Now is the time to start tracking Comet C/2021 A1 Leonard, as it starts its dawn dive sunward.
The days following New Year’s 2021 saw a comet discovery with potential. On the night of January 3rd, exactly one year to the day prior to perihelion, astronomer Gregory J. Leonard working at the Mount Lemmon Observatory near Tucson Arizona discovered the first long-period comet of the year, C/2021 A1 Leonard. Shining at magnitude +19 and 5 Astronomical Units (AU) distant (about the distance of JupiterJupiter is the largest planet in the solar system and the fifth planet from the sun. It is a gas giant with a mass greater then all of the other planets combined. Its name comes from the Roman god Jupiter.”>Jupiter from the Sun) at the time of discovery, early indications hinted that comet A1 Leonard might prove to be something special, come the end of 2021.
On an 80,000 year orbit inbound, Comet A1 Leonard is due for ejection from the solar system after its perihelion passage early next year. The comet reached aphelion 3,500 AU distant in the Oort Cloud about 35,000 years ago. The upcoming perihelion pass on January 3rd, 2022 will be 0.62 AU from the Sun, interior to the orbit of VenusVenus, the second planet from the sun, is named after the Roman goddess of love and beauty. After the moon, it is the second-brightest natural object in the night sky. Its rotation (243 Earth days) takes longer than its orbit of the Sun (224.7 Earth days). It is sometimes called Earth’s “sister planet” because of their similar composition, size, mass, and proximity to the Sun. It has no natural satellites.”>Venus.
Keep in mind, A1 Leonard may be a seasoned long-term visitor to the inner solar system with a potential to over-perform as it nears the Sun. Current predictions have the comet reaching +4th magnitude, and it may flirt with naked eye brightness. The comet passes just 0.233 AU (21.7 million miles or 34.9 million kilometers) from the Earth on December 12th, another plus.
Often, dynamically new comets exhibit a burst of activity as they approach the inner solar system for the first time, heat up, and sublimate their outer layers. This can also fake out observers initially, leading to overly optimistic predictions. We all remember the Great Comet that wasn’t during the 1973 passage of C/1973 E1 Kohoutek. A comet such as A1 Leonard has survived a perihelion passage before without disintegrating… though this one will be its last.
Currently, A1 Leonard is located high at dawn for northern hemisphere observers in the constellation Canes Venatici, and begins the plunge sunward during the first half of the month. We actually cross the plane of the comet’s orbit on December 8th, and the comet may exhibit a sharp ‘anti-tail’ spike sunward around this time.
Another intriguing effect may also come into play during the December apparition of Comet A1 Leonard. The the Sun-Earth-Comet phase-angle for the tail will sit at greater than 120 degrees from December 9th to December 22nd, and reach a maximum of 160 degrees on December 14th just after it passes closest to the Earth on December 12th. This sets up conditions ideal for a possible surge in brightness, adding the brightness of the tail to the coma of the comet itself.
It’s always tough to know exactly what comets will do. The planet Venus actually passes through the tail of Comet A1 Leonard on December 19th, possibly creating a Venusian meteor shower in the process. Currently, only JAXAFormed in 2003, the Japan Aerospace Exploration Agency (JAXA) was born through the merger of three institutions, namely the Institute of Space and Astronautical Science (ISAS), the National Aerospace Laboratory of Japan (NAL) and the National Space Development Agency of Japan (NASDA). JAXA performs various activities related to aerospace, from basic research in the aerospace field to development and utilization and is responsible for research, technology development, and launch of satellites into orbit, and is involved in advanced missions such as asteroid exploration and possible human exploration of the Moon.”>JAXA’s Akatsuki mission in on-hand and active in orbit around Venus.
Unfortunately, the evening apparition for Comet A1 Leonard will be a bashful one after it flips from morning to the dusk sky around December 15th. For northern hemisphere observers the comet stays low in the dusk. Southern hemisphere viewers will, however, get a better view as the comet fades, receding in the direction of the constellation of Piscis Austrinus in early 2022.
Here are some key celestial dates with destiny for Comet A1 Leonard (note ‘close’ means within a degree, unless otherwise indicated):
28-Crosses into Coma Berenices
1-Crosses into Canes Venatici
3-Photo op: passes very near the globular cluster Messier 3
4-Crosses into Boötes
6-Passes 4 degrees from the bright star Arcturus
8-Orbit edge-on as seen from Earth
9-Crosses into Serpens Caput
10-Crosses into Hercules
11-Crosses into Ophiuchus
12-Crosses the celestial equator southward, and passes 0.233 AU (34.9 million km) from the Earth, moving half a degree (the span of a Full Moon) per hour.
13-Flips over from the morning to evening sky, and may top out at +4th magnitude.
14-Passes near +3.3 magnitude star Nu Ophiuchi, and into Serpens Cauda
14-Transits Messier 16, and passes 15 degrees from the Sun.
15-Crosses the galactic plane southward
15-Briefly crosses into Scutum, passes near comet 252P LINEAR, passes 1.5 degrees from Messier 17, and crosses into Sagittarius
16-Passes near the stars: +3.5 magnitude Xi^2 Sagittarii, +3.8 Omicron Sagittarii and +2.8 Albaldah, and crosses the ecliptic southward
17-Passes five degrees from Venus
18-Passes just 0.028 AU (4.2 million km) from Venus
21-Crosses into Microscopium
30-Passes into Piscis Austrinus
3-Reaches perihelion at 0.62 AU from the Sun
1-Drops back down below +10th magnitude
As you can see, mid-December is a busy one for Comet A1 Leonard, as it nears the bustling galactic plane.
Binoculars are your best friend when it comes to sweeping up a comet: simply scan the suspect target field, and look for the faint fuzzy that refuses to snap into focus. At this stage, comets frequently look like globular clusters that refuse to resolve into individual stars. ‘If’ Comet A1 Leonard over-performs and breaks into naked eye territory, things could get really interesting. Like Comet F3 NEOWISE, A1 Leonard would then have the potential to pose with foreground objects in the dawn, making for a truly photogenic comet.
Plan on braving the morning December cold to capture sight of Comet A1 Leonard at dawn.
Originally published on Universe Today.