Earth’s magnetic field is about 0.32 gauss (G), but current exoplanet findings do not support a simple ranking of other worlds against it. A peer-reviewed 2026 study inferred fields of at most a few gauss for seven ultra-hot Jupiters from atmospheric winds. A September 2026 preprint, by contrast, interprets radio bursts from beta Pictoris b as indicating at least 1.25 kilogauss (kG) at the radio-emission source. These are different kinds of estimates from different locations, and the beta Pictoris b result is not yet peer reviewed.
What the reported field strengths show
The figures below are useful reference points, not like-for-like measurements. Earth’s value comes from a modeling paper; the hot-giant estimate is inferred from atmospheric behavior; and the beta Pictoris b figure applies to the region producing the radio emission, not necessarily to the planet’s surface or global magnetic field.
| World or sample | Reported field strength | How the figure was obtained and what it describes |
|---|---|---|
| Earth | Approximately 0.32 G | Reference value used in a 2024 Proxima b space-weather modeling study by Peña-Moñino and colleagues. It is an approximation, not a complete account of how Earth’s field varies by place and time. |
| Seven transiting ultra-hot Jupiters | At most a few G | Seidel and colleagues’ peer-reviewed June 2026 study inferred possible field strengths from temperature-related changes in atmospheric winds. The estimate is described as comparable with Jupiter’s equatorial field. |
| beta Pictoris b | At least 1.25 kG (1,250 G) at the emission source | A September 2026 arXiv preprint interprets recurring, highly circularly polarized radio bursts as electron-cyclotron maser emission. This is a source-region inference, not an established measurement of the planet’s global or surface field. |
The beta Pictoris b number is much larger than the Earth reference when the units are converted, but the comparison has a crucial limitation: it contrasts a radio-emission source-region estimate with an approximate reference value for Earth. It does not show that beta Pictoris b’s whole magnetic field, or its surface dipole, is a particular number of times stronger than Earth’s.
How researchers infer magnetic fields at a distance
Atmospheric wind measurements and magnetic drag
In ultra-hot Jupiter atmospheres, some species are ionized and can interact with a magnetic field. Researchers use high-resolution spectroscopy of iron lines to measure Doppler shifts that trace atmospheric winds. Seidel and colleagues measured winds on seven transiting ultra-hot Jupiters and found a temperature trend consistent with magnetic drag. They used that interpretation to estimate fields of at most a few gauss.
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This is an inference from atmospheric observations and models, not an in-situ reading from a spacecraft magnetometer. The European Southern Observatory’s June 2026 summary gives wind speeds in the sample of about 7,200 km/h to over 25,000 km/h, compared with about 1,500 km/h for Jupiter’s fastest winds. Those figures describe winds, not magnetic field strength.
Radio bursts and the local field at an emission source
Electron-cyclotron maser emission is a mechanism that can produce strongly polarized radio waves at frequencies related to the magnetic field where the emission originates. If the signal can be confidently attributed to a planet and its emission frequency identified, the radio observation can constrain the field in that source region.
The September 2026 beta Pictoris b preprint reports recurring, highly circularly polarized bursts between 0.85 and 3.5 GHz and interprets them as planetary electron-cyclotron maser emission. That interpretation implies a field of at least 1.25 kG at the source. The result remains provisional: the paper is a preprint, so it needs peer review and independent confirmation before it should be treated as settled.
Why a signal in a planetary system is not enough by itself
Radio or chromospheric signals can also arise from interactions between a planet and its host star. Stellar activity and the physics of those interactions make attribution difficult: a signal detected from a planetary system is not automatically emission from the planet. Establishing the origin of a signal is therefore part of making a credible field inference.
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Why the numbers are not a planetary leaderboard
- The methods measure different things. The hot-Jupiter result interprets wind behavior through magnetic drag; the beta Pictoris b claim infers a field from radio emission.
- The locations differ. A field at a radio-emission source need not equal a global surface dipole. The wind-based estimate is likewise an interpretation of atmospheric observations, not a direct surface reading.
- The worlds and environments differ. Earth is a rocky planet; the comparison cases are ultra-hot Jupiters and a young giant. Their interiors, atmospheres, irradiation, and stellar environments are not interchangeable.
- The evidence has different status. The hot-Jupiter study was peer reviewed; the beta Pictoris b result was an arXiv preprint as of September 2026.
A 2024 review, Exoplanet Magnetic Fields, said, “At present we have no unambiguous measurements of magnetic fields on exoplanets.” That statement describes the state of the field when the review was published on 1 July 2024; it should not be repeated as a present-day summary after the later 2026 findings. Those findings represent emerging evidence, but they do not yet provide a catalog of directly measured exoplanet surface fields.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Does a stronger field mean better protection or habitability?
Not on its own. A magnetic field can be relevant to how a planet interacts with stellar wind and space weather, but its effects depend on more than its strength. Field geometry and tilt, the planet’s atmosphere, the host star’s activity and wind, and processes inside the planet all matter. NASA’s 2026 exogeoscience review treats magnetism as one part of a wider set of interacting factors, not a standalone habitability test.
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It is therefore not possible to infer from the reported field figures alone whether an exoplanet can retain its atmosphere, preserve water, or support life. The available findings help researchers investigate magnetic environments; they do not by themselves establish a planet’s habitability.
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