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A/2019 O4
ephemeris date magn radius delta ra dec elong phase PA
Nearest approach5 Sep 201921.13.879 AU3.037 AU 21h41m+26°59'141.7°9.3°149°
Perihelion11 Feb 202021.73.641 AU4.306 AU 20h29m+25°06'42.6°10.6°336°
Today12 Feb 202626.814.548 AU13.692 AU 11h23m-04°33'149.0°2.0°307°
A/2019 O4- 2026-02-12
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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 displayed light curve is calculated under the assumption that the object remains inactive. (H=15.10; G=.15).



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 A/2019 O4 are: 

    e (Eccentricity)                : 0.8903270
    q (Perihelion distance)         : 3.6412010
    i (Inclination)                 : 114.98290
    Ω (Longitude of ascending node) : 354.92390
    ω (Argument of perihelion)      : 61.80710
    L (Longitude of perihelion)     : 316.68898
    B (Latitude of perihelion)      : 53.02484
    T (Time of perihelion passage)  : 2458890.56580
    P (Orbital period in years)     : 191.30

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2021-P47

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-02-11 00:00 UT   11 24 02.4   -04 34 13    13.698   14.541  147.5    2.1   306   26.8 
2026-02-12 00:00 UT   11 23 45.7   -04 33 31    13.694   14.545  148.5    2.0   306   26.8 
2026-02-12 11:35 UT   11 23 37.6   -04 33 11    13.692   14.548  149.0    2.0   307   26.8 
2026-02-13 00:00 UT   11 23 28.9   -04 32 48    13.690   14.550  149.6    2.0   307   26.8 
2026-02-14 00:00 UT   11 23 12.0   -04 32 04    13.686   14.555  150.6    1.9   307   26.8 
2026-02-15 00:00 UT   11 22 54.9   -04 31 17    13.682   14.559  151.6    1.8   308   26.8 
2026-02-16 00:00 UT   11 22 37.7   -04 30 30    13.679   14.564  152.7    1.8   309   26.8 
2026-02-17 00:00 UT   11 22 20.4   -04 29 41    13.676   14.569  153.7    1.7   310   26.8 
2026-02-18 00:00 UT   11 22 03.0   -04 28 51    13.673   14.574  154.7    1.7   310   26.8 
2026-02-19 00:00 UT   11 21 45.4   -04 27 59    13.671   14.578  155.7    1.6   311   26.8 
2026-02-20 00:00 UT   11 21 27.8   -04 27 06    13.669   14.583  156.8    1.5   312   26.8 
2026-02-21 00:00 UT   11 21 10.1   -04 26 12    13.667   14.588  157.8    1.5   313   26.8 
2026-02-22 00:00 UT   11 20 52.2   -04 25 17    13.666   14.592  158.8    1.4   314   26.8 




    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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