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	3.639 AU	4.303 AU	20h29m	+25°08'	42.6°	10.6°	336°
Today	9 Mar 2026	26.7	14.668 AU	13.685 AU	11h16m	-04°10'	171.2°	0.6°	1°

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)                : 0.8906720
    q (Perihelion distance)         : 3.6385070
    i (Inclination)                 : 114.95990
    Ω (Longitude of ascending node) : 354.90580
    ω (Argument of perihelion)      : 61.82200
    L (Longitude of perihelion)     : 316.67749
    B (Latitude of perihelion)      : 53.04969
    T (Time of perihelion passage)  : 2458890.75740
    P (Orbital period in years)     : 191.99

    Epoch                           : 2026 Mar 08
    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
2026-03-08 00:00 UT   11 16 27.9   -04 11 29    13.681   14.662  170.6    0.6   354   26.7 
2026-03-09 00:00 UT   11 16 09.5   -04 10 19    13.684   14.666  171.1    0.6   360   26.7 
2026-03-09 05:40 UT   11 16 05.2   -04 10 03    13.685   14.668  171.2    0.6     1   26.7 
2026-03-10 00:00 UT   11 15 51.1   -04 09 09    13.688   14.671  171.5    0.6     7   26.7 
2026-03-11 00:00 UT   11 15 32.8   -04 07 58    13.692   14.676  171.7    0.6    14   26.7 
2026-03-12 00:00 UT   11 15 14.4   -04 06 46    13.696   14.681  171.8    0.6    21   26.7 
2026-03-13 00:00 UT   11 14 56.1   -04 05 34    13.701   14.685  171.7    0.6    29   26.7 
2026-03-14 00:00 UT   11 14 37.8   -04 04 21    13.705   14.690  171.6    0.6    36   26.7 
2026-03-15 00:00 UT   11 14 19.6   -04 03 08    13.711   14.695  171.2    0.6    43   26.7 
2026-03-16 00:00 UT   11 14 01.4   -04 01 54    13.716   14.699  170.8    0.6    49   26.7 
2026-03-17 00:00 UT   11 13 43.2   -04 00 39    13.722   14.704  170.3    0.7    55   26.7 
2026-03-18 00:00 UT   11 13 25.1   -03 59 25    13.728   14.709  169.7    0.7    60   26.7 
2026-03-19 00:00 UT   11 13 07.1   -03 58 10    13.734   14.713  169.0    0.7    65   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.