P/2021 J3 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	15 May 2019	16.9	4.890 AU	3.910 AU	15h33m	-03°03'	164.2°	3.2°	187°
Perihelion	29 Jun 2019	17.0	4.884 AU	4.179 AU	15h17m	-03°56'	129.1°	9.3°	117°
Today	11 Mar 2026	22.5	10.540 AU	11.435 AU	01h01m	-07°48'	24.5°	2.2°	98°

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 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. (7.0 + 5 log[∆] + 10.0 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)

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 P/2021 J3 (ATLAS) are:

    e (Eccentricity)                : 0.4498800
    q (Perihelion distance)         : 4.8840680
    i (Inclination)                 : 14.51100
    Ω (Longitude of ascending node) : 110.91580
    ω (Argument of perihelion)      : 125.54310
    L (Longitude of perihelion)     : 57.34202
    B (Latitude of perihelion)      : 11.76395
    T (Time of perihelion passage)  : 2458664.37720
    P (Orbital period in years)     : 26.45

    Epoch                           : 2026 Mar 10
    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
2026-03-10 00:00 UT   01 00 60.0   -07 51 16    11.426   10.537   25.4    2.3    96   22.5 
2026-03-11 00:00 UT   01 01 22.2   -07 48 30    11.434   10.539   24.7    2.3    98   22.5 
2026-03-11 04:15 UT   01 01 26.1   -07 48 00    11.435   10.540   24.5    2.2    98   22.5 
2026-03-12 00:00 UT   01 01 44.5   -07 45 44    11.442   10.541   23.9    2.2    99   22.5 
2026-03-13 00:00 UT   01 02 06.9   -07 42 58    11.450   10.543   23.2    2.1   100   22.5 
2026-03-14 00:00 UT   01 02 29.4   -07 40 13    11.457   10.545   22.4    2.1   101   22.5 
2026-03-15 00:00 UT   01 02 52.0   -07 37 28    11.465   10.547   21.7    2.0   103   22.5 
2026-03-16 00:00 UT   01 03 14.7   -07 34 44    11.472   10.549   21.0    1.9   104   22.5 
2026-03-17 00:00 UT   01 03 37.6   -07 32 01    11.478   10.551   20.4    1.9   106   22.5 
2026-03-18 00:00 UT   01 04 00.5   -07 29 18    11.485   10.553   19.7    1.8   108   22.5 
2026-03-19 00:00 UT   01 04 23.5   -07 26 36    11.491   10.555   19.0    1.8   110   22.5 
2026-03-20 00:00 UT   01 04 46.5   -07 23 55    11.497   10.557   18.4    1.7   112   22.5 
2026-03-21 00:00 UT   01 05 09.7   -07 21 14    11.503   10.559   17.8    1.7   114   22.5 

    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.