Unveiling the Fastest Interstellar Visitor in Our Solar System
Astronomers have captured a groundbreaking image of an interstellar comet, offering the clearest view yet of an object that has traveled through our solar system from beyond. This remarkable discovery is providing new insights into the nature of these rare visitors and their origins.
The Hubble Space Telescope, equipped with its Wide Field Camera 3, captured a detailed image of the comet 3I/ATLAS on July 21. At the time, the object was 277 million miles (445 million kilometers) away from Earth. The image reveals a teardrop-shaped dust cocoon emanating from the comet’s icy nucleus, which is the solid core made up of ice, dust, and rocks. As comets travel near stars, heat causes them to release gas and dust, creating the signature tails that are visible from Earth.
This comet, first discovered on July 1, is moving at an astonishing speed of 130,000 miles (209,000 kilometers) per hour. This makes 3I/ATLAS the fastest interstellar object ever observed passing through our solar system. Its velocity is a key indicator that it originated from outside our solar system.
New observations from Hubble have also provided more information about the comet’s size. While the small nucleus cannot be directly seen, it could range from as large as 3.5 miles (5.6 kilometers) in diameter to as small as 1,000 feet (305 meters) across, according to a recent paper accepted by The Astrophysical Journal Letters.
Other space-based telescopes, including the James Webb Space Telescope, the Transiting Exoplanet Survey Satellite, and the Neil Gehrels Swift Observatory, along with ground-based observations from the W.M. Keck Observatory in Hawaii, are being used to study the comet’s chemical composition. Scientists expect the comet to remain visible to ground-based telescopes through September before it gets too close to the sun to be spotted again until early December.
Despite these advancements, many questions about 3I/ATLAS remain unanswered. One of the most intriguing mysteries is its origin. According to David Jewitt, lead study author and professor of astronomy at the University of California, Los Angeles, it is difficult to determine where the comet came from. He compared it to glimpsing a rifle bullet for a thousandth of a second, making it nearly impossible to trace back accurately.
The comet’s high speed is one of the key factors that indicate it is an interstellar visitor. Scientists estimate that 3I/ATLAS has been traveling through interstellar space for billions of years. As objects move through space, they experience a gravitational slingshot effect from nearby stars and stellar nurseries, which increases their momentum. Therefore, the longer 3I/ATLAS has spent in space, the faster it moves.
So far, 3I/ATLAS is only the third known interstellar object to have been observed in our solar system after ‘Oumuamua in 2017 and 2I/Borisov in 2019. Matthew Hopkins, a recent doctoral student at the University of Oxford, highlighted the significance of 3I/ATLAS’s velocity in his research. He and his colleagues have been developing a model to predict properties of interstellar objects based on their velocity.
For Hopkins, the discovery of 3I/ATLAS was incredibly fortuitous. It occurred just five days after he completed his doctoral work, which involved making predictions about future interstellar object discoveries. In a few months, he will begin a postdoctoral research fellowship at the University of Canterbury in New Zealand, where he will continue to study 3I/ATLAS.
During his doctoral studies, Hopkins and his collaborators developed the Ōtautahi–Oxford model, which combines data from the Milky Way’s star population and models of how planetary systems form. This model could help astronomers determine what interstellar object populations should look like. Now, Hopkins is the lead author of a separate preprint study about 3I/ATLAS.
The Future of Interstellar Object Detection
Detecting the age of interstellar objects is challenging, but Hopkins and his colleagues believe 3I/ATLAS has about a 67% chance of being more than 7.6 billion years old. This is significantly older than our sun, solar system, and its comets, which are only 4.5 billion years old.
Hopkins explained that while it is pure chance that the interstellar comet crossed into our solar system, it is not entirely rare. However, we don’t see these visitors most of the time because they are often too small to detect unless they get very close to Earth.
Scientists are eager to use the Vera C. Rubin Observatory, which released its first images this summer, to scan the skies for interstellar objects. With its massive primary mirror spanning 28 feet (8.4 meters) across, the observatory can spot small, faint, and distant objects. It scans the entire sky every three nights, allowing it to better catch sight of rapidly moving interstellar objects.
Hopkins’ coauthors estimate that Rubin could potentially spy between five and 50 interstellar objects over the next 10 years. Hopkins is optimistic about the higher end of this range. Discovering more interstellar objects could help astronomers determine how varied or similar they are, especially since the first three have been so different from one another.
“This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene that will gradually emerge,” said Jewitt. “This is now possible because we have powerful sky survey capabilities that we didn’t have before. We’ve crossed a threshold.”
As technology continues to advance, the ability to detect and study interstellar objects will improve, providing new insights into the universe and the origins of these mysterious visitors.
