74P/Smirnova-Chernykh 2018-Apr-20 04:12:12 UTC
2018-Apr-20 04:12:12 UTC
stack 4 x 600 secs
Sky motion 0.19 "/min PA 264.5 deg
Magnitude 16.5 R aperture radius 10.25 arc sec UCAC4
Coma 29" x 22" extended pa 290 deg
Tail 1.6 arc minutes PA 290 deg
Charles Bell H47 Vicksburg
0.3-m Schmidt-Cassegrain + CCD + R filter
t - T = +83.37492 days
Delta = 2.760 AU
r = 3.549 AU
Elongation = 135.7 deg
Phase = 11.4 deg
PsAng = 22.1 deg
PsAMV = 293.0 deg
PlAng = -1.deg
The positiion angle of the tail is near the PA of the negative velocity vector indicating heavier dust particles giving only a small curvature.
Comet 74P was discovered by T. M. Smirnova N. S. Chernykh, Crimean Astrophysical Observatory in March 1975 at magnitude 15 as a diffuse condensation with no tail on photographic plates exposed on March 4 and 16, 1975 (IAUC 1764).
Comet 74P peaked in brightness near its perihelion on 2018-Jan-26 at 3.536 AU. It returns approximately every 8.48 years orbiting between Mars and Jupiter. Its nuclear radius is given as 2.23 km in Comets II. Because its Jupiter Tisserand value is slightly above 3, this comet is classified dynamically as an Encke type comet T_jup = 3.007 a = 4.16 AU. An Encke-type comet, as defined by Levison and Duncan (TJupiter > 3; a < aJupiter). This comet experienced close enounters with Jupiter in Oct 1955 and 1963 and is expected to pass close to Jupiter again in 2021 and 2030.
Prior to October 28, 1955, the object was orbiting outside of the orbit of Jupiter. After the close approach on 1955-Oct-28 at 0.246 au, the object began orbiting inside the ellipse of Jupiter, i.e. capture of a centaur. The comet was discovered within a subsequent revolution in 1975 after its period and perihelion distance had been shortened. At time of discovery the object was about 5 months prior tp perihelion.
1975 Mar. 4.77955 = 1975-Mar-04 18:42:33
t - T = -154.454151389 days or about 5 months
r = 3.607 au
delta = 2.704 au
Elongation = 151.5 deg
Orbital Elements at Epoch 2442640.5 (1975-Aug-16.0) TDB
Reference: SAO/1975 (heliocentric ecliptic J2000)