65P/Gunn
Metadata
| Parameter | Value |
|---|---|
| Designation | 65P/Gunn |
| Type | P |
| Perihelion (tp_cal, UTC) | 2017-10-17T19:32:32.288640Z |
| Orbit solution date (soln_date, UTC) | 2026-09-21T15:25:25Z |
| Obs used | 3168 |
| NEO | - |
| M1 | 11.600 |
| K1 | 6.500 |
| PC | - |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2020-09-15.0000000 |
| e | 0.24977704 |
| q (au) | 2.914295 |
| a (au) | 3.884571 |
| i (deg) | 9.182398 |
| Ω (om, deg) | 62.020378 |
| ω (w, deg) | 213.819148 |
| M (ma, deg) | 136.866938 |
Magnitude
Scatter + Global Linear
$$ M_a = (11.077 + 2.676\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.077 |
| n | 2.676 |
| gf | 0.801 |
| gb | -0.500 |
| k | 0.987 |
| δ90 | 1.000 |
| 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 |
|---|---|---|---|
| 2021-12-05 | 2024-04-28 | -5.7601 | +2.940 |
| 2024-04-28 | 2026-09-17 | +0.6993 | -0.080 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Finding Chart
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-09-20 00:00 | 00:36:51.17 | -07:52:07.2 | HIP 2811 | 15.99 |
| 2026-09-20 12:00 | 00:36:31.21 | -07:53:54.4 | HIP 2811 | 10.93 |
| 2026-09-21 00:00 | 00:36:11.18 | -07:55:40.7 | HIP 2811 | 6.18 |
| 2026-09-21 12:00 | 00:35:51.07 | -07:57:26.4 | HIP 2811 | 3.50 |
| 2026-09-22 00:00 | 00:35:30.90 | -07:59:11.2 | HIP 2811 | 6.49 |
| 2026-09-22 12:00 | 00:35:10.67 | -08:00:55.1 | HIP 2811 | 11.31 |
| 2026-09-23 00:00 | 00:34:50.38 | -08:02:38.3 | HIP 2721 | 15.51 |
| 2026-09-23 12:00 | 00:34:30.04 | -08:04:20.5 | HIP 2721 | 13.68 |
| 2026-09-24 00:00 | 00:34:09.66 | -08:06:01.9 | HIP 2721 | 13.82 |
| 2026-09-24 12:00 | 00:33:49.23 | -08:07:42.3 | HIP 2721 | 15.86 |
| 2026-09-25 00:00 | 00:33:28.76 | -08:09:21.7 | HIP 2721 | 19.23 |
| 2026-09-25 12:00 | 00:33:08.25 | -08:11:00.2 | HIP 2721 | 23.35 |
| 2026-09-26 00:00 | 00:32:47.72 | -08:12:37.6 | HIP 2721 | 27.90 |
| 2026-09-26 12:00 | 00:32:27.16 | -08:14:14.0 | HIP 2394 | 30.56 |
| 2026-09-27 00:00 | 00:32:06.59 | -08:15:49.4 | HIP 2394 | 26.35 |
| 2026-09-27 12:00 | 00:31:45.99 | -08:17:23.6 | HIP 2394 | 22.62 |
| 2026-09-28 00:00 | 00:31:25.39 | -08:18:56.8 | HIP 2394 | 19.62 |
| 2026-09-28 12:00 | 00:31:04.77 | -08:20:28.8 | HIP 2394 | 17.74 |
| 2026-09-29 00:00 | 00:30:44.16 | -08:21:59.6 | HIP 2394 | 17.33 |
| 2026-09-29 12:00 | 00:30:23.54 | -08:23:29.3 | HIP 2394 | 18.49 |
| 2026-09-30 00:00 | 00:30:02.94 | -08:24:57.8 | HIP 2394 | 20.96 |
| 2026-09-30 12:00 | 00:29:42.34 | -08:26:25.0 | HIP 2394 | 24.33 |
| 2026-10-01 00:00 | 00:29:21.76 | -08:27:50.9 | HIP 2394 | 28.28 |
| 2026-10-01 12:00 | 00:29:01.20 | -08:29:15.6 | HIP 2167 | 26.90 |
| 2026-10-02 00:00 | 00:28:40.66 | -08:30:39.0 | HIP 2167 | 21.68 |
| 2026-10-02 12:00 | 00:28:20.15 | -08:32:01.1 | HIP 2167 | 16.51 |
| 2026-10-03 00:00 | 00:27:59.68 | -08:33:21.8 | HIP 2167 | 11.45 |
| 2026-10-03 12:00 | 00:27:39.24 | -08:34:41.1 | HIP 2167 | 6.67 |
| 2026-10-04 00:00 | 00:27:18.85 | -08:35:59.1 | HIP 2167 | 3.55 |
| 2026-10-04 12:00 | 00:26:58.50 | -08:37:15.6 | HIP 2167 | 5.91 |
| 2026-10-05 00:00 | 00:26:38.20 | -08:38:30.7 | HIP 2167 | 10.53 |
| 2026-10-05 12:00 | 00:26:17.97 | -08:39:44.3 | HIP 2167 | 15.48 |
| 2026-10-06 00:00 | 00:25:57.79 | -08:40:56.4 | HIP 2038 | 19.90 |
| 2026-10-06 12:00 | 00:25:37.68 | -08:42:07.1 | HIP 2038 | 21.35 |
| 2026-10-07 00:00 | 00:25:17.64 | -08:43:16.2 | HIP 2038 | 23.81 |
| 2026-10-07 12:00 | 00:24:57.67 | -08:44:23.7 | HIP 2038 | 26.98 |
| 2026-10-08 00:00 | 00:24:37.79 | -08:45:29.7 | HIP 2038 | 30.62 |
| 2026-10-08 12:00 | 00:24:17.98 | -08:46:34.1 | HIP 2038 | 34.59 |
| 2026-10-09 00:00 | 00:23:58.27 | -08:47:36.9 | HIP 1792 | 31.68 |
| 2026-10-09 12:00 | 00:23:38.65 | -08:48:38.1 | HIP 1792 | 28.33 |
| 2026-10-10 00:00 | 00:23:19.13 | -08:49:37.6 | HIP 1792 | 25.54 |
| 2026-10-10 12:00 | 00:22:59.71 | -08:50:35.5 | HIP 1792 | 23.49 |
| 2026-10-11 00:00 | 00:22:40.40 | -08:51:31.7 | HIP 1792 | 22.36 |