399P/PANSTARRS
Metadata
| Parameter | Value |
|---|---|
| Designation | 399P/PANSTARRS |
| Type | P |
| Perihelion (tp_cal, UTC) | 2021-05-26T11:27:46.031040Z |
| Orbit solution date (soln_date, UTC) | 2023-12-06T01:15:28Z |
| Obs used | 407 |
| NEO | - |
| M1 | 15.900 |
| K1 | 4.500 |
| PC | - |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2017-11-18.0000000 |
| e | 0.44196144 |
| q (au) | 2.126918 |
| a (au) | 3.811418 |
| i (deg) | 13.345891 |
| Ω (om, deg) | 207.564221 |
| ω (w, deg) | 213.321157 |
| M (ma, deg) | 189.729777 |
Magnitude
Scatter + Global Linear
$$ M_a = (14.628 + 2.269\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 14.628 |
| n | 2.269 |
| gf | 0.952 |
| gb | -0.851 |
| k | 0.999 |
| δ90 | 8.671 |
| 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 | +2.5717 | -0.611 |
| 2021-11-02 | 2022-03-07 | -4.0897 | +1.124 |
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 | 18:29:25.31 | -11:40:44.0 | HIP 90774 | 28.83 |
| 2026-03-26 12:00 | 18:29:34.80 | -11:39:16.4 | HIP 90774 | 27.49 |
| 2026-03-27 00:00 | 18:29:44.11 | -11:37:48.6 | HIP 90774 | 26.40 |
| 2026-03-27 12:00 | 18:29:53.25 | -11:36:20.7 | HIP 90774 | 25.58 |
| 2026-03-28 00:00 | 18:30:02.22 | -11:34:52.6 | HIP 90774 | 25.06 |
| 2026-03-28 12:00 | 18:30:11.01 | -11:33:24.3 | HIP 90774 | 24.84 |
| 2026-03-29 00:00 | 18:30:19.62 | -11:31:55.9 | HIP 90774 | 24.91 |
| 2026-03-29 12:00 | 18:30:28.05 | -11:30:27.3 | HIP 90849 | 24.06 |
| 2026-03-30 00:00 | 18:30:36.31 | -11:28:58.5 | HIP 90849 | 22.79 |
| 2026-03-30 12:00 | 18:30:44.38 | -11:27:29.6 | HIP 90849 | 21.78 |
| 2026-03-31 00:00 | 18:30:52.28 | -11:26:00.6 | HIP 90849 | 21.04 |
| 2026-03-31 12:00 | 18:31:00.00 | -11:24:31.4 | HIP 90849 | 20.59 |
| 2026-04-01 00:00 | 18:31:07.53 | -11:23:02.1 | HIP 90849 | 20.46 |
| 2026-04-01 12:00 | 18:31:14.88 | -11:21:32.7 | HIP 90849 | 20.62 |
| 2026-04-02 00:00 | 18:31:22.06 | -11:20:03.1 | HIP 90849 | 21.06 |
| 2026-04-02 12:00 | 18:31:29.04 | -11:18:33.4 | HIP 90849 | 21.76 |
| 2026-04-03 00:00 | 18:31:35.85 | -11:17:03.6 | HIP 90849 | 22.68 |
| 2026-04-03 12:00 | 18:31:42.47 | -11:15:33.8 | HIP 90849 | 23.78 |
| 2026-04-04 00:00 | 18:31:48.90 | -11:14:03.8 | HIP 90849 | 25.04 |
| 2026-04-04 12:00 | 18:31:55.15 | -11:12:33.7 | HIP 90804 | 25.85 |
| 2026-04-05 00:00 | 18:32:01.21 | -11:11:03.5 | HIP 90804 | 24.89 |
| 2026-04-05 12:00 | 18:32:07.08 | -11:09:33.3 | HIP 90804 | 24.06 |
| 2026-04-06 00:00 | 18:32:12.76 | -11:08:02.9 | HIP 90804 | 23.36 |
| 2026-04-06 12:00 | 18:32:18.26 | -11:06:32.5 | HIP 90804 | 22.80 |
| 2026-04-07 00:00 | 18:32:23.56 | -11:05:02.0 | HIP 90804 | 22.37 |
| 2026-04-07 12:00 | 18:32:28.67 | -11:03:31.5 | HIP 90804 | 22.09 |
| 2026-04-08 00:00 | 18:32:33.59 | -11:02:00.9 | HIP 90943 | 21.17 |
| 2026-04-08 12:00 | 18:32:38.32 | -11:00:30.3 | HIP 90943 | 19.36 |
| 2026-04-09 00:00 | 18:32:42.86 | -10:58:59.6 | HIP 90943 | 17.57 |
| 2026-04-09 12:00 | 18:32:47.20 | -10:57:28.9 | HIP 90943 | 15.83 |
| 2026-04-10 00:00 | 18:32:51.35 | -10:55:58.2 | HIP 90943 | 14.11 |
| 2026-04-10 12:00 | 18:32:55.30 | -10:54:27.4 | HIP 90943 | 12.44 |
| 2026-04-11 00:00 | 18:32:59.06 | -10:52:56.7 | HIP 90943 | 10.81 |
| 2026-04-11 12:00 | 18:33:02.62 | -10:51:25.9 | HIP 90943 | 9.24 |
| 2026-04-12 00:00 | 18:33:05.98 | -10:49:55.1 | HIP 90943 | 7.74 |
| 2026-04-12 12:00 | 18:33:09.14 | -10:48:24.3 | HIP 90943 | 6.34 |
| 2026-04-13 00:00 | 18:33:12.11 | -10:46:53.6 | HIP 90943 | 5.11 |
| 2026-04-13 12:00 | 18:33:14.88 | -10:45:22.8 | HIP 90943 | 4.17 |
| 2026-04-14 00:00 | 18:33:17.44 | -10:43:52.1 | HIP 90943 | 3.72 |
| 2026-04-14 12:00 | 18:33:19.81 | -10:42:21.4 | HIP 90943 | 3.90 |
| 2026-04-15 00:00 | 18:33:21.97 | -10:40:50.8 | HIP 90943 | 4.63 |
| 2026-04-15 12:00 | 18:33:23.94 | -10:39:20.2 | HIP 90943 | 5.69 |
| 2026-04-16 00:00 | 18:33:25.70 | -10:37:49.7 | HIP 90943 | 6.91 |