Interstellar Comet 3I/ATLAS: Closest Approach to Earth

 

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3I/ATLAS is a very important object in astronomy. The designation "3I" (Interstellar 3) means it is the third confirmed interstellar object discovered to have originated from outside our solar system.

This comet will make its closest approach to Earth on December 19, 2025.

• At that time, the distance from the comet to Earth will be approximately 1.8 Astronomical Units (AU). This measurement in Astronomical Units (AU) indicates that the comet will pass at a distance about 1.8 times the distance between the Sun and Earth. In kilometers, this distance is approximately 270 million kilometers. Due to this safe distance, there is no risk to Earth from this comet.

Other Important Details

• The comet reached its closest point to the Sun (Perihelion) on October 29, 2025.
• It is faint, requiring at least a small telescope to be seen, as its brightness (magnitude) is around 11 to 15.
• Its travel speed and its orbit confirm to scientists that it is not a part of our solar system.

This interstellar comet offers scientists a wonderful opportunity to study objects originating from other star systems.

How and Where Did This Interstellar Comet Originate?

1. The Origin of Comet 3I/ATLAS

3I/ATLAS was not born in our solar system; instead, it formed around some other distant star in the galaxy.

• Birthplace: It originally formed in a cloud of dust and ice (a Protoplanetary Disk) around another star. The ice and dust in its composition may be chemically different from the comets in our solar system.
• Ejection: During the early stages of planetary formation, when large planets (like our Jupiter or Saturn) were forming, their intense gravitational force likely caused this small comet to be ejected at high speed from its parent star system.
• In this way, the comet was freed from the gravity of its original star and began traveling through the vast, empty space between the stars.

2. The Interstellar Journey

After leaving its parent star, Comet 3I/ATLAS would have traveled through space for millions of years.

• Long Voyage: It has traveled millions of kilometers in the Interstellar space between the stars. It remained cold and dark during this journey.
• Unexpected Visit: Eventually, its celestial path led it towards our solar system. It entered the gravitational field of our Sun and approached its surface.
• Exit: The orbit of this comet is Hyperbolic (open, not closed). This means it will never orbit our Sun. After passing close to Earth in December 2025, it will once again return to the infinite space and likely never return to our solar system.

             

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By studying this object, scientists can learn how other star systems function and what the composition of ice and dust is in those systems.

Which Other Interstellar Objects Have Been Discovered Besides This Comet?

Exactly! 3I/ATLAS is the third interstellar object discovered. The following two interstellar objects had passed through our solar system before it:

1. 1I/ʻOumuamua

This was the first confirmed interstellar visitor, which surprised scientists the most.

• Discovery: Found in October 2017.
• Meaning of Name: In the Hawaiian language, it means "a messenger from afar arriving first."
• Shape: It was very unusual. Most scientists believe it had a cigar- or pancake-like shape, meaning its length was up to 10 times greater than its width.
• Activity: It did not look like a comet because no cloud of dust or gas (Coma) was observed around it even as it approached the Sun.
• However, its speed increased slightly due to some unknown, non-gravitational force, which scientists are still researching.

2. 2I/Borisov

2I/Borisov was the first interstellar comet that behaved like a regular comet.

• Discovery: Found in August 2019 by Gennadiy Borisov, an amateur astronomer in Crimea.
• Type: Comet.
• Special Feature: Unlike 'Oumuamua, when it came close to the Sun, it clearly formed a Tail and a Coma.
• This indicates that it is made of ice and dust, similar to the comets in our solar system. This provided scientists with the first opportunity to study the chemical composition of an object from another star system.

               

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These three objects (1I/ʻOumuamua, 2I/Borisov, and 3I/ATLAS) have proven that objects from other star systems regularly travel through our galaxy. As our telescope technology improves, it is likely that more such interstellar visitors will be discovered in the future.