What would happen if 3I/ATLAS actually hits Earth? How did it enter solar system from another galaxy?

What is Comet 3I/ATLAS: A comet that originated from a distant star world billions of years ago is now heading toward our Sun. This is Comet 3I/ATLAS—the third object from outside the Solar System. Scientists have detected glowing nickel vapor in it, which seems impossible so far from the Sun, where temperatures are extremely cold.

This discovery reveals secrets about the world of other stars. Let's address the most important question: Will this comet collide with Earth?

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No, it absolutely will not. It will pass close to the Sun (closest approach on October 29, 2025), but will remain at a safe distance from Earth. The paths of objects like comets are calculated in advance. The ATLAS system also provides collision warnings. This is simply a great opportunity for scientists, not a threat.

How was this astronaut found?

On July 1, 2025, Chile's Asteroid Terrestrial-Impact Last Alert System (ATLAS) spotted a glowing object during a routine sky survey. At first, it was thought to be an ordinary comet, but it was soon discovered to be a wandering space traveler from outside the solar system.

What is Comet 3I/ATLAS...

It was named 3I/ATLAS. There were two previous such objects: the mysterious 'Oumuamua (2017) and Comet Borisov (2019). But 3I/ATLAS was detected very early, when it was far from the Sun. This allowed scientists to observe it in action—like an old book being opened.

How did it enter our solar system from another galaxy?

These space objects are time capsules. They are billions of years old, having come from other stars (exoplanet systems). We can never visit those worlds, but they reveal their chemical and physical secrets. 3I/ATLAS is probably older than our solar system—billions of years old.

What did the Chilean VLT telescope reveal?

Our international team (scientists from Chile, Belgium, the UK, Canada, New Zealand, the US, and Italy) used Chile's Very Large Telescope (VLT). It is equipped with the X-shooter and UVES spectrographs, which break down light to reveal chemicals.

The first big clue on July 20th: The comet was 3.88 AU (1 AU = Earth-Sun distance, approximately 150 million km) from the Sun. The temperature there was very cold (less than -150°C). Nevertheless, lines of nickel atomic vapor were visible in the spectrum. Nickel is a metal that shouldn't ignite in such cold temperatures. This gas glowed in the thin air (coma) surrounding the comet.

How much nickel?

It was measured that nickel atoms were rapidly accreting from the comet. As it approached the Sun, they increased 10-20 times. But surprisingly, no iron, which is usually present with nickel, was detected.

New signal in mid-August: Upon reaching 3.07 AU, cyanogen (CN) gas was detected, which is common in solar system comets. CN is a molecule made of carbon and nitrogen.

Statistics: The VLT detected spectral lines at 400-500 nanometer wavelengths, which are accurate for nickel. The coma was 10,000-20,000 km in diameter.

How did the metal fly in the cold?

This discovery is surprising. Metals require temperatures above 1000°C to become gases. But at 3.88 AU, 3I/ATLAS observed the temperature at only -100°C. Scientists speculate...

Special molecule: Nickel is likely bound to carbon monoxide (CO) or organic compounds. Sunlight (UV rays) breaks these molecules apart, releasing nickel. This process works at lower temperatures.

Why the difference? In the Sun's metallic comets, nickel and iron come together, but not here. Perhaps a chemical change occurred during space travel.

Scientific fact: Nickel atoms were being released at a rate of 10^12 to 10^14 per second. This is linked to photodissociation (breaking down by light).

With the help of the James Webb Space Telescope (JWST), the JWST observed the coma (the comet's gas cloud). Surprisingly, more carbon dioxide (CO2, soda gas) was found than water. In comets from the Sun, the opposite occurs—more water, along with particles of water ice and CO gas.

Is there a threat to Earth? Absolutely not

The obvious answer: 3I/ATLAS will not collide with Earth. Its path has already been calculated. At perihelion (closest point to the Sun) on October 29th, it will be 1.5-2 AU away—2-3 times the distance from Earth. Systems like ATLAS and NASA's are able to detect collision-prone objects early. This comet will only pass by, leaving the solar system by 2026.

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