C/2017 D2 (Barros)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	9 Jul 2017	15.5	2.511 AU	1.646 AU	22h11m	-32°34'	140.0°	15.1°	274°
Nearest approach	8 Aug 2017	15.4	2.532 AU	1.535 AU	21h46m	-27°14'	166.3°	5.4°	322°
Today	3 Oct 2026	30.7	22.478 AU	22.350 AU	06h18m	+51°26'	96.0°	2.5°	269°

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 10.4 + 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/2017 D2 (Barros) are:

    e (Eccentricity)                : 0.9989990
    q (Perihelion distance)         : 2.5114770
    i (Inclination)                 : 31.19150
    Ω (Longitude of ascending node) : 331.28400
    ω (Argument of perihelion)      : 334.42670
    L (Longitude of perihelion)     : 309.02134
    B (Latitude of perihelion)      : -12.91819
    T (Time of perihelion passage)  : 2457944.34650
    P (Orbital period in years)     : 125673.21

    Epoch                           : 2026 May 29
    Reference                       : MPC194150

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-10-02 00:00 UT   06 18 22.4   +51 24 33    22.367   22.470   94.6    2.5   270   30.7 
2026-10-03 00:00 UT   06 18 22.2   +51 25 43    22.357   22.475   95.5    2.5   269   30.7 
2026-10-03 15:59 UT   06 18 21.8   +51 26 29    22.350   22.478   96.0    2.5   269   30.7 
2026-10-04 00:00 UT   06 18 21.6   +51 26 52    22.347   22.480   96.3    2.5   269   30.7 
2026-10-05 00:00 UT   06 18 20.7   +51 28 02    22.337   22.485   97.2    2.5   268   30.7 
2026-10-06 00:00 UT   06 18 19.6   +51 29 12    22.327   22.490   98.1    2.5   268   30.7 
2026-10-07 00:00 UT   06 18 18.1   +51 30 22    22.317   22.494   98.9    2.5   267   30.7 
2026-10-08 00:00 UT   06 18 16.4   +51 31 31    22.307   22.499   99.8    2.5   267   30.7 
2026-10-09 00:00 UT   06 18 14.4   +51 32 41    22.297   22.504  100.7    2.5   266   30.7 
2026-10-10 00:00 UT   06 18 12.1   +51 33 50    22.287   22.509  101.6    2.5   266   30.7 
2026-10-11 00:00 UT   06 18 09.4   +51 34 59    22.277   22.514  102.4    2.5   265   30.7 
2026-10-12 00:00 UT   06 18 06.5   +51 36 08    22.267   22.518  103.3    2.5   265   30.7 
2026-10-13 00:00 UT   06 18 03.3   +51 37 17    22.258   22.523  104.2    2.5   264   30.7 

    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.