Astronomers have detected a rare interstellar comet, named 3I/ATLAS, passing through the solar system- providing scientists with a unique opportunity to study material formed around another star. It is only the third confirmed interstellar object ever discovered, after:
- 1I/‘Oumuamua (2017)
- 2I/Borisov (2019)
Key Facts
| Parameter | Details |
| Name | 3I/ATLAS |
| Type | Interstellar Comet |
| Discovery Date | July 1, 2025 |
| Discovered By | Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope, Chile |
| Funded By | NASA |
| Operated By | University of Hawaii’s Institute for Astronomy |
| Designation Meaning | 3I = Third Interstellar Object; ATLAS = Discovery Telescope |
| Confirmed By | NASA |
| Orbit Type | Hyperbolic Orbit (Not gravitationally bound to the Sun) |
| Closest Approach to Earth | December 19, 2025 (~270 million km away) |
| Threat Level | None – safe distance |
| Photographed By | China’s Tianwen-1 Mars orbiter (first-ever images of such a distant interstellar object) |
Why It’s Important ?
- 3I/ATLAS gives scientists a direct glimpse into matter formed around another star system.
- It can reveal how planetary systems form and evolve elsewhere in the galaxy.
- Studying its composition helps understand the chemical diversity of interstellar space.
Nature and Composition
Physical Characteristics
- Shape: Teardrop-shaped cocoon of dust (coma) around its icy nucleus.
- Nucleus Size: Estimated between 440 meters and 5.6 km across.
- Coma Composition: Rich in carbon dioxide (CO₂) and dust — indicating formation in a very cold region far from its parent star.
Chemical and Structural Features
- Volatile Content: Similar to solar system comets but altered due to long-term cosmic radiation exposure.
- Activity: Actively releasing gas and dust as it nears the Sun — showing outgassing behavior typical of comets.
Surface Alteration:
- JWST observations suggest its surface has been chemically processed by cosmic rays during billions of years of interstellar travel.
- Hubble data confirms an active, dust-rich coma several thousand km wide.
Orbit and Motion
- Hyperbolic trajectory– Confirms it originated outside the solar system.
- Shows non-gravitational acceleration — movement slightly altered due to outgassing, not just gravity.
- The comet will exit the solar system after its brief passage near the Sun.
Naming Convention: Understanding “3I/ATLAS”
Comets are named after their discoverer(s) or the project that discovered them — in this case, NASA’s ATLAS survey team.
| Component | Meaning |
| 3 | Third interstellar object discovered |
| I | “Interstellar” object (not bound to the Sun) |
| ATLAS | Name of the discovering telescope |
Scientific Observations & Missions Tracking 3I/ATLAS
| Mission | Objective / Role |
| Hubble Space Telescope | Captured first high-resolution images of 3I/ATLAS (July 2025). |
| James Webb Space Telescope (JWST) | Analyzed the comet’s surface chemistry and carbon compounds. |
| Mars Rovers (Perseverance & Curiosity) | Provided contextual observations from Mars’ orbit. |
| Mars Reconnaissance Orbiter | Contributed to trajectory and brightness tracking. |
| Europa Clipper (Launched Oct 14, 2024) | Observing from deep space en route to Jupiter’s moon Europa. |
| Lucy & Psyche Missions (Launched 2017) | Monitoring the comet’s position relative to Jupiter’s orbit. |
| Parker Solar Probe (Launched 2018) | Studying solar wind’s effect on the comet’s tail formation. |
| PUNCH Mission (Launched March 2025) | Observing solar wind and interstellar dust interactions. |
| SOHO (Solar and Heliospheric Observatory) | Tracking near-Sun comet activity from the L1 Lagrange point. |
ESA and CNSA Contributions
- ESA’s JUICE Mission (Launched 2023): Monitoring the comet en route to Jupiter’s moons.
- China’s Tianwen-1 Orbiter: Captured first images of 3I/ATLAS near Mars — a major feat in interplanetary imaging.
What Are Interstellar Objects?
- Celestial bodies originating outside our solar system and passing through it temporarily.
- They usually follow hyperbolic orbits, meaning they will not return.
Previously Known Interstellar Objects
| Object | Year of Discovery | Type | Discovering Telescope | Key Features |
| 1I/‘Oumuamua | 2017 | Asteroid-like | Pan-STARRS, Hawaii | First detected interstellar visitor; cigar-shaped, highly reflective, no visible coma. |
| 2I/Borisov | 2019 | Comet | Gennadiy Borisov (Crimea) | First confirmed interstellar comet; contained cyanide and water, similar to solar comets. |
| 3I/ATLAS | 2025 | Comet | ATLAS, Chile | Active comet with CO₂-rich coma; third interstellar object known. |
Scientific Importance
- Helps scientists study organic molecules and cosmic dust beyond our solar system.
- Offers clues about planetary formation processes in other star systems.
- Enables testing of spacecraft and telescope coordination for interplanetary and interstellar observation.
ATLAS: Asteroid Terrestrial-impact Last Alert System
- Established by: NASA
- Operated by: University of Hawaii’s Institute for Astronomy
- Purpose: Early detection of near-Earth asteroids and potential impact threats.
- Observatories: Located in Hawaii, Chile, and South Africa.
- First Light (Operational): 2015
- Detects moving objects by scanning the entire night sky every 24 hours.
Tianwen-1
- Agency: CNSA (China National Space Administration)
- Launched: July 23, 2020
- Arrived at Mars: February 2021
- Components: Orbiter, Lander, and Zhurong Rover
- Significance: China’s first successful Mars exploration mission.
- Now: Still operational, capturing interplanetary data.
Hubble Space Telescope
- Launched: 1990 (NASA & ESA collaboration)
- Orbit: Low Earth Orbit (~547 km)
- Key Contribution: Provided high-resolution images of galaxies, exoplanets, and interstellar phenomena.
James Webb Space Telescope (JWST)
- Launched: December 25, 2021
- Operated by: NASA, ESA & CSA
- Location: Sun–Earth Lagrange Point L2 (~1.5 million km away)
- Speciality: Infrared telescope capable of analyzing ancient and distant cosmic objects.
ESA’s JUICE Mission
- Full Form: Jupiter Icy Moons Explorer
- Launched: April 14, 2023
- Destination: Ganymede, Callisto, and Europa (Jupiter’s moons)
- Goal: Study habitability and subsurface oceans.