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C/2021 A9 (PANSTARRS)
ephemeris date magn radius delta ra dec elong phase PA
Perihelion4 Dec 202319.17.767 AU6.979 AU 07h17m+09°29'140.8°4.6°294°
Nearest approach3 Jan 202419.17.770 AU6.811 AU 06h52m+09°09'166.3°1.7°2°
Today17 Jun 202620.99.575 AU10.382 AU 03h51m-00°23'35.7°3.5°226°
C/2021 A9 (PANSTARRS)- 2026-06-17
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. 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. (6.0 + 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/2021 A9 (PANSTARRS) are: 

    e (Eccentricity)                : 1.0000260
    q (Perihelion distance)         : 7.7674830
    i (Inclination)                 : 158.01760
    Ω (Longitude of ascending node) : 314.84830
    ω (Argument of perihelion)      : 211.69970
    L (Longitude of perihelion)     : 285.04833
    B (Latitude of perihelion)      : -11.34369
    T (Time of perihelion passage)  : 2460283.37400

    Epoch                           : 2026 Jun 16
    Reference                       : MPC194172

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-06-16 00:00 UT   03 51 03.3   +00 22 30    10.388    9.572   34.8    3.5   225   20.9 
2026-06-17 00:00 UT   03 51 14.0   +00 23 03    10.383    9.575   35.6    3.5   226   20.9 
2026-06-17 02:32 UT   03 51 15.1   +00 23 06    10.382    9.575   35.7    3.5   226   20.9 
2026-06-18 00:00 UT   03 51 24.6   +00 23 37    10.378    9.578   36.3    3.6   227   20.9 
2026-06-19 00:00 UT   03 51 35.1   +00 24 14    10.373    9.582   37.1    3.7   228   20.9 
2026-06-20 00:00 UT   03 51 45.3   +00 24 54    10.367    9.585   37.8    3.7   229   20.9 
2026-06-21 00:00 UT   03 51 55.5   +00 25 36    10.362    9.589   38.6    3.8   230   20.9 
2026-06-22 00:00 UT   03 52 05.4   +00 26 20    10.356    9.592   39.4    3.9   231   20.9 
2026-06-23 00:00 UT   03 52 15.2   +00 27 06    10.350    9.596   40.2    3.9   231   20.9 
2026-06-24 00:00 UT   03 52 24.7   +00 27 55    10.343    9.599   41.0    4.0   232   20.9 
2026-06-25 00:00 UT   03 52 34.1   +00 28 46    10.337    9.602   41.7    4.0   233   20.9 
2026-06-26 00:00 UT   03 52 43.3   +00 29 40    10.330    9.606   42.5    4.1   233   20.9 
2026-06-27 00:00 UT   03 52 52.4   +00 30 36    10.323    9.609   43.3    4.2   234   20.9 




    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.

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