New Exoplanet Discoveries Challenge Models
Astronomers Image Active Planet Formation While Discovering Mysterious Backward Orbiting Exoplanet
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GJ 3090 b is a sub-Neptune with a radius about 2.2 times Earth’s and a mass roughly 4.5 times Earth’s; the planet was discovered in 2022.
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The researchers reconstructed GJ 3090 b’s orbit in three dimensions, finding that its 136-degree angle is measured relative to the host star’s equatorial plane; by comparison, the Solar System’s planets are only a few degrees from the Sun’s equatorial plane.
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Researchers said they found neither a wide stellar companion nor evidence of a sufficiently massive outer planet in the GJ 3090 system, ruling out the usual explanation for such an extreme orbit and prompting consideration of alternative formation mechanisms.
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The GJ 3090 b study was led by the University of Geneva’s Department of Astronomy, used the NIRPS instrument partly built in Geneva, and was published in the journal Astronomy & Astrophysics.
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WISPIT 2b is notable because it provides, in one system, observations of all three major components of planet formation: an actively accreting planet, its surrounding protoplanetary disk, and the gas swirl generated by their interaction.
Astronomers have captured the first direct images of a growing gas giant sculpting its birth disk, revealing how planets forge themselves from swirling cosmic dust. The observations show WISPIT 2b—a planet five times Jupiter's mass—carving a visible spiral wake through its parent disk, offering a rare window into planet formation itself. Separately, researchers discovered an exoplanet called GJ 3090 b that orbits backwards around its star, defying conventional theories about how planetary systems organize themselves.
These two discoveries challenge astronomers' understanding of how planets build themselves and arrange their orbits. The findings suggest planetary systems can develop in ways not yet fully explained by existing models.
ALMA Captures Planet Sculpting Its Disk in Real Time
The ALMA observatory in Chile has imaged WISPIT 2b actively carving through its protoplanetary disk, revealing the exact gas spiral the planet creates as it interacts with surrounding material. Newsy Today reports this marks the first complete picture of all three major planet-formation components: the growing planet, its disk, and the visible disturbance between them. The swirling pattern acts like a fingerprint that astronomers can now use to spot hidden planets in other star systems.
The observation uses advanced data-extraction techniques developed by the exoALMA project to pull detail from Chile's high-altitude observatory. National Tribune notes the image shows exactly how a protoplanet heats and shapes the gas around it, laying bare the violent dance of planet birth.
Neptune-Sized Planet Orbits Its Star Backwards
Astronomers using the NIRPS near-infrared spectrograph discovered GJ 3090 b, a Neptune-sized world 73 light-years away that orbits at a 136-degree angle to its host star—traveling completely opposite to the star's rotation. Newsy Today reports the planet's backward path breaks a pattern seen in our solar system, where planets orbit nearly flat with their star's equator.
The researchers mapped GJ 3090 b in three dimensions to measure this extreme tilt. At 2.2 times Earth's radius and 4.5 times Earth's mass, the sub-Neptune planet was discovered in 2022 but only now has scientists fully traced its unusual orbit.
Mystery of the Retrograde Orbit Remains Unsolved
Backward orbits typically signal gravitational violence—a massive planet, brown dwarf, or companion star has yanked the planet sideways over time. Yet Newsy Today reports the research team found no companion star and no outer giant planet massive enough to explain GJ 3090 b's extreme tilt, ruling out the standard explanation.
The discovery, led by the University of Geneva's Department of Astronomy and published in *Astronomy & Astrophysics*, forces researchers to consider alternative formation mechanisms. The system may have assembled differently than current models predict, suggesting planets can rearrange their orbits through processes not yet understood.
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