Earth’s magnetic field is about 0.32 gauss (G), but scientists do not yet have a definitive, like-for-like measurement of an exoplanet’s global surface field. A peer-reviewed 2026 study inferred fields of at most a few gauss for seven ultra-hot Jupiters from atmospheric wind behavior. A September 2026 preprint, meanwhile, interprets radio bursts from the young giant beta Pictoris b as requiring at least 1.25 kilogauss at the radio emission source. Those are very different kinds of evidence and locations, so they do not establish a simple ranking of exoplanets against Earth.
What the current comparisons show
The figures below are useful reference points, not measurements made in the same way. Earth’s value comes from a modeling paper; the hot-Jupiter estimate is inferred from winds; and the beta Pictoris b estimate comes from interpreting radio emission. In particular, a field at a radio source is not automatically the planet’s surface or global dipole field.
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| World or sample | Reported field figure | Evidence and qualification |
|---|---|---|
| Earth | Approximately 0.32 G | Used as a reference value in Peña-Moñino et al.’s 2024 Proxima b space-weather modeling paper. It is an approximate model input, not a complete account of how Earth’s field varies by location and time. |
| Seven transiting ultra-hot Jupiters | Possible fields of at most a few G | Seidel et al.’s peer-reviewed June 2026 study inferred this range from observed atmospheric winds and their temperature trend; it was not an in-situ magnetometer reading. |
| Beta Pictoris b | At least 1.25 kilogauss (kG) at the emission source | Ortiz Ceballos, Berger and Cendes reported this interpretation in a September 2026 arXiv preprint, based on radio bursts attributed to the planet. The result is provisional and describes the inferred emission region, not an established global surface field. |
One kilogauss equals 1,000 G, so the beta Pictoris b preprint’s source-region estimate is numerically far above Earth’s approximate reference. But comparing those numbers as if they measured equivalent locations on equivalent planets would be misleading. The hot-Jupiter estimate and radio estimate also rely on different physical signals and assumptions.
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How astronomers infer an exoplanet’s magnetic field
Atmospheric magnetic drag
On ultra-hot Jupiters, some atmospheric material is ionized and can interact with a magnetic field. Researchers use high-resolution spectroscopy of iron lines to estimate wind speeds, then examine how those winds change with planetary temperature. A trend consistent with magnetic drag can support an estimate of field strength, as in Seidel et al.’s seven-planet study. The field is inferred from atmospheric behavior; no spacecraft measured it directly.
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The European Southern Observatory’s June 2026 summary reported wind speeds in the sample ranging from about 7,200 km/h to more than 25,000 km/h. Those are wind speeds, not magnetic-field measurements. ESO compared them with Jupiter’s fastest winds, at about 1,500 km/h.
Radio emission from near a planet
Some planetary auroras produce radio waves through a process called electron-cyclotron maser emission. The emission frequency is tied to the magnetic field where the radio waves originate. If astronomers can establish that a signal comes from a planet and identify its frequency, they can infer a local field strength.
The September 2026 beta Pictoris b preprint reports recurring, highly circularly polarized radio bursts across 0.85–3.5 GHz and interprets them as planetary electron-cyclotron maser emission. On that interpretation, the field at the emission source is at least 1.25 kG. Because this is a preprint rather than a peer-reviewed result, and because attribution and interpretation matter, it should be treated as a promising claim requiring independent confirmation—not as settled consensus.
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Radio or chromospheric activity in a planetary system can also arise from interaction between a planet and its host star. Such a signal does not by itself prove that the planet emitted it: stellar activity and the details of the interaction complicate attribution. Nature Astronomy’s 2024 review of radio signatures discusses this interpretive challenge.
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Have scientists measured exoplanet fields directly?
There is not yet a named catalog of directly measured exoplanet surface fields supported by these results. The 2024 review Exoplanet Magnetic Fields stated at its publication that “At present we have no unambiguous measurements of magnetic fields on exoplanets.” That was an assessment as of July 2024, not a description of every later claim. The 2026 wind study adds an indirect estimate, while the later beta Pictoris b preprint offers a radio-based inference that remains provisional.
In this context, “measured” can refer to observing a signal and then inferring a field from a physical model. It does not necessarily mean a probe detected the field in place, or that researchers have mapped a planet’s global magnetic geometry. The method and the location represented by each estimate are essential to interpreting it.
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Why Earth is a useful reference—but not a universal benchmark
Earth’s approximate 0.32 G value helps readers orient themselves, but the planets in these early comparisons are very different. The 2026 atmospheric study concerns ultra-hot gas giants, while beta Pictoris b is a young giant planet. Their atmospheres, interiors, irradiation and interactions with their stars differ from Earth’s. A single field-strength number cannot capture those conditions.
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Magnetic-field strength also does not by itself determine whether a planet can retain an atmosphere or support habitable conditions. Stellar wind and space weather, field geometry and tilt, atmospheric properties, and the processes generating a field inside a planet all matter. NASA GISS and Space Science Reviews’ 2026 exogeoscience review treats magnetism as one part of this wider set of interacting planetary factors.
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What to take from the comparison
- Earth’s approximately 0.32 G is a reference drawn from a 2024 modeling paper, not a universal standard for planets.
- The peer-reviewed hot-Jupiter result points to possible fields of at most a few G, inferred indirectly from winds.
- The much larger beta Pictoris b figure is a September 2026 preprint’s estimate for the radio emission region, not a confirmed surface-field measurement.
- These findings show that astronomers are developing ways to investigate exoplanet magnetism, but they do not yet support a definitive ranking of exoplanet surface fields against Earth’s.
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