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Comet PanSTARRS passes through perigee this Sunday (26) at 72 million km from Earth with an estimated magnitude of 3 and brightness that can reach minus 2 due to forward scattering, but the best observation window in Brazil will be in the first days of May on the western horizon.
The comet that could become the brightest of 2026 makes its closest approach to Earth this Sunday (26), passing just over 72 million kilometers from our planet after having survived its passage by the Sun on April 19. C/2025 R3 (PanSTARRS) reached perigee with an estimated magnitude of 3, an intensity that under ideal conditions would already allow naked-eye viewing, but observers in Brazil face difficulty this Sunday because the comet will be only 6 degrees of separation from the Sun, a position that makes it practically invisible in the daytime sky. The good news is that the best observation window in the Southern Hemisphere begins in the first days of May, when the comet will appear on the western horizon shortly after sunset.
What makes this comet especially interesting is its potential brightness, which would exceed any initial prediction. According to Marcelo Zurita, president of the Paraíba Astronomy Association and columnist for Olhar Digital, a phenomenon called forward scattering can amplify the comet’s luminosity to the point of making it reach magnitude minus 2, a value that would surpass the brightness of Sirius, the brightest star in the night sky. If this occurs, PanSTARRS will not only be the brightest comet of the year but one of the most spectacular astronomical events of the decade for observers who manage to locate it under suitable conditions of clear sky and low light pollution.
Why Comet PanSTARRS could shine brighter than any star
The comet’s trajectory towards the Sun explains the progressive increase in luminosity. Since it was identified with a magnitude close to 20, practically invisible even to powerful telescopes, PanSTARRS has been gaining brightness as it approaches the star: in January it already registered magnitude 17 with the appearance of the coma (a cloud of gas and dust around the nucleus), and this month it reached magnitude 6, the threshold of visibility under ideal dark sky conditions. The process occurs because solar heat causes the comet’s icy material to evaporate, and this material reflects sunlight, increasing luminosity and forming characteristic structures such as the coma and tail.
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The forward scattering mentioned by Zurita is the factor that can transform the comet from a modest object into an exceptional spectacle. When a comet positions itself between Earth and the Sun at a favorable angle, the dust released by the nucleus acts as a curtain of microparticles that scatters sunlight towards the terrestrial observer, an effect that can multiply the apparent brightness far beyond what the object’s natural magnitude would suggest. If the geometric conditions are confirmed, PanSTARRS could achieve brightness comparable to that of Venus, transforming it into a luminous point visible even during twilight.
When and how to observe the comet in Brazil
Observation this Sunday (26) will be difficult for Brazilians. The comet will be only 6 degrees from the Sun, insufficient separation for the object to stand out in the daytime glare, and its position makes it essentially invisible to the naked eye even during dawn or dusk. For those who wish to try, the recommendation is to seek locations away from urban areas with a completely unobstructed western horizon and use binoculars to identify the coma and tail in the minutes before nightfall.
The best window for observers in the Southern Hemisphere occurs in the first days of May. From that date, the comet will gain sufficient angular separation from the Sun to appear low on the western horizon shortly after sunset, a position that requires attention to the exact time of twilight and a field of view free of buildings, hills, or tall vegetation that block the horizon line. Binoculars are still recommended to enhance the experience, especially if the comet’s brightness does not reach the most optimistic levels predicted by astronomers.
What the SOHO space telescope revealed about the comet
PanSTARRS recently entered the field of view of the LASCO (Large Angle and Spectrometric Coronagraph) instrument, mounted on NASA’s SOHO spacecraft, equipment designed for solar observation that allows tracking objects passing near the star. Images captured by LASCO enable more precise calculations of the comet’s trajectory and provide data on the evaporation rate of the nucleus material, information that helps astronomers refine brightness estimates for the coming weeks. The SOHO website provides the instrument’s most recent images, allowing anyone to follow the comet’s progress in near real-time.
Monitoring by SOHO also confirmed that the comet survived its passage through perihelion, the point of closest approach to the Sun, without fragmenting. Not all comets withstand the extreme heat of this approach: many disintegrate when solar heating exceeds the structural capacity of the icy nucleus, and PanSTARRS’ integrity after perihelion is a necessary condition for it to maintain sufficient brightness during the following weeks. The comet’s survival means that material continues to evaporate in a controlled manner, feeding the coma and tail that reflect sunlight and create the brightness that terrestrial observers will try to capture in May.
What to expect from the comet in the coming weeks
The most optimistic estimates place PanSTARRS at magnitude minus 2, a brightness that would be visible even in areas with moderate light pollution. The more conservative estimates keep the prediction around magnitude 3, visible to the naked eye only in dark skies with a favorable horizon. The difference between the two scenarios depends on variables including the composition of the material ejected from the nucleus, the exact geometry between the comet, Sun, and Earth, and the intensity of forward scattering that may or may not amplify the perceived luminosity.
For those who want to prepare, the recommendation is to mark the first days of May on the calendar and identify in advance an observation point with a clear view of the western horizon. The comet will appear low in the sky shortly after dusk, and the visibility window will be short: just a few minutes between the moment the Sun sets and the instant the comet itself follows the star below the horizon line. If PanSTARRS reaches its predicted maximum brightness, it will be the kind of event people remember for decades, and missing the window of observation by not knowing the right time would be a waste no sky enthusiast should accept.
And you, will you try to observe comet PanSTARRS in early May? Have you ever seen a comet with the naked eye? Leave your opinion in the comments.
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