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	29 Jun 2026	30.6	22.015 AU	22.908 AU	06h01m	+50°14'	27.8°	1.2°	344°

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
2026-06-28 00:00 UT   06 01 06.5   +50 14 30    22.902   22.005   27.4    1.2   347   30.6 
2026-06-29 00:00 UT   06 01 23.9   +50 14 34    22.905   22.010   27.6    1.2   346   30.6 
2026-06-29 23:48 UT   06 01 41.0   +50 14 39    22.908   22.015   27.8    1.2   344   30.6 
2026-06-30 00:00 UT   06 01 41.2   +50 14 39    22.908   22.015   27.8    1.2   344   30.6 
2026-07-01 00:00 UT   06 01 58.5   +50 14 44    22.911   22.020   28.0    1.2   342   30.6 
2026-07-02 00:00 UT   06 02 15.7   +50 14 51    22.914   22.024   28.3    1.3   340   30.6 
2026-07-03 00:00 UT   06 02 32.9   +50 14 59    22.916   22.029   28.6    1.3   338   30.6 
2026-07-04 00:00 UT   06 02 50.1   +50 15 08    22.918   22.034   28.9    1.3   337   30.6 
2026-07-05 00:00 UT   06 03 07.2   +50 15 18    22.920   22.039   29.2    1.3   335   30.6 
2026-07-06 00:00 UT   06 03 24.2   +50 15 28    22.922   22.044   29.6    1.3   333   30.6 
2026-07-07 00:00 UT   06 03 41.2   +50 15 40    22.923   22.049   30.0    1.3   332   30.6 
2026-07-08 00:00 UT   06 03 58.1   +50 15 53    22.924   22.054   30.4    1.3   330   30.6 
2026-07-09 00:00 UT   06 04 15.0   +50 16 07    22.925   22.058   30.8    1.4   329   30.6 

    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.