Scientists crack mystery of 'interstellar object' racing through our solar system

Daily Mail​

10-07-2025

A renowned physicist believes he's cracked the mystery of where a giant unidentified object hurtling through our solar system came from.
Harvard physicist Avi Loeb and student researcher Shokhruz Kakharov have traced the path of the interstellar object known as 3I/ATLAS to a thicker part of the Milky Way galaxy's disk, where older stars are found.
This 12-mile-wide visitor, traveling at 150,000 miles per hour, is now believed to be older than our sun, which is 4.6 billion years old.
'Simply put, 3I/ATLAS is among the elders in our cosmic block,' Loeb said.
While astronomers are still waiting for this high-speed giant to get closer to Earth, Loeb revealed that 3I/ATLAS is starting to show signs it may be a comet.
The scientist compared it to the interstellar comet 2I/Borisov that passed through our solar system in 2019.
Initial observations by Earth-based telescopes are also hinting that 3I/ATLAS is a gigantic comet, with the International Astronomical Union noting the mystery object appears to have a cloud of gas and dust surrounding it and a short tail.
The new study also delved into the mysterious origins of the last two interstellar objects that flew through the solar system, Borisov and 1I/Oumuamua, which Loeb still contends may have been an extraterrestrial probe, not a space rock.
Loeb and Kakharov found that all three objects traveled a few thousand light-years closer to our galaxy's center than our sun has as it moves through space.
The Milky Way is shaped like a flat disk spinning around its center, with a thin middle layer where younger stars form and a thicker layer where older stars tend to hang out.
These stars have been scattered over billions of years by gravitational tugs from things like star clusters or galaxy collisions.
By tracing the path of 3I/ATLAS backward, Loeb found that it traveled greater distances vertically through the galaxy, straying farther from the Milky Way's flat central plane than the sun does.
This suggests the object is older than our solar system and originated within a region of the galaxy located roughly a few thousand light-years above the Milky Way's mid-plane, the imaginary flat surface that runs through its center.
For reference, our solar system lies within about a thousand light-years of the central plane.
The origin point of 3I/ATLAS is believed to be made up of stars, gas, and dust, with older stars spread out more due to their longer journeys through the cosmos.
Loeb's study found that 3I/ATLAS took about 800 million years to travel across part of the Milky Way to reach our solar system.
The scientists traced the paths of the other two interstellar objects using their speeds relative to the average motion of stars near the sun, a measurement called the Local Standard of Rest.
Loeb said 1I/Oumuamua was moving in a relatively stable path to nearby stars before entering our solar system in 2017, suggesting it came from the thin disk where younger stars live.
According to the findings in Astronomy & Astrophysics, Oumuamua took about one billion years to cross from the opposite side of the Milky Way's disk.
Compared to the more than 4.6 billion-year-old 3I/ATLAS, the one to two billion-year-old Oumuamua is an interstellar 'kid' traveling through the cosmos.
Meanwhile, 2I/Borisov's path was more similar to our sun's, suggesting it's about the same age as our home star, like a 'young adult' floating through the 14 billion-year-old universe.
That comet took about 1.7 billion years to travel across the Milky Way to reach our solar system from the thin disk of younger stars.
While 2I/Borisov was categorized as a comet, and 3I/ATLAS may soon follow, Loeb has maintained that Oumuamua has too many strange traits to dismiss the possibility that it is a UFO.
Most notably, Oumuamua experienced an unexpected increase in speed as it passed through our solar system eight years ago - something that couldn't be explained by the gravitational pull of any planets, moons, or the sun.
'1I/`Oumuamua is anomalous relative to 2I/Borisov and 3I/ATLAS, not only because it is much younger than they are, but also because it had an extreme disk-like shape, it exhibited a non-gravitational acceleration and it did not show any evidence for cometary activity,' Loeb wrote in an article on Medium Wednesday.
Astronomers will be tracking 3I/ATLAS over the next year, with the object expected to make its closest pass to Earth on December 17.
Scientists don't project that the mystery object will get anywhere near Earth. On its current trajectory, it'll come within 2.4 astronomical units of the planet (223 million miles).
An astronomical unit (AU) is equal to the distance between Earth and the sun, 93 million miles. Technically, 3I/ATLAS is already in the solar system, and was 3.8 AU away from Earth as of July 2.
In October, the object from outside the solar system is expected to make its closest pass to a planet, coming within 0.4 AU (37 million miles) of Mars.
Scientists will look to gather information on its trajectory using telescopes like the Rubin Observatory in Chile, and possibly the James Webb Space Telescope in space.
They'll hope to confirm that 3I/ATLAS is staying on its expected route, passing the sun in late October, swinging by Earth at a safe distance in December, and then flying past Jupiter in March 2026.