C/2015 G2 (MASTER)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	14 May 2015	8.3	0.808 AU	0.467 AU	03h24m	-33°04'	51.5°	101.5°	179°
Perihelion	25 May 2015	9.0	0.777 AU	0.673 AU	06h32m	-13°58'	50.1°	88.3°	133°
Today	16 Dec 2025	32.3	26.369 AU	25.596 AU	02h57m	+45°57'	141.0°	1.3°	112°

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. (11.0 + 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/2015 G2 (MASTER) are:

    e (Eccentricity)                : 1.0006430
    q (Perihelion distance)         : 0.7771870
    i (Inclination)                 : 147.66290
    Ω (Longitude of ascending node) : 110.24850
    ω (Argument of perihelion)      : 257.61690
    L (Longitude of perihelion)     : 34.81490
    B (Latitude of perihelion)      : -31.49710
    T (Time of perihelion passage)  : 2457167.77290

    Epoch                           : 2020 Sep 26
    Reference                       : MPC109142

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-12-15 00:00 UT   02 57 57.0   +45 59 15    25.579   26.363  142.0    1.3   114   32.2 
2025-12-16 00:00 UT   02 57 46.0   +45 58 06    25.591   26.367  141.3    1.3   112   32.3 
2025-12-16 10:19 UT   02 57 41.4   +45 57 36    25.596   26.369  141.0    1.3   112   32.3 
2025-12-17 00:00 UT   02 57 35.2   +45 56 56    25.603   26.372  140.6    1.4   111   32.3 
2025-12-18 00:00 UT   02 57 24.6   +45 55 45    25.615   26.377  139.9    1.4   110   32.3 
2025-12-19 00:00 UT   02 57 14.2   +45 54 34    25.628   26.382  139.2    1.4   109   32.3 
2025-12-20 00:00 UT   02 57 03.9   +45 53 23    25.641   26.386  138.5    1.4   108   32.3 
2025-12-21 00:00 UT   02 56 53.7   +45 52 11    25.654   26.391  137.7    1.4   107   32.3 
2025-12-22 00:00 UT   02 56 43.8   +45 50 58    25.668   26.396  136.9    1.5   105   32.3 
2025-12-23 00:00 UT   02 56 34.0   +45 49 45    25.681   26.400  136.2    1.5   104   32.3 
2025-12-24 00:00 UT   02 56 24.4   +45 48 32    25.695   26.405  135.4    1.5   103   32.3 
2025-12-25 00:00 UT   02 56 14.9   +45 47 18    25.709   26.410  134.6    1.5   102   32.3 
2025-12-26 00:00 UT   02 56 05.7   +45 46 04    25.723   26.414  133.8    1.5   101   32.3 

    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.