| Parameter |
Value |
| Designation |
C/2017 Y2 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2020-11-04T13:33:04.429440Z |
| Orbit solution date (soln_date, UTC) |
2024-02-25T22:12:25Z |
| Obs used |
961 |
| NEO |
- |
| M1 |
8.600 |
| K1 |
8.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2020-09-02.0000000 |
| e |
1.00096403 |
| q (au) |
4.632068 |
| a (au) |
-4804.896119 |
| i (deg) |
128.421418 |
| Ω (om, deg) |
65.986420 |
| ω (w, deg) |
147.860404 |
| M (ma, deg) |
-0.000188 |
Magnitude
Scatter + Global Linear
$$
M_a = (8.195 + 3.722\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
8.195 |
| n |
3.722 |
| gf |
0.963 |
| gb |
-0.841 |
| k |
0.994 |
| 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 |
| 2017-12-24 |
2020-10-30 |
+1.7402 |
-1.104 |
| 2020-11-05 |
2022-02-23 |
-10.1087 |
+6.757 |
| 2022-02-23 |
2022-07-31 |
+14.3389 |
-12.242 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
09:39:31.96 |
-42:08:45.7 |
HIP 47438 |
8.74 |
| 2026-05-12 12:00 |
09:39:29.57 |
-42:06:51.4 |
HIP 47438 |
7.72 |
| 2026-05-13 00:00 |
09:39:27.27 |
-42:04:57.3 |
HIP 47438 |
7.08 |
| 2026-05-13 12:00 |
09:39:25.08 |
-42:03:03.5 |
HIP 47438 |
6.94 |
| 2026-05-14 00:00 |
09:39:22.97 |
-42:01:10.1 |
HIP 47438 |
7.31 |
| 2026-05-14 12:00 |
09:39:20.96 |
-41:59:16.9 |
HIP 47438 |
8.12 |
| 2026-05-15 00:00 |
09:39:19.05 |
-41:57:24.1 |
HIP 47438 |
9.24 |
| 2026-05-15 12:00 |
09:39:17.23 |
-41:55:31.6 |
HIP 47438 |
10.58 |
| 2026-05-16 00:00 |
09:39:15.51 |
-41:53:39.4 |
HIP 47438 |
12.05 |
| 2026-05-16 12:00 |
09:39:13.87 |
-41:51:47.6 |
HIP 47438 |
13.61 |
| 2026-05-17 00:00 |
09:39:12.34 |
-41:49:56.2 |
HIP 47438 |
15.24 |
| 2026-05-17 12:00 |
09:39:10.89 |
-41:48:05.1 |
HIP 47438 |
16.90 |
| 2026-05-18 00:00 |
09:39:09.54 |
-41:46:14.4 |
HIP 47438 |
18.58 |
| 2026-05-18 12:00 |
09:39:08.28 |
-41:44:24.0 |
HIP 47326 |
19.27 |
| 2026-05-19 00:00 |
09:39:07.11 |
-41:42:34.1 |
HIP 47326 |
17.46 |
| 2026-05-19 12:00 |
09:39:06.03 |
-41:40:44.6 |
HIP 47326 |
15.68 |
| 2026-05-20 00:00 |
09:39:05.05 |
-41:38:55.4 |
HIP 47326 |
13.93 |
| 2026-05-20 12:00 |
09:39:04.15 |
-41:37:06.7 |
HIP 47326 |
12.21 |
| 2026-05-21 00:00 |
09:39:03.34 |
-41:35:18.4 |
HIP 47326 |
10.53 |
| 2026-05-21 12:00 |
09:39:02.63 |
-41:33:30.5 |
HIP 47326 |
8.93 |
| 2026-05-22 00:00 |
09:39:02.00 |
-41:31:43.0 |
HIP 47326 |
7.44 |
| 2026-05-22 12:00 |
09:39:01.47 |
-41:29:56.0 |
HIP 47326 |
6.12 |
| 2026-05-23 00:00 |
09:39:01.02 |
-41:28:09.4 |
HIP 47326 |
5.12 |
| 2026-05-23 12:00 |
09:39:00.66 |
-41:26:23.3 |
HIP 47326 |
4.64 |
| 2026-05-24 00:00 |
09:39:00.38 |
-41:24:37.6 |
HIP 47326 |
4.81 |
| 2026-05-24 12:00 |
09:39:00.20 |
-41:22:52.4 |
HIP 47326 |
5.58 |
| 2026-05-25 00:00 |
09:39:00.10 |
-41:21:07.7 |
HIP 47326 |
6.73 |
| 2026-05-25 12:00 |
09:39:00.08 |
-41:19:23.4 |
HIP 47326 |
8.10 |
| 2026-05-26 00:00 |
09:39:00.15 |
-41:17:39.6 |
HIP 47326 |
9.59 |
| 2026-05-26 12:00 |
09:39:00.31 |
-41:15:56.3 |
HIP 47326 |
11.15 |
| 2026-05-27 00:00 |
09:39:00.55 |
-41:14:13.5 |
HIP 47326 |
12.74 |
| 2026-05-27 12:00 |
09:39:00.88 |
-41:12:31.2 |
HIP 47425 |
12.06 |
| 2026-05-28 00:00 |
09:39:01.29 |
-41:10:49.4 |
HIP 47425 |
10.89 |
| 2026-05-28 12:00 |
09:39:01.78 |
-41:09:08.1 |
HIP 47425 |
9.86 |
| 2026-05-29 00:00 |
09:39:02.35 |
-41:07:27.3 |
HIP 47425 |
9.01 |
| 2026-05-29 12:00 |
09:39:03.01 |
-41:05:47.0 |
HIP 47425 |
8.42 |
| 2026-05-30 00:00 |
09:39:03.75 |
-41:04:07.3 |
HIP 47425 |
8.11 |
| 2026-05-30 12:00 |
09:39:04.58 |
-41:02:28.1 |
HIP 47425 |
8.12 |
| 2026-05-31 00:00 |
09:39:05.48 |
-41:00:49.4 |
HIP 47425 |
8.45 |
| 2026-05-31 12:00 |
09:39:06.46 |
-40:59:11.2 |
HIP 47425 |
9.06 |
| 2026-06-01 00:00 |
09:39:07.53 |
-40:57:33.6 |
HIP 47425 |
9.88 |
| 2026-06-01 12:00 |
09:39:08.67 |
-40:55:56.6 |
HIP 47428 |
9.87 |
| 2026-06-02 00:00 |
09:39:09.89 |
-40:54:20.1 |
HIP 47428 |
8.69 |