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A/2019 O4
ephemeris date magn radius delta ra dec elong phase PA
Nearest approach5 Sep 201921.13.876 AU3.034 AU 21h41m+26°58'141.7°9.3°149°
Perihelion11 Feb 202021.73.638 AU4.302 AU 20h29m+25°07'42.6°10.6°336°
Today19 Sep 202627.315.565 AU16.551 AU 11h11m-04°38'10.5°0.7°234°
A/2019 O4- 2026-09-19
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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)                : 0.8905950
    q (Perihelion distance)         : 3.6380920
    i (Inclination)                 : 114.94770
    Ω (Longitude of ascending node) : 354.90370
    ω (Argument of perihelion)      : 61.81160
    L (Longitude of perihelion)     : 316.70028
    B (Latitude of perihelion)      : 53.04983
    T (Time of perihelion passage)  : 2458890.58820
    P (Orbital period in years)     : 191.76

    Epoch                           : 2026 May 29
    Reference                       : MPC194162

    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
2026-09-18 00:00 UT   11 11 28.7   -04 35 38    16.547   15.558    9.9    0.6   228   27.3 
2026-09-19 00:00 UT   11 11 39.9   -04 37 29    16.550   15.563   10.3    0.7   232   27.3 
2026-09-19 11:06 UT   11 11 45.0   -04 38 20    16.551   15.565   10.5    0.7   234   27.3 
2026-09-20 00:00 UT   11 11 50.9   -04 39 20    16.552   15.567   10.8    0.7   237   27.3 
2026-09-21 00:00 UT   11 12 02.0   -04 41 12    16.555   15.572   11.3    0.7   241   27.3 
2026-09-22 00:00 UT   11 12 13.0   -04 43 04    16.557   15.576   11.9    0.8   244   27.3 
2026-09-23 00:00 UT   11 12 24.0   -04 44 56    16.559   15.581   12.5    0.8   247   27.3 
2026-09-24 00:00 UT   11 12 34.9   -04 46 48    16.560   15.586   13.2    0.8   250   27.3 
2026-09-25 00:00 UT   11 12 45.7   -04 48 41    16.562   15.590   13.9    0.9   253   27.3 
2026-09-26 00:00 UT   11 12 56.5   -04 50 34    16.563   15.595   14.6    0.9   255   27.3 
2026-09-27 00:00 UT   11 13 07.3   -04 52 27    16.563   15.599   15.3    1.0   257   27.3 
2026-09-28 00:00 UT   11 13 17.9   -04 54 21    16.564   15.604   16.1    1.0   259   27.3 
2026-09-29 00:00 UT   11 13 28.6   -04 56 14    16.564   15.608   16.9    1.1   261   27.3 




    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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