C/2021 P2 (PANSTARRS)
| 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) |
| 2026-02-03 00:00 |
15:34:47.94 |
-10:13:33.6 |
HIP 76219 |
13.39 |
| 2026-02-03 12:00 |
15:34:46.07 |
-10:13:27.9 |
HIP 76219 |
13.01 |
| 2026-02-04 00:00 |
15:34:44.10 |
-10:13:21.8 |
HIP 76219 |
12.61 |
| 2026-02-04 12:00 |
15:34:42.01 |
-10:13:15.3 |
HIP 76219 |
12.20 |
| 2026-02-05 00:00 |
15:34:39.82 |
-10:13:08.3 |
HIP 76219 |
11.77 |
| 2026-02-05 12:00 |
15:34:37.52 |
-10:13:00.9 |
HIP 76219 |
11.33 |
| 2026-02-06 00:00 |
15:34:35.11 |
-10:12:53.0 |
HIP 76219 |
10.88 |
| 2026-02-06 12:00 |
15:34:32.58 |
-10:12:44.7 |
HIP 76219 |
10.43 |
| 2026-02-07 00:00 |
15:34:29.95 |
-10:12:36.0 |
HIP 76219 |
9.98 |
| 2026-02-07 12:00 |
15:34:27.20 |
-10:12:26.9 |
HIP 76219 |
9.54 |
| 2026-02-08 00:00 |
15:34:24.35 |
-10:12:17.3 |
HIP 76219 |
9.11 |
| 2026-02-08 12:00 |
15:34:21.38 |
-10:12:07.2 |
HIP 76219 |
8.70 |
| 2026-02-09 00:00 |
15:34:18.30 |
-10:11:56.8 |
HIP 76219 |
8.33 |
| 2026-02-09 12:00 |
15:34:15.10 |
-10:11:45.9 |
HIP 76219 |
8.01 |
| 2026-02-10 00:00 |
15:34:11.79 |
-10:11:34.6 |
HIP 76219 |
7.75 |
| 2026-02-10 12:00 |
15:34:08.37 |
-10:11:22.8 |
HIP 76219 |
7.56 |
| 2026-02-11 00:00 |
15:34:04.84 |
-10:11:10.7 |
HIP 76219 |
7.47 |
| 2026-02-11 12:00 |
15:34:01.19 |
-10:10:58.1 |
HIP 76219 |
7.49 |
| 2026-02-12 00:00 |
15:33:57.42 |
-10:10:45.0 |
HIP 76219 |
7.63 |
| 2026-02-12 12:00 |
15:33:53.54 |
-10:10:31.6 |
HIP 76219 |
7.89 |
| 2026-02-13 00:00 |
15:33:49.55 |
-10:10:17.7 |
HIP 76219 |
8.27 |
| 2026-02-13 12:00 |
15:33:45.44 |
-10:10:03.4 |
HIP 76219 |
8.76 |
| 2026-02-14 00:00 |
15:33:41.21 |
-10:09:48.7 |
HIP 76219 |
9.37 |
| 2026-02-14 12:00 |
15:33:36.87 |
-10:09:33.5 |
HIP 76219 |
10.07 |
| 2026-02-15 00:00 |
15:33:32.41 |
-10:09:18.0 |
HIP 76219 |
10.85 |
| 2026-02-15 12:00 |
15:33:27.83 |
-10:09:02.0 |
HIP 76219 |
11.72 |
| 2026-02-16 00:00 |
15:33:23.14 |
-10:08:45.6 |
HIP 76219 |
12.66 |
| 2026-02-16 12:00 |
15:33:18.33 |
-10:08:28.8 |
HIP 76219 |
13.66 |
| 2026-02-17 00:00 |
15:33:13.41 |
-10:08:11.5 |
HIP 76219 |
14.72 |
| 2026-02-17 12:00 |
15:33:08.37 |
-10:07:53.9 |
HIP 76219 |
15.83 |
| 2026-02-18 00:00 |
15:33:03.21 |
-10:07:35.8 |
HIP 76219 |
16.99 |
| 2026-02-18 12:00 |
15:32:57.93 |
-10:07:17.4 |
HIP 76219 |
18.20 |
| 2026-02-19 00:00 |
15:32:52.53 |
-10:06:58.5 |
HIP 76219 |
19.45 |
| 2026-02-19 12:00 |
15:32:47.02 |
-10:06:39.2 |
HIP 76219 |
20.74 |
| 2026-02-20 00:00 |
15:32:41.39 |
-10:06:19.5 |
HIP 76079 |
20.81 |
| 2026-02-20 12:00 |
15:32:35.64 |
-10:05:59.4 |
HIP 76079 |
20.79 |
| 2026-02-21 00:00 |
15:32:29.77 |
-10:05:38.9 |
HIP 76079 |
20.88 |
| 2026-02-21 12:00 |
15:32:23.78 |
-10:05:18.1 |
HIP 76079 |
21.07 |
| 2026-02-22 00:00 |
15:32:17.68 |
-10:04:56.8 |
HIP 76079 |
21.37 |
| 2026-02-22 12:00 |
15:32:11.46 |
-10:04:35.1 |
HIP 76079 |
21.79 |
| 2026-02-23 00:00 |
15:32:05.12 |
-10:04:13.0 |
HIP 76079 |
22.32 |
| 2026-02-23 12:00 |
15:31:58.66 |
-10:03:50.6 |
HIP 76079 |
22.97 |
| 2026-02-24 00:00 |
15:31:52.09 |
-10:03:27.7 |
HIP 76079 |
23.72 |