#United States #Flagstaff #Lowell Observatory #Comet 3I/ATLAS #Interstellar Objects

Insights into Comet 3I/ATLAS from Lowell Observatory

In an exciting recent development, astronomer Dr. Qicheng Zhang at Lowell Observatory has captured the first ground-based optical images of the interstellar comet 3I/ATLAS. This remarkable achievement highlights the capabilities of the 4.3-meter Lowell Discovery Telescope, which is uniquely designed to observe celestial objects located close to the horizon. Unlike typical research telescopes that usually cannot track targets less than 15 to 20 degrees above the horizon, the Lowell Discovery Telescope can focus as low as five degrees. This became crucial for observing ATLAS just after it had passed the Sun on October 31, 2025.

Initially detected in July 2025 by the NASA-supported Asteroid Terrestrial-Impact Last Alert System (ATLAS) Survey in Chile, 3I/ATLAS marks only the third known interstellar object to traverse our solar system. While its chemical makeup appears similar to a broad range of native comets in our solar system, these rare visitors continue to offer invaluable information about planetary system formation.

Dr. Zhang explained the observational challenges posed by the comet's proximity to the Sun, stating, "When the comet was closest to the Sun, it was temporarily hidden from our view." To observe it, their team had to look at a specific angle near the Sun. Cometary behavior changes as it approaches the Sun, a process termed outgassing, during which ice converted into gas increases the comet's brightness. Analyzing a comet during this phase can yield vital information about its composition and characteristics.

Prior to Dr. Zhang's successful imaging, only low-resolution optical images and radar observations of 3I/ATLAS were available, gathered by heliophysics missions like SOHO and PUNCH due to the comet's positioning near the Sun. Using the Lowell Discovery Telescope, Zhang managed to secure critical optical images right after the comet reemerged from solar obscuration. "The image was captured through narrowband filters that isolate specific gases," Zhang elaborated. "This enables us to analyze the emission of various gases and compare these ratios with those from solar system comets, revealing that ATLAS's gas ratios lie within an expected range."

Dr. David Schleicher, who specializes in the physical and chemical behavior of comets, is currently focused on in-depth analysis of the comet’s composition using the Hall 42-inch Telescope located at Lowell's Anderson Mesa Dark Sky Site. By comparing his findings to a database containing over 240 documented comets, including the previous two identified interstellar comets, new insights are emerging. "While we're primarily investigating the comet's chemical properties, we are also analyzing its rate of gas output as it approaches and recedes from the Sun," said Schleicher.

As the observations continue, experts anticipate that this research will yield further insights not only into 3I/ATLAS but also how interstellar comets compare to those emerging from our solar system. Looking ahead, Dr. Schleicher is optimistic about future discoveries, especially with the upcoming Vera C. Rubin Observatory. He noted, "The Rubin Telescope will greatly enhance our ability to detect interstellar objects, potentially identifying many before they approach Vicinity of planets like Saturn or Neptune. Although we might see a close approach every 5-10 years, we will likely discover many others that remain too distant to shine brightly."

The exploration of interstellar comets like 3I/ATLAS provides a rare opportunity to delve into the foundational elements that contribute to distant planetary systems. With advancements in astronomical survey technology, the frequency of such discoveries is expected to rise, ushering in a new era of understanding regarding our cosmic neighborhood.

About the Lowell Discovery Telescope

The Lowell Discovery Telescope (LDT) stands as Lowell Observatory's premier research facility and is celebrated as one of the world's most versatile optical telescopes. Its innovative design accommodates multiple instruments for diverse scientific observations throughout the night. The telescope operates under the guidance of Lowell Observatory and is a collaborative project involving institutions such as Boston University, University of Maryland, University of Toledo, Yale University, and Northern Arizona University.

About Lowell Observatory

Founded in 1894, Lowell Observatory is a distinguished nonprofit research institution located in Flagstaff, Arizona. It has been the backdrop for historic findings, including the first evidence of the expanding universe and the discovery of Pluto. Today, the observatory employs both terrestrial and space telescopes, alongside NASA spacecraft, to engage in varied research in astronomy and planetary science. The observatory attracts over 100,000 visitors annually, providing educational tours, presentations, and telescope viewing through its premium facilities.