize exoplanets in much more detail. “We want to take pictures of exoplanets that are as sharp as the pictures we can take of planets in our own solar system,” said study researcher Bruce Macintosh.

Gravity lens

The researchers have in mind a special telescope capable of taking very bright pictures of exoplanets. How? Through a gravitational lens. A gravitational lens is like a cosmic magnifying glass and bends the light from distant objects. And according to the researchers, it should be possible to use this phenomenon to produce images that are at least 1000 times sharper than the strongest imaging technology currently in use.

More about gravity lenses
Currently, astronomers use gravitational lensing to study distant galaxies. As mentioned, a gravitational lens is like a cosmic magnifying glass and bends the light from distant objects. Unlike a magnifying glass with a curved surface that bends light, a gravitational lens has a curved space-time that makes it possible to image distant objects. Suppose two galaxies are – seen from Earth – one behind the other. One galaxy is five billion light-years from our planet, while the other is eight billion light-years away. Light from the distant galaxy travels past the foreground galaxy, diffracting and amplifying it.

As described above, therefore, galaxies can act as a gravitational lens. But our own sun also acts like such a lens. The researchers therefore propose to build a telescope that uses the sun as a lens.

Sun

How does that work? The telescope, the sun and an exoplanet must align, with the sun at the center. That way, scientists can use the sun’s gravitational field to magnify the light from the exoplanet. “With this technology, we hope to create a picture of a planet 100 light-years away that is as sharp as the picture of Earth taken during Apollo 8,” Macintosh said.

Diagram showing a conceptual imaging technique that uses the sun’s gravitational field to magnify the light from exoplanets. This would allow very sophisticated reconstructions of what exoplanets look like. Image: Alexander Madurowicz

It sounds promising. For this technique will enable us to accurately characterize distant worlds. And that will greatly facilitate our search for aliens. “The Sun’s gravitational lens opens up a whole new window for observation,” said researcher Alexander Madurowicz. “This will make it possible to investigate the detailed dynamics of an exoplanet’s atmosphere, as well as clouds and surface features; properties that we cannot yet study.”

But…

However, there is a big but to this story. To take a picture of an exoplanet through a ‘sun gravity lens’, a telescope would have to be at least 14 times farther from the sun than Pluto. That’s beyond the edge of our solar system and far beyond any human-built spacecraft has ever been. It means we need much faster spacecraft. Because with current technology, it will certainly take 100 years to reach that point. According to the researchers, it will take at least another fifty years – perhaps even longer – before their technology can be implemented.

The realization of the promising plan, set out in the trade journal The Astrophysical Journal, is possibly still far away. But the researchers are enthusiastic anyway. “The possibility that we can find out whether some exoplanets have continents or oceans is what drives us,” Macintosh says. The researchers hope to one day be able to take a picture of another planet. “If we then see green spots that represent forests or can see the blue of the sea, it would be difficult to claim that there is no life,” he concludes.