Key Takeaways

  1. Comet C/2021 A1 (Leonard) was discovered on January 3, 2021, by G. J. Leonard at the Mount Lemmon Observatory.
  2. Leonard’s comet had a retrograde orbit and an impressive 1 km nucleus, making it a unique celestial object.
  3. The comet had a close encounter with Venus, marking the closest-known cometary approach to the planet.
  4. Despite early brightening, the comet experienced possible disintegration, leading to its eventual demise.
  5. The comet’s orbital path indicated a long period of over 80,000 years, and after perihelion, it would be ejected from the Solar System.

Comet Leonard, officially known as C/2021 A1, captured the attention of astronomers worldwide when G. J. Leonard discovered it on January 3, 2021, at the Mount Lemmon Observatory. This comet’s peculiar journey began about a year before its perihelion, 5 astronomical units (750 million km) away from the Sun. Its retrograde orbit, moving opposite to most objects in the Solar System, was just the beginning of its fascinating characteristics.

Astronomers observed Leonard’s comet closely as it traversed its path, offering insights into its nature and behavior. The comet displayed a coma of about 10″ and a broad 5″ tail, with an estimated magnitude of 19.0. Precovery images traced back to April 11, 2020, provided valuable early data.

As the comet neared Venus, it approached within a mere 4 million km (2.5 million mi) of the planet. This marked the closest-known cometary approach to Venus, offering astronomers a rare opportunity to study such interactions.

In the following months, the comet went through a series of events that puzzled scientists. Initially, it showed a short but dense dust tail in October 2021. However, as November approached, instead of brightening as expected, Leonard’s comet began to fade, raising suspicions about possible disintegration.

Despite this, the comet showcased impressive outbursts, briefly brightening up to magnitude 2.5, thanks to forward scattering of light and modest outbursts. Its tails, particularly the ion tail, presented a complex and captivating sight, with knots and streamers that fascinated both experts and amateurs alike.

By December 2021, naked-eye observations by experienced observers became possible. However, the comet’s low surface brightness made it challenging to observe in urban areas. Still, its brightness peaked around apparent magnitude 4, making it an excellent binocular comet for observers in the Southern hemisphere.

As the new year arrived, Leonard’s comet experienced another outburst, brightening by 1.5 magnitudes after perihelion. However, ominous signs began to emerge. Observations in February 2022 indicated a lack of central concentration, suggesting possible disintegration or complete evaporation of the nucleus.

In April 2022, the Hubble Space Telescope confirmed the disintegration, showing no surviving fragments. The disintegration likely began in mid-December 2021, leaving astronomers eager to understand the events leading to its demise.

The comet’s orbital trajectory revealed its incredible journey, spending the last 40,000 years inbound from approximately 3,700 astronomical units (550 billion km). After perihelion, it will bid farewell to the Solar System, with its barycentric orbit remaining hyperbolic.

Comet Leonard’s brief but captivating appearance left astronomers and skywatchers with numerous questions. While its disintegration remains an enigma, the insights gained from this celestial visitor will undoubtedly pave the way for future discoveries in the vast expanse of our cosmic neighborhood.


Comet C/2021 A1 (Leonard) from La Parguera, Lajas, PR by Raymond Negrón.


John Ashley was in Arivaca, Arizona, when he caught Comet Leonard – 2021’s best comet – in the evening sky


Comet C/2021 A1 (Leonard) on December 17, 2021 as seen from Rincon, Puerto Rico by Raymond Negron.


Chris Zurita near Tucson, Arizona, USA, captured this sunset with Comet Leonard (C/2021 A1) on December 16, 2021


C/2021 A1 (Leonard) on December 7, 2021, via Steven Bellavia in Southold, New York.


John Ashley captured this time-lapse image of Comet Leonard before sunup yesterday. He wrote: “Early Saturday morning, Comet Leonard cruised past the square MMT Observatory … on top of Mount Hopkins, near Amado Arizona. Comet images were approximately 30-seconds apart in this interval photo, which also includes a meteor and vehicle headlights leaving the observatory.”


On December 3, 2021, comet C/2021 A1 (Leonard) was near in the sky to the stunning globular star cluster Messier 3. Via Patrick Prokop in Savannah, Georgia


Comet Leonard (C/2021 A1 Leonard) photographed on October 29, 2021, by Michael Jager (@komet123jager on Twitter) from Austria. Thank you, Michael!

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