Alien Comet: Why everyone is watching 3I/ATLAS and is it dangerous

In December 2025, Comet 3I/ATLAS will move through the constellations Virgo and Leo, moving from the morning sky to the night sky. On December 19, the comet is expected to make its closest approach to Earth — the object will be located at a distance of 273 million km. At this time, it will be possible to take a picture of him. Read more about the comet in the Izvestia article.

The oldest comet

Comet 3I/ATLAS is the third known interstellar object to become a "guest" in the Solar System. The first was asteroid 1I/Oumuamua, discovered in 2017, and the second was comet 2I/Borisov, discovered in 2019 by amateur astronomer Gennady Borisov.

The letter "I" in their names indicates that the object is interstellar, that is, it came from outside our Solar system, and the numbers show their ordinal numbers as they are discovered.

Comet 3I/ATLAS was discovered on July 1, 2025 by the ATLAS telescope in Chile (funded by NASA). At that time, it was located at a distance of about 670 million km from the Sun, within the orbit of Jupiter.

The trajectory of the comet indicates that it "hails" from that part of the Milky Way, which is called the Thick Disk. This is a layer of ancient stars, they are located above and below the Thin Disk where the Sun and most of the stars of the galaxy are located.

How old is she and what is she "made of"?

Researchers believe that 3I/ATLAS may be the oldest comet ever discovered. Its age probably exceeds 7 billion years — that is, it is 3 billion years older than the Solar system.

At the time of detection, the comet was moving at a speed of 221,000 km per hour. As it approached the Sun, its speed increased, and at the point of maximum convergence — perihelion — increased to 246 thousand km per hour.

The comet's core consists of ice, surrounded by a cloud of gas and dust called a coma. The coma and the nucleus form the "head" of the comet. According to scientists, the diameter of the core of 3I/ATLAS ranges from 440 meters to 5.6 km.

New observations show that the comet may be covered with erupting cryovolcanoes, which are also called "ice volcanoes." They became more active as the comet approached the Sun. Scientists believe that the comet has a lot in common with trans-Neptunian objects, such as Pluto.

Is the comet dangerous for earthlings

Astronomers have classified 3I/ATLAS as an interstellar object due to the hyperbolic shape of its orbit - the comet does not move around the Sun. It does not pose a threat to the Earth — the comet can approach our planet at a maximum distance of 270 million km. It will happen on December 19th.

3I/ATLAS is expected to be visible with an amateur telescope later this year and early next year. The best time for this is before dawn.

In March, the comet will approach Jupiter, flying from it at a distance of 53 million km. 3I/ATLAS is likely to cross Neptune's orbit in 2028. Eventually, the comet will pass through the Solar System and continue its journey through interstellar space.

Alien connections

When Oumuamua was discovered, experts suggested that it was a disguised spacecraft, rather than an asteroid or comet, due to a number of unusual features.

Now, as we study 3I/ATLAS, similar hypotheses have begun to appear. They are based on data that the comet slightly changed course after passing perihelion. However, scientists have found an explanation for this and are inclined to believe that 3I/ATLAS behaves like an ordinary comet and is not an "alien ship."