78P/Gehrels 2
Metadata
| Parameter | Value |
|---|---|
| Designation | 78P/Gehrels 2 |
| Type | P |
| Perihelion (tp_cal, UTC) | 2019-04-03T05:21:38.623680Z |
| Orbit solution date (soln_date, UTC) | 2026-07-28T20:12:01Z |
| Obs used | 6074 |
| NEO | - |
| M1 | 9.100 |
| K1 | 13.250 |
| PC | 0.030 |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2016-01-28.0000000 |
| e | 0.46117657 |
| q (au) | 2.013856 |
| a (au) | 3.737506 |
| i (deg) | 6.250279 |
| Ω (om, deg) | 210.558824 |
| ω (w, deg) | 192.733097 |
| M (ma, deg) | 201.602988 |
Magnitude
Scatter + Global Linear
$$ M_a = (7.393 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 7.393 |
| 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 | 2026-01-16 | +23.6789 | -8.659 |
| 2026-01-16 | 2025-10-23 | -9.7374 | +3.872 |
| 2025-10-23 | 2026-07-26 | +4.3399 | -2.028 |
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 | 05:11:56.09 | +20:44:58.0 | HIP 24116 | 19.35 |
| 2026-07-29 12:00 | 05:13:06.37 | +20:45:10.5 | HIP 24456 | 25.31 |
| 2026-07-30 00:00 | 05:14:16.56 | +20:45:20.8 | HIP 24456 | 10.75 |
| 2026-07-30 12:00 | 05:15:26.66 | +20:45:28.9 | HIP 24456 | 11.34 |
| 2026-07-31 00:00 | 05:16:36.67 | +20:45:34.9 | HIP 24456 | 26.03 |
| 2026-07-31 12:00 | 05:17:46.58 | +20:45:38.7 | HIP 24778 | 14.20 |
| 2026-08-01 00:00 | 05:18:56.39 | +20:45:40.3 | HIP 24778 | 5.54 |
| 2026-08-01 12:00 | 05:20:06.11 | +20:45:39.7 | HIP 24945 | 8.51 |
| 2026-08-02 00:00 | 05:21:15.73 | +20:45:37.0 | HIP 24945 | 9.78 |
| 2026-08-02 12:00 | 05:22:25.26 | +20:45:32.2 | HIP 25230 | 21.69 |
| 2026-08-03 00:00 | 05:23:34.67 | +20:45:25.2 | HIP 25230 | 10.97 |
| 2026-08-03 12:00 | 05:24:43.99 | +20:45:16.0 | HIP 25337 | 11.96 |
| 2026-08-04 00:00 | 05:25:53.20 | +20:45:04.8 | HIP 25337 | 14.19 |
| 2026-08-04 12:00 | 05:27:02.31 | +20:44:51.3 | HIP 25337 | 27.97 |
| 2026-08-05 00:00 | 05:28:11.31 | +20:44:35.8 | HIP 25668 | 21.13 |
| 2026-08-05 12:00 | 05:29:20.19 | +20:44:18.2 | HIP 25777 | 17.04 |
| 2026-08-06 00:00 | 05:30:28.97 | +20:43:58.4 | HIP 25777 | 11.35 |
| 2026-08-06 12:00 | 05:31:37.64 | +20:43:36.5 | HIP 25936 | 20.91 |
| 2026-08-07 00:00 | 05:32:46.19 | +20:43:12.5 | HIP 26072 | 19.22 |
| 2026-08-07 12:00 | 05:33:54.62 | +20:42:46.5 | HIP 26072 | 14.79 |
| 2026-08-08 00:00 | 05:35:02.94 | +20:42:18.3 | HIP 26281 | 18.89 |
| 2026-08-08 12:00 | 05:36:11.13 | +20:41:48.1 | HIP 26381 | 12.20 |
| 2026-08-09 00:00 | 05:37:19.21 | +20:41:15.8 | HIP 26381 | 4.71 |
| 2026-08-09 12:00 | 05:38:27.16 | +20:40:41.4 | HIP 26381 | 20.05 |
| 2026-08-10 00:00 | 05:39:34.99 | +20:40:05.0 | HIP 26381 | 35.86 |
| 2026-08-10 12:00 | 05:40:42.69 | +20:39:26.5 | HIP 26880 | 24.00 |
| 2026-08-11 00:00 | 05:41:50.25 | +20:38:46.0 | HIP 26880 | 8.29 |
| 2026-08-11 12:00 | 05:42:57.69 | +20:38:03.4 | HIP 26880 | 7.85 |
| 2026-08-12 00:00 | 05:44:05.00 | +20:37:18.8 | HIP 27181 | 22.52 |
| 2026-08-12 12:00 | 05:45:12.17 | +20:36:32.2 | HIP 27181 | 8.20 |
| 2026-08-13 00:00 | 05:46:19.21 | +20:35:43.6 | HIP 27181 | 11.06 |
| 2026-08-13 12:00 | 05:47:26.11 | +20:34:53.0 | HIP 27287 | 19.25 |
| 2026-08-14 00:00 | 05:48:32.86 | +20:34:00.4 | HIP 27421 | 18.33 |
| 2026-08-14 12:00 | 05:49:39.48 | +20:33:05.8 | HIP 27585 | 13.41 |
| 2026-08-15 00:00 | 05:50:45.96 | +20:32:09.3 | HIP 27585 | 6.69 |
| 2026-08-15 12:00 | 05:51:52.29 | +20:31:10.8 | HIP 27746 | 12.85 |
| 2026-08-16 00:00 | 05:52:58.47 | +20:30:10.4 | HIP 27829 | 13.14 |
| 2026-08-16 12:00 | 05:54:04.51 | +20:29:08.0 | HIP 27913 | 13.28 |
| 2026-08-17 00:00 | 05:55:10.40 | +20:28:03.7 | HIP 27913 | 15.96 |
| 2026-08-17 12:00 | 05:56:16.14 | +20:26:57.5 | HIP 28041 | 17.62 |
| 2026-08-18 00:00 | 05:57:21.72 | +20:25:49.3 | HIP 28294 | 24.18 |
| 2026-08-18 12:00 | 05:58:27.16 | +20:24:39.3 | HIP 28294 | 13.15 |
| 2026-08-19 00:00 | 05:59:32.44 | +20:23:27.4 | HIP 28294 | 15.27 |