C/2021 P4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Jul 2022	10.3	1.114 AU	1.959 AU	09h14m	+27°57'	24.3°	22.1°	81°
Perihelion	30 Jul 2022	10.2	1.079 AU	1.976 AU	09h59m	+14°17'	19.9°	18.7°	105°
Today	8 Aug 2026	27.4	13.159 AU	12.307 AU	22h51m	-42°47'	145.9°	2.5°	313°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.3 + 5 log[∆] + 12.2 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 C/2021 P4 (ATLAS) are:

    e (Eccentricity)                : 0.9964530
    q (Perihelion distance)         : 1.0785600
    i (Inclination)                 : 56.43270
    Ω (Longitude of ascending node) : 347.95100
    ω (Argument of perihelion)      : 175.84680
    L (Longitude of perihelion)     : 345.65183
    B (Latitude of perihelion)      : 3.45967
    T (Time of perihelion passage)  : 2459791.16560
    P (Orbital period in years)     : 5302.43

    Epoch                           : 2026 Aug 07
    Reference                       : MPC194175

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-08-07 00:00 UT   22 51 49.7   -42 45 05    12.303   13.152  145.5    2.5   311   27.4 
2026-08-08 00:00 UT   22 51 28.6   -42 47 02    12.306   13.158  145.8    2.5   313   27.4 
2026-08-08 00:43 UT   22 51 28.0   -42 47 06    12.307   13.159  145.9    2.5   313   27.4 
2026-08-09 00:00 UT   22 51 07.3   -42 48 58    12.310   13.165  146.1    2.5   315   27.4 
2026-08-10 00:00 UT   22 50 45.9   -42 50 51    12.314   13.171  146.4    2.4   317   27.4 
2026-08-11 00:00 UT   22 50 24.2   -42 52 42    12.319   13.177  146.6    2.4   319   27.4 
2026-08-12 00:00 UT   22 50 02.4   -42 54 31    12.323   13.184  146.9    2.4   320   27.4 
2026-08-13 00:00 UT   22 49 40.5   -42 56 17    12.328   13.190  147.0    2.4   322   27.4 
2026-08-14 00:00 UT   22 49 18.4   -42 58 01    12.333   13.197  147.2    2.4   324   27.4 
2026-08-15 00:00 UT   22 48 56.1   -42 59 43    12.338   13.203  147.3    2.4   326   27.4 
2026-08-16 00:00 UT   22 48 33.7   -43 01 21    12.344   13.209  147.4    2.4   328   27.4 
2026-08-17 00:00 UT   22 48 11.2   -43 02 58    12.350   13.216  147.5    2.4   330   27.4 
2026-08-18 00:00 UT   22 47 48.6   -43 04 31    12.356   13.222  147.5    2.4   332   27.4 

    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.