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Comets News 3 July 2025 - 17 September 2025

Mysterious Comet SWAN R2: New Interstellar Visitor or Oort Cloud Wanderer?

Mysterious Comet SWAN R2: New Interstellar Visitor or Oort Cloud Wanderer?

Discovery of Comet C/2025 R2 (SWAN) Comet C/2025 R2 (SWAN) was spotted in early September 2025 in a rather unconventional way – by searching for faint glows in SOHO satellite images. The SOHO spacecraft’s SWAN instrument scans the entire sky in ultraviolet light, primarily to track solar wind interaction with hydrogen. Astrophotographers and amateur astronomers often comb through these SWAN images for telltale moving smudges that betray new comets. On 11 September 2025, Ukrainian amateur Vladimir Bezugly noticed such a moving fuzzball in SWAN’s data universetoday.com. Within hours it was confirmed by others and reported, earning the provisional label “SWAN25B”
17 September 2025
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Interstellar Comet 3I/ATLAS Shrouded in CO₂ Fog – NASA’s SPHEREx Reveals a Cosmic Visitor’s Secrets

Interstellar Comet 3I/ATLAS Shrouded in CO₂ Fog – NASA’s SPHEREx Reveals a Cosmic Visitor’s Secrets

3I/ATLAS (C/2025 N1 ATLAS) was discovered July 1, 2025 by the ATLAS survey telescope in Chile and is on a hyperbolic, unbound path with eccentricity ~6.2, making it the third confirmed interstellar object after 1I/‘Oumuamua and 2I/Borisov. Early estimates suggested a diameter of several kilometers, and Hubble data later indicated a nucleus of about 5–6 km across, making 3I/ATLAS the largest interstellar object observed. SPHEREx detected a huge CO₂ cloud around 3I/ATLAS, with the coma extending at least 348,000 km from the nucleus, alongside evidence of water ice in the nucleus. JWST measurements found a CO₂-to-H₂O ratio of roughly 8:1
5 September 2025
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Interstellar Comet 3I/ATLAS: A Visitor from Beyond the Solar System

Interstellar Comet 3I/ATLAS: A Visitor from Beyond the Solar System

3I/ATLAS was first spotted on July 1, 2025 by the ATLAS telescope in Río Hurtado, Chile, and officially designated 3I/2025 A1 (ATLAS), the third confirmed interstellar object after 1I/‘Oumuamua (2017) and 2I/Borisov (2019). It is traveling through the inner solar system at about 60–61 kilometers per second relative to the Sun on a hyperbolic trajectory, with perihelion near the orbit of Mars in late October 2025 (about 1.4 AU). Its closest approach to Earth will be roughly 1.6–1.8 AU (240–270 million kilometers), and it will be behind the Sun from Earth’s perspective at that time, posing no threat. The Hubble
19 August 2025
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3I/ATLAS: The Fastest Interstellar Comet Ever—Here’s What Scientists Are Saying

Interstellar Comet 3I/ATLAS – Third Cosmic Visitor Unveiled, Fast and Enormous

3I/ATLAS is the third interstellar object ever recorded. It was first spotted on July 1, 2025 by the ATLAS survey telescope in Río Hurtado, Chile. The designation 3I/ATLAS marks it as the third interstellar object in our solar system. Its orbit is hyperbolic with an eccentricity of about 6.2, meaning it is unbound and will exit the solar system. A faint coma was observed around 3I/ATLAS within days of discovery, confirming it is a comet. The object was traveling over 60 km/s at discovery and about 68 km/s at perihelion. Perihelion was predicted for October 29–30, 2025 at roughly 1.4
2 August 2025
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Astronomers Spot a 7-Billion-Year-Old Interstellar Comet – Could It Be the Oldest Ever Seen?

Astronomers Spot a 7-Billion-Year-Old Interstellar Comet – Could It Be the Oldest Ever Seen?

On July 1, 2025, the ATLAS telescope in Río Hurtado, Chile, detected 3I/ATLAS near Jupiter’s orbit with a hyperbolic, interstellar trajectory. 3I/ATLAS is the third interstellar object identified, following 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019. Estimates place 3I/ATLAS at 7–10 billion years old if formed in the Milky Way’s thick disk, making it possibly the oldest comet we’ve seen. Backward-orbit modeling using Gaia data and the Ōtautahi–Oxford model suggests an origin in the Milky Way’s thick disk. The nucleus is estimated to be 6–15 miles (10–24 km) across, larger than 1I/ʻOumuamua (~0.25 mile) and 2I/Borisov (~0.67 mile). It travels
17 July 2025
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Interstellar Comet 3I/ATLAS: Origin, Trajectory and Scientific Stakes In 2025’s Third‑Ever Extrasolar Visitor

Interstellar Comet 3I/ATLAS: Origin, Trajectory and Scientific Stakes In 2025’s Third‑Ever Extrasolar Visitor

<li ATLAS imaged the interstellar candidate on 1 July 2025, with precovery back to 14 June 2025, and it was designated C/2025 N1 (ATLAS) and later 3I/ATLAS as the third confirmed interstellar object after Oumuamua and Borisov. <li A JPL orbital solution yields eccentricity e = 6.1 ± 0.1 and hyperbolic excess velocity V∞ ≈ 58 km/s, indicating an extrasolar origin from Galactic longitude about 5° toward the Galactic Center. <li The object’s nucleus is estimated at 9–20 km in diameter, with a developing coma and tail already visible, including a compact coma at about 4.5 AU from the Sun.
8 July 2025
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3I/ATLAS: The Fastest Interstellar Comet Ever—Here’s What Scientists Are Saying

3I/ATLAS: The Fastest Interstellar Comet Ever—Here’s What Scientists Are Saying

3I/ATLAS (C/2025 N1) is the third identified interstellar object, discovered on 1 July 2025 by the ATLAS telescope in Chile. It is on an extremely hyperbolic trajectory with a velocity of about 68 km/s and will reach perihelion on 29 October 2025 at 1.36 au, inside Mars’s orbit. It poses no threat to Earth. Early images show a faint coma and a short 3-arcsecond tail, confirming cometary activity. Detected at 4.5 au from the Sun months before perihelion, it offers an unprecedented window to study its composition, rotation, and size. The hyperbolic excess velocity v∞ is 57 km/s, making 3I/ATLAS
3 July 2025
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