C/2019 Y4 (ATLAS)

C/2019 Y4 (ATLAS) was a comet with a near-parabolic orbit discovered by the ATLAS survey on December 28, 2019. Early predictions based on the brightening rate suggested that the comet could become as bright as magnitude 0 matching the brightness of Vega. It received widespread media coverage due to its dramatic increase in brightness and orbit similar to the Great Comet of 1844, but on 22 March 2020, the comet started disintegrating. Such fragmentation events are very common for Kreutz Sungrazers. The comet continues to fade and did not reach naked eye visibility. By mid-May, comet ATLAS appeared very diffuse even in a telescope. C/2019 Y4 (ATLAS) has not been seen since 21 May 2020.

C/2019 Y4 (ATLAS) was the brightest on March 30 when it had an apparent magnitude of about 7, but after disintegrating, it continued to fade, until it was last observed on May 21. It is located in the constellation Monoceros but is no longer visible. It reached its nearest point to Earth on May 23 and come to perihelion (closest to the Sun) on May 31.

In April 2020, astronomers reported, on The Astronomer's Telegram, the possible disintegration of Comet ATLAS. The comet has fragmented into at least 4 pieces. NASA subsequently reported that the Hubble Space Telescope has identified that there could be as many as roughly "30 fragments on April 20, and 25 pieces on April 23." The fragmentation may be the result of outgassing causing an increase in the centrifugal force of the comet. Subsequent observations from the Lowell Observatory between July and September 2020 failed to see any remnants of the comet, indicating that it either had completely disintegrated or the surviving fragments, estimated to be no larger than 0.25 km (0.16 mi) in radius, simply went inactive.

The Solar Orbiter flew through the ion tail of comet ATLAS between May 31 and June 1 and the dust tail on June 6.