Chile’s ATLAS survey telescope discovered the comet ‘3I/ATLAS’

The ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope, funded by NASA and located in Río Hurtado (Chile), has discovered the comet 3I/ATLAS. This is the third interstellar object discovered by humans so far.

• 3I/ATLAS is a comet discovered in 2025 by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope located in Río Hurtado (Chile).
• It is the third interstellar object discovered by humans so far, identified as a comet with a coma and tail, and is traveling in an open-ended, hyperbolic orbit, indicating that it originated from outside our solar system.
• Interstellar space, whose trajectory shows that it is a visitor from another star system.
• It is a fast-traveling comet with a coma and tail, and it appears quite red from the Sun.
• It provides astronomers with a valuable opportunity to study its composition and origin and offers clues about the formation of other star systems.

Objects outside the solar system

• The first was 1I/’Oumuamua in 2017 and the second was the comet 2I/Borisov in 2019. Due to the hyperbolic shape of its orbital path, it has been classified as interstellar. It does not follow a closed orbital path around the Sun.

Naming

• Comets are usually named after their discoverer(s), in this case, the ATLAS survey team. The letter "I" stands for "interstellar," indicating that the object came from outside our solar system. This is the third known interstellar object, hence the "3" in the name.

Hubble estimated the size

• NASA’s Hubble Space Telescope took the below image of the interstellar comet 3I/ATLAS on July 21, 2025, when the comet was 277 million miles away from Earth. Hubble’s observations enable astronomers to make a more accurate estimate of the comet’s nucleus size.
• According to researchers, its diameter upper limit is 3.5 miles (5.6 kilometers), although it could be as small as 1,000 feet (320 meters).
• When it was discovered, this interstellar comet was traveling at a speed of about 137,000 miles per hour (221,000 kilometers per hour, or 61 kilometers per second), and as it approaches the Sun, its speed will increase further.

ATLAS Telescope

• The ATLAS telescope at Río Hurtado, Chile, is one of the four telescopes that are part of the Asteroid Terrestrial-impact Last Alert System (ATLAS). It was developed by the University of Hawaii.
• The ATLAS survey began in 2015 with telescopes in Hawaii and became a two-telescope system in 2017. Chile’s participation with the ATLAS survey telescope began in early 2022. The network of telescopes includes sites in Hawaii, Chile, and South Africa.