On Mar. 13, 2014 the Brazilian amateur Cristovao Jacques discovered a comet near the border of the constellations Centaurus / Hydra, using the 45-cm SONEAR telescope. On the images comet C/2014 E2 (Jacques) was a magnitude 15 object with a significantly condensed 35" coma and a fan-shaped 65" tail in p.a. 290-340°. Additional observers noted a strongly condensed inner part and a very diffuse, 2.8' outer coma, plus a 3' tail in p.a. 15°. The total brightness was of magnitude 12.0. The comet will reach perihelion at the beginning of July at a quite close solar distance, expected to reach a maximum brightness of about 8.0 mag (CBET 3828 / MPEC 2014-G81). From mid-European latitudes it may be observed until the first week of May in the evening sky (then about 10.0 mag, and located in the constellation Monoceros). It reappears in the morning sky in the second half of July – then located in the constellation Auriga – at 8.0 mag. It should remain brighter than 16.0 mag until December, passing through the constellations of Perseus, Cassiopeia, Cepheus, Cygnus, Vulpecula, Sagitta and Aquila.

Based on 115 reports from 10 members of the German Comet Section and 535 international observations three separate periods of brightness evolution can be distinguished. While the comet showed a high degree of activity during the first phase (until May 15 = 50 days prior to perihelion), this came to a halt in the second phase. After perihelion the comet showed a steady activity decrease. Pre-perihelion the maximum brightness observed was 7.4 mag. Post-perihelion the comet displayed its maximum brightness of 6.4 mag during the days it reappeared in the morning sky (around July 10). The observations seem to show the comet 0.4 mag brighter during those days. However, the comet was then a twilight object very low above the horizon. Thus these observations feature a larger uncertainty, for which reason I prefer a value derived by the formula. The brightness evolution may be described with the following formulae:

Heliocentric Magnitude versus r

The apparent coma diameter increased steadily from 3' at the beginning of the apparition to 9' at the end of April; during the final days of May it measured still 8'. The significant decrease thereafter may be primarily the result of the deteriorating observing conditions (plus the influence of the increasing impact of the solar wind during those days). The suboptimal conditions are again responsible for the reported diameters of only 2.5' in the first days of the morning apparition. The combination of improving observing conditions and the comet approaching Earth (with perigee at 0.56 AU on Aug. 28) are responsible for the increase of the apparent coma diameter, which reached its maximum of 13' around Aug. 25. Immediately thereafter the apparent coma diameter decreased continuously and rapidly, measuring only 1.5' at the start of November. The absolute coma diameter increased from 150.000 km at the start of the apparition to the maximum of 575.000 km at the end of May. The following decrease to 375.000 km was primarily the result of the deteriorating conditions. These affected also the absolute coma diameter of only 175.000 km at the beginning of the morning visibility. At the end of July the derived absolute coma diameter measured 375.000 km. This value remained constant until the end of September. Thereafter it decreased slowly, measuring only 100.000 km during the first days of November.

Total Brightness and Coma Diameter

The degree of condensation was DC 4-5 at the beginning of the apparition, but surprisingly dropped to DC 3 until mid-May! In parallel to the change of the brightness parameters it increased significantly, peaking at DC 6 by mid-June. During the first three weeks after perihelion it was estimated to be still DC 6, but decreased during the following weeks, reaching DC 2 at the end of September. This value has been constant since. While the coma was compact with a high surface brightness when it reappeared, it showed a large and very diffuse outer and a significantly brighter inner coma around perigee. The false nucleus peaked around magnitude 11. In mid-September the false nucleus could only barely seen, instead a small central knot was observed.

Tail Length

Visual tail sightings have been reported between end of May and end of September, with the length reaching about 1.0° (3.5 Mio. km). Pre-perihelion the tail pointed towards SE, post-perihelion it rotated from NW towards E.

Andreas Kammerer

FGK observations