Comet Leonard (C/2021 A1)

Comet Leonard (C2021A1) with the American flag; Captured 8 December 2021 in Colorado Springs, Colorado

Comet Leonard (C/2021 A1) – 8 December 2021

Fun facts

C/2021 A1 (Leonard) was a long period comet that was discovered by G. J. Leonard at the Mount Lemmon Observatory on 3 January 2021 (a year before perihelion) when the comet was 5 AU (750 million km) from the Sun. The comet appeared to have a 10″ coma and a 5″ broad tail in the photographs taken as part of the Mt. Lemmon Survey and its magnitude was estimated to be 19.0. Precovery images dated back to April 11, 2020. It had a retrograde orbit. The nucleus was about 1 km (0.6 mi) across. It came within 4 million km (2.5 million mi) of Venus, the closest-known cometary approach to Venus.

On 10 October the comet showed a short but dense dust tail.[6] In late November the comet appeared to stop brightening as expected and to fade instead, indicating a possible disintegration of the nucleus. In early December the comet had an apparent magnitude (coma+nucleus) of around 6. The first reports of naked-eye observations by experienced observers started coming in on 5 December 2021. Much like observing Messier 33, the low surface brightness of the comet can make it difficult to observe near urban areas. On 3 December 2021 many emission lines of NH2, C2, and [OI] were detected in the spectrum of the comet in the wavelength range between 5000 and 7000 Å. On the morning of 6 December 2021 the comet was about 5 degrees from the star Arcturus. On 14 December 2021 the comet was 14.7 degrees from the Sun and quickly became better seen from the southern hemisphere.

The forward scattering of light helped the comet to briefly brighten to as much as magnitude 2.5, but was also enhanced by a modest outburst. The comet experienced outbursts on December 15, 20 and 23, thus reaching third magnitude before dimming back to 4th magnitude. The ion tail of the comet appeared complex, with knots and steamers. The comet’s discoverer called the tails “some of the best ever observed”.[17] In stacked photos the tail could be traced for 60 degrees in the sky. While the comet was lower in the sky, atmospheric extinction offset much of the brightening. As of 22 December 2021, the comet was around apparent magnitude 4, making it a good binocular comet for the Southern hemisphere. It was the brightest comet of 2021. One more outburst took place after perihelion, on 6-8 January 2022, when the comet brightened by 1.5 magnitudes.

On 23 February 2022 the comet was observed with the SLOOH telescope in Chile, operated by Martin Masek. The comet lacked a central concentration, which indicates that the nucleus of the comet disintegrated or evaporated completely. Further observations confirmed the lack of concentration. In April 2022, the disintegrating comet was observed using the Hubble Space Telescope, with further observations planned for June 2022.[20] No surviving fragments were found by the Hubble Space Telescope, while the Swan Hill observatory imaged an extensive debris cloud. The disintegration of the comet probably started in mid December 2021.

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Imaging stream: Orion 8″ f/8 Ritchey-Chretien Astrograph Telescope, Canon EOS Ra
Mount: Sky-Watcher EQ6-R Pro Equatorial Mount (controlled by EQMOD)
Autoguider: Orion 60mm Multi-Use Guide Scope, Orion StarShoot AutoGuider Pro Mono Astrophotography Camera (Controlled by PHD2)

Equipment controlled by HP Probook running Sequence Generator Pro v3.2.0.660

Capture & processing notes

Captured Comet Leonard from the HCH front patio on 8 December 2021. Created a composite image with the HCH flag and a stacked version of the comet images.
Sequence Plan: ISO1600, 26x180seconds; 8Dec2021 0444 – 0558MST

Capture: 8 December 2021; 0444 – 0558MST
Shooting location: Colorado Springs, Colorado
Processing: Stacked in APP; processed in LR/PS

Comet Leonard (C/2021 A1); Captured at HCH Colorado Springs, Colorado; 8 December 2021