NASA and space agencies monitor the interstellar comet 3I/ATLAS, the third known object from outside the solar system, which crosses our celestial region.
Discovered in July 2025 by the ATLAS telescope in Chile, the comet follows a hyperbolic trajectory, confirming an external origin.
It reached its closest point to the Sun on October 30, 2025, 1.4 astronomical units, within the orbit of Mars, without risk to Earth.
Minimum approach to the planet occurs in December, at 1.8 astronomical units, or 270 million kilometers.
Hyperbolic trajectory intrigues scientists
Comet 3I/ATLAS travels at 137,000 miles per hour, accelerating as it approaches the Sun.
Its open orbit does not close around the star, proving that it came from another star system, possibly Sagittarius.
Formed billions of years ago, it carries primitive materials that help us understand distant planetary formation.
Accidental discovery in Chile
The NASA-funded ATLAS telescope detected the object on July 1, 2025, in Rio Hurtado.
Previous observations from June 14 came from telescope archives in Hawaii, South Africa and California.
The designation “3I” marks the third interstellar, after 1I/ʻOumuamua and 2I/Borisov, named after the ATLAS team.
The find ininitial image showed a reddish coma, indicating dust and cometary activity.
Hubble observations reveal details
The Hubble Space Telescope captured an image on July 21, 2025, 277 million miles from Earth.
The photo showed a drop-shaped dust cocoon surrounding the icy core, with stars blurred by the tracking.
Estimates indicate a core diameter of between 440 meters and 5.6 kilometers, refined by continuous data.
No brightness explosion occurred until August, maintaining stable activity.
NASA Missions in Joint Action
Several NASA probes have been collecting data on 3I/ATLAS since July.
- Hubble: images and size measurements.
- James Webb: spectrum in August, detecting CO2, water, CO and ice.
- TESS: early activity in May 2025, 6.4 astronomical units from the Sun.
- SPHEREx: observations from August 7th to 15th, analyzing composition.
Others include Swift, Perseverance, Curiosity, Mars Reconnaissance Orbiter, Europa Clipper, Lucy, Psyche, Parker Solar Probe and PUNCH.
Radio signals confirm natural nature
Astronomers used the MeerKAT radio telescope in South Africa to detect the signal on October 24, 2025.
Absorption lines of hydroxyl radicals at 1665 and 1667 MHz indicate sublimation of ice, forming gaseous coma.
The detection occurred close to perihelion, favoring radio absorption, in line with the behavior of comets.
This reinforces that 3I/ATLAS is a natural body, ruling out hypotheses of artificial origin, despite initial speculation.
November updates show stability
On November 10, 2025, the StarFront Observatory recorded morning video of the comet, post-approach to Venus on November 3.
Photometric analysis indicates a stable luminous nucleus, without fragmentation, with a 16-hour rotation cycle.
Brightness modulation at 97% stability, with subtle interactions of the solar wind in the outer coma.
The object crosses the orbital plane on November 19, approaching Earth by 0.24 astronomical units on December 19.
Chemical composition exposes ancient origins
The James Webb Telescope identified carbon dioxide, carbon monoxideo, carbonyl sulfide and water ice released.
Nickel vapor was detected in the atmosphere, signaling an age greater than the solar system, 3 to 11 billion years old.
Preliminary studies suggest thick irradiated crust, altered by interstellar travel, but preserving traces of the natal system.
The reddish color of the coma, similar to 2I/Borisov, points to organic dust and cosmic evolution.
Mars observations capture proximity
The Mars Reconnaissance Orbiter photographed the comet on October 2-3, 2025, 30 million kilometers from Mars.
Images from HiRISE, with a resolution of 30 km per pixel, surpass those from Hubble, showing detailed coma and tail.
Perseverance and Curiosity rovers recorded environmental data during the passage, with no interference detected.
ESA missions such as Mars Express and ExoMars Trace Gas Orbiter contributed spectra in October.
Visible future for amateur telescopes
The comet reappears visible in December 2025, passing through Virgo and Leo, with a magnitude above 12.
Telescopes of at least 20 centimeters in aperture detect it, requiring tracking mounting for stability.
Updates from NASA and ESA provide accurate times, with continuous monitoring until exit from the solar system.
This unique passage allows the study of interstellar dynamics before definitive departure.
