A proposal for new telescope design from astrophysicist Professor Heidi Newberg at Rensselaer Polytechnic Institute could change the way astronomers search for habitable, Earth-like planets
Professor Newberg’s team’s latest research, published in Frontiers in Astronomy and Space Sciences, suggests that replacing the traditional circular telescope mirror with a long rectangular one could make it far easier to detect Earth-like planets orbiting nearby stars.
Life beyond Earth
Earth is the only known planet to support life, as its conditions make life possible, especially the presence of water; however, these conditions could exist on other worlds. Scientists believe that the sun, like stars, is the best target for finding habitable planets, as it offers the right balance of stability and longevity for life to evolve.
Out of the hundreds of billions of stars in our galaxy, only about 60 sun-like stars lie within 30 light-years of Earth. These are the perfect candidates in the search for potentially habitable exoplanets.
Imaging challenges: Changing and improving telescope designs
Detecting an Earth-like planet near one of these stars is difficult. Even under ideal conditions, the Earth is about a million times dimmer than the star it orbits. Without extremely high-resolution imaging, the two objects blur into a single point of light, making it impossible to detect the planet directly.
Telescopes need to collect light over a considerable distance, at least 20 meters, at infrared wavelengths to separate such closely spaced objects in space. Infrared light is key because Earth-like planets emit most of their detectable energy at these wavelengths, particularly around 10 microns. Unfortunately, no current space telescope, including the James Webb Space Telescope (JWST), comes close to this capability. JWST’s mirror is only 6.5 meters wide.
Current alternative options
Some scientists have proposed using formations of multiple small telescopes that work together like a much larger one. Others have considered using a “starshade” to block the light from a star so the planet can be seen more easily. However, these approaches require either ultra-precise positioning or the deployment of multiple spacecraft, both of which are beyond the reach of current technology.
Newberg’s team offers a more practical solution. Instead of a large circular mirror, they suggest a rectangular one measuring one by 20 meters. This shape would provide the telescope with the necessary resolution in one direction to distinguish planets from their host stars. By rotating the mirror to align with the direction of the planet-star separation, astronomers could scan the entire sky for nearby Earth-like planets.
This design could detect about half of all Earth-sized planets orbiting sun-like stars within 30 light-years, and this in under three years. It also avoids the major technical hurdles of the other proposals. The telescope would still need to be in space to prevent image distortion from Earth’s atmosphere, but the rectangular mirror would be much easier to launch than a giant circular one.
Creating another Earth?
If the design performs as expected, scientists could quickly identify dozens of promising planets. These worlds could then be studied for signs of life, such as oxygen-rich atmospheres produced by photosynthesis. In the long term, the most promising candidates could even be visited by robotic probes.