Artist concept of Gaia23bra b, a super-Jupiter exoplanet orbiting an orange dwarf star 40,000 light-years from Earth. The planet appears as a large Jupiter-like world with pale orange and cream bands against the black of space, with its orange dwarf star glowing dimly in the distance. NASA Goddard Space Flight Center artist concept.
Artist concept of Gaia23bra b, a super-Jupiter exoplanet orbiting an orange dwarf star 40,000 light-years from Earth. It was the first planet TESS identified using gravitational microlensing, where the planet's gravity bent and magnified the light of a more distant background star. Credit: NASA's Goddard Space Flight Center.

NASA's TESS satellite was designed to find planets by watching them cross in front of their stars. It has discovered thousands of worlds that way, mostly giant planets in scorchingly close orbits. But in July 2026, astronomers announced that TESS had done something it was never built to do: find a planet by watching it warp the fabric of spacetime.

The planet, named Gaia23bra b, is a super-Jupiter about 1.63 times the mass of Jupiter orbiting an orange dwarf star roughly 80 percent the mass of the Sun. It sits at a distance similar to Jupiter's orbit around our own Sun. And it is nearly 40,000 light-years from Earth, far beyond TESS's usual detection range of about 150 light-years.

"When TESS launched, no one expected it to ever be capable of finding this kind of planet," said Diana Dragomir, a professor at the University of New Mexico and co-author of the study published July 1 in The Astrophysical Journal Letters. "The discovery implies that there are probably other so-called microlensing planets hiding in TESS's data that we had not previously thought to look for."

How to find a planet with bent light

The technique that revealed Gaia23bra b is called gravitational microlensing. It works like this: when two stars align almost perfectly from Earth's perspective, the gravity of the closer star acts like a cosmic magnifying glass, bending and focusing the light from the more distant star behind it. The result is a temporary brightening that can last days or weeks.

If the foreground star has planets, those planets act as their own tiny lenses. Each planet produces a brief additional blip in the brightness curve of the background star, a deviation that reveals the planet's presence and allows astronomers to measure its mass relative to its host star.

Out of more than 6,000 known exoplanets, only about 5 percent have been found through microlensing. The technique is rare because it requires a near-perfect alignment that happens once and never repeats. But it is uniquely valuable because it can detect planets at orbital distances where the transit method cannot reach.

"Transits and microlensing are complementary because they each reveal a category of planet the other may not be able to detect," Dragomir said. "Transits give us the size of a planet. Microlensing gives us masses and orbital distances for planets we would otherwise never see."

A planet hiding in archived data

The story of Gaia23bra b begins in 2023. ESA's Gaia space telescope, which was mapping a billion stars across the Milky Way, flagged a star that had suddenly brightened. The signature looked like a microlensing event, but Gaia's scans were too widely spaced in time to reveal whether a planet was involved.

Mallory Harris, a Ph.D. candidate at the University of New Mexico and lead author on the study, went looking through TESS's archived data from the same patch of sky. TESS had been monitoring that area during the event, and its much denser time coverage showed what Gaia had missed: extra structure in the light curve that could only come from a planet.

"Gaia's observations were too sparse to pick up on the planet," Harris said. "TESS happened to be monitoring the same area of the sky during the event, and its denser time coverage showed extra features in the light curve caused by a planet."

The discovery means TESS's eight years of archived data may contain more microlensing planets that were recorded but never recognized. No one had looked for them before because TESS was not expected to have the sensitivity or time coverage for this technique. Gaia23bra b proved the concept works.

Diagram showing gravitational microlensing: light from a distant background star bends around a foreground star and its planet, magnifying the background star's brightness. The light curves below show how the planet creates an additional spike in the brightness signal.
Gravitational microlensing explained. When a foreground star passes in front of a more distant one, its gravity bends the background star's light like a lens. If the foreground star hosts a planet, the planet adds its own subtle blip to the brightness curve. Generated illustration for Impossible Universe.

Why microlensing matters for planet hunting

The transit method, which TESS was designed for, is the most productive planet-finding technique in astronomy. It works by watching for the tiny dip in starlight when a planet crosses in front of its star. That makes it excellent at finding large planets in close orbits. Microlensing is its mirror image: it is most sensitive to planets at Earth-like distances or farther from their stars, orbiting at the same scale as the planets in our own solar system.

Most known exoplanets are hot Jupiters and ultra-short-period worlds that orbit their stars in days or hours. That is not because those planets are the most common. It is because they are the easiest to find. Microlensing offers a way to see the cooler, more distant planets that the transit method misses, giving astronomers a more complete census of what planetary systems actually look like.

The discovery is also a preview of what is coming next. NASA's Nancy Grace Roman Space Telescope, scheduled to launch on August 30, 2026, will carry a dedicated microlensing survey as one of its three core science programs. Over its five-year primary mission, Roman is expected to find roughly 2,600 exoplanets using microlensing, including potentially the first Earth-mass planets in the habitable zone. Gaia23bra b is proof that the technique works and that archived data from existing missions can still yield surprises.

"The main advantage of microlensing lies in the kinds of planets it is sensitive to," the team wrote. Planets that orbit very close to their stars essentially blend with the star's mass and do not produce a distinct microlensing signal. With microlensing, astronomers can find planets at orbital distances impossible for the transit method, filling in the missing middle of the exoplanet population.

What lies in TESS's archive

TESS has been surveying the sky since 2018, returning to the same patches of sky year after year. Its eight years of continuous monitoring create an enormous data set where rare events like microlensing alignments may be captured, recorded, and waiting to be found.

The Gaia23bra b discovery opens a new chapter for TESS, not as the transit survey it was designed to be, but as a serendipitous microlensing observatory. The same data that revealed thousands of close-in planets may contain dozens more distant worlds, hidden in the light curves of stars that happened to align perfectly, just once, while TESS was watching.

Sources

Related on Impossible Universe

Hero image: NASA Goddard Space Flight Center artist concept of Gaia23bra b (public domain). Inline microlensing diagram: Generated illustration for Impossible Universe. Research published in The Astrophysical Journal Letters (Harris et al., July 1, 2026).