A/2019 O4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	5 Sep 2019	21.1	3.881 AU	3.039 AU	21h41m	+26°59'	141.7°	9.3°	149°
Perihelion	11 Feb 2020	21.7	3.643 AU	4.307 AU	20h29m	+25°06'	42.6°	10.6°	336°
Today	11 May 2025	26.6	13.215 AU	12.704 AU	11h13m	+00°28'	118.4°	3.9°	111°

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.)

The orbital elements of A/2019 O4 are:

            e (Eccentricity)                : 0.8904030
            q (Perihelion distance)         : 3.6427130
            i (Inclination)                 : 115.01100
            Ω (Longitude of ascending node) : 354.92700
            ω (Argument of perihelion)      : 61.82950
            L (Longitude of perihelion)     : 316.63661
            B (Latitude of perihelion)      : 53.02338
            T (Time of perihelion passage)  : 2458890.64420
            P (Orbital period in years)     : 191.62

            Epoch                           : 2025 May 10
            Reference                       : MPEC 2021-P47

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); Halley type (P < 200 years)
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve indicates the expected brightness if this object is a comet (15.50 + 5 log[∆] + 5.00 log[r]), whereas the red curve indicates the expected lightcurve for an asteroid (H=15.10; G=.15).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-05-11 00:00 UT   11 13 59.9   +00 28 32    12.694   13.212  118.9    3.8   111   26.6 
2025-05-11 12:52 UT   11 13 54.4   +00 28 48    12.704   13.215  118.4    3.9   111   26.6 
2025-05-12 00:00 UT   11 13 49.6   +00 29 02    12.714   13.217  117.9    3.9   111   26.6 
2025-05-13 00:00 UT   11 13 39.7   +00 29 30    12.734   13.222  116.9    3.9   111   26.6 
2025-05-14 00:00 UT   11 13 30.0   +00 29 57    12.754   13.227  115.9    3.9   111   26.6 
2025-05-15 00:00 UT   11 13 20.6   +00 30 22    12.774   13.232  114.9    4.0   111   26.6 
2025-05-16 00:00 UT   11 13 11.5   +00 30 46    12.794   13.237  113.9    4.0   111   26.6 
2025-05-17 00:00 UT   11 13 02.7   +00 31 08    12.815   13.242  112.9    4.0   111   26.6 
2025-05-18 00:00 UT   11 12 54.1   +00 31 28    12.835   13.247  111.9    4.1   111   26.6 
2025-05-19 00:00 UT   11 12 45.9   +00 31 47    12.856   13.252  110.9    4.1   111   26.6 
2025-05-20 00:00 UT   11 12 38.0   +00 32 04    12.877   13.257  110.0    4.1   111   26.6 
2025-05-21 00:00 UT   11 12 30.3   +00 32 20    12.898   13.262  109.0    4.1   112   26.6 

    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.