C/2017 M4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	17 Jan 2019	14.0	3.230 AU	3.954 AU	17h19m	-13°09'	37.6°	10.7°	287°
Nearest approach	13 May 2019	13.3	3.416 AU	2.465 AU	16h00m	-40°12'	156.6°	6.8°	336°
Today	7 Jul 2026	26.7	18.783 AU	19.328 AU	06h09m	-32°02'	56.3°	2.6°	196°

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 4.8 + 5 log[∆] + 12.1 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/2017 M4 (ATLAS) are:

    e (Eccentricity)                : 0.9998200
    q (Perihelion distance)         : 3.2304270
    i (Inclination)                 : 105.65100
    Ω (Longitude of ascending node) : 65.96360
    ω (Argument of perihelion)      : 167.32500
    L (Longitude of perihelion)     : 69.43566
    B (Latitude of perihelion)      : 12.19767
    T (Time of perihelion passage)  : 2458500.70790

    Epoch                           : 2026 Jul 07
    Reference                       : MPC194152

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-07-06 00:00 UT   06 09 33.9   -32 02 13    19.322   18.773   56.0    2.6   194   26.7 
2026-07-07 00:00 UT   06 09 46.8   -32 02 26    19.325   18.778   56.2    2.6   195   26.7 
2026-07-07 22:16 UT   06 09 58.7   -32 02 40    19.328   18.783   56.3    2.6   196   26.7 
2026-07-08 00:00 UT   06 09 59.6   -32 02 41    19.328   18.783   56.3    2.6   196   26.7 
2026-07-09 00:00 UT   06 10 12.4   -32 02 59    19.331   18.789   56.4    2.6   197   26.7 
2026-07-10 00:00 UT   06 10 25.1   -32 03 19    19.334   18.794   56.5    2.6   198   26.7 
2026-07-11 00:00 UT   06 10 37.8   -32 03 42    19.337   18.799   56.7    2.6   199   26.7 
2026-07-12 00:00 UT   06 10 50.3   -32 04 07    19.340   18.804   56.8    2.6   200   26.7 
2026-07-13 00:00 UT   06 11 02.8   -32 04 34    19.343   18.809   57.0    2.6   201   26.7 
2026-07-14 00:00 UT   06 11 15.3   -32 05 03    19.345   18.814   57.2    2.6   202   26.7 
2026-07-15 00:00 UT   06 11 27.6   -32 05 35    19.347   18.819   57.4    2.6   203   26.7 
2026-07-16 00:00 UT   06 11 39.9   -32 06 09    19.349   18.824   57.6    2.6   204   26.7 
2026-07-17 00:00 UT   06 11 52.1   -32 06 45    19.351   18.829   57.8    2.6   206   26.7 

    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.