A/2019 O4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	5 Sep 2019	21.1	3.876 AU	3.034 AU	21h41m	+26°58'	141.7°	9.3°	149°
Perihelion	11 Feb 2020	21.7	3.638 AU	4.302 AU	20h29m	+25°07'	42.6°	10.6°	336°
Today	17 Oct 2026	27.4	15.693 AU	16.520 AU	11h16m	-05°31'	32.9°	2.0°	279°

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
2026-10-16 00:00 UT   11 16 15.8   -05 28 31    16.527   15.685   31.4    1.9   278   27.4 
2026-10-17 00:00 UT   11 16 24.7   -05 30 24    16.523   15.690   32.3    1.9   278   27.4 
2026-10-17 15:34 UT   11 16 30.4   -05 31 37    16.520   15.693   32.9    2.0   279   27.4 
2026-10-18 00:00 UT   11 16 33.4   -05 32 17    16.518   15.695   33.3    2.0   279   27.4 
2026-10-19 00:00 UT   11 16 42.1   -05 34 10    16.513   15.699   34.2    2.0   279   27.4 
2026-10-20 00:00 UT   11 16 50.5   -05 36 02    16.508   15.704   35.1    2.1   280   27.4 
2026-10-21 00:00 UT   11 16 58.9   -05 37 54    16.502   15.708   36.0    2.1   280   27.4 
2026-10-22 00:00 UT   11 17 07.1   -05 39 46    16.497   15.713   36.9    2.2   281   27.4 
2026-10-23 00:00 UT   11 17 15.2   -05 41 37    16.491   15.717   37.8    2.2   281   27.4 
2026-10-24 00:00 UT   11 17 23.1   -05 43 28    16.485   15.722   38.7    2.3   281   27.4 
2026-10-25 00:00 UT   11 17 30.9   -05 45 18    16.479   15.726   39.7    2.3   282   27.4 
2026-10-26 00:00 UT   11 17 38.5   -05 47 09    16.472   15.731   40.6    2.4   282   27.4 
2026-10-27 00:00 UT   11 17 46.0   -05 48 58    16.465   15.735   41.5    2.4   282   27.4 

    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.