Astronomy and space this week

A small spacecraft for a rare asteroid encounter

When Apophis passes close to Earth in April 2029, our planet’s gravity could disturb the asteroid’s loosely assembled surface. A proposed student-led mission from Tsinghua University, called START, aims to watch that response at close range. Its designers describe a 300-kilogram spacecraft launching into low Earth orbit in early 2028, then using solar electric propulsion to reach a higher Earth orbit positioned for a fast encounter just seven kilometres from Apophis.

The planned cameras and near-infrared imagers would collect centimetre-scale pictures and metre-scale information about surface composition. The scientific prize is a view of how an asteroid responds to strong tidal forces as they act—not simply a comparison of its appearance long before and after an encounter. This preprint presents a mission plan, rather than results from flight, but it offers a potentially economical complement to larger international efforts to study Apophis.

Read: The START mission: Probing the 2029 Apophis Flyby via a Low-Cost Geocentric SmallSat

A persistent X-ray source with a flaring habit

An X-ray source in the direction of the galaxy M81 has been shining brightly for two decades while repeatedly producing flares lasting only a few hundred seconds. Combining observations from several missions, researchers find that the source, M81F4, can reach peak luminosities of a few billion billion billion watts. Its flares rise quickly and fade more slowly, without a significant change in the relative balance of lower- and higher-energy X-rays.

The authors argue that familiar classes of neutron-star bursts do not readily explain this combination of persistent brightness and brief outbursts. Their preferred explanation is a magnetized neutron star drawing matter from an intermediate-mass companion, with instabilities where the incoming disk meets the star’s magnetic field. That interpretation remains unconfirmed. If correct, the source could point to an overlooked population in which magnetic regulation allows short episodes of exceptionally intense emission.

Read: The Dancing Bonfire: An Unusual Persistent X-ray Source in M81 Exhibiting Recurrent Luminous Flares

A supernova’s second brightening is not a second energy peak

The Type Ib supernova SN 2025wiu brightened again in optical observations about 38 days after its first maximum. Yet when researchers reconstructed its total light output across wavelengths, they found no distinct second peak—only a slower decline. The distinction matters: a rise in one slice of the spectrum does not necessarily mean the explosion’s overall radiated power has risen too.

A model combining radioactive decay with collisions between the expanding debris and surrounding material reproduces the reconstructed light curve. But the spectra lack the narrow emission features often associated with such interactions. The authors suggest that the surrounding material may lie in an engulfed disk-like structure, allowing collision energy to be absorbed and re-emitted beneath the visible surface of the ejecta. This is a model-dependent interpretation, not a direct measurement of that geometry, and the paper underscores why several wavelength bands are needed to diagnose a supernova’s power source.

Read: SN 2025wiu: A Type Ib Supernova with Post-Peak Optical Rebrightening

Tracing a severe solar storm back to its magnetic surroundings

A new reconstruction follows the January 18–19, 2026 solar eruption from the Sun to Earth, where it produced a severe G4 geomagnetic storm. The team combines solar images, measurements from Solar Orbiter and Wind, and magnetic-fluid simulations. Their model broadly reproduces the eruption’s shape, magnetic measurements and the evolution of Earth’s geomagnetic disturbance, although it leaves out filament material that the authors identify as a source of disagreement.

The study argues that a neighbouring coronal hole—a region whose magnetic field opens into space—helped determine the outcome. Its magnetic alignment with the eruption limited the loss of the eruption’s magnetic structure, preserving the strong southward field that made it effective at disturbing Earth’s magnetic environment. A following fast solar-wind stream then prolonged the recovery. In this account, conditions near the Sun largely set the storm’s strength, while the surrounding solar wind controlled its duration.

Read: Characterizing the Martin Luther King Event: Sun to Earth Evolution of the January 19, 2026 Geomagnetic Storm

Could planetary rings outshine the planets?

Saturn-like rings could make some giant exoplanets much easier to detect in reflected starlight, according to new modelling for the Roman Space Telescope’s Coronagraph Instrument. In the authors’ calculations, rings can outshine their host planet by factors of ten to a hundred or more. That could bring otherwise inaccessible systems within reach—but could also make a planet appear intrinsically brighter than it really is.

The proposed way to separate the signals is to observe repeatedly as the system moves around its star. Ringed systems can produce a distinctive brightness pattern with four turning points over an orbit, rather than the two expected for an unringed planet. Simulated observations of Epsilon Eridani b suggest that a Saturn-like ring system there would be detectable. These are forecasts, not evidence that the planet has rings, but they show how repeated measurements could turn an ambiguity into a test.

Read: Detecting Exoplanetary Rings with Roman CGI Reflected Light Phase Curve Observations

The Hubble tension depends on which supernovae enter the calculation

Can changes in the Universe’s recent expansion history resolve the mismatch between local measurements of the Hubble constant and the value inferred from the early Universe? A new preprint argues that an important test depends strongly on the supernova catalogue used. Combining DESI galaxy-clustering distances with DES-Dovekie supernovae, while assuming a standard early-Universe sound horizon, the researchers infer about 76 kilometres per second per megaparsec. Adding older, “legacy” supernova samples lowers the result to about 68—shifting it from compatibility with the SH0ES local measurement to substantial disagreement.

Under the authors’ reference cosmological model, only 1.24 percent of simulated catalogues produce so large a shift from the change in redshift sampling alone. They interpret this as evidence of systematic tension between the datasets. Their tests leave room for late-time solutions with the homogeneous DES sample, but not with the legacy data as published; allowing a relative recalibration changes that conclusion. The result does not settle the Hubble tension. It makes the consistency of nearby supernova samples a central part of deciding which explanations remain viable.

Read: Does the inverse distance ladder rule out late-time solutions to the Hubble tension? A model-independent test using DES-Dovekie supernovae and DESI DR2 BAO

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These preprints share a concern with how appearances become physical explanations. A supernova can brighten in one band without gaining total luminosity; rings can masquerade as a brighter planet; a change of catalogue can alter a cosmological verdict. Close encounters, repeated observations and comparisons across instruments offer ways to break those ambiguities. Across very different scales, the next useful advance may come less from seeing something brighter than from seeing it in another way.