C/2021 A1 (Leonard)
ephemeris date magn radius delta ra dec elong phase PA
Today16 Jan 202118.84.946 AU4.654 AU14h06m+43°07'101.5°11.2°288°
Nearest approach12 Dec 20212.30.772 AU0.234 AU17h08m-01°47'21.4°152.2°354°
Perihelion3 Jan 20226.20.615 AU0.918 AU21h37m-35°45'37.5°77.0°99°

Please be aware that cometary behaviour is difficult to predict by nature. Predictions on this page are based on standard models and the latest observations available to me, and will gradually improve with time. The ability of comets to either disappoint or pleasantly surprise us, is one of many things that make them so interesting.

C/2021 A1 (Leonard)- 2021-01-16

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The interactive orbit chart above shows the comet's path through the solar system and its position at the given date. Green and blue lines are shown perpendicular to the ecliptic plane: Green if the path is above the ecliptic plane, blue if it is below. (Left-click and drag to rotate the view; Right-click and drag to move the view; Use scroll wheel to zoom in our out.)

The orbital elements of C/2021 A1 (Leonard), as provided by the minor planet center, are:

            e (eccentricity)                : 1.0000500
            q (perihelion distance)         : 0.6149940
            i (inclination)                 : 132.68590
            Ω (Longitude of ascending node) : 255.87410
            ω (Argument of perihelion)      : 225.09050
            L (Longitude of perihelion)     : 221.65354
            B (Latitude of perihelion)      : -31.37260
            T (Time of perihelion passage)  : 2459582.80790
            P (Orbital period in years)     : > 9999.99 
            Epoch                           : 2021 Jan 15
            Reference                       : MPEC 2021-A99

            Family/Group:                   : Nearly isotropic

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The light curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the minor planet center. (8.50 + 5 log[∆] + 10.00 log[r]). The additional green curve shows the effect of forward scattering, occurring when the comet is between the earth and the sun, for a gas-to-dust light ratio δ90 of 0.30. (See Marcus 2007)

The all-sky chart below shows the path of the comet over the same period as the light curve. The comet's current position is marked yellow.

The following chart shows the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.
A more printer-friendly version of the same chart can be found further down this page as well.