78P/Gehrels 2
Metadata
| Parameter | Value |
|---|---|
| Designation | 78P/Gehrels 2 |
| Type | P |
| Perihelion (tp_cal, UTC) | 2019-04-03T05:24:15.050880Z |
| Orbit solution date (soln_date, UTC) | 2026-03-07T15:22:14Z |
| Obs used | 6064 |
| NEO | - |
| M1 | 9.100 |
| K1 | 13.250 |
| PC | 0.030 |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2016-01-21.0000000 |
| e | 0.46118333 |
| q (au) | 2.013818 |
| a (au) | 3.737483 |
| i (deg) | 6.250321 |
| Ω (om, deg) | 210.558992 |
| ω (w, deg) | 192.733774 |
| M (ma, deg) | 200.646435 |
Magnitude
Scatter + Global Linear
$$ M_a = (7.459 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 7.459 |
| n | 6.000 |
| gf | 1.000 |
| gb | -1.000 |
| k | 1.000 |
| δ90 | 10.000 |
| 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 |
|---|---|---|---|
| 2025-04-25 | 2025-10-23 | -9.8145 | +3.836 |
| 2025-10-23 | 2026-01-25 | +4.6435 | -2.223 |
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) |
|---|---|---|---|---|
| 2026-06-01 00:00 | 02:51:51.38 | +16:14:45.7 | HIP 13358 | 15.11 |
| 2026-06-01 12:00 | 02:53:03.32 | +16:19:00.1 | HIP 13448 | 10.21 |
| 2026-06-02 00:00 | 02:54:15.30 | +16:23:12.9 | HIP 13601 | 15.58 |
| 2026-06-02 12:00 | 02:55:27.33 | +16:27:23.9 | HIP 13601 | 9.16 |
| 2026-06-03 00:00 | 02:56:39.40 | +16:31:33.3 | HIP 13786 | 18.25 |
| 2026-06-03 12:00 | 02:57:51.52 | +16:35:41.0 | HIP 13786 | 18.87 |
| 2026-06-04 00:00 | 02:59:03.68 | +16:39:47.0 | HIP 13786 | 31.78 |
| 2026-06-04 12:00 | 03:00:15.88 | +16:43:51.2 | HIP 14098 | 26.01 |
| 2026-06-05 00:00 | 03:01:28.12 | +16:47:53.7 | HIP 14098 | 17.64 |
| 2026-06-05 12:00 | 03:02:40.40 | +16:51:54.5 | HIP 14098 | 24.01 |
| 2026-06-06 00:00 | 03:03:52.72 | +16:55:53.5 | HIP 14098 | 38.36 |
| 2026-06-06 12:00 | 03:05:05.09 | +16:59:50.8 | HIP 14569 | 43.39 |
| 2026-06-07 00:00 | 03:06:17.49 | +17:03:46.2 | HIP 14569 | 26.12 |
| 2026-06-07 12:00 | 03:07:29.92 | +17:07:39.9 | HIP 14569 | 10.60 |
| 2026-06-08 00:00 | 03:08:42.40 | +17:11:31.8 | HIP 14569 | 13.10 |
| 2026-06-08 12:00 | 03:09:54.91 | +17:15:21.9 | HIP 14682 | 3.44 |
| 2026-06-09 00:00 | 03:11:07.46 | +17:19:10.2 | HIP 14901 | 16.44 |
| 2026-06-09 12:00 | 03:12:20.04 | +17:22:56.6 | HIP 14901 | 4.96 |
| 2026-06-10 00:00 | 03:13:32.66 | +17:26:41.2 | HIP 14901 | 20.18 |
| 2026-06-10 12:00 | 03:14:45.31 | +17:30:23.9 | HIP 15052 | 25.46 |
| 2026-06-11 00:00 | 03:15:57.99 | +17:34:04.8 | HIP 15285 | 17.74 |
| 2026-06-11 12:00 | 03:17:10.70 | +17:37:43.8 | HIP 15285 | 3.37 |
| 2026-06-12 00:00 | 03:18:23.44 | +17:41:20.9 | HIP 15285 | 18.31 |
| 2026-06-12 12:00 | 03:19:36.21 | +17:44:56.1 | HIP 15519 | 15.86 |
| 2026-06-13 00:00 | 03:20:49.01 | +17:48:29.4 | HIP 15519 | 21.92 |
| 2026-06-13 12:00 | 03:22:01.84 | +17:52:00.8 | HIP 15724 | 11.20 |
| 2026-06-14 00:00 | 03:23:14.69 | +17:55:30.2 | HIP 15724 | 15.62 |
| 2026-06-14 12:00 | 03:24:27.56 | +17:58:57.7 | HIP 15954 | 19.66 |
| 2026-06-15 00:00 | 03:25:40.46 | +18:02:23.3 | HIP 15954 | 18.16 |
| 2026-06-15 12:00 | 03:26:53.38 | +18:05:46.9 | HIP 15954 | 29.95 |
| 2026-06-16 00:00 | 03:28:06.32 | +18:09:08.5 | HIP 16077 | 39.22 |
| 2026-06-16 12:00 | 03:29:19.28 | +18:12:28.2 | HIP 16271 | 32.52 |
| 2026-06-17 00:00 | 03:30:32.26 | +18:15:45.9 | HIP 16414 | 22.67 |
| 2026-06-17 12:00 | 03:31:45.26 | +18:19:01.5 | HIP 16414 | 23.45 |
| 2026-06-18 00:00 | 03:32:58.27 | +18:22:15.2 | HIP 16613 | 14.68 |
| 2026-06-18 12:00 | 03:34:11.30 | +18:25:26.9 | HIP 16613 | 12.97 |
| 2026-06-19 00:00 | 03:35:24.34 | +18:28:36.5 | HIP 16811 | 15.57 |
| 2026-06-19 12:00 | 03:36:37.40 | +18:31:44.1 | HIP 16811 | 10.56 |
| 2026-06-20 00:00 | 03:37:50.47 | +18:34:49.7 | HIP 16944 | 6.67 |
| 2026-06-20 12:00 | 03:39:03.55 | +18:37:53.2 | HIP 17076 | 16.38 |
| 2026-06-21 00:00 | 03:40:16.63 | +18:40:54.7 | HIP 17076 | 20.52 |
| 2026-06-21 12:00 | 03:41:29.73 | +18:43:54.2 | HIP 17282 | 32.47 |
| 2026-06-22 00:00 | 03:42:42.84 | +18:46:51.5 | HIP 17421 | 18.80 |