Interstellar comet 3I/ATLAS has returned to visibility from Earth after completing its journey behind the sun. This remarkable sight is thanks to Qicheng Zhang, a postdoctoral fellow at Lowell Observatory, who captured what is believed to be the first optical image of the comet since it swung around our star on October 29th.
Zhang utilized the observatory’s powerful Discovery Telescope in Arizona to obtain this groundbreaking shot just days after the comet passed perihelion – its closest point to the sun. Notably, the images show the comet as a faint smudge against the pre-dawn sky, and Zhang emphasizes that it’s becoming increasingly visible every day for those equipped with standard amateur telescopes across the Northern Hemisphere.
“All you need is a clear sky and a very low eastern horizon,” Zhang explains, “It won’t look very impressive, just a smudge, but an increasingly visible one over the next few days.” This sighting marks a significant milestone as 3I/ATLAS became the third interstellar object ever recorded to enter our solar system.
Since its initial discovery in July, this cosmic traveler has captivated astronomers with its unusual trajectory and blazing speed. Estimated at over 130,000 mph (210,000 km/h), 3I/ATLAS is hurtling through our celestial neighborhood on a strikingly flat and straight path, vastly different from the typical orbits of comets within our solar system.
While hidden behind the sun during its closest approach, astronomers diligently tracked its movements using data gathered by space telescopes like the SOHO spacecraft and others. This allowed them to continue piecing together its journey even while it was obscured from direct view on Earth.
Unveiling the Comet’s Secrets
Even before perihelion, researchers, including Zhang, observed intriguing changes in the comet. They noted a rapid brightening preceding the close encounter with the sun and discovered that 3I/ATLAS exhibited a distinct bluish hue compared to our star. This suggests that gases emanating from the comet played a significant role in its enhanced brightness near perihelion. While Zhang believes the comet might be continuing to brighten, further observations are needed to confirm this trend.
The Lowell Discovery Telescope played a crucial role in capturing these early post-perihelion images. Its strategic positioning and capability to point low on the horizon allowed for observation during this critical phase. As the comet moves northward from our perspective, away from the northeastern horizon, amateur astronomers with even smaller telescopes can now join in the celestial hunt.
A Comet’s Evolution and Unanswered Questions
The coming weeks promise to be a period of intense study for 3I/ATLAS. As it moves further from the sun, the comet will continue to heat up, causing its icy surface to sublimate and release gas. This process offers valuable insights into the comet’s composition – essentially allowing astronomers to peer deeper into its makeup.
Despite media speculation about its potential alien origins, the scientific consensus leans towards 3I/ATLAS being a genuine comet from an undiscovered star system within our Milky Way galaxy. It may even hold the title of oldest comet ever observed, potentially dating back to three billion years before the formation of our own solar system.
Adding another layer of intrigue, preliminary research suggests that prolonged exposure to interstellar radiation has profoundly altered 3I/ATLAS. This could have resulted in a thick, irradiated crust, making it significantly different from comets originating within familiar star systems. Deciphering this transformed shell and understanding its origins will pose significant challenges for scientists. Nevertheless, the coming months promise a wealth of new research as 3I/ATLAS continues to grace our night sky.
“The comet is rapidly rising from the sun,” Zhang notes, “Within a week it’s going to be about 25 or 30 degrees away from the sun, by which point many other large telescopes around the world will also be able to start following it up.”
