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P/2021 R8 (Sheppard)
ephemeris date magn radius delta ra dec elong phase PA
Today19 Oct 202526.53.169 AU4.022 AU15h26m-17°02'27.2°8.3°101°
Nearest approach5 Aug 202622.82.339 AU1.336 AU20h11m-17°23'168.6°4.9°90°
Perihelion5 Jan 202723.92.137 AU2.600 AU22h34m-09°22'51.8°21.2°69°
P/2021 R8 (Sheppard)- 2025-10-19
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. (18.5 + 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 P/2021 R8 (Sheppard) are: 

    e (Eccentricity)                : 0.2924630
    q (Perihelion distance)         : 2.1370860
    i (Inclination)                 : 2.20260
    Ω (Longitude of ascending node) : 167.06080
    ω (Argument of perihelion)      : 190.81160
    L (Longitude of perihelion)     : 177.86460
    B (Latitude of perihelion)      : -0.41307
    T (Time of perihelion passage)  : 2461411.30860
    P (Orbital period in years)     : 5.25

    Epoch                           : 2025 Oct 18
    Reference                       : MPEC 2021-Y10

    Classification(s):              : Ecliptic; Active asteroid
    Tisserand (Jupiter)             : 3.179

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-18 00:00 UT   15 23 50.4   -16 52 38     4.015    3.174   28.4    8.6   101   26.5 
2025-10-19 00:00 UT   15 25 13.1   -16 57 50     4.018    3.171   27.8    8.4   101   26.5 
2025-10-19 21:42 UT   15 26 28.1   -17 02 32     4.022    3.169   27.2    8.3   101   26.5 
2025-10-20 00:00 UT   15 26 36.1   -17 03 01     4.022    3.169   27.1    8.2   101   26.5 
2025-10-21 00:00 UT   15 27 59.5   -17 08 11     4.026    3.166   26.5    8.1   101   26.5 
2025-10-22 00:00 UT   15 29 23.3   -17 13 19     4.029    3.163   25.8    7.9   101   26.5 
2025-10-23 00:00 UT   15 30 47.5   -17 18 26     4.032    3.161   25.2    7.7   100   26.5 
2025-10-24 00:00 UT   15 32 12.1   -17 23 31     4.036    3.158   24.6    7.5   100   26.5 
2025-10-25 00:00 UT   15 33 37.0   -17 28 34     4.038    3.155   23.9    7.3   100   26.5 
2025-10-26 00:00 UT   15 35 02.3   -17 33 36     4.041    3.152   23.3    7.2   100   26.5 
2025-10-27 00:00 UT   15 36 28.0   -17 38 36     4.044    3.150   22.6    7.0    99   26.5 
2025-10-28 00:00 UT   15 37 54.1   -17 43 34     4.046    3.147   22.0    6.8    99   26.5 
2025-10-29 00:00 UT   15 39 20.4   -17 48 30     4.049    3.144   21.3    6.6    99   26.5 




    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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