A newly discovered comet, designated as Comet C/2025 R2 (SWAN), is expected to make its appearance in the evening sky this October. The discovery was made on September 10, 2023, by Vladimir Bezugly in Dnipro, Ukraine, while he analyzed images from the Solar Wind Anisotropies (SWAN) camera aboard the Solar and Heliospheric Observer (SOHO) spacecraft. The comet emerged as a bright object close to the sun, marking it as the twentieth official SWAN comet identified to date.
Following its discovery, the comet has been observed by many amateur astronomers, particularly in the Southern Hemisphere. On September 15, the International Astronomical Union (IAU) officially recognized the comet’s designation. Observations indicate that Comet SWAN has a brightness magnitude of approximately +7, which places it just beyond naked-eye visibility under optimal dark sky conditions. Nevertheless, good binoculars can facilitate viewing.
Viewing Prospects and Path to Earth
The brightness of celestial bodies is measured using a numerical scale known as magnitude. In this scale, lower numbers signify brighter objects. For context, the brightest stars register at magnitude 0 or +1, while objects with a magnitude of +6.5 can be seen without optical aid in dark conditions. Comet SWAN’s current magnitude suggests it is just out of reach for unaided observers.
As it approaches Earth, predictions from various astronomers indicate that the comet may reach a magnitude between +6 and +7 during the third week of October, potentially becoming visible to the naked eye. Daniel W.E. Green from the Central Bureau for Astronomical Telegrams forecasts that the comet will hover near magnitude +6 from October 2 to October 20, with a brief chance of being visible without assistance around October 12.
On October 21, Comet SWAN will make its closest approach to Earth, at a distance of 25.10 million miles (40.38 million km). Its orbital characteristics suggest that it will take approximately 1,400 years to complete a full orbit around the sun.
Locating Comet SWAN in the Night Sky
Currently, Comet SWAN has mainly been visible from the Southern Hemisphere, as it has been too close to the sun for ease of visibility north of the equator. However, its path will shift northward by the end of September, rising higher in the southwest sky throughout early October. By the end of the first ten days of October, it will reach an altitude of 12 degrees above the horizon after sunset.
As a reference, a clenched fist held at arm’s length represents approximately 10 degrees. By October 28, the comet’s altitude is expected to increase to 30 degrees, making it more accessible for northern observers.
During its journey, Comet SWAN will traverse the constellations of Libra, Scorpius, and Sagittarius, among others. Observers may find it challenging to spot the comet in areas affected by light pollution, as it may not appear like a sharp star but rather as a diffuse light source.
The comet’s composition is primarily gaseous, resulting in a bluish-white glow rather than the dusty appearance typical of other comets. Thus, it may appear as a circular cloud, brighter at the center and with a faint tail extending from the coma.
While there has been speculation on social media regarding a potential meteor shower associated with Comet SWAN around October 4 to 6, experts clarify that this is unlikely. The comet’s orbit does not intersect with Earth’s path closely enough for significant meteor activity to occur.
As the October sky approaches, amateur astronomers and skywatchers alike are encouraged to prepare their binoculars and telescopes to witness this remarkable cosmic event.
