Exoplanet hunters want to block starlight with a giant orbiting shade

Over the past decade, finding Earth-like exoplanets has become a major focus in astronomy. Although searching for such planets amidst billions of stars and galaxies is a monumental task, a new NASA initiative aims to significantly enhance our ability to detect them.

The proposed project, known as the Hybrid Observatory for Earth-like Exoplanets (HOEE), involves creating a dual observatory system with components both on Earth and in space. This system would combine next-generation ground-based telescopes, like the Giant Magellan Telescope and the Extremely Large Telescope (ELT) in Chile, with a space-based tool called a “starshade,” designed to block out the light of bright stars.

Currently, there are two primary methods for directly observing exoplanets. One involves using high-resolution cameras on telescopes to capture images of these distant worlds. For instance, the Hubble Space Telescope has detected hundreds of exoplanets using this method. The second method, known as transit spectroscopy, involves analyzing the light from a star that has passed through a planet’s atmosphere. This technique allows scientists to gather data about the planet’s atmospheric composition. The James Webb Space Telescope has used this method to study exoplanets like Wasp-96. However, the JWST’s main focus is not on the search for extraterrestrial life, which is where a hybrid observatory could be beneficial.

The challenge of detecting faint, Earth-like planets is compounded by the brightness of their host stars. John Mather, a senior astrophysicist at NASA’s Goddard Space Flight Center and lead for the HOEE project, notes that the brightness of stars like our Sun makes it difficult to spot smaller, fainter planets. A starshade could help by blocking the light from these stars, making it easier to observe the planets.

A starshade would be a large structure positioned in space, designed to shield a telescope from the light of a star. It would need to be over 300 feet in diameter and positioned at least 100,000 miles from Earth. This makes it challenging to design and deploy, as the structure must operate autonomously and be compact enough to fit into a rocket.

Currently, the technology for constructing such a starshade is still in development. Past designs have been too large to fit into existing rockets, but researchers are working on more feasible solutions, including deployable concepts similar to the James Webb Space Telescope’s folded mirrors. NASA has not yet pursued development, but it has launched the Ultralight Starshade Structural Design Challenge to gather innovative design ideas from the public. The top five submissions will be awarded prizes, with the first-place winner receiving $3,000. The deadline for entries is August 22, and Mather hopes that public input will help advance the concept.

“We are tackling some very challenging engineering problems,” says Mather. “But it’s an effort worth pursuing.”