C/2017 G3 (PANSTARRS)
| Parameter |
Value |
| Designation |
C/2017 G3 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-04-15T00:45:00.587520Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:33Z |
| Obs used |
155 |
| NEO |
- |
| M1 |
14.500 |
| K1 |
9.250 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-05-26.0000000 |
| e |
0.99105792 |
| q (au) |
2.590476 |
| a (au) |
289.694902 |
| i (deg) |
159.051707 |
| Ω (om, deg) |
279.473026 |
| ω (w, deg) |
73.096573 |
| M (ma, deg) |
0.008189 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.161 + 3.830\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.161 |
| n |
3.830 |
| gf |
0.963 |
| gb |
-0.606 |
| k |
0.903 |
| δ90 |
7.076 |
| Parameter |
Symbol |
Range |
Description |
| Absolute magnitude at 1 AU from Sun and Earth |
H0 |
-5 to 20 |
Intrinsic brightness of the comet |
| Photometric slope parameter |
n |
2 to 6 |
Rate of brightness change with heliocentric distance |
| Forward scattering asymmetry factor |
gf |
0.8 to 1 |
Degree of forward scattering |
| Backward scattering asymmetry factor |
gb |
-1 to -0.5 |
Degree of backward scattering |
| Partitioning coefficient |
k |
0.8 to 1 |
Ratio between forward/backward scattering contributions |
| Dust-to-gas brightness ratio |
δ90 |
1 to 10 |
Relative contribution of dust scattering to gas emission |
Reference: EPSC-DPS2025-160
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2017-04-15 |
2017-11-29 |
+5.0987 |
-2.138 |
| 2017-11-29 |
2018-03-16 |
-13.0180 |
+7.888 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
04:23:06.15 |
+09:56:04.6 |
HIP 20447 |
10.48 |
| 2026-02-03 12:00 |
04:23:03.37 |
+09:56:11.0 |
HIP 20447 |
10.36 |
| 2026-02-04 00:00 |
04:23:00.63 |
+09:56:17.5 |
HIP 20447 |
10.28 |
| 2026-02-04 12:00 |
04:22:57.94 |
+09:56:24.2 |
HIP 20447 |
10.26 |
| 2026-02-05 00:00 |
04:22:55.31 |
+09:56:31.1 |
HIP 20447 |
10.29 |
| 2026-02-05 12:00 |
04:22:52.71 |
+09:56:38.1 |
HIP 20447 |
10.36 |
| 2026-02-06 00:00 |
04:22:50.17 |
+09:56:45.3 |
HIP 20447 |
10.47 |
| 2026-02-06 12:00 |
04:22:47.68 |
+09:56:52.6 |
HIP 20447 |
10.62 |
| 2026-02-07 00:00 |
04:22:45.23 |
+09:57:00.1 |
HIP 20447 |
10.81 |
| 2026-02-07 12:00 |
04:22:42.84 |
+09:57:07.7 |
HIP 20447 |
11.02 |
| 2026-02-08 00:00 |
04:22:40.49 |
+09:57:15.5 |
HIP 20447 |
11.27 |
| 2026-02-08 12:00 |
04:22:38.19 |
+09:57:23.5 |
HIP 20447 |
11.54 |
| 2026-02-09 00:00 |
04:22:35.94 |
+09:57:31.6 |
HIP 20447 |
11.83 |
| 2026-02-09 12:00 |
04:22:33.74 |
+09:57:39.8 |
HIP 20447 |
12.14 |
| 2026-02-10 00:00 |
04:22:31.59 |
+09:57:48.2 |
HIP 20447 |
12.46 |
| 2026-02-10 12:00 |
04:22:29.49 |
+09:57:56.7 |
HIP 20447 |
12.80 |
| 2026-02-11 00:00 |
04:22:27.43 |
+09:58:05.4 |
HIP 20447 |
13.15 |
| 2026-02-11 12:00 |
04:22:25.43 |
+09:58:14.3 |
HIP 20447 |
13.50 |
| 2026-02-12 00:00 |
04:22:23.48 |
+09:58:23.2 |
HIP 20447 |
13.86 |
| 2026-02-12 12:00 |
04:22:21.57 |
+09:58:32.3 |
HIP 20447 |
14.23 |
| 2026-02-13 00:00 |
04:22:19.72 |
+09:58:41.6 |
HIP 20447 |
14.60 |
| 2026-02-13 12:00 |
04:22:17.91 |
+09:58:51.0 |
HIP 20447 |
14.97 |
| 2026-02-14 00:00 |
04:22:16.16 |
+09:59:00.5 |
HIP 20447 |
15.34 |
| 2026-02-14 12:00 |
04:22:14.45 |
+09:59:10.2 |
HIP 20447 |
15.71 |
| 2026-02-15 00:00 |
04:22:12.80 |
+09:59:20.0 |
HIP 20447 |
16.08 |
| 2026-02-15 12:00 |
04:22:11.19 |
+09:59:30.0 |
HIP 20447 |
16.45 |
| 2026-02-16 00:00 |
04:22:09.63 |
+09:59:40.1 |
HIP 20447 |
16.81 |
| 2026-02-16 12:00 |
04:22:08.13 |
+09:59:50.3 |
HIP 20447 |
17.17 |
| 2026-02-17 00:00 |
04:22:06.67 |
+10:00:00.6 |
HIP 20447 |
17.53 |
| 2026-02-17 12:00 |
04:22:05.26 |
+10:00:11.1 |
HIP 20447 |
17.88 |
| 2026-02-18 00:00 |
04:22:03.90 |
+10:00:21.7 |
HIP 20447 |
18.23 |
| 2026-02-18 12:00 |
04:22:02.60 |
+10:00:32.4 |
HIP 20447 |
18.57 |
| 2026-02-19 00:00 |
04:22:01.34 |
+10:00:43.3 |
HIP 20447 |
18.91 |
| 2026-02-19 12:00 |
04:22:00.13 |
+10:00:54.3 |
HIP 20447 |
19.24 |
| 2026-02-20 00:00 |
04:21:58.97 |
+10:01:05.4 |
HIP 20447 |
19.57 |
| 2026-02-20 12:00 |
04:21:57.86 |
+10:01:16.6 |
HIP 20447 |
19.89 |
| 2026-02-21 00:00 |
04:21:56.80 |
+10:01:27.9 |
HIP 20447 |
20.20 |
| 2026-02-21 12:00 |
04:21:55.79 |
+10:01:39.4 |
HIP 20447 |
20.51 |
| 2026-02-22 00:00 |
04:21:54.83 |
+10:01:51.0 |
HIP 20447 |
20.81 |
| 2026-02-22 12:00 |
04:21:53.92 |
+10:02:02.7 |
HIP 20447 |
21.11 |
| 2026-02-23 00:00 |
04:21:53.06 |
+10:02:14.5 |
HIP 20447 |
21.40 |
| 2026-02-23 12:00 |
04:21:52.25 |
+10:02:26.4 |
HIP 20447 |
21.68 |
| 2026-02-24 00:00 |
04:21:51.49 |
+10:02:38.4 |
HIP 20447 |
21.95 |