78P/Gehrels 2
Metadata
| Parameter | Value |
|---|---|
| Designation | 78P/Gehrels 2 |
| Type | P |
| Perihelion (tp_cal, UTC) | 2019-04-03T03:01:02.026560Z |
| Orbit solution date (soln_date, UTC) | 2026-10-01T14:58:09Z |
| Obs used | 6319 |
| NEO | - |
| M1 | 9.000 |
| K1 | 13.500 |
| PC | 0.030 |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2016-07-07.0000000 |
| e | 0.46111112 |
| q (au) | 2.014293 |
| a (au) | 3.737864 |
| i (deg) | 6.249765 |
| Ω (om, deg) | 210.556335 |
| ω (w, deg) | 192.718778 |
| M (ma, deg) | 223.597168 |
Magnitude
Scatter + Global Linear
$$ M_a = (7.361 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 7.361 |
| 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 | 2026-01-25 | +23.0128 | -7.750 |
| 2026-01-25 | 2025-10-23 | -15.0502 | +6.193 |
| 2025-10-23 | 2026-09-29 | +4.9738 | -2.321 |
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) |
|---|---|---|---|---|
| 2026-09-25 00:00 | 07:11:13.38 | +17:42:07.3 | HIP 34738 | 18.15 |
| 2026-09-25 12:00 | 07:12:02.88 | +17:39:11.4 | HIP 34738 | 16.46 |
| 2026-09-26 00:00 | 07:12:52.11 | +17:36:14.7 | HIP 34902 | 11.84 |
| 2026-09-26 12:00 | 07:13:41.06 | +17:33:17.2 | HIP 34902 | 9.16 |
| 2026-09-27 00:00 | 07:14:29.75 | +17:30:19.0 | HIP 34902 | 17.76 |
| 2026-09-27 12:00 | 07:15:18.17 | +17:27:20.0 | HIP 34902 | 28.82 |
| 2026-09-28 00:00 | 07:16:06.31 | +17:24:20.2 | HIP 35369 | 40.21 |
| 2026-09-28 12:00 | 07:16:54.18 | +17:21:19.8 | HIP 35369 | 29.60 |
| 2026-09-29 00:00 | 07:17:41.77 | +17:18:18.7 | HIP 35369 | 20.37 |
| 2026-09-29 12:00 | 07:18:29.08 | +17:15:16.9 | HIP 35369 | 15.17 |
| 2026-09-30 00:00 | 07:19:16.11 | +17:12:14.4 | HIP 35369 | 17.80 |
| 2026-09-30 12:00 | 07:20:02.86 | +17:09:11.3 | HIP 35369 | 25.92 |
| 2026-10-01 00:00 | 07:20:49.33 | +17:06:07.5 | HIP 35658 | 24.60 |
| 2026-10-01 12:00 | 07:21:35.51 | +17:03:03.2 | HIP 35658 | 19.81 |
| 2026-10-02 00:00 | 07:22:21.40 | +16:59:58.3 | HIP 35720 | 15.51 |
| 2026-10-02 12:00 | 07:23:07.01 | +16:56:52.8 | HIP 35720 | 18.25 |
| 2026-10-03 00:00 | 07:23:52.32 | +16:53:46.7 | HIP 35875 | 13.31 |
| 2026-10-03 12:00 | 07:24:37.34 | +16:50:40.2 | HIP 35875 | 15.60 |
| 2026-10-04 00:00 | 07:25:22.06 | +16:47:33.1 | HIP 36107 | 13.45 |
| 2026-10-04 12:00 | 07:26:06.48 | +16:44:25.5 | HIP 36107 | 5.73 |
| 2026-10-05 00:00 | 07:26:50.61 | +16:41:17.5 | HIP 36107 | 11.38 |
| 2026-10-05 12:00 | 07:27:34.43 | +16:38:09.0 | HIP 36107 | 21.60 |
| 2026-10-06 00:00 | 07:28:17.95 | +16:35:00.0 | HIP 36408 | 24.99 |
| 2026-10-06 12:00 | 07:29:01.16 | +16:31:50.7 | HIP 36408 | 22.31 |
| 2026-10-07 00:00 | 07:29:44.06 | +16:28:41.0 | HIP 36406 | 19.22 |
| 2026-10-07 12:00 | 07:30:26.66 | +16:25:30.9 | HIP 36406 | 21.04 |
| 2026-10-08 00:00 | 07:31:08.94 | +16:22:20.5 | HIP 36689 | 24.45 |
| 2026-10-08 12:00 | 07:31:50.91 | +16:19:09.7 | HIP 36689 | 14.41 |
| 2026-10-09 00:00 | 07:32:32.56 | +16:15:58.6 | HIP 36689 | 6.42 |
| 2026-10-09 12:00 | 07:33:13.89 | +16:12:47.3 | HIP 36689 | 9.69 |
| 2026-10-10 00:00 | 07:33:54.91 | +16:09:35.6 | HIP 36716 | 15.76 |
| 2026-10-10 12:00 | 07:34:35.60 | +16:06:23.8 | HIP 36760 | 22.00 |
| 2026-10-11 00:00 | 07:35:15.97 | +16:03:11.7 | HIP 37019 | 18.06 |
| 2026-10-11 12:00 | 07:35:56.01 | +15:59:59.4 | HIP 37019 | 9.55 |
| 2026-10-12 00:00 | 07:36:35.73 | +15:56:46.9 | HIP 37019 | 7.86 |
| 2026-10-12 12:00 | 07:37:15.11 | +15:53:34.3 | HIP 37019 | 15.28 |
| 2026-10-13 00:00 | 07:37:54.17 | +15:50:21.5 | HIP 37242 | 21.31 |
| 2026-10-13 12:00 | 07:38:32.89 | +15:47:08.6 | HIP 37242 | 19.41 |
| 2026-10-14 00:00 | 07:39:11.28 | +15:43:55.6 | HIP 37242 | 22.20 |
| 2026-10-14 12:00 | 07:39:49.33 | +15:40:42.5 | HIP 37242 | 28.25 |
| 2026-10-15 00:00 | 07:40:27.05 | +15:37:29.4 | HIP 37499 | 19.46 |
| 2026-10-15 12:00 | 07:41:04.42 | +15:34:16.2 | HIP 37499 | 10.32 |
| 2026-10-16 00:00 | 07:41:41.46 | +15:31:03.0 | HIP 37499 | 4.15 |