| 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) |
| 2026-03-26 00:00 |
15:21:49.61 |
-09:30:18.9 |
HIP 75185 |
10.04 |
| 2026-03-26 12:00 |
15:21:36.35 |
-09:29:37.3 |
HIP 75185 |
10.15 |
| 2026-03-27 00:00 |
15:21:23.00 |
-09:28:55.6 |
HIP 75185 |
11.32 |
| 2026-03-27 12:00 |
15:21:09.56 |
-09:28:13.6 |
HIP 75185 |
13.27 |
| 2026-03-28 00:00 |
15:20:56.02 |
-09:27:31.5 |
HIP 75185 |
15.74 |
| 2026-03-28 12:00 |
15:20:42.40 |
-09:26:49.2 |
HIP 75081 |
16.40 |
| 2026-03-29 00:00 |
15:20:28.68 |
-09:26:06.7 |
HIP 75081 |
17.01 |
| 2026-03-29 12:00 |
15:20:14.88 |
-09:25:24.0 |
HIP 75081 |
18.27 |
| 2026-03-30 00:00 |
15:20:01.00 |
-09:24:41.2 |
HIP 74982 |
18.61 |
| 2026-03-30 12:00 |
15:19:47.02 |
-09:23:58.2 |
HIP 74982 |
16.41 |
| 2026-03-31 00:00 |
15:19:32.97 |
-09:23:15.0 |
HIP 74982 |
14.73 |
| 2026-03-31 12:00 |
15:19:18.83 |
-09:22:31.7 |
HIP 74982 |
13.76 |
| 2026-04-01 00:00 |
15:19:04.60 |
-09:21:48.2 |
HIP 74982 |
13.69 |
| 2026-04-01 12:00 |
15:18:50.30 |
-09:21:04.5 |
HIP 74982 |
14.54 |
| 2026-04-02 00:00 |
15:18:35.91 |
-09:20:20.8 |
HIP 74982 |
16.18 |
| 2026-04-02 12:00 |
15:18:21.44 |
-09:19:36.8 |
HIP 74982 |
18.41 |
| 2026-04-03 00:00 |
15:18:06.89 |
-09:18:52.8 |
HIP 74785 |
16.89 |
| 2026-04-03 12:00 |
15:17:52.27 |
-09:18:08.6 |
HIP 74785 |
13.66 |
| 2026-04-04 00:00 |
15:17:37.57 |
-09:17:24.2 |
HIP 74785 |
10.71 |
| 2026-04-04 12:00 |
15:17:22.79 |
-09:16:39.8 |
HIP 74785 |
8.37 |
| 2026-04-05 00:00 |
15:17:07.94 |
-09:15:55.2 |
HIP 74785 |
7.29 |
| 2026-04-05 12:00 |
15:16:53.01 |
-09:15:10.5 |
HIP 74785 |
8.01 |
| 2026-04-06 00:00 |
15:16:38.01 |
-09:14:25.7 |
HIP 74785 |
10.18 |
| 2026-04-06 12:00 |
15:16:22.93 |
-09:13:40.8 |
HIP 74785 |
13.12 |
| 2026-04-07 00:00 |
15:16:07.79 |
-09:12:55.8 |
HIP 74785 |
16.42 |
| 2026-04-07 12:00 |
15:15:52.57 |
-09:12:10.7 |
HIP 74785 |
19.93 |
| 2026-04-08 00:00 |
15:15:37.29 |
-09:11:25.6 |
HIP 74785 |
23.55 |
| 2026-04-08 12:00 |
15:15:21.94 |
-09:10:40.3 |
HIP 74785 |
27.25 |
| 2026-04-09 00:00 |
15:15:06.52 |
-09:09:54.9 |
HIP 74548 |
26.07 |
| 2026-04-09 12:00 |
15:14:51.03 |
-09:09:09.5 |
HIP 74548 |
24.37 |
| 2026-04-10 00:00 |
15:14:35.49 |
-09:08:24.0 |
HIP 74548 |
23.21 |
| 2026-04-10 12:00 |
15:14:19.87 |
-09:07:38.4 |
HIP 74560 |
21.97 |
| 2026-04-11 00:00 |
15:14:04.20 |
-09:06:52.7 |
HIP 74560 |
20.87 |
| 2026-04-11 12:00 |
15:13:48.46 |
-09:06:07.0 |
HIP 74560 |
20.49 |
| 2026-04-12 00:00 |
15:13:32.67 |
-09:05:21.3 |
HIP 74410 |
19.51 |
| 2026-04-12 12:00 |
15:13:16.81 |
-09:04:35.5 |
HIP 74410 |
16.81 |
| 2026-04-13 00:00 |
15:13:00.90 |
-09:03:49.7 |
HIP 74410 |
14.70 |
| 2026-04-13 12:00 |
15:12:44.93 |
-09:03:03.8 |
HIP 74410 |
13.47 |
| 2026-04-14 00:00 |
15:12:28.91 |
-09:02:17.9 |
HIP 74410 |
13.39 |
| 2026-04-14 12:00 |
15:12:12.83 |
-09:01:32.0 |
HIP 74371 |
12.31 |
| 2026-04-15 00:00 |
15:11:56.70 |
-09:00:46.0 |
HIP 74371 |
10.45 |
| 2026-04-15 12:00 |
15:11:40.52 |
-09:00:00.1 |
HIP 74371 |
9.99 |
| 2026-04-16 00:00 |
15:11:24.28 |
-08:59:14.1 |
HIP 74371 |
11.12 |