A newly discovered comet, designated C/2025 R2 (SWAN), is currently approaching Earth and may become faintly visible to the naked eye for observers in the Northern Hemisphere during October. The comet was first identified in early September using data from a NASA and ESA spacecraft.
Key Takeaways
- Comet C/2025 R2 (SWAN) was discovered on September 10 by an amateur astronomer using public spacecraft imagery.
- The comet will make its closest approach to Earth on October 21, coming within 25.10 million miles (40.38 million km).
- Forecasts suggest its brightness could peak around magnitude +6, which is on the edge of naked-eye visibility in dark skies.
- Despite online speculation, the comet will not produce a meteor shower in early October as its orbit is too far from Earth's.
Discovery and Designation
The comet was first spotted by Vladimir Bezugly, an observer from Dnipro, Ukraine, on September 10. He was analyzing public images captured between September 5 and September 9 by the Solar Wind Anisotropies (SWAN) camera aboard the Solar and Heliospheric Observer (SOHO) spacecraft.
Bezugly identified a moving, bright object near the sun, which was later confirmed to be a comet. He noted that it was one of the brightest comets ever found in SWAN imagery. Following the initial sighting, amateur astronomers, primarily in the Southern Hemisphere, began observing the object.
The SWAN Instrument
The SWAN camera on the SOHO spacecraft is designed to map hydrogen distribution in the solar system. Comets release large amounts of hydrogen as they near the sun, making them visible to this specific instrument. This is the 20th official comet discovery credited to the SWAN camera.
On September 15, the International Astronomical Union (IAU) officially designated the object as Comet C/2025 R2 (SWAN), acknowledging its discovery through the SOHO instrument.
Brightness and Orbital Path
Astronomers measure the brightness of celestial objects using a scale called magnitude, where lower numbers indicate brighter objects. The limit for unaided human vision in a dark, clear sky is typically around magnitude +6.5.
Recent observations place Comet SWAN at a magnitude of approximately +7. This brightness level makes it slightly too dim for naked-eye viewing but easily observable with a good pair of binoculars or a small telescope. Observers describe it as having a small, dense head, known as a coma, and a faint, thin tail.
Comet SWAN's Journey
- Perihelion (Closest to Sun): September 12
- Distance at Perihelion: 46.74 million miles (75.20 million km)
- Perigee (Closest to Earth): October 21
- Distance at Perigee: 25.10 million miles (40.38 million km)
- Estimated Orbital Period: Roughly 1,400 years
The comet has already passed its closest point to the sun (perihelion) but is now moving closer to Earth. Its closest approach to our planet (perigee) will occur on October 21. Based on its orbital characteristics, astronomers estimate that it takes about 1,400 years for Comet SWAN to complete one full orbit around the sun.
Viewing Prospects for October
While the comet has been primarily a target for observers in the Southern Hemisphere, its trajectory is now carrying it northward. By the end of September, it will become accessible to skywatchers in northern latitudes.
How Bright Will It Get?
Several experts have provided forecasts for the comet's peak brightness. Seiichi Yoshida, a Japanese comet expert, and Gideon Van Buitenen, a Dutch expert, both predict the comet will reach a magnitude between +6 and +7 during the third week of October. This would place it right at the threshold of naked-eye visibility.
Daniel W.E. Green of the Central Bureau for Astronomical Telegrams suggests the comet will remain near magnitude +6 from October 2 to October 20. He notes it could become slightly brighter around October 12, potentially making it faintly visible without optical aid under ideal conditions.
Where to Look in the Sky
Throughout October, Comet SWAN will travel across several constellations, including Libra, Scorpius, Ophiuchus, and Sagittarius. Its position in the sky will improve for Northern Hemisphere observers as the month progresses.
In early October, it will appear low in the southwest sky shortly after sunset. By October 28, its altitude will have increased to about 30 degrees above the south-southwest horizon at the end of evening twilight, making it much easier to locate. A simple way to measure this is to hold your clenched fist at arm's length; it covers about 10 degrees of the sky.
For the best chance of spotting the comet, find a location away from city lights with an unobstructed view of the horizon. Since it is a gaseous comet, it will appear as a diffuse, glowing patch rather than a sharp point of light. This composition gives it a bluish-white color, as the gas is illuminated by solar radiation.
Addressing Meteor Shower Speculation
There has been considerable discussion on social media suggesting that Comet SWAN could produce a meteor shower between October 4 and October 6. This theory arose from two-dimensional diagrams that appear to show the comet's orbit intersecting with Earth's orbit around October 5.
However, this speculation is incorrect. While the orbital paths look close on a flat map, the reality in three-dimensional space is very different. According to detailed calculations, the comet's orbit will actually pass approximately 4.4 million miles (7 million km) above Earth's orbital plane. This is far too great a distance for any debris from the comet to enter our atmosphere.
Furthermore, two other factors make a meteor shower highly unlikely:
- Timing: Earth will reach the apparent intersection point on October 5, a full 16 days before the comet itself arrives. Any potential debris trail would be behind the comet, not ahead of it.
- Composition: Comet SWAN is primarily composed of gas, not dust. Dusty comets are the ones that shed the solid particles (meteoroids) that create meteor showers. Gaseous comets leave behind very little debris.
Therefore, skywatchers should not expect any unusual meteor activity related to Comet C/2025 R2 (SWAN) in early October. The main event remains the potential to view the comet itself as it makes its close approach to Earth.