C/2025 D1 (Groeller)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	18 May 2026	18.7	14.511 AU	14.813 AU	08h55m	+30°32'	70.8°	3.8°	102°
Nearest approach	3 Feb 2028	18.3	14.125 AU	13.141 AU	08h58m	+13°41'	176.6°	0.2°	32°
Perihelion	22 May 2028	18.5	14.116 AU	14.459 AU	08h42m	+12°15'	68.3°	3.8°	107°

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. (1.2 + 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 C/2025 D1 (Groeller) are:

    e (Eccentricity)                : 1.0031590
    q (Perihelion distance)         : 14.1159950
    i (Inclination)                 : 84.44940
    Ω (Longitude of ascending node) : 312.90340
    ω (Argument of perihelion)      : 185.95690
    L (Longitude of perihelion)     : 313.48165
    B (Latitude of perihelion)      : -5.92887
    T (Time of perihelion passage)  : 2461913.91140

    Epoch                           : 2026 May 18
    Reference                       : MPEC 2026-G41

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-05-17 00:00 UT   08 55 36.3   +30 37 25    14.786   14.512   72.4    3.8   102   18.7 
2026-05-18 00:00 UT   08 55 39.3   +30 34 50    14.801   14.511   71.5    3.8   102   18.7 
2026-05-18 19:33 UT   08 55 42.0   +30 32 44    14.813   14.511   70.8    3.8   102   18.7 
2026-05-19 00:00 UT   08 55 42.7   +30 32 15    14.815   14.510   70.6    3.8   102   18.7 
2026-05-20 00:00 UT   08 55 46.3   +30 29 39    14.830   14.509   69.7    3.7   102   18.7 
2026-05-21 00:00 UT   08 55 50.2   +30 27 03    14.844   14.508   68.8    3.7   101   18.7 
2026-05-22 00:00 UT   08 55 54.4   +30 24 27    14.859   14.507   67.8    3.7   101   18.7 
2026-05-23 00:00 UT   08 55 58.8   +30 21 50    14.873   14.506   66.9    3.7   101   18.7 
2026-05-24 00:00 UT   08 56 03.5   +30 19 12    14.887   14.505   66.0    3.7   101   18.7 
2026-05-25 00:00 UT   08 56 08.5   +30 16 35    14.901   14.504   65.1    3.6   101   18.7 
2026-05-26 00:00 UT   08 56 13.7   +30 13 57    14.915   14.503   64.2    3.6   100   18.7 
2026-05-27 00:00 UT   08 56 19.2   +30 11 18    14.929   14.502   63.3    3.6   100   18.7 
2026-05-28 00:00 UT   08 56 24.9   +30 08 39    14.943   14.501   62.4    3.6   100   18.7 

    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.