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C/2021 G2 (ATLAS)
ephemeris date magn radius delta ra dec elong phase PA
Nearest approach15 Apr 202413.55.109 AU4.238 AU 11h55m-33°41'147.1°6.1°49°
Perihelion9 Sep 202414.04.982 AU5.743 AU 13h07m-18°50'37.6°7.1°127°
Today21 Oct 202515.05.866 AU6.674 AU 15h53m-01°14'33.2°5.3°72°
C/2021 G2 (ATLAS)- 2025-10-21
astro.vanbuitenen.nl


 
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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.)


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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 3.2 + 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/2021 G2 (ATLAS) are: 

    e (Eccentricity)                : 1.0008670
    q (Perihelion distance)         : 4.9821320
    i (Inclination)                 : 48.46360
    Ω (Longitude of ascending node) : 221.09270
    ω (Argument of perihelion)      : 343.26470
    L (Longitude of perihelion)     : 209.81673
    B (Latitude of perihelion)      : -12.44727
    T (Time of perihelion passage)  : 2460562.62930

    Epoch                           : 2025 Oct 20
    Reference                       : MPC188409

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-20 00:00 UT   15 51 42.1   -01 14 06     6.654    5.859   34.3    5.5    74   15.0 
2025-10-21 00:00 UT   15 52 28.2   -01 14 27     6.665    5.863   33.7    5.4    73   15.0 
2025-10-21 20:39 UT   15 53 08.0   -01 14 44     6.674    5.866   33.2    5.3    72   15.0 
2025-10-22 00:00 UT   15 53 14.5   -01 14 47     6.676    5.867   33.1    5.3    72   15.0 
2025-10-23 00:00 UT   15 54 00.9   -01 15 05     6.686    5.871   32.4    5.2    71   15.1 
2025-10-24 00:00 UT   15 54 47.6   -01 15 21     6.696    5.875   31.8    5.1    70   15.1 
2025-10-25 00:00 UT   15 55 34.3   -01 15 35     6.706    5.879   31.2    5.0    69   15.1 
2025-10-26 00:00 UT   15 56 21.3   -01 15 48     6.716    5.882   30.6    4.9    68   15.1 
2025-10-27 00:00 UT   15 57 08.4   -01 15 59     6.726    5.886   30.0    4.8    66   15.1 
2025-10-28 00:00 UT   15 57 55.6   -01 16 07     6.735    5.890   29.5    4.8    65   15.1 
2025-10-29 00:00 UT   15 58 43.0   -01 16 14     6.744    5.894   28.9    4.7    64   15.1 
2025-10-30 00:00 UT   15 59 30.5   -01 16 19     6.753    5.898   28.3    4.6    63   15.1 
2025-10-31 00:00 UT   16 00 18.1   -01 16 22     6.762    5.902   27.8    4.5    62   15.1 




    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.

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