A/2019 O4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	5 Sep 2019	21.1	3.879 AU	3.037 AU	21h41m	+26°59'	141.7°	9.3°	149°
Perihelion	11 Feb 2020	21.7	3.641 AU	4.306 AU	20h29m	+25°06'	42.6°	10.6°	336°
Today	30 Dec 2025	27.0	14.340 AU	14.085 AU	11h32m	-04°37'	103.1°	3.8°	295°

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
2025-12-29 00:00 UT   11 32 53.3   -04 36 51    14.105   14.333  101.5    3.9   295   27.0 
2025-12-30 00:00 UT   11 32 46.6   -04 37 26    14.092   14.338  102.5    3.8   295   27.0 
2025-12-30 13:51 UT   11 32 42.7   -04 37 46    14.085   14.340  103.1    3.8   295   27.0 
2025-12-31 00:00 UT   11 32 39.7   -04 37 60    14.080   14.342  103.5    3.8   295   27.0 
2026-01-01 00:00 UT   11 32 32.4   -04 38 31    14.068   14.347  104.6    3.8   295   27.0 
2026-01-02 00:00 UT   11 32 24.9   -04 39 01    14.056   14.352  105.6    3.8   295   27.0 
2026-01-03 00:00 UT   11 32 17.1   -04 39 29    14.044   14.356  106.6    3.8   296   27.0 
2026-01-04 00:00 UT   11 32 09.1   -04 39 55    14.032   14.361  107.7    3.7   296   27.0 
2026-01-05 00:00 UT   11 32 00.8   -04 40 19    14.020   14.366  108.7    3.7   296   27.0 
2026-01-06 00:00 UT   11 31 52.2   -04 40 41    14.008   14.371  109.7    3.7   296   27.0 
2026-01-07 00:00 UT   11 31 43.3   -04 41 02    13.997   14.375  110.8    3.7   296   27.0 
2026-01-08 00:00 UT   11 31 34.2   -04 41 21    13.985   14.380  111.8    3.6   296   27.0 
2026-01-09 00:00 UT   11 31 24.8   -04 41 38    13.974   14.385  112.9    3.6   296   27.0 

    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.