Wolf-Rayet stars of type WC9d are known as active producers of carbon dust. Occasionally they can dim sharply when dust clouds obscure their light. However, for WR 59 such an event had never been recorded before. The problem is that this star lies only 11 arcseconds from a brighter companion of magnitude 11.7. Automated sky surveys such as ASAS-SN or ATLAS use wide pixel apertures and blend the light of the two stars, so their data show an overestimated and smoothed brightness. As a result, rare and short dust-induced dimming events can be completely missed. This work sits somewhat apart from neighboring studies of gamma-ray bursts, cosmic rays, and fast radio bursts, but its topic, the variability of Wolf-Rayet stars, is closely related to the study of jets and mass loss from massive stars.
Rod Stubbings conducted regular visual observations of WR 59 starting in April 2017 using a 22-inch (0.56 m) telescope at 270× magnification with a Tele Vue Ethos 8 mm eyepiece. This setup allowed a limiting magnitude of 17.3 and clearly resolved the two stars separated by 11 arcseconds. On May 11, 2021 (Julian date 2459346), he noticed that the star had faded to magnitude 15.2. Over the next day, he made seven independent visual brightness estimates, recording the deep minimum. He then requested independent confirmation from another visual observer, Stephen Howells, who confirmed the dimming. Later, in 2026, Stubbings compared his data with archival observations from the TESS space telescope (sector 38), which happened to observe the same field in May 2021.
The visual light curve showed a sharp drop from 13.9 to 15.2 magnitudes over a very short time. The minimum lasted about a day, after which the star began to recover and returned to its original level after 14 days. TESS independently recorded the event: its light curve showed a minimum around Julian date 2459345.5, matching the visual observations. Moreover, TESS detected short-period brightness fluctuations during the recovery phase that coincided with visual estimates. This confirmed that the observed changes were real physical processes in the dust shell, not observer errors. A key difference: TESS showed a drop of only 0.7 magnitudes (to 14.55) due to blending with the companion, whereas visual observations isolated WR 59 and revealed the full depth of 1.3 magnitudes (to 15.2). The visual observations also filled a 22.58-hour gap in TESS data when the satellite was busy transmitting telemetry to Earth.
This work provides the first evidence that WR 59 is an active dust-producing system capable of sudden, deep eclipses. Previously considered stable, it is now clear that the star can change brightness by 1.3 magnitudes within hours. Unlike neighboring studies of gamma-ray bursts and fast radio bursts, this work examines not an explosive process but the slow accumulation and ejection of dust in a stellar wind. The method is also unique: instead of automated surveys with wide pixels, the observer's eye with high magnification resolved the close pair. This is the first test of whether visual observations can catch events that modern robotic telescopes miss.
Stubbings continues nightly observations of WR 59 and has already recorded ten more similar dimming events. Full light curves of these events will be published in a separate paper. In the future, more detailed studies of the star's dust shell using interferometry or high-resolution spectroscopy could reveal how dust clouds form and dissipate. Combining visual observations with real-time space telescope data also holds promise for not missing short minimum phases.
The discovery highlights the value of amateur visual observations in the era of large sky surveys. It also provides a new target for studying dust formation in Wolf-Rayet stars, which is important for understanding mass loss from massive stars and the enrichment of the interstellar medium with carbon dust.
Publication of the full set of ten subsequent dimming events of WR 59. Coordination of multiwavelength observations (including infrared spectroscopy) during future minima to study the composition and dynamics of the dust.
For the field of Wolf-Rayet stars, a key unresolved problem remains the mechanism of dust formation in their dense winds. Dimming events offer a unique opportunity to probe the geometry and evolution of dust clouds. This work shows that even a single star once thought to be quiescent can be far more active than assumed, and that detecting such events requires methods capable of resolving close pairs.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study reports the first recorded dimming of the Wolf-Rayet star WR 59 in May 2021. The event was spotted visually by an amateur astronomer and later confirmed with TESS data. The authors show that visual observations allowed them to isolate the light of WR 59 from its close companion and capture the full depth of the brightness drop, unlike the blended TESS data.
Where its strength is
The strength of the work lies in demonstrating that visual observations with high angular resolution can compete with space telescopes when studying close binary systems. This paves the way for systematic monitoring of such objects that are inaccessible to automated surveys.
Where it could go next
Worth trying
Why this may matter
Such observations could fill a gap in the study of short-period variability in massive stars caused by dust ejections, and improve our understanding of mass loss in the late stages of stellar evolution.
Nearby works in our archive
The archive is sparse around this work: the closest review is only 0.52, against a usual 0.64. It looks like few have drilled nearby.
During the minimum, WR 59 became almost 3.3 times fainter than usual, but it would still remain invisible to the naked eye: at magnitude 15.2, it is 4000 times fainter than the faintest stars visible to the eye on a dark sky.