P/2025 D4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	14 Feb 2025	20.7	3.255 AU	2.918 AU	14h37m	-23°47'	101.0°	17.3°	290°
Nearest approach	29 Apr 2025	20.2	3.304 AU	2.300 AU	14h38m	-20°06'	174.0°	1.8°	335°
Today	27 Dec 2025	22.7	4.000 AU	4.959 AU	17h43m	-16°43'	11.4°	2.8°	307°

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. (13.2 + 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/2025 D4 (ATLAS) are:

    e (Eccentricity)                : 0.6346570
    q (Perihelion distance)         : 3.2548530
    i (Inclination)                 : 15.93900
    Ω (Longitude of ascending node) : 233.11820
    ω (Argument of perihelion)      : 332.89130
    L (Longitude of perihelion)     : 206.91010
    B (Latitude of perihelion)      : -7.18861
    T (Time of perihelion passage)  : 2460720.80860
    P (Orbital period in years)     : 26.59

    Epoch                           : 2025 Dec 26
    Reference                       : MPC188413

    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
2025-12-26 00:00 UT   17 41 48.1   -16 45 04     4.957    3.995   10.7    2.6   309   22.7 
2025-12-27 00:00 UT   17 43 05.8   -16 43 44     4.959    4.000   11.3    2.8   307   22.7 
2025-12-27 04:09 UT   17 43 19.2   -16 43 30     4.959    4.000   11.4    2.8   307   22.7 
2025-12-28 00:00 UT   17 44 23.3   -16 42 21     4.961    4.004   11.9    2.9   305   22.7 
2025-12-29 00:00 UT   17 45 40.7   -16 40 55     4.962    4.008   12.5    3.1   303   22.7 
2025-12-30 00:00 UT   17 46 57.8   -16 39 26     4.963    4.012   13.1    3.2   302   22.7 
2025-12-31 00:00 UT   17 48 14.6   -16 37 53     4.964    4.016   13.8    3.3   300   22.7 
2026-01-01 00:00 UT   17 49 31.3   -16 36 17     4.965    4.020   14.4    3.5   299   22.7 
2026-01-02 00:00 UT   17 50 47.7   -16 34 38     4.965    4.024   15.1    3.6   297   22.7 
2026-01-03 00:00 UT   17 52 03.9   -16 32 56     4.966    4.028   15.7    3.8   296   22.7 
2026-01-04 00:00 UT   17 53 19.8   -16 31 11     4.966    4.032   16.4    3.9   295   22.7 
2026-01-05 00:00 UT   17 54 35.5   -16 29 22     4.966    4.036   17.0    4.1   294   22.7 
2026-01-06 00:00 UT   17 55 50.9   -16 27 30     4.966    4.040   17.7    4.2   293   22.7 

    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.