Astronomers may be trapped in the age and origin of interstellar comet 3i/Atlas as they barrel towards the center of our solar system.
A new study modelling the last 4 million years of cometary journeys through the Milky Way provides hints that interstellar visitors come from afar. This could be derived from the wild frontier where the oldest and youngest stars of the Galaxy meet. If so, comets could be relics of early galaxies and be billions of years older than the Earth’s Sun.
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Galaxy Grand Tour
According to NASA, visitors in this universe are currently running a month-long sightseeing tour of our inner solar system, completing a close approach to Mars on Friday (October 3) and poised to rush past the Sun on October 30th. It then passes Jupiter in March 2026, then eventually disappears from view, then heads back into interstellar space. Comets pose no threat to Earth.
The immediate trajectory of 3i/Atlas is easy to predict, but it is much more difficult to understand where it came from.
Traveling at approximately 130,000 miles per hour (210,000 kmh), the Renegade Iceball has speeded up by millions, if not billions of years. It leaves it vulnerable to the gravity pull of an invaluable number of Milky Way stars. Just as NASA uses the effects of gravity on planets in the solar system into deep orbits on slingshot spacecraft, 3i/Atlas could have been easily knocked out of its original trajectory due to the gravity of the giant stars intervening in its path.
Now, a new study published on Preprint Server Arxiv makes its best efforts to identify the origin of a comet by examining whether nearby stars may have affected their orbit.
Using data from the European Space Agency’s now retired Gaia Space Telescope, the research authors tracked the comet’s trajectory at a time of 47 million years ago, identifying 62 nearby stars that interstellar objects likely encountered along the way. Using Gaia’s high-resolution data on star movement, velocity and size, the research authors concluded that none of them significantly alter the comet’s orbit.
“We have discovered that every star in the solar neighbour can explain the trajectory and high velocity of the 3i/Atlas,” Xabier Pérez-Couto, a graduate student in astrophysics at DaCoruña, a Spanish university student, told Live Science via email. Nearby stars measuring about 70% of the solar mass appear to have had a total impact on the comet’s trajectory, but only negligible amounts, researchers added to their paper.
This has led to the team saying, “3i/Atlas is a very old object and is on the road. [billions of years]and its origin belongs to the boundary of a thin disc,” Perez Koot said.
Objects from the wild frontier?
What’s so special about that? A spiral galaxy, like the Milky Way, divides the stars between thin and thick discs. Slicing the central bulge of our galaxy, the young, small, thin discs are thought to contain most of the Milky Way stars and star-forming gases. Most of them are rich in elements heavier than hydrogen and helium, and are picked up from the older generation of stars who lived and died before them. In contrast, wider, thicker discs wrapped around the boundaries of thin discs have long stopped star formation. According to Swinburne Institute of Technology in Australia, it includes small, but much older – sampling of stars with poor heavy metals.
If Comet 3i/Atlas actually came from the boundary between these two disks, that could mean that the object is incredibly old. According to Pérez-Couto, the comet appears to have been “defeated from the primitive discs of early formed planetary systems,” potentially becoming a valuable time capsule of the ancient Milky Way.
However, new research acknowledges the limitations of that approach. Looking at nearby stars, the analysis explains only millions of years of the comet’s long history, and its exact origin is still very uncertain. As 3i/Atlas continues to zoom in the solar system, scientific instruments from Earth and Mars, as well as scientific instruments in orbit around Jupiter, will soon have the opportunity to study it in more detail. Unraveling the composition of interstellar objects provides essential clues to their universe’s homes and could open valuable windows into the galaxy’s past.
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