Mysterious interstellar visitor approaches NASA's spacecraft

The mysterious celestial body 3I/ATLAS, coming from outside the Solar System, will pass close to NASA 's Europa Clipper and the European Space Agency's (ESA) Hera spacecraft in a few weeks.

Scientists say this encounter, expected to occur between October 25 and November 6, 2025, could be the first "interstellar comet ion tail observation" in human history.

"WE WILL DIVE INTO ITS TAIL"

According to the European researchers' paper, which has not yet been peer-reviewed, two spacecraft will enter the ion tail of 3I/ATLAS. This will provide an opportunity to directly study particles in the ion tail of an object from outside the Solar System.

The ion tail consists of charged particles that erupt from the comet's nucleus and extend millions of kilometers away. Encounters with such tails are extremely rare and valuable because they allow scientists to directly analyze raw material from beyond the Solar System.

These calculations were made using a program called Tailcatcher, developed by the researchers. The software calculates the closest approach point to a spacecraft's ion tail, taking into account the direction and speed of the solar wind.

The closest distance calculated for 3I/ATLAS is approximately 8 million km. Scientists state that although Europa Clipper cannot measure all ion components, it can provide important data in understanding the structure and composition of the comet's ion tail.

"ALIEN" DEBATE

Meanwhile, the interstellar object 3I/ATLAS, hurtling through the Solar System, continues to fascinate astronomers. First discovered in July 2025 and estimated to be the size of a city, this object has generated significant interest in both scientific and speculative circles. While most scientists consider it a natural comet, Harvard University astrophysicist Dr. Avi Loeb suggests that 3I/ATLAS could be the product of "alien technology ."

Loeb's humorous reference to the October 29th date in a recent interview sparked speculation on social media and in the press.

ANTI-TAIL DEBATE

Recent observations with the Keck II Telescope in Hawaii have revealed that 3I/ATLAS exhibits an "anti-tail" extending in the direction of the Sun. Harvard astronomer Avi Loeb argues in a blog post published last week that this phenomenon "shows an unusual orientation."

In a study that has not yet been peer-reviewed, researchers used Keck data to confirm that the object is emitting cyanide and nickel gas. The ejection of these gases both toward and away from the Sun is considered clear evidence of the "anti-tail" phenomenon.

Most surprising, according to Loeb, was the lack of a classic cometary tail in 3I/ATLAS's white-light images. Normally, dust particles are pushed back by the pressure of light from the Sun, creating a bright tail. But this object appears different.

Other scientists suggest that this peculiar appearance could be explained by natural processes. It's thought that Earth's position in space could create an optical illusion from a comet's broad tail, or that large dust grains, capable of resisting the thrust of the solar wind, could form an extension toward the Sun.

"Large particles from a spinning comet nucleus can accumulate both in front of and behind it along its orbit, creating this appearance," University of California planetary scientist Michael Busch said on social media.

OBSERVATION CAMPAIGN

However, due to this unusual behavior, the International Asteroid Warning Network (IAWN) has placed 3I/ATLAS on a special investigation list, marking the first time in the network's history that an interstellar object has been included in its potential threat assessment campaign.

IAWN collaborates with telescopes and observatories around the world to monitor near-Earth objects and assess potential collision risks.

Officials added the object to a special tracking program called the Comet Astrometry Campaign, noting that predicting 3I/ATLAS's orbit presents "unique challenges."

IAWN will launch a global observation and training exercise from November 27, 2025, to January 27, 2026.

In the meantime, telescopes and tracking systems worldwide will focus on 3I/ATLAS, trying to pinpoint the interstellar visitor's precise location in the sky.