3I/ATLAS
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	29 Oct 2025	9.6	1.357 AU	2.307 AU	13h29m	-06°57'	12.8°	9.4°	302°
Nearest approach	19 Dec 2025	11.5	2.288 AU	1.798 AU	10h46m	+07°06'	107.0°	24.3°	292°
Today	30 Sep 2026	23.0	11.798 AU	11.940 AU	07h13m	+19°15'	79.3°	4.8°	277°

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 6.4 + 5 log[∆] + 10.5 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 3I/ATLAS are:

    e (Eccentricity)                : 6.1398840
    q (Perihelion distance)         : 1.3565070
    i (Inclination)                 : 175.11290
    Ω (Longitude of ascending node) : 322.15350
    ω (Argument of perihelion)      : 128.00550
    L (Longitude of perihelion)     : 14.04671
    B (Latitude of perihelion)      : 3.84903
    T (Time of perihelion passage)  : 2460977.98250

    Epoch                           : 2025 Nov 21
    Reference                       : MPEC 2026-G41

    Classification(s):              : Interstellar

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-09-29 00:00 UT   07 13 45.1   +19 15 35    11.921   11.758   78.1    4.8   277   23.0 
2026-09-30 00:00 UT   07 13 39.8   +19 15 23    11.937   11.792   79.1    4.8   277   23.0 
2026-09-30 04:22 UT   07 13 38.8   +19 15 21    11.940   11.798   79.3    4.8   277   23.0 
2026-10-01 00:00 UT   07 13 34.2   +19 15 11    11.954   11.825   80.1    4.8   277   23.0 
2026-10-02 00:00 UT   07 13 28.2   +19 15 00    11.970   11.859   81.1    4.8   277   23.1 
2026-10-03 00:00 UT   07 13 21.9   +19 14 50    11.987   11.893   82.1    4.8   277   23.1 
2026-10-04 00:00 UT   07 13 15.2   +19 14 40    12.003   11.927   83.1    4.8   277   23.1 
2026-10-05 00:00 UT   07 13 08.2   +19 14 30    12.019   11.961   84.2    4.8   277   23.1 
2026-10-06 00:00 UT   07 13 00.9   +19 14 22    12.036   11.995   85.2    4.8   277   23.1 
2026-10-07 00:00 UT   07 12 53.2   +19 14 14    12.052   12.029   86.2    4.8   277   23.1 
2026-10-08 00:00 UT   07 12 45.2   +19 14 06    12.068   12.063   87.2    4.7   277   23.1 
2026-10-09 00:00 UT   07 12 36.9   +19 13 59    12.084   12.097   88.2    4.7   277   23.2 
2026-10-10 00:00 UT   07 12 28.2   +19 13 53    12.101   12.131   89.2    4.7   277   23.2 

    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.