It has now been nearly a quarter of a century since we have been treated to a spectacularly bright comet: Comet Hale-Bopp passed by during the spring of 1997 and Comet Hyakutake did so exactly one year earlier. Both were truly "great" comets, very bright and fantastically structured; in very dark conditions, Hyakutake's tail appeared to stretch more than halfway across the sky.
So now, after a "comet drought," Comet ATLAS may finally enliven the evening skies of early spring. Or then again, maybe not.
Astronomers using the ATLAS (Asteroid Terrestrial-impact Last Alert System) in Hawaii discovered Comet C/2019 Y4 (ATLAS) on December 28, 2019. As of mid-late March, it shines at about the brightness of an eighth-magnitude star – not visible to the eye yet – but within reach of medium-sized telescopes in dark skies.
The comet is currently crossing Mars’ orbit and is approaching the inner solar system. As it gets closer to us, it’ll get brighter still.
Comet ATLAS should become bright enough to be easily visible in binoculars, and perhaps bright enough to be seen with the unaided eye from dark sky locations.
Just know that comets are notoriously erratic and inherently unpredictable! We will have to wait to see how Comet Atlas performs.
Comet C/2019 Y4 (ATLAS) will come closest to Earth on May 23. Its perihelion, or closest approach to the sun, will occur on May 31.
Orbit of Comet C/2019 Y4 (ATLAS) Courtesy NASA/JPL
If predictions are correct, Comet ATLAS might reach a visual magnitude of +5 around May 1.
That is theoretically bright enough to be see with the eye, but the fuzziness of faint comets can make them harder to spot than comparably bright stars.
How close to our planet will the comet come? The celestial visitor will pass at a huge distance, at some 72,610,769 million miles away (116,855,706 km).
Comet C/2019 Y4 (ATLAS) will pass very close the sun, and thus may disintegrate before becoming bright enough to be seen with the unaided eye.
It will pass at some 23,517,819 miles (37,848,261 km) from the sun, which is closer to our star than Mercury’s elliptical orbit (about 36 million miles or 57.9 million km on average).
Calculations by NASA/JPL indicate Comet ATLAS takes some 6,025 years to complete an orbit around the sun. Observations show it has a similar orbit to the Great Comet of 1844, which suggest Comet Atlas may be a fragment of the same 1844 comet.
Will Comet C/2019 Y4 provide a good show or just fizzle out? Let’s keep a close eye on it, just in case!