A starshade in orbit could give giant Earth-based telescopes a new job
A NASA-backed concept is proposing a different route to one of astronomy’s hardest goals: directly imaging rocky, Earth-sized exoplanets around nearby stars. Instead of relying on a fully space-based observatory, the idea would combine a free-flying orbital starshade with the next generation of extremely large ground telescopes.
The concept, called the Hybrid Observatory for Earth-like Exoplanets, or HOEE, is designed to block a target star’s overwhelming glare before that light ever reaches a telescope on the ground. If it works as envisioned, astronomers could directly observe reflected optical light from small rocky worlds in nearby planetary systems rather than inferring their existence indirectly.
That matters because Earth-like exoplanets are exceptionally hard to see. According to the supplied source text, a rocky planet observed in optical light can be about a billion times fainter than its parent star. That contrast problem is the central obstacle. A starshade is meant to solve it by creating what is effectively an artificial eclipse.
How the hybrid system would work
In the HOEE concept, the starshade would operate from an elliptical orbit around Earth and position itself roughly 175,000 kilometers from the observing telescope’s line of sight. The source text says the first likely pairing would be with the European Southern Observatory’s Extremely Large Telescope in northern Chile, which is currently scheduled to achieve scientific first light by late 2030.
The starshade would sit directly between the telescope and the target star, suppressing starlight so that reflected light from an orbiting planet can emerge from the background. That would allow ground-based optical observations of nearby solar systems, with the concept focused on targets within roughly 20 light-years of Earth.
The design described in the source text is ambitious. The proposed starshade would include a 50-meter central disk and 48 petals, each 24.5 meters long. Its job would not simply be to block light in a crude sense, but to cast what the project team describes as a highly controlled shadow across the telescope. To do that, the spacecraft would need to reposition with accuracy on the order of six meters, likely using microthrusters powered by hot hydrogen gas.
That precision requirement underscores the challenge. The system depends on exact alignment between a star, a spacecraft tens of thousands of kilometers away, and one of the largest telescopes ever built on Earth. The appeal is that it could bypass some of the cost and timing constraints associated with building a dedicated flagship space mission for the same goal.
Why researchers think this approach could fill a gap
The argument behind HOEE is that current and near-term instruments are not well suited to directly observing Earth-like exoplanets in optical light. The supplied source text specifically says that instruments such as the James Webb Space Telescope’s Near Infrared Camera and the planned coronagraph aboard NASA’s Roman Space Telescope are not capable of directly observing true Earth analogs.
That limitation has pushed exoplanet science toward indirect methods such as transits and radial velocity measurements, which are powerful but do not provide the same kind of direct optical view of a planet. Direct imaging could open the door to richer characterization, especially for understanding rocky planets around nearby stars.
The HOEE team’s pitch is essentially pragmatic: use a starshade to extend the reach of observatories already being built, rather than waiting for a future all-in-one mission. In the source text, project team member Vladimir Airapetian frames the concept as something more efficient and available sooner than alternatives that remain farther from deployment.
That does not mean the concept is mature. The team has applied for Phase B support through NASA’s Innovative Advanced Concepts program, with the hope of securing that funding by 2027. NIAC is known for backing early-stage, high-upside ideas, so the application itself signals promise rather than programmatic commitment.
What success could change
If the concept progresses, its scientific payoff could be substantial. Direct optical imaging of nearby rocky worlds would offer a new path for studying planetary systems that resemble our own neighborhood more closely than the gas giants and hot exoplanets that have often dominated direct-imaging efforts so far.
The target list is also telling. By focusing on systems within around 20 light-years, the concept aims at a small but scientifically valuable set of nearby stars where any detected rocky planets would be especially important follow-up candidates for atmospheric and comparative planetology studies.
Just as important, HOEE reflects a broader shift in astronomy toward hybrid architectures. Rather than treating space telescopes and ground telescopes as separate tracks, the concept combines the strengths of both. The spacecraft handles the light suppression that Earth’s atmosphere and conventional optics make difficult, while the ground telescope provides the enormous collecting area that would be expensive to replicate in space.
That systems-level thinking is increasingly attractive as observatories grow more capable and more expensive. A starshade paired with an extremely large telescope would effectively turn an existing terrestrial facility into part of a distributed observatory.
A long-range idea with a concrete scientific target
There is still a large distance between concept studies and operations. The starshade would require complex formation geometry, high-precision control, and sustained coordination with a major observatory. It also depends on the Extremely Large Telescope coming online on its current timeline and on the starshade project itself advancing through NASA’s concept pipeline.
Even so, the HOEE proposal stands out because it is aimed at a very specific frontier: obtaining direct images of small, rocky exoplanets in nearby systems. That is a sharper scientific objective than a general technology demonstration, and it ties the engineering directly to one of the most sought-after outcomes in observational astronomy.
For now, the project remains a NASA-backed concept, not an approved mission. But the underlying idea is clear. If astronomers can place a precisely shaped, precisely positioned shadow in space, Earth’s biggest telescopes may be able to do something they cannot do alone: pick out faint, rocky worlds next to bright stars and bring the search for other Earth-like planets into direct view.
This article is based on reporting by Universe Today. Read the original article.
Originally published on universetoday.com