399P/PANSTARRS
Metadata
| Parameter | Value |
|---|---|
| Designation | 399P/PANSTARRS |
| Type | P |
| Perihelion (tp_cal, UTC) | 2021-05-26T08:38:38.169600Z |
| Orbit solution date (soln_date, UTC) | 2026-06-09T11:12:48Z |
| Obs used | 411 |
| NEO | - |
| M1 | 15.900 |
| K1 | 4.500 |
| PC | - |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2017-11-29.0000000 |
| e | 0.44202403 |
| q (au) | 2.126592 |
| a (au) | 3.811261 |
| i (deg) | 13.345760 |
| Ω (om, deg) | 207.563782 |
| ω (w, deg) | 213.319811 |
| M (ma, deg) | 191.191937 |
Magnitude
Scatter + Global Linear
$$ M_a = (14.631 + 2.270\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 14.631 |
| n | 2.270 |
| gf | 0.946 |
| gb | -0.851 |
| k | 0.999 |
| δ90 | 8.448 |
| 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 |
|---|---|---|---|
| 2020-07-30 | 2021-02-17 | +2.5704 | -0.611 |
| 2021-11-02 | 2022-03-07 | -4.0919 | +1.125 |
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 | 17:48:11.88 | -08:31:15.8 | HIP 87050 | 14.98 |
| 2026-07-29 12:00 | 17:47:59.13 | -08:32:00.2 | HIP 87050 | 11.76 |
| 2026-07-30 00:00 | 17:47:46.56 | -08:32:45.2 | HIP 87050 | 8.59 |
| 2026-07-30 12:00 | 17:47:34.17 | -08:33:30.9 | HIP 87050 | 5.50 |
| 2026-07-31 00:00 | 17:47:21.95 | -08:34:17.3 | HIP 87050 | 2.62 |
| 2026-07-31 12:00 | 17:47:09.91 | -08:35:04.3 | HIP 87050 | 1.72 |
| 2026-08-01 00:00 | 17:46:58.05 | -08:35:51.9 | HIP 87050 | 4.21 |
| 2026-08-01 12:00 | 17:46:46.38 | -08:36:40.2 | HIP 87050 | 7.10 |
| 2026-08-02 00:00 | 17:46:34.89 | -08:37:29.1 | HIP 87050 | 10.01 |
| 2026-08-02 12:00 | 17:46:23.58 | -08:38:18.6 | HIP 87050 | 12.91 |
| 2026-08-03 00:00 | 17:46:12.46 | -08:39:08.7 | HIP 87050 | 15.77 |
| 2026-08-03 12:00 | 17:46:01.53 | -08:39:59.5 | HIP 87050 | 18.60 |
| 2026-08-04 00:00 | 17:45:50.78 | -08:40:50.8 | HIP 86838 | 19.06 |
| 2026-08-04 12:00 | 17:45:40.23 | -08:41:42.7 | HIP 86838 | 16.31 |
| 2026-08-05 00:00 | 17:45:29.87 | -08:42:35.2 | HIP 86838 | 13.61 |
| 2026-08-05 12:00 | 17:45:19.70 | -08:43:28.3 | HIP 86838 | 10.95 |
| 2026-08-06 00:00 | 17:45:09.73 | -08:44:22.0 | HIP 86838 | 8.34 |
| 2026-08-06 12:00 | 17:44:59.95 | -08:45:16.2 | HIP 86838 | 5.77 |
| 2026-08-07 00:00 | 17:44:50.36 | -08:46:11.0 | HIP 86838 | 3.29 |
| 2026-08-07 12:00 | 17:44:40.98 | -08:47:06.3 | HIP 86838 | 1.15 |
| 2026-08-08 00:00 | 17:44:31.79 | -08:48:02.2 | HIP 86838 | 2.03 |
| 2026-08-08 12:00 | 17:44:22.81 | -08:48:58.6 | HIP 86838 | 4.32 |
| 2026-08-09 00:00 | 17:44:14.03 | -08:49:55.5 | HIP 86838 | 6.66 |
| 2026-08-09 12:00 | 17:44:05.44 | -08:50:53.0 | HIP 86838 | 8.97 |
| 2026-08-10 00:00 | 17:43:57.07 | -08:51:51.0 | HIP 86838 | 11.25 |
| 2026-08-10 12:00 | 17:43:48.90 | -08:52:49.4 | HIP 86734 | 10.01 |
| 2026-08-11 00:00 | 17:43:40.93 | -08:53:48.4 | HIP 86734 | 8.05 |
| 2026-08-11 12:00 | 17:43:33.17 | -08:54:47.9 | HIP 86734 | 6.26 |
| 2026-08-12 00:00 | 17:43:25.62 | -08:55:47.8 | HIP 86734 | 4.79 |
| 2026-08-12 12:00 | 17:43:18.28 | -08:56:48.2 | HIP 86734 | 3.94 |
| 2026-08-13 00:00 | 17:43:11.14 | -08:57:49.1 | HIP 86734 | 4.03 |
| 2026-08-13 12:00 | 17:43:04.22 | -08:58:50.4 | HIP 86734 | 4.98 |
| 2026-08-14 00:00 | 17:42:57.51 | -08:59:52.1 | HIP 86734 | 6.37 |
| 2026-08-14 12:00 | 17:42:51.01 | -09:00:54.3 | HIP 86661 | 7.34 |
| 2026-08-15 00:00 | 17:42:44.72 | -09:01:56.9 | HIP 86661 | 5.48 |
| 2026-08-15 12:00 | 17:42:38.65 | -09:03:00.0 | HIP 86661 | 3.67 |
| 2026-08-16 00:00 | 17:42:32.79 | -09:04:03.4 | HIP 86661 | 1.94 |
| 2026-08-16 12:00 | 17:42:27.14 | -09:05:07.3 | HIP 86661 | 0.74 |
| 2026-08-17 00:00 | 17:42:21.71 | -09:06:11.5 | HIP 86661 | 1.85 |
| 2026-08-17 12:00 | 17:42:16.49 | -09:07:16.1 | HIP 86661 | 3.46 |
| 2026-08-18 00:00 | 17:42:11.49 | -09:08:21.1 | HIP 86661 | 5.09 |
| 2026-08-18 12:00 | 17:42:06.71 | -09:09:26.4 | HIP 86661 | 6.69 |
| 2026-08-19 00:00 | 17:42:02.14 | -09:10:32.1 | HIP 86661 | 8.26 |