A/2019 O4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	5 Sep 2019	21.1	3.877 AU	3.035 AU	21h41m	+26°57'	141.7°	9.3°	149°
Perihelion	11 Feb 2020	21.7	3.638 AU	4.303 AU	20h29m	+25°07'	42.6°	10.6°	336°
Today	23 Mar 2026	26.8	14.734 AU	13.767 AU	11h11m	-03°52'	165.4°	1.0°	79°

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)                : 0.8906660
    q (Perihelion distance)         : 3.6384570
    i (Inclination)                 : 114.95870
    Ω (Longitude of ascending node) : 354.90560
    ω (Argument of perihelion)      : 61.82100
    L (Longitude of perihelion)     : 316.67971
    B (Latitude of perihelion)      : 53.04972
    T (Time of perihelion passage)  : 2458890.74430
    P (Orbital period in years)     : 191.97

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

    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
2026-03-22 00:00 UT   11 12 13.5   -03 54 23    13.756   14.727  166.7    0.9    75   26.8 
2026-03-23 00:00 UT   11 11 55.7   -03 53 07    13.763   14.732  165.8    0.9    78   26.8 
2026-03-23 12:05 UT   11 11 46.9   -03 52 29    13.767   14.734  165.4    1.0    79   26.8 
2026-03-24 00:00 UT   11 11 38.1   -03 51 51    13.771   14.737  164.9    1.0    80   26.8 
2026-03-25 00:00 UT   11 11 20.6   -03 50 34    13.780   14.741  164.0    1.1    82   26.8 
2026-03-26 00:00 UT   11 11 03.2   -03 49 18    13.788   14.746  163.1    1.1    84   26.8 
2026-03-27 00:00 UT   11 10 45.9   -03 48 01    13.797   14.751  162.2    1.2    86   26.8 
2026-03-28 00:00 UT   11 10 28.7   -03 46 45    13.807   14.755  161.2    1.2    87   26.8 
2026-03-29 00:00 UT   11 10 11.6   -03 45 29    13.816   14.760  160.3    1.3    89   26.8 
2026-03-30 00:00 UT   11 09 54.7   -03 44 12    13.826   14.765  159.3    1.4    90   26.8 
2026-03-31 00:00 UT   11 09 37.9   -03 42 56    13.836   14.769  158.3    1.4    91   26.8 
2026-04-01 00:00 UT   11 09 21.2   -03 41 40    13.847   14.774  157.4    1.5    92   26.9 
2026-04-02 00:00 UT   11 09 04.7   -03 40 24    13.857   14.779  156.4    1.6    93   26.9 

    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.