The Solar Gravitational Lens

Photographing distant worlds by turning the Sun into a telescope.

January 22, 2026

Photographing a Distant World

Picture a spacecraft far beyond Pluto—fourteen times its distance from the Sun. The spacecraft doesn’t point at the planet it wants to see. It points at the Sun. Around the Sun, in the glare, is a thread-thin ring of light — an image encoded in gravity. Over months, a world resolves.

I. Turning the Sun into a Telescope

The Sun has been bending starlight for billions of years. And in that bending is a telescope we’ve never been able to reach.

Einstein finished general relativity in 1915^[1]. General relativity describes how matter shapes spacetime, and spacetime shapes motion.

Light also traces the curvature of spacetime. Rays skimming the Sun are curved, which creates a long focal line^[2]. For rays at the solar edge, the focal line begins around 547 AU—roughly fourteen times Pluto’s distance—and continues outward. Unlike a glass lens, the Sun’s gravity doesn’t focus to a single point, but along a line. It’s an extended focal region. In 1979, physicist V.R. Eshleman proposed using this “solar lens” for astronomy^[3].

The Numbers Are Extraordinary

At visible wavelengths, the Solar Gravitational Lens (SGL) can amplify light by a factor of ~10¹¹ near the optical axis^[4]. That’s not a better telescope—it’s a different regime of astronomy.

A modest one-metre telescope at that distance could resolve continents on a distant Earth — enough to draw coastlines, then over time, map seasons, ice extent, and persistent cloud belts as they shift.^[4]

Without the SGL, comparable detail likely requires extremely large space interferometers—baselines on the order of hundreds of kilometres or more. Or you use the one lens in the solar system already that large: the Sun.

A lens the size of the Sun. The Sun has been a telescope for billions of years. The only question is when we decide to use it.

II. Cosmic Cartography

We’ve confirmed thousands of exoplanets. We know their sizes, orbits, and something of their atmospheres. We can infer whether a world is temperate. We can detect carbon dioxide in its air.

But we can’t see them.

The best images are single pixels. Enough to confirm a planet exists. Not enough to understand it.

The Solar Gravitational Lens changes that.

From Pixels to Geography

The SGL doesn’t take pictures. It reconstructs worlds.

What arrives is an Einstein ring: every point on it contains a blurred contribution from much of the planet’s disk. The spacecraft steps laterally through the focal region, records how the ring’s brightness shifts at each position, and builds a dataset. Then reconstruction inverts that dataset into a map.

It’s closer to medical imaging than photography — reconstructing an object from encoded signals rather than capturing a direct image. The physics is the instrument. Computation is the camera.

A 1-metre telescope at 550 AU could reconstruct a megapixel map of an Earth-like world at ~30 parsecs—tens-of-kilometres-class surface features—with months of integration^{[4] [5]}.

You could see geography. A slow reveal: coastlines, cloud patterns, bright ice, assembled over months of light and computation. The marks of a world still changing, or one long frozen in place.

III. The Engineering Challenge

The physics is settled.

The optics already exist.

What remains is the journey.

Distance and Time

547 AU is far. Pluto orbits at roughly 40 AU. Voyager 1 — launched in 1977 — is still short of 550 AU^[7]. At that range, the Sun itself shrinks to a bright star in the sky. At Voyager’s pace, reaching the focal line would take well over a century.

Multiple propulsion concepts could get us there in 15–25 years. Solar sails diving close to the Sun can reach extreme exit velocities; laser propulsion could push faster still^[8][9]. The propulsion is not the hard part.

A mission launched in the 2030s could return data in the 2040s or 2050s—fast enough that the people who build it could see its first maps.

The Hard Parts

The biggest challenge is station-keeping. Each metre of lateral drift blurs the reconstructed image — because every shift changes which part of the ring you sample. Holding that precision for years, 550 AU from home, is the real test. Ion thrusters are ideal: low thrust, high efficiency, flight-proven.

SGL imaging is computational astronomy. You sample the ring over time, then solve an inverse problem to recover the map—physics as the instrument, computation as the camera. The physics is known. The hard part is building a system that can trust its own reconstruction^{[4] [5]}.

The Mission

Mission studies favour a swarm: a handful of small probes, each dedicated to a single target, rather than one large flagship^[11].

Each carries a metre-class telescope, a coronagraph to block the Sun’s glare, and ion propulsion for years of station-keeping. Power from RTGs. Communication via optical laser links — a thread of light across half the solar system.

The SGL is not a search instrument — it’s a follow-up instrument. You already know which world you’re looking at. You commit one probe, one star, one long stare. A year of observation to build the first map.

What remains is engineering, funding, and will.

IV. Cataloguing The Galaxy

Over the coming decades, we could build a catalogue: not spectral hints, but maps. Coastlines resolved. Ice caps tracked across seasons. Biosignature concentrations pinpointed to hemispheres^[4].

Each probe is a dedicated observatory: one star, one world, one long stare. So we’d prioritise the nearest candidates—temperate worlds with atmospheric hints worth following up. Proxima b. TRAPPIST-1e. Kepler-442b. Worlds we’ve already found, now ready to characterise in detail.

The SGL shifts the question from “Are there other Earths?” to “Where do we go first?”

V. An Age of Wonders Lies Beyond

The Solar Gravitational Lens has existed since the Sun formed. Every star creates one. The physics is settled. The price is institutional: decades of patience, billions of dollars, and a mission that pays off only once it’s farther than any spacecraft we’ve ever flown.

It’s a spacecraft, a telescope, a mission profile—flagship-class in ambition. Buildable with today’s physics—and engineering we already know how to do, at scale.

For most of history, knowledge required presence. Then, telescopes made distance visible. The SGL would do something stranger: turn a star into an instrument and make geography visible at interstellar range.

You don’t send a crewed mission to another star without knowing which worlds are worth visiting. The SGL is the map that makes the rest possible.

At 550 AU, a small spacecraft stares at a thread-thin ring of light around the Sun—an Einstein ring carrying light from another world. Over months, a coastline appears. Then the continents. The first resolved map of an exo-Earth will be an Earthrise-level moment.

The Sun built the lens. We can build the mission.

What Comes Next

Once you’ve mapped a coastline 30 light-years away, you likely want to go there. The SGL gives us the map. But maps demand vessels.

The Free Starship (coming soon) explores what happens when a spacecraft can refuel from gas giants and operate indefinitely without supply chains from Earth—traversing the entire galaxy.

Notes & References

[1] Einstein, A. (1915).
”Die Feldgleichungen der Gravitation.” Sitzungsberichte der Königlich Preußischen Akademie der Wissenschaften (Berlin), 844-847.
(Einstein’s field equations establishing general relativity; foundation for gravitational lensing.)

[2] Einstein, A. (1936).
”Lens-Like Action of a Star by the Deviation of Light in the Gravitational Field.”
Science 84 (2188): 506-507 — https://science.sciencemag.org/content/84/2188/506
(Einstein’s original calculation showing the Sun acts as a gravitational lens.)

[3] Eshleman, V.R. (1979).
”Gravitational lens of the sun: its potential for observations and communications over interstellar distances.”
Science 205 (4411): 1133-1135 — https://science.sciencemag.org/content/205/4411/1133
(First proposal to use the solar gravitational lens for astronomy.)

[4] Turyshev, S.G. & Toth, V.T. (2020).
”Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravity Lens Mission.”
arXiv:2002.11871 — https://arxiv.org/abs/2002.11871
(Analysis showing a 1-m telescope at 550 AU could image an Earth-analog at 30 pc with ~10 km resolution.)

[5] Turyshev, S.G. & Toth, V.T. (2023).
”Imaging faint sources with the extended solar gravitational lens.”
arXiv:2301.07495 — https://arxiv.org/abs/2301.07495
(Updated modelling of imaging faint sources and deconvolution feasibility.)

[6] Turyshev, S.G. & Toth, V.T. (2017).
”Diffraction of light by the gravitational field of the Sun and the solar corona.”
arXiv:1704.06824 — https://arxiv.org/abs/1704.06824
(Theoretical modelling of the SGL including solar corona noise effects.)

[7] NASA Jet Propulsion Laboratory.
”Voyager Mission Status.”
https://voyager.jpl.nasa.gov/mission/status/
(Current probe distances for context on deep-space timelines.)

[8] Landis, G.A. (2016).
”Mission to the Gravitational Focus of the Sun: A Critical Analysis.”
arXiv:1604.06351 — https://arxiv.org/abs/1604.06351
(Critical analysis of SGL mission feasibility and propulsion challenges, including solar sail architectures.)

[9] Manchester, Z. & Loeb, A. (2017).
”Stability of a Light Sail Riding on a Laser Beam.”
arXiv:1609.09506 — https://arxiv.org/abs/1609.09506
(Technical analysis of laser-assisted propulsion relevant to SGL mission profiles.)

[10] Breakthrough Initiatives.
”Breakthrough Starshot.”
https://breakthroughinitiatives.org/initiative/3
(Laser sail mission concept with relevance to SGL delivery architectures.)

[11] NASA Innovative Advanced Concepts (NIAC) (2020).
”Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravitational Lens Mission.”
https://www.nasa.gov/general/direct-multipixel-imaging-and-spectroscopy-of-an-exoplanet-with-a-solar-gravitational-lens-mission/
(NASA-funded mission concept development for SGL observatory.)

Technical Notes

Values are representative of published mission studies; exact figures depend on wavelength, coronagraph design, and reconstruction assumptions.

• Focal distance: The focal line begins at ~547 AU (where f = R☉²/2rg) and extends outward. Light grazing the Sun’s limb is deflected by ~1.75 arcseconds. See [2], [4] for derivations.

• Optical gain: ~10¹⁰–10¹¹ brightness amplification at optical/near-IR wavelengths [4]. This pushes the photon budget into a fundamentally different regime from conventional telescopes.

• Image formation: The planet appears as an Einstein ring; meter-scale motion in the image plane corresponds (order-of-magnitude) to tens-of-kilometres-class changes in the reconstructed surface footprint, depending on wavelength, coronagraph performance, and noise assumptions. Deconvolution recovers the map—analogous to Event Horizon Telescope imaging.

• Integration time: Months to a year for megapixel-class maps of Earth-analogs at tens of parsecs [4, 5]. Nearer targets (e.g., Proxima b at 1.3 pc) require substantially less time.

• Propulsion: Solar sails with sundiver maneuvers can achieve tens of AU/year exit velocities [8]. Laser propulsion could reduce times further [9].

• Station-keeping: Sub-kilometre accuracy maintained for years via ion thrusters. The Sun, telescope, and target must remain extremely well aligned to sub-microradian precision—so well that tiny pointing errors distort what you measure.

• Mission architecture: Swarm concepts with multiple small probes provide redundancy and enable parallel observations [11]. Optical laser links return data at tractable rates even from 550+ AU.

• Why no alternative works: Space interferometers need ~100 km baselines; fast flybys spend only minutes at target with prohibitive communication challenges. Each non-SGL approach falls 2–5 orders of magnitude short [4].