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
$$ M_a = (7.453 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 7.453 |
| 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 | -5.9460 | +2.177 |
| 2025-10-23 | 2026-01-12 | +4.4137 | -2.105 |
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) |
|---|---|---|---|---|
| 2026-03-26 00:00 | 00:20:04.12 | +04:02:48.1 | HIP 1455 | 32.64 |
| 2026-03-26 12:00 | 00:21:07.81 | +04:08:48.2 | HIP 1628 | 39.64 |
| 2026-03-27 00:00 | 00:22:11.56 | +04:14:48.4 | HIP 1894 | 39.26 |
| 2026-03-27 12:00 | 00:23:15.37 | +04:20:48.6 | HIP 1894 | 36.65 |
| 2026-03-28 00:00 | 00:24:19.24 | +04:26:48.9 | HIP 2046 | 39.60 |
| 2026-03-28 12:00 | 00:25:23.18 | +04:32:49.2 | HIP 2195 | 35.14 |
| 2026-03-29 00:00 | 00:26:27.18 | +04:38:49.5 | HIP 2195 | 19.16 |
| 2026-03-29 12:00 | 00:27:31.24 | +04:44:49.9 | HIP 2195 | 8.94 |
| 2026-03-30 00:00 | 00:28:35.36 | +04:50:50.3 | HIP 2195 | 19.36 |
| 2026-03-30 12:00 | 00:29:39.55 | +04:56:50.7 | HIP 2358 | 8.95 |
| 2026-03-31 00:00 | 00:30:43.80 | +05:02:51.0 | HIP 2358 | 14.24 |
| 2026-03-31 12:00 | 00:31:48.11 | +05:08:51.4 | HIP 2510 | 18.09 |
| 2026-04-01 00:00 | 00:32:52.49 | +05:14:51.7 | HIP 2659 | 21.66 |
| 2026-04-01 12:00 | 00:33:56.94 | +05:20:52.0 | HIP 2659 | 24.33 |
| 2026-04-02 00:00 | 00:35:01.44 | +05:26:52.2 | HIP 2918 | 28.86 |
| 2026-04-02 12:00 | 00:36:06.01 | +05:32:52.3 | HIP 2918 | 15.08 |
| 2026-04-03 00:00 | 00:37:10.65 | +05:38:52.4 | HIP 2918 | 14.52 |
| 2026-04-03 12:00 | 00:38:15.35 | +05:44:52.3 | HIP 2991 | 6.93 |
| 2026-04-04 00:00 | 00:39:20.12 | +05:50:52.2 | HIP 3033 | 15.44 |
| 2026-04-04 12:00 | 00:40:24.95 | +05:56:51.9 | HIP 3033 | 27.84 |
| 2026-04-05 00:00 | 00:41:29.84 | +06:02:51.5 | HIP 3338 | 27.28 |
| 2026-04-05 12:00 | 00:42:34.81 | +06:08:51.0 | HIP 3393 | 27.36 |
| 2026-04-06 00:00 | 00:43:39.83 | +06:14:50.3 | HIP 3393 | 20.21 |
| 2026-04-06 12:00 | 00:44:44.93 | +06:20:49.5 | HIP 3393 | 25.74 |
| 2026-04-07 00:00 | 00:45:50.09 | +06:26:48.4 | HIP 3697 | 29.17 |
| 2026-04-07 12:00 | 00:46:55.32 | +06:32:47.2 | HIP 3697 | 13.62 |
| 2026-04-08 00:00 | 00:48:00.61 | +06:38:45.8 | HIP 3697 | 10.81 |
| 2026-04-08 12:00 | 00:49:05.97 | +06:44:44.2 | HIP 3869 | 21.99 |
| 2026-04-09 00:00 | 00:50:11.40 | +06:50:42.3 | HIP 3972 | 13.41 |
| 2026-04-09 12:00 | 00:51:16.89 | +06:56:40.2 | HIP 3972 | 4.22 |
| 2026-04-10 00:00 | 00:52:22.45 | +07:02:37.8 | HIP 4067 | 14.81 |
| 2026-04-10 12:00 | 00:53:28.08 | +07:08:35.2 | HIP 4219 | 9.35 |
| 2026-04-11 00:00 | 00:54:33.77 | +07:14:32.3 | HIP 4219 | 11.13 |
| 2026-04-11 12:00 | 00:55:39.53 | +07:20:29.1 | HIP 4445 | 18.88 |
| 2026-04-12 00:00 | 00:56:45.36 | +07:26:25.6 | HIP 4445 | 2.71 |
| 2026-04-12 12:00 | 00:57:51.26 | +07:32:21.8 | HIP 4526 | 4.69 |
| 2026-04-13 00:00 | 00:58:57.22 | +07:38:17.6 | HIP 4601 | 4.88 |
| 2026-04-13 12:00 | 01:00:03.25 | +07:44:13.1 | HIP 4601 | 16.03 |
| 2026-04-14 00:00 | 01:01:09.35 | +07:50:08.2 | HIP 4763 | 11.92 |
| 2026-04-14 12:00 | 01:02:15.51 | +07:56:02.9 | HIP 4832 | 2.18 |
| 2026-04-15 00:00 | 01:03:21.74 | +08:01:57.3 | HIP 4906 | 10.57 |
| 2026-04-15 12:00 | 01:04:28.04 | +08:07:51.2 | HIP 5103 | 18.39 |
| 2026-04-16 00:00 | 01:05:34.41 | +08:13:44.7 | HIP 5103 | 6.68 |