C/2021 P4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Jul 2022	10.3	1.114 AU	1.958 AU	09h14m	+27°58'	24.4°	22.1°	81°
Perihelion	30 Jul 2022	10.2	1.078 AU	1.975 AU	09h59m	+14°18'	20.0°	18.7°	105°
Today	25 Mar 2026	27.1	12.286 AU	12.958 AU	22h49m	-39°24'	45.9°	3.3°	211°

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)                : 0.9964100
    q (Perihelion distance)         : 1.0783470
    i (Inclination)                 : 56.41530
    Ω (Longitude of ascending node) : 347.96720
    ω (Argument of perihelion)      : 175.83030
    L (Longitude of perihelion)     : 345.65782
    B (Latitude of perihelion)      : 3.47271
    T (Time of perihelion passage)  : 2459791.07100
    P (Orbital period in years)     : 5205.90

    Epoch                           : 2026 Mar 21
    Reference                       : MPEC 2026-E44

    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
2026-03-24 00:00 UT   22 49 03.6   -39 25 46    12.962   12.275   44.7    3.3   210   27.1 
2026-03-25 00:00 UT   22 49 24.4   -39 24 51    12.960   12.281   45.4    3.3   211   27.1 
2026-03-25 17:16 UT   22 49 39.2   -39 24 13    12.958   12.286   45.9    3.3   211   27.1 
2026-03-26 00:00 UT   22 49 45.0   -39 23 59    12.958   12.288   46.1    3.4   212   27.1 
2026-03-27 00:00 UT   22 50 05.4   -39 23 09    12.955   12.294   46.8    3.4   212   27.1 
2026-03-28 00:00 UT   22 50 25.7   -39 22 22    12.953   12.301   47.5    3.4   213   27.1 
2026-03-29 00:00 UT   22 50 45.8   -39 21 38    12.950   12.307   48.2    3.5   214   27.1 
2026-03-30 00:00 UT   22 51 05.7   -39 20 56    12.947   12.314   48.9    3.5   215   27.1 
2026-03-31 00:00 UT   22 51 25.5   -39 20 18    12.944   12.320   49.6    3.5   215   27.1 
2026-04-01 00:00 UT   22 51 45.1   -39 19 41    12.941   12.327   50.3    3.6   216   27.1 
2026-04-02 00:00 UT   22 52 04.5   -39 19 08    12.937   12.334   51.0    3.6   217   27.1 
2026-04-03 00:00 UT   22 52 23.7   -39 18 37    12.934   12.340   51.7    3.6   218   27.1 
2026-04-04 00:00 UT   22 52 42.7   -39 18 09    12.930   12.347   52.4    3.7   218   27.1 

    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.