P/2021 J3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	15 May 2019	16.9	4.900 AU	3.920 AU	15h34m	-03°06'	164.2°	3.2°	187°
Perihelion	30 Jun 2019	17.0	4.894 AU	4.192 AU	15h18m	-03°59'	128.8°	9.3°	117°
Today	18 Jul 2025	22.0	10.048 AU	9.772 AU	01h09m	-08°17'	102.9°	5.7°	250°

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 P/2021 J3 (ATLAS) are:

            e (Eccentricity)                : 0.4494270
            q (Perihelion distance)         : 4.8940940
            i (Inclination)                 : 14.51470
            Ω (Longitude of ascending node) : 110.99430
            ω (Argument of perihelion)      : 125.62280
            L (Longitude of perihelion)     : 57.50148
            B (Latitude of perihelion)      : 11.75505
            T (Time of perihelion passage)  : 2458664.78670
            P (Orbital period in years)     : 26.50

            Epoch                           : 2025 Jul 17
            Reference                       : MPEC 2024-F34

            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 light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (7.00 + 5 log[∆] + 10.00 log[r]).

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
2025-07-18 00:00 UT   01 09 55.6   -08 15 59     9.784   10.045  102.0    5.7   250   22.0 
2025-07-18 22:45 UT   01 09 58.4   -08 17 13     9.772   10.048  102.9    5.7   250   22.0 
2025-07-19 00:00 UT   01 09 58.6   -08 17 18     9.771   10.048  102.9    5.7   250   22.0 
2025-07-20 00:00 UT   01 10 01.2   -08 18 39     9.758   10.050  103.9    5.6   251   22.0 
2025-07-21 00:00 UT   01 10 03.5   -08 20 02     9.745   10.052  104.8    5.6   251   22.0 
2025-07-22 00:00 UT   01 10 05.4   -08 21 28     9.731   10.054  105.7    5.6   251   22.0 
2025-07-23 00:00 UT   01 10 07.0   -08 22 55     9.718   10.056  106.6    5.6   251   22.0 
2025-07-24 00:00 UT   01 10 08.1   -08 24 25     9.705   10.059  107.6    5.5   252   22.0 
2025-07-25 00:00 UT   01 10 08.9   -08 25 57     9.693   10.061  108.5    5.5   252   22.0 
2025-07-26 00:00 UT   01 10 09.4   -08 27 31     9.680   10.063  109.4    5.5   252   22.0 
2025-07-27 00:00 UT   01 10 09.4   -08 29 07     9.667   10.065  110.3    5.4   253   22.0 
2025-07-28 00:00 UT   01 10 09.1   -08 30 45     9.654   10.067  111.3    5.4   253   22.0 

    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.