| Parameter |
Value |
| Designation |
C/2021 P2 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2023-01-22T16:20:24.480960Z |
| Orbit solution date (soln_date, UTC) |
2025-06-26T10:12:45Z |
| Obs used |
408 |
| NEO |
- |
| M1 |
7.500 |
| K1 |
11.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-08-07T12:35:04.617600Z |
| Discovery magnitude (MPC) |
21.50 w |
| Discovery observatory (MPC) |
F51 · Pan-STARRS 1, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2023-02-01.0000000 |
| e |
0.99795112 |
| q (au) |
5.069092 |
| a (au) |
2474.083378 |
| i (deg) |
150.063521 |
| Ω (om, deg) |
32.079344 |
| ω (w, deg) |
76.687326 |
| M (ma, deg) |
0.000075 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.160 + 4.825\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.160 |
| n |
4.825 |
| gf |
1.000 |
| gb |
-0.500 |
| 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 |
| 2021-06-19 |
2022-11-22 |
+5.2167 |
-3.679 |
| 2023-04-26 |
2025-05-21 |
-4.7366 |
+3.148 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-06-01 00:00 |
14:46:00.11 |
-07:59:53.3 |
HIP 72218 |
12.52 |
| 2026-06-01 12:00 |
14:45:45.11 |
-07:59:28.7 |
HIP 72218 |
13.62 |
| 2026-06-02 00:00 |
14:45:30.18 |
-07:59:04.5 |
HIP 72218 |
15.55 |
| 2026-06-02 12:00 |
14:45:15.32 |
-07:58:40.7 |
HIP 72218 |
18.05 |
| 2026-06-03 00:00 |
14:45:00.53 |
-07:58:17.3 |
HIP 72047 |
20.43 |
| 2026-06-03 12:00 |
14:44:45.81 |
-07:57:54.3 |
HIP 72047 |
18.96 |
| 2026-06-04 00:00 |
14:44:31.17 |
-07:57:31.8 |
HIP 72047 |
18.11 |
| 2026-06-04 12:00 |
14:44:16.60 |
-07:57:09.7 |
HIP 72047 |
17.98 |
| 2026-06-05 00:00 |
14:44:02.11 |
-07:56:48.1 |
HIP 72047 |
18.55 |
| 2026-06-05 12:00 |
14:43:47.69 |
-07:56:26.8 |
HIP 72047 |
19.77 |
| 2026-06-06 00:00 |
14:43:33.35 |
-07:56:06.1 |
HIP 72047 |
21.50 |
| 2026-06-06 12:00 |
14:43:19.09 |
-07:55:45.7 |
HIP 72047 |
23.63 |
| 2026-06-07 00:00 |
14:43:04.90 |
-07:55:25.8 |
HIP 72047 |
26.05 |
| 2026-06-07 12:00 |
14:42:50.79 |
-07:55:06.4 |
HIP 72047 |
28.69 |
| 2026-06-08 00:00 |
14:42:36.77 |
-07:54:47.4 |
HIP 71769 |
26.42 |
| 2026-06-08 12:00 |
14:42:22.82 |
-07:54:28.8 |
HIP 71769 |
22.96 |
| 2026-06-09 00:00 |
14:42:08.96 |
-07:54:10.7 |
HIP 71769 |
19.52 |
| 2026-06-09 12:00 |
14:41:55.17 |
-07:53:53.1 |
HIP 71769 |
16.11 |
| 2026-06-10 00:00 |
14:41:41.48 |
-07:53:35.9 |
HIP 71769 |
12.72 |
| 2026-06-10 12:00 |
14:41:27.86 |
-07:53:19.2 |
HIP 71769 |
9.36 |
| 2026-06-11 00:00 |
14:41:14.33 |
-07:53:02.9 |
HIP 71769 |
6.06 |
| 2026-06-11 12:00 |
14:41:00.88 |
-07:52:47.1 |
HIP 71769 |
2.89 |
| 2026-06-12 00:00 |
14:40:47.53 |
-07:52:31.8 |
HIP 71769 |
1.52 |
| 2026-06-12 12:00 |
14:40:34.25 |
-07:52:16.9 |
HIP 71769 |
4.25 |
| 2026-06-13 00:00 |
14:40:21.07 |
-07:52:02.5 |
HIP 71769 |
7.43 |
| 2026-06-13 12:00 |
14:40:07.97 |
-07:51:48.6 |
HIP 71769 |
10.65 |
| 2026-06-14 00:00 |
14:39:54.97 |
-07:51:35.1 |
HIP 71769 |
13.86 |
| 2026-06-14 12:00 |
14:39:42.05 |
-07:51:22.2 |
HIP 71769 |
17.05 |
| 2026-06-15 00:00 |
14:39:29.22 |
-07:51:09.7 |
HIP 71769 |
20.22 |
| 2026-06-15 12:00 |
14:39:16.49 |
-07:50:57.6 |
HIP 71769 |
23.38 |
| 2026-06-16 00:00 |
14:39:03.85 |
-07:50:46.1 |
HIP 71720 |
26.23 |
| 2026-06-16 12:00 |
14:38:51.29 |
-07:50:35.0 |
HIP 71720 |
28.23 |
| 2026-06-17 00:00 |
14:38:38.84 |
-07:50:24.5 |
HIP 71720 |
30.40 |
| 2026-06-17 12:00 |
14:38:26.47 |
-07:50:14.4 |
HIP 71720 |
32.71 |
| 2026-06-18 00:00 |
14:38:14.20 |
-07:50:04.7 |
HIP 71720 |
35.12 |
| 2026-06-18 12:00 |
14:38:02.03 |
-07:49:55.6 |
HIP 71720 |
37.61 |
| 2026-06-19 00:00 |
14:37:49.95 |
-07:49:47.0 |
HIP 71720 |
40.15 |
| 2026-06-19 12:00 |
14:37:37.97 |
-07:49:38.8 |
HIP 71600 |
42.37 |
| 2026-06-20 00:00 |
14:37:26.08 |
-07:49:31.1 |
HIP 71600 |
43.34 |
| 2026-06-20 12:00 |
14:37:14.29 |
-07:49:23.9 |
HIP 71344 |
41.93 |
| 2026-06-21 00:00 |
14:37:02.60 |
-07:49:17.2 |
HIP 71344 |
40.22 |
| 2026-06-21 12:00 |
14:36:51.00 |
-07:49:11.0 |
HIP 71344 |
38.66 |
| 2026-06-22 00:00 |
14:36:39.50 |
-07:49:05.3 |
HIP 71344 |
37.26 |