C/2020 A3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	2 May 2019	19.1	5.767 AU	4.954 AU	13h11m	-50°56'	140.5°	6.4°	33°
Perihelion	26 Jun 2019	19.3	5.754 AU	5.422 AU	12h11m	-40°44'	104.0°	9.9°	109°
Today	9 Jan 2026	25.9	15.872 AU	14.898 AU	07h26m	+30°19'	171.7°	0.5°	188°

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.)

Light curve

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations from COBS. The light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (8.0 + 5 log[∆] + 10.0 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)

Charts

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.

Orbital elements

The orbital elements of C/2020 A3 (ATLAS) are:

    e (Eccentricity)                : 0.9983560
    q (Perihelion distance)         : 5.7538020
    i (Inclination)                 : 146.61480
    Ω (Longitude of ascending node) : 120.79590
    ω (Argument of perihelion)      : 268.21970
    L (Longitude of perihelion)     : 32.92772
    B (Latitude of perihelion)      : -33.36698
    T (Time of perihelion passage)  : 2458660.55480
    P (Orbital period in years)     : 207052.10

    Epoch                           : 2026 Jan 08
    Reference                       : MPEC 2023-A50

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-08 00:00 UT   07 27 23.2   +30 17 42    14.891   15.865  171.6    0.5   200   25.9 
2026-01-09 00:00 UT   07 27 01.7   +30 18 52    14.896   15.870  171.7    0.5   192   25.9 
2026-01-09 12:41 UT   07 26 50.4   +30 19 28    14.898   15.872  171.7    0.5   188   25.9 
2026-01-10 00:00 UT   07 26 40.3   +30 20 01    14.901   15.875  171.7    0.5   184   25.9 
2026-01-11 00:00 UT   07 26 18.8   +30 21 09    14.906   15.880  171.5    0.5   177   25.9 
2026-01-12 00:00 UT   07 25 57.4   +30 22 16    14.911   15.885  171.2    0.5   170   25.9 
2026-01-13 00:00 UT   07 25 35.9   +30 23 22    14.917   15.889  170.8    0.6   163   25.9 
2026-01-14 00:00 UT   07 25 14.5   +30 24 28    14.923   15.894  170.3    0.6   157   25.9 
2026-01-15 00:00 UT   07 24 53.1   +30 25 32    14.930   15.899  169.7    0.6   152   25.9 
2026-01-16 00:00 UT   07 24 31.8   +30 26 35    14.937   15.904  169.0    0.7   147   25.9 
2026-01-17 00:00 UT   07 24 10.5   +30 27 38    14.944   15.909  168.3    0.7   143   25.9 
2026-01-18 00:00 UT   07 23 49.3   +30 28 39    14.951   15.914  167.5    0.8   140   25.9 
2026-01-19 00:00 UT   07 23 28.1   +30 29 40    14.959   15.919  166.6    0.8   136   25.9 

    Terminology:
            
    delta:  distance between comet and earth in AU
    radius: distance between comet and sun in AU
    magn:   magnitude (brightness) estimate    
    ra:     right ascension in hours (24h = 360deg)
    dec:    declination in degrees
    elong:  elongation in degrees (angle sun-earth-comet)    
    phase:  phase angle in degrees (angle sun-comet-earth)        
    AU:     Astronomical Unit (mean distance between earth and sun: 149597870.7 km      
    

Orbital elements usually provided by the MPC (Minor Planet Center).
Observations contributed by observers worldwide, via COBS (Comet Observation Database) or the MPC (Minor Planet Center)
Calculations by a modified version of AAPlus, a C# implementation of the AA+ project by PJ Naughter from the algorithms presented in the book "Astronomical Algorithms" by Jean Meeus.
NGC2000 dso catalog and star labels from VizieR as provided by the Strasbourg astronomical Data Center.
Tycho2 catalog from the ESO archive.