Study Findings: Regression to the Mean Can Explain Saturation of Geomagnetic Storms

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Image (Credit): A May 2024 image of a solar flare captured by NASA’s Solar Dynamics Observatory (SDO). (NASA SDO)

Nature abstract of study findings:

Extreme space weather events on Earth occur during intervals of strong solar wind driving. The solar wind drives plasma convection and currents in the near-Earth space environment. For low values of the driver, the Earth’s response is linear, estimated by parameters such as the polar cap index based on ground magnetometer activity. Curiously, for extreme solar wind driving, the Earth’s response appears not to increase beyond a saturation limit. Theorists have advanced a host of explanations for this saturation effect, but there is no consensus. Here we demonstrate that this saturation is a manifestation of the regression to the mean effect arising from random uncertainty in the timing and magnitude of solar wind measurements. Our results reveal that data analysis underpinning the saturation theories is nonlinearly biased, thereby challenging the validity of the theories. Correcting for the uncertainties reveals that the Earth’s response to solar wind driving is linear throughout, and that the impact of extreme geomagnetic storms can be twice as large as previously thought. We show that regression to the mean is a fundamental property of the relationship between measurement and the truth, where the truth corresponding to the measurement is closer to the mean. This effect is particularly pronounced for uncertain measurements of extreme values and is likely to manifest across various fields, from extreme climate studies to chronic medical pain.

Citation: Sivadas, N., Sibeck, D., Subramanyan, V. et al. Regression to the mean can explain saturation of geomagnetic storms. Nature 655, 1143–1147 (2026).

DOI: https://doi.org/10.1038/s41586-026-10757-4

Study-related stories:

Wired – “An Extreme Solar Storm May Be Even More Devastating Than Previously Imagined”

SciTechDaily – “Earth May Be Twice As Vulnerable to Extreme Solar Storms As Scientists Thought”

NASA – “New NASA Study Says Possibly No Limit to Solar Storm Effects”

Study Findings: The Barnard’s Star Planetary System: Stability, Composition, and Evolution of Four Sub-Earth Exoplanets

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Credit: NASA Photojournal

Monthly Notices of the Royal Astronomical Society abstract of study findings:

Barnard’s Star is the nearest single star to the Sun (1.8 pc⁠⁠), and hosts four recently discovered planets. The star also has well-characterized stellar abundances of important rock-forming elements, including Fe, Mg, and Si. For refractory elements like these, the planets have likely inherited similar bulk elemental abundance ratios to the star, facilitating modelling of their interior structures. We present here an analysis of the Barnard’s Star planetary system on several fronts. We perform a detailed stability analysis of the system, ascertaining that all four planets likely have masses between 0.19 and 0.84 M⁠, and are likely tidally locked, whereas a 4:3 mean-motion resonance chain for the inner three planets cannot be ruled out. Using atmospheric evolution models, we show that the prospect of extant primary atmospheres is highly unlikely on any of the planets. Barnard’s Star’s abnormally high Mg/Si ratio and low Th/Mg ratio imply planetary mantles which (a) are rich in (Mg,Fe)O ferropericlase; (b) have less than half the water capacity as Earth; (c) generate about half of the radiogenic heating as Earth; and (d) are cool and unlikely to have outgassed secondary atmospheres. Our analysis of this system presents an accessible set of first steps for the study of other nearby exoplanetary systems, as well as sub-Earth planets which will be increasingly discovered over the coming years.

Citation: Byrne, X., Guimond, C.M., Bonsor, A., et al. The Barnard’s Star planetary system: stability, composition, and evolution of four sub-Earth exoplanet. Monthly Notices of the Royal Astronomical Society, Volume 550, Issue 2 (2026).

DOI: https://doi.org/10.1093/mnras/stag1207

Study-related stories:

University of Cambridge – “Astronomers Find Nearby Planets To Be Small, Strange, and Utterly Uninhabitable”

Sci.News – “Barnard’s Star Planetary System May Be Filled with Water-Poor Rocky Worlds”

Daily Galaxy – “Scientists Studied a Nearby Star and Found Four Planets That Look Nothing Like Earth”

Study Findings: Accurate Distances of the Galactic Spiral Arms from Dust-scattered X-ray Emission of Gamma-ray Bursts

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Image (Credit): An artist’s rendering of the Milky Way Galaxy illustrating the results of the recent study discussed below. The position of our Sun is also provided in the image.(ESA/Gaia/DPAC, Stefan Payne-Wardenaar, ESA/XMM-Newton and NASA/Chandra)

Astronomy & Astrophysics abstract of study findings:

The details of the spiral structure of the Milky Way are still debated due to the large uncertainties in the distance estimates obtained through the most common tracers. However, X-ray dust scattering rings produced by short extragalactic X-ray transients provide a direct method to measure the 3D distribution of interstellar clouds up to the edges of our Galaxy with a precision of a few percent. We report on an analysis of all the available XMM-Newton and Chandra follow-up observations of three low-latitude gamma-ray bursts: GRB 031203 (l ≃ 255°, b ≃ −5°), GRB 160623A (l ≃ 84°, b ≃ −3°), and GRB 221009A (l ≃ 53°, b ≃ 4°). The previous detection of X-ray rings in these observations, produced by dust clouds located beyond 5 kpc, can be associated with dust in the Perseus, Outer, and Outer Scutum-Centaurus arms, thus providing direct distance measurements to these structures along three distinct lines of sight. We identify two additional rings in the direction of GRB 160623A produced by dusty clouds at 6.91  ±  0.06 kpc and 9.9  ±  0.6 kpc, and we confirm – through a second XMM-Newton observation – the presence of one cloud at 9.7  ±  0.4 kpc toward GRB 031203. We also accurately measured the distance of dusty clouds up to 19.0  ±  0.2 kpc based on the analysis of one Chandra and four XMM-Newton observations of GRB 221009A. The small statistical and systematic uncertainties of these measurements place tight constraints on the geometry of the outer Milky Way and reveal significant deviations from current models, which critically depend on spectroscopy-based Galactic rotation curves at large distances.

Citation: Vaia, B., Fornasiero, I., Tiengo, A. et al. Accurate distances of the Galactic spiral arms from dust-scattered X-ray emission of gamma-ray bursts. A&A (2026).

DOI: https://doi.org/10.1051/0004-6361/202557431

Study-related stories:

Live Science – “’Astronomers Have To Revise Estimates’: The Milky Way May Be Larger, Heavier and More Lopsided Than We Realized”

Earth Sky – “The Milky Way’s Arms Might Not Look As We Thought”

European Space Agency – “XMM-Newton Helps Revise Distance to Outer Spiral Arms”

Study Findings: Isotopic Evidence for a Cold and Distant Origin of 3I/ATLAS

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Credit: NASA

Nature abstract of study findings:

Interstellar objects provide the only directly observable samples of icy planetesimals formed around other stars, and can therefore provide insight into the diversity of physical and chemical conditions occurring during exoplanet formation. Here we report isotopic measurements of the interstellar comet 3I/ATLAS, which reveal an elemental composition unlike any Solar System body. The water in 3I/ATLAS is enriched in deuterium, at a level of D/H = (0.98 ± 0.06)%, which is more than an order of magnitude higher than in known comets, while its range of 12C/13C ratios (141–191 for CO2 and 123–172 for CO) exceeds typical values found in the Solar System, as well as nearby interstellar clouds and protoplanetary disks. Such extreme isotopic signatures indicate formation at temperatures ≲ 30 K in a relatively metal-poor environment. When interpreted with respect to models for Galactic chemical evolution, the carbon isotopic composition implies that 3I/ATLAS may have accreted as long ago as 12 billion years, following a period of intense, early star formation. 3I/ATLAS thus represents a preserved fragment of an ancient planetary system.

Citation: Cordiner, M., Roth, N.X., Micheli, M. et al. Isotopic evidence for a cold and distant origin of 3I/ATLAS. Nature (2026).

DOI: https://doi.org/10.1038/s41586-026-10771-6

Study-related stories:

Scientific American – “Interstellar Comet 3I/ATLAS is Almost as Old as the Universe Itself”

CBS News – “Interstellar Comet that Zoomed Past Earth Could Be Oldest and Coldest Object Ever Seen in Solar System, Astronomers Say”

Live Science – “’Interstellar Messenger’ 3I/ATLAS Could Be Nearly as Old as the Universe Itself, James Webb Telescope Observations Reveal”

Space Stories: ESA & China Are Smiling, Blue Origin Beats SpaceX to the Moon, and JWST Analyzes Exoplanet Atmosphere

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Here are some recent space-related stories.

—European Space Agency: “Smile Lifts Off on Quest to Reveal Earth’s Invisible Shield Against the Solar Wind“

The Smile spacecraft lifted off on a Vega-C rocket from Europe’s Spaceport in French Guiana at 04:52 BST / 05:52 CEST (00:52 local time) on 19 May 2026. The launch marks the beginning of an ambitious mission to better understand solar storms, geomagnetic storms, and the science of space weather…Smile is a collaboration between the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS). It will reveal how Earth responds to the streams of particles and bursts of radiation from the Sun, using an X-ray camera to make the world’s first X-ray observations of Earth’s magnetic shield, and an ultraviolet camera to watch the resulting northern lights non-stop for 45 hours at a time.

—The Guardian: “Nasa Selects Jeff Bezos’s Blue Origin for First of Three Uncrewed Lunar Missions“

Nasa announced on Tuesday ambitious plans for three uncrewed lunar missions this year to kickstart construction of a $20bn moon base, and said it had chosen the Amazon founder Jeff Bezos’s Blue Origin, ahead of Elon Musk’s SpaceX, to conduct the first...[NASA’s Administrator] said the three missions planned for 2026 would be followed by “more than a dozen” more in the coming years to test systems and equipment. He said the highly successful Artemis II mission last month that sent four astronauts around the moon for the first time since 1972 had been both a catalyst and incentive to advance the moon base plan.

—Astrobiology: “Astronomers Observe Exoplanet Atmospheres With New Cloud-detecting Method“

Every morning, clouds roll in, and by evening, they have cleared off. This sounds like a weather forecast for a coastal city here on Earth — but it’s for WASP-94A b, a well-studied gas giant orbiting a star located nearly 700 light-years away. A new study published in the journal Science documents the first detection of repeating cloud cycles on a hot Jupiter exoplanet. The first author of the study is Sagnick Mukherjee, a 51 Pegasi b postdoctoral fellow at Arizona State University’s School of Earth and Space Exploration. Mukherjee is part of a research team that analyzed data from the James Webb Space Telescope targeting WASP-94 A b, a gas giant in the constellation Microscopium. The team discovered that the planet’s morning side is blanketed in clouds of magnesium silicate, the same mineral found in common rocks, while its evening side is under clear skies.

Note: Here is the podcast version of this post.