Six years after Comet C/2019 Y4 ATLAS dramatically broke apart in the inner solar system, astronomers continue to investigate whether any substantial remnants survive. The comet, once predicted to be a spectacular sight during the 2020 pandemic lockdowns, fragmented unexpectedly, leaving scientists questioning if its nucleus completely disintegrated or if a fragment persists in orbit.
The Comet’s Unexpected Demise
Discovered in late 2019, C/2019 Y4 ATLAS was initially projected to pass within 23 million miles of the sun, making it potentially visible to the naked eye. However, in April 2020, the comet unexpectedly shattered into dozens of pieces, dashing hopes of a clear sky spectacle. Subsequent observations with telescopes like Hubble and STEREO tracked debris clusters, but the fate of the nucleus remained unclear.
Lingering Questions About the Nucleus
A recent study led by Salvatore A. Cordova Quijano from Boston University suggests that a fragment up to half a kilometer in diameter might still be orbiting the sun. The team scanned the skies in 2020 using the Lowell Discovery Telescope and the Zwicky Transient Facility, finding no immediate evidence. However, they acknowledge that a smaller, inactive fragment could have evaded detection.
The survival of such a fragment would provide valuable insights into how comets break apart under intense solar heat, and whether larger comets occasionally leave behind smaller, long-lived remnants. This also raises the broader question of how many other “disrupted” comets may have survived in reduced form, continuing their millennia-long orbits around the sun.
Understanding Comet Disintegration
The study of C/2019 Y4 offers clues about the violent process of comet disintegration near the sun. The comet’s breakup likely involved rapid sublimation of its icy material, causing fragments to lose mass quickly. The largest piece of debris, fragment B, was initially 1.2 kilometers wide in May 2020, but its size by October 2020 remained uncertain, with the possibility that it had further fragmented below detectable limits.
Future Observations and Lessons Learned
Astronomers have only observed a handful of comet disintegration events, and follow-up observations are crucial to confirm whether large fragments survive. The researchers recommend that future studies prioritize deep searches two to three months after a comet passes behind the sun, as this would provide the best opportunity to detect any remaining debris.
The case of C/2019 Y4 highlights the importance of continued monitoring of comets as they approach the sun, helping scientists understand the dynamics of these icy travelers and the conditions that lead to their spectacular, yet often unpredictable, breakups.
The mystery of C/2019 Y4 ATLAS serves as a reminder that even in the well-studied realm of astronomy, some celestial events remain incomplete, prompting further investigation and observation.
