| Parameter |
Value |
| Designation |
C/2017 P2 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2017-12-06T13:31:41.891520Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:33:35Z |
| Obs used |
50 |
| NEO |
- |
| M1 |
9.300 |
| K1 |
23.750 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2017-09-13.0000000 |
| e |
0.99796653 |
| q (au) |
2.461777 |
| a (au) |
1210.625678 |
| i (deg) |
50.084856 |
| Ω (om, deg) |
165.546359 |
| ω (w, deg) |
132.238805 |
| M (ma, deg) |
359.998021 |
Magnitude
Scatter + Global Linear
$$
M_a = (16.551 + 5.128\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
16.551 |
| n |
5.128 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
0.800 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
05:23:12.64 |
-25:08:21.5 |
HIP 25108 |
28.15 |
| 2026-05-12 12:00 |
05:23:18.42 |
-25:07:46.9 |
HIP 25108 |
29.13 |
| 2026-05-13 00:00 |
05:23:24.22 |
-25:07:12.7 |
HIP 25273 |
28.45 |
| 2026-05-13 12:00 |
05:23:30.04 |
-25:06:38.9 |
HIP 25273 |
27.41 |
| 2026-05-14 00:00 |
05:23:35.88 |
-25:06:05.6 |
HIP 25273 |
26.41 |
| 2026-05-14 12:00 |
05:23:41.75 |
-25:05:32.8 |
HIP 25273 |
25.45 |
| 2026-05-15 00:00 |
05:23:47.64 |
-25:05:00.3 |
HIP 25273 |
24.55 |
| 2026-05-15 12:00 |
05:23:53.54 |
-25:04:28.4 |
HIP 25273 |
23.70 |
| 2026-05-16 00:00 |
05:23:59.47 |
-25:03:56.8 |
HIP 25273 |
22.93 |
| 2026-05-16 12:00 |
05:24:05.41 |
-25:03:25.7 |
HIP 25273 |
22.22 |
| 2026-05-17 00:00 |
05:24:11.38 |
-25:02:55.1 |
HIP 25273 |
21.60 |
| 2026-05-17 12:00 |
05:24:17.36 |
-25:02:24.9 |
HIP 25273 |
21.07 |
| 2026-05-18 00:00 |
05:24:23.37 |
-25:01:55.1 |
HIP 25273 |
20.63 |
| 2026-05-18 12:00 |
05:24:29.39 |
-25:01:25.9 |
HIP 25273 |
20.29 |
| 2026-05-19 00:00 |
05:24:35.43 |
-25:00:57.0 |
HIP 25273 |
20.06 |
| 2026-05-19 12:00 |
05:24:41.48 |
-25:00:28.6 |
HIP 25273 |
19.95 |
| 2026-05-20 00:00 |
05:24:47.55 |
-25:00:00.7 |
HIP 25273 |
19.94 |
| 2026-05-20 12:00 |
05:24:53.64 |
-24:59:33.2 |
HIP 25273 |
20.06 |
| 2026-05-21 00:00 |
05:24:59.75 |
-24:59:06.2 |
HIP 25273 |
20.28 |
| 2026-05-21 12:00 |
05:25:05.87 |
-24:58:39.7 |
HIP 25273 |
20.61 |
| 2026-05-22 00:00 |
05:25:12.01 |
-24:58:13.6 |
HIP 25273 |
21.05 |
| 2026-05-22 12:00 |
05:25:18.16 |
-24:57:48.0 |
HIP 25273 |
21.59 |
| 2026-05-23 00:00 |
05:25:24.33 |
-24:57:22.8 |
HIP 25273 |
22.22 |
| 2026-05-23 12:00 |
05:25:30.51 |
-24:56:58.1 |
HIP 25273 |
22.93 |
| 2026-05-24 00:00 |
05:25:36.70 |
-24:56:33.9 |
HIP 25273 |
23.71 |
| 2026-05-24 12:00 |
05:25:42.91 |
-24:56:10.1 |
HIP 25273 |
24.57 |
| 2026-05-25 00:00 |
05:25:49.13 |
-24:55:46.8 |
HIP 25273 |
25.49 |
| 2026-05-25 12:00 |
05:25:55.37 |
-24:55:24.0 |
HIP 25273 |
26.46 |
| 2026-05-26 00:00 |
05:26:01.61 |
-24:55:01.6 |
HIP 25273 |
27.49 |
| 2026-05-26 12:00 |
05:26:07.87 |
-24:54:39.7 |
HIP 25273 |
28.56 |
| 2026-05-27 00:00 |
05:26:14.14 |
-24:54:18.3 |
HIP 25273 |
29.67 |
| 2026-05-27 12:00 |
05:26:20.42 |
-24:53:57.3 |
HIP 25521 |
30.59 |
| 2026-05-28 00:00 |
05:26:26.72 |
-24:53:36.8 |
HIP 25521 |
30.21 |
| 2026-05-28 12:00 |
05:26:33.02 |
-24:53:16.8 |
HIP 25521 |
29.89 |
| 2026-05-29 00:00 |
05:26:39.34 |
-24:52:57.2 |
HIP 25521 |
29.63 |
| 2026-05-29 12:00 |
05:26:45.66 |
-24:52:38.1 |
HIP 25521 |
29.44 |
| 2026-05-30 00:00 |
05:26:52.00 |
-24:52:19.5 |
HIP 25521 |
29.30 |
| 2026-05-30 12:00 |
05:26:58.34 |
-24:52:01.4 |
HIP 25521 |
29.24 |
| 2026-05-31 00:00 |
05:27:04.69 |
-24:51:43.7 |
HIP 25521 |
29.23 |
| 2026-05-31 12:00 |
05:27:11.06 |
-24:51:26.5 |
HIP 25521 |
29.30 |
| 2026-06-01 00:00 |
05:27:17.43 |
-24:51:09.8 |
HIP 25521 |
29.43 |
| 2026-06-01 12:00 |
05:27:23.81 |
-24:50:53.5 |
HIP 25521 |
29.62 |
| 2026-06-02 00:00 |
05:27:30.19 |
-24:50:37.7 |
HIP 25521 |
29.88 |