3I/ATLAS
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	20 Jul 2025	16.9	3.876 AU	3.013 AU	17h23m	-18°11'	143.5°	9.0°	100°
Perihelion	29 Oct 2025	11.8	1.356 AU	2.307 AU	13h29m	-06°57'	12.8°	9.4°	302°
Nearest approach	19 Dec 2025	13.5	2.287 AU	1.797 AU	10h46m	+07°06'	107.0°	24.3°	292°

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.)

The orbital elements of 3I/ATLAS are:

            e (Eccentricity)                : 6.1387060
            q (Perihelion distance)         : 1.3564230
            i (Inclination)                 : 175.11240
            Ω (Longitude of ascending node) : 322.14810
            ω (Argument of perihelion)      : 128.00180
            L (Longitude of perihelion)     : 14.04499
            B (Latitude of perihelion)      : 3.84961
            T (Time of perihelion passage)  : 2460977.98860

            Epoch                           : 2025 May 05
            Reference                       : MPEC 2025-N89

            Classification(s):              : Interstellar
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. The gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (11.70 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.62 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-07-20 00:00 UT   17 23 39.4   -18 12 15     3.018    3.884  143.8    8.9   100   16.9 
2025-07-20 05:48 UT   17 23 02.0   -18 11 37     3.013    3.876  143.5    9.0   100   16.9 
2025-07-21 00:00 UT   17 21 04.1   -18 09 33     2.997    3.851  142.3    9.3   100   16.9 
2025-07-22 00:00 UT   17 18 27.6   -18 06 42     2.978    3.818  140.7    9.7   100   16.8 
2025-07-23 00:00 UT   17 15 50.0   -18 03 44     2.959    3.785  139.2   10.1   100   16.8 
2025-07-24 00:00 UT   17 13 11.3   -18 00 37     2.940    3.753  137.6   10.5   100   16.7 
2025-07-25 00:00 UT   17 10 31.8   -17 57 23     2.922    3.720  136.0   10.9   100   16.7 
2025-07-26 00:00 UT   17 07 51.3   -17 53 60     2.905    3.687  134.4   11.3   100   16.6 
2025-07-27 00:00 UT   17 05 10.0   -17 50 29     2.888    3.654  132.8   11.8   100   16.6 
2025-07-28 00:00 UT   17 02 28.0   -17 46 50     2.872    3.622  131.2   12.2   100   16.5 
2025-07-29 00:00 UT   16 59 45.4   -17 43 02     2.856    3.589  129.6   12.6   100   16.4 
2025-07-30 00:00 UT   16 57 02.1   -17 39 07     2.840    3.557  128.0   13.0   100   16.4 

    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.