A/2019 O4
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	5 Sep 2019	21.1	3.880 AU	3.038 AU	21h41m	+26°59'	141.7°	9.3°	149°
Perihelion	11 Feb 2020	21.7	3.642 AU	4.307 AU	20h29m	+25°06'	42.6°	10.6°	336°
Today	15 Jul 2025	26.8	13.535 AU	14.077 AU	11h12m	+00°03'	56.0°	3.6°	116°

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)                : 0.8903850
            q (Perihelion distance)         : 3.6422280
            i (Inclination)                 : 115.00260
            Ω (Longitude of ascending node) : 354.92620
            ω (Argument of perihelion)      : 61.82280
            L (Longitude of perihelion)     : 316.65240
            B (Latitude of perihelion)      : 53.02382
            T (Time of perihelion passage)  : 2458890.63480
            P (Orbital period in years)     : 191.53

            Epoch                           : 2025 Jul 14
            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
2025-07-15 00:00 UT   11 12 35.1   +00 04 23    14.061   13.531   56.8    3.6   116   26.8 
2025-07-15 20:46 UT   11 12 41.0   +00 03 19    14.077   13.535   56.0    3.6   116   26.8 
2025-07-16 00:00 UT   11 12 41.9   +00 03 10    14.079   13.535   55.8    3.6   116   26.8 
2025-07-17 00:00 UT   11 12 48.8   +00 01 55    14.098   13.540   54.9    3.5   116   26.8 
2025-07-18 00:00 UT   11 12 56.0   +00 00 39    14.117   13.545   54.0    3.5   116   26.8 
2025-07-19 00:00 UT   11 13 03.3   +00 00 38    14.135   13.550   53.1    3.4   116   26.8 
2025-07-20 00:00 UT   11 13 10.8   +00 01 57    14.154   13.555   52.2    3.4   117   26.8 
2025-07-21 00:00 UT   11 13 18.5   +00 03 17    14.172   13.560   51.3    3.4   117   26.8 
2025-07-22 00:00 UT   11 13 26.4   +00 04 38    14.190   13.565   50.4    3.3   117   26.8 
2025-07-23 00:00 UT   11 13 34.4   +00 06 00    14.207   13.570   49.5    3.3   117   26.8 
2025-07-24 00:00 UT   11 13 42.6   +00 07 24    14.225   13.574   48.6    3.2   117   26.8 
2025-07-25 00:00 UT   11 13 51.0   +00 08 49    14.242   13.579   47.6    3.2   117   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.