65P/Gunn
Metadata
| Parameter | Value |
|---|---|
| Designation | 65P/Gunn |
| Type | P |
| Perihelion (tp_cal, UTC) | 2017-10-17T19:31:35.273280Z |
| Orbit solution date (soln_date, UTC) | 2026-07-20T21:56:35Z |
| Obs used | 3136 |
| NEO | - |
| M1 | 11.600 |
| K1 | 6.500 |
| PC | - |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2020-08-20.0000000 |
| e | 0.24981305 |
| q (au) | 2.914034 |
| a (au) | 3.884410 |
| i (deg) | 9.182676 |
| Ω (om, deg) | 62.020549 |
| ω (w, deg) | 213.811389 |
| M (ma, deg) | 133.528294 |
Magnitude
Scatter + Global Linear
$$ M_a = (11.214 + 2.704\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.214 |
| n | 2.704 |
| gf | 0.851 |
| gb | -0.500 |
| k | 0.951 |
| 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 | 2024-04-01 | -7.0757 | +3.602 |
| 2024-04-01 | 2026-07-23 | +5.0768 | -2.814 |
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) |
|---|---|---|---|---|
| 2026-07-29 00:00 | 00:53:48.77 | -05:09:35.3 | HIP 4308 | 26.36 |
| 2026-07-29 12:00 | 00:53:52.61 | -05:10:11.7 | HIP 4308 | 25.23 |
| 2026-07-30 00:00 | 00:53:56.18 | -05:10:49.6 | HIP 4308 | 24.15 |
| 2026-07-30 12:00 | 00:53:59.48 | -05:11:29.0 | HIP 4308 | 23.09 |
| 2026-07-31 00:00 | 00:54:02.51 | -05:12:09.9 | HIP 4308 | 22.08 |
| 2026-07-31 12:00 | 00:54:05.27 | -05:12:52.3 | HIP 4308 | 21.10 |
| 2026-08-01 00:00 | 00:54:07.76 | -05:13:36.2 | HIP 4308 | 20.16 |
| 2026-08-01 12:00 | 00:54:09.98 | -05:14:21.7 | HIP 4308 | 19.25 |
| 2026-08-02 00:00 | 00:54:11.93 | -05:15:08.6 | HIP 4308 | 18.40 |
| 2026-08-02 12:00 | 00:54:13.60 | -05:15:57.0 | HIP 4308 | 17.59 |
| 2026-08-03 00:00 | 00:54:15.00 | -05:16:46.9 | HIP 4308 | 16.83 |
| 2026-08-03 12:00 | 00:54:16.13 | -05:17:38.2 | HIP 4308 | 16.13 |
| 2026-08-04 00:00 | 00:54:16.98 | -05:18:31.1 | HIP 4308 | 15.50 |
| 2026-08-04 12:00 | 00:54:17.56 | -05:19:25.4 | HIP 4308 | 14.95 |
| 2026-08-05 00:00 | 00:54:17.86 | -05:20:21.1 | HIP 4308 | 14.48 |
| 2026-08-05 12:00 | 00:54:17.89 | -05:21:18.3 | HIP 4308 | 14.13 |
| 2026-08-06 00:00 | 00:54:17.64 | -05:22:17.0 | HIP 4308 | 13.88 |
| 2026-08-06 12:00 | 00:54:17.11 | -05:23:17.0 | HIP 4308 | 13.77 |
| 2026-08-07 00:00 | 00:54:16.30 | -05:24:18.5 | HIP 4308 | 13.80 |
| 2026-08-07 12:00 | 00:54:15.22 | -05:25:21.5 | HIP 4308 | 13.97 |
| 2026-08-08 00:00 | 00:54:13.85 | -05:26:25.8 | HIP 4308 | 14.29 |
| 2026-08-08 12:00 | 00:54:12.21 | -05:27:31.5 | HIP 4308 | 14.76 |
| 2026-08-09 00:00 | 00:54:10.29 | -05:28:38.6 | HIP 4308 | 15.38 |
| 2026-08-09 12:00 | 00:54:08.10 | -05:29:47.1 | HIP 4308 | 16.14 |
| 2026-08-10 00:00 | 00:54:05.62 | -05:30:56.9 | HIP 4156 | 16.05 |
| 2026-08-10 12:00 | 00:54:02.86 | -05:32:08.1 | HIP 4156 | 14.98 |
| 2026-08-11 00:00 | 00:53:59.83 | -05:33:20.6 | HIP 4156 | 13.89 |
| 2026-08-11 12:00 | 00:53:56.52 | -05:34:34.4 | HIP 4156 | 12.79 |
| 2026-08-12 00:00 | 00:53:52.93 | -05:35:49.6 | HIP 4156 | 11.71 |
| 2026-08-12 12:00 | 00:53:49.06 | -05:37:06.0 | HIP 4156 | 10.67 |
| 2026-08-13 00:00 | 00:53:44.91 | -05:38:23.7 | HIP 4156 | 9.71 |
| 2026-08-13 12:00 | 00:53:40.49 | -05:39:42.7 | HIP 4156 | 8.90 |
| 2026-08-14 00:00 | 00:53:35.79 | -05:41:02.9 | HIP 4156 | 8.32 |
| 2026-08-14 12:00 | 00:53:30.82 | -05:42:24.3 | HIP 4156 | 8.05 |
| 2026-08-15 00:00 | 00:53:25.57 | -05:43:46.9 | HIP 4156 | 8.17 |
| 2026-08-15 12:00 | 00:53:20.05 | -05:45:10.8 | HIP 4156 | 8.70 |
| 2026-08-16 00:00 | 00:53:14.25 | -05:46:35.8 | HIP 4156 | 9.62 |
| 2026-08-16 12:00 | 00:53:08.18 | -05:48:01.9 | HIP 4156 | 10.85 |
| 2026-08-17 00:00 | 00:53:01.84 | -05:49:29.2 | HIP 4156 | 12.34 |
| 2026-08-17 12:00 | 00:52:55.23 | -05:50:57.6 | HIP 4156 | 14.04 |
| 2026-08-18 00:00 | 00:52:48.35 | -05:52:27.1 | HIP 4068 | 11.90 |
| 2026-08-18 12:00 | 00:52:41.20 | -05:53:57.6 | HIP 4068 | 9.57 |
| 2026-08-19 00:00 | 00:52:33.79 | -05:55:29.2 | HIP 4068 | 7.18 |