| 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
$$
M_a = (5.684 + 5.099\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
5.684 |
| n |
5.099 |
| gf |
1.000 |
| gb |
-1.000 |
| 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 |
+5.2257 |
-3.680 |
| 2023-04-26 |
2025-05-21 |
-4.1164 |
+2.668 |
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 |
14:56:45.60 |
-08:21:28.0 |
HIP 73255 |
30.40 |
| 2026-05-12 12:00 |
14:56:28.69 |
-08:20:49.3 |
HIP 72943 |
29.75 |
| 2026-05-13 00:00 |
14:56:11.79 |
-08:20:10.8 |
HIP 72943 |
25.66 |
| 2026-05-13 12:00 |
14:55:54.92 |
-08:19:32.6 |
HIP 72943 |
21.63 |
| 2026-05-14 00:00 |
14:55:38.08 |
-08:18:54.6 |
HIP 72943 |
17.69 |
| 2026-05-14 12:00 |
14:55:21.27 |
-08:18:17.0 |
HIP 72943 |
13.91 |
| 2026-05-15 00:00 |
14:55:04.48 |
-08:17:39.6 |
HIP 72943 |
10.48 |
| 2026-05-15 12:00 |
14:54:47.73 |
-08:17:02.6 |
HIP 72943 |
7.82 |
| 2026-05-16 00:00 |
14:54:31.01 |
-08:16:25.8 |
HIP 72943 |
6.90 |
| 2026-05-16 12:00 |
14:54:14.32 |
-08:15:49.4 |
HIP 72943 |
8.30 |
| 2026-05-17 00:00 |
14:53:57.66 |
-08:15:13.2 |
HIP 72943 |
11.17 |
| 2026-05-17 12:00 |
14:53:41.04 |
-08:14:37.4 |
HIP 72943 |
14.66 |
| 2026-05-18 00:00 |
14:53:24.46 |
-08:14:01.9 |
HIP 72943 |
18.42 |
| 2026-05-18 12:00 |
14:53:07.91 |
-08:13:26.7 |
HIP 72844 |
21.31 |
| 2026-05-19 00:00 |
14:52:51.41 |
-08:12:51.9 |
HIP 72844 |
21.83 |
| 2026-05-19 12:00 |
14:52:34.94 |
-08:12:17.4 |
HIP 72844 |
23.09 |
| 2026-05-20 00:00 |
14:52:18.52 |
-08:11:43.2 |
HIP 72606 |
23.91 |
| 2026-05-20 12:00 |
14:52:02.14 |
-08:11:09.3 |
HIP 72606 |
19.93 |
| 2026-05-21 00:00 |
14:51:45.81 |
-08:10:35.9 |
HIP 72606 |
16.01 |
| 2026-05-21 12:00 |
14:51:29.52 |
-08:10:02.7 |
HIP 72606 |
12.21 |
| 2026-05-22 00:00 |
14:51:13.29 |
-08:09:29.9 |
HIP 72606 |
8.66 |
| 2026-05-22 12:00 |
14:50:57.09 |
-08:08:57.5 |
HIP 72606 |
5.83 |
| 2026-05-23 00:00 |
14:50:40.95 |
-08:08:25.4 |
HIP 72606 |
5.05 |
| 2026-05-23 12:00 |
14:50:24.86 |
-08:07:53.7 |
HIP 72606 |
7.02 |
| 2026-05-24 00:00 |
14:50:08.82 |
-08:07:22.4 |
HIP 72606 |
10.25 |
| 2026-05-24 12:00 |
14:49:52.84 |
-08:06:51.4 |
HIP 72606 |
13.88 |
| 2026-05-25 00:00 |
14:49:36.90 |
-08:06:20.8 |
HIP 72566 |
17.36 |
| 2026-05-25 12:00 |
14:49:21.03 |
-08:05:50.6 |
HIP 72566 |
19.44 |
| 2026-05-26 00:00 |
14:49:05.21 |
-08:05:20.7 |
HIP 72566 |
22.03 |
| 2026-05-26 12:00 |
14:48:49.44 |
-08:04:51.3 |
HIP 72566 |
24.98 |
| 2026-05-27 00:00 |
14:48:33.74 |
-08:04:22.2 |
HIP 72566 |
28.15 |
| 2026-05-27 12:00 |
14:48:18.09 |
-08:03:53.5 |
HIP 72496 |
31.18 |
| 2026-05-28 00:00 |
14:48:02.51 |
-08:03:25.2 |
HIP 72218 |
31.18 |
| 2026-05-28 12:00 |
14:47:46.98 |
-08:02:57.3 |
HIP 72218 |
27.66 |
| 2026-05-29 00:00 |
14:47:31.52 |
-08:02:29.8 |
HIP 72218 |
24.26 |
| 2026-05-29 12:00 |
14:47:16.12 |
-08:02:02.7 |
HIP 72218 |
21.04 |
| 2026-05-30 00:00 |
14:47:00.79 |
-08:01:36.0 |
HIP 72218 |
18.09 |
| 2026-05-30 12:00 |
14:46:45.52 |
-08:01:09.7 |
HIP 72218 |
15.52 |
| 2026-05-31 00:00 |
14:46:30.31 |
-08:00:43.9 |
HIP 72218 |
13.57 |
| 2026-05-31 12:00 |
14:46:15.18 |
-08:00:18.4 |
HIP 72218 |
12.50 |
| 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 |