| Parameter |
Value |
| Designation |
C/2021 O3 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2022-04-21T00:59:54.507840Z |
| Orbit solution date (soln_date, UTC) |
2024-08-08T14:32:18Z |
| Obs used |
760 |
| NEO |
- |
| M1 |
13.600 |
| K1 |
4.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-07-26T11:32:37.104000Z |
| Discovery magnitude (MPC) |
19.87 i |
| Discovery observatory (MPC) |
F51 · Pan-STARRS 1, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-10-30.0000000 |
| e |
1.00015130 |
| q (au) |
0.287322 |
| a (au) |
-1899.062785 |
| i (deg) |
56.772789 |
| Ω (om, deg) |
189.027335 |
| ω (w, deg) |
299.983286 |
| M (ma, deg) |
-0.002061 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.384 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.384 |
| n |
2.000 |
| gf |
0.800 |
| gb |
-0.680 |
| k |
0.800 |
| 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 |
| 2021-07-26 |
2021-09-18 |
+2.7400 |
-1.427 |
| 2021-09-18 |
2021-11-07 |
+8.8781 |
-4.666 |
| 2021-11-07 |
2021-12-08 |
+4.2020 |
-2.285 |
| 2021-12-08 |
2022-04-19 |
+4.8581 |
-2.406 |
| 2022-04-22 |
2022-07-12 |
-0.0579 |
+1.173 |
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 |
19:45:50.18 |
+35:27:07.7 |
HIP 97259 |
1.97 |
| 2026-05-12 12:00 |
19:45:46.04 |
+35:28:35.0 |
HIP 97259 |
3.17 |
| 2026-05-13 00:00 |
19:45:41.82 |
+35:30:01.8 |
HIP 97259 |
4.69 |
| 2026-05-13 12:00 |
19:45:37.52 |
+35:31:28.2 |
HIP 97259 |
6.29 |
| 2026-05-14 00:00 |
19:45:33.14 |
+35:32:54.0 |
HIP 97259 |
7.94 |
| 2026-05-14 12:00 |
19:45:28.68 |
+35:34:19.3 |
HIP 97259 |
9.60 |
| 2026-05-15 00:00 |
19:45:24.14 |
+35:35:44.1 |
HIP 97259 |
11.27 |
| 2026-05-15 12:00 |
19:45:19.51 |
+35:37:08.3 |
HIP 97259 |
12.95 |
| 2026-05-16 00:00 |
19:45:14.81 |
+35:38:32.1 |
HIP 97259 |
14.64 |
| 2026-05-16 12:00 |
19:45:10.03 |
+35:39:55.2 |
HIP 97259 |
16.33 |
| 2026-05-17 00:00 |
19:45:05.17 |
+35:41:17.9 |
HIP 97259 |
18.02 |
| 2026-05-17 12:00 |
19:45:00.23 |
+35:42:39.9 |
HIP 97259 |
19.71 |
| 2026-05-18 00:00 |
19:44:55.22 |
+35:44:01.5 |
HIP 97259 |
21.41 |
| 2026-05-18 12:00 |
19:44:50.12 |
+35:45:22.4 |
HIP 97232 |
22.42 |
| 2026-05-19 00:00 |
19:44:44.95 |
+35:46:42.7 |
HIP 97232 |
21.76 |
| 2026-05-19 12:00 |
19:44:39.70 |
+35:48:02.5 |
HIP 97228 |
21.23 |
| 2026-05-20 00:00 |
19:44:34.38 |
+35:49:21.7 |
HIP 97228 |
20.82 |
| 2026-05-20 12:00 |
19:44:28.98 |
+35:50:40.3 |
HIP 97228 |
20.57 |
| 2026-05-21 00:00 |
19:44:23.50 |
+35:51:58.2 |
HIP 96995 |
19.97 |
| 2026-05-21 12:00 |
19:44:17.95 |
+35:53:15.6 |
HIP 96995 |
19.43 |
| 2026-05-22 00:00 |
19:44:12.33 |
+35:54:32.3 |
HIP 96995 |
19.01 |
| 2026-05-22 12:00 |
19:44:06.63 |
+35:55:48.4 |
HIP 96995 |
18.72 |
| 2026-05-23 00:00 |
19:44:00.85 |
+35:57:03.9 |
HIP 96995 |
18.56 |
| 2026-05-23 12:00 |
19:43:55.01 |
+35:58:18.7 |
HIP 96995 |
18.55 |
| 2026-05-24 00:00 |
19:43:49.09 |
+35:59:32.9 |
HIP 96995 |
18.68 |
| 2026-05-24 12:00 |
19:43:43.10 |
+36:00:46.5 |
HIP 96995 |
18.95 |
| 2026-05-25 00:00 |
19:43:37.04 |
+36:01:59.3 |
HIP 96949 |
17.25 |
| 2026-05-25 12:00 |
19:43:30.90 |
+36:03:11.6 |
HIP 96949 |
15.53 |
| 2026-05-26 00:00 |
19:43:24.70 |
+36:04:23.1 |
HIP 96949 |
13.81 |
| 2026-05-26 12:00 |
19:43:18.43 |
+36:05:34.0 |
HIP 96949 |
12.08 |
| 2026-05-27 00:00 |
19:43:12.08 |
+36:06:44.2 |
HIP 96949 |
10.35 |
| 2026-05-27 12:00 |
19:43:05.67 |
+36:07:53.7 |
HIP 96949 |
8.63 |
| 2026-05-28 00:00 |
19:42:59.19 |
+36:09:02.6 |
HIP 96949 |
6.90 |
| 2026-05-28 12:00 |
19:42:52.64 |
+36:10:10.7 |
HIP 96949 |
5.17 |
| 2026-05-29 00:00 |
19:42:46.03 |
+36:11:18.1 |
HIP 96949 |
3.46 |
| 2026-05-29 12:00 |
19:42:39.34 |
+36:12:24.8 |
HIP 96949 |
1.79 |
| 2026-05-30 00:00 |
19:42:32.59 |
+36:13:30.8 |
HIP 96949 |
0.74 |
| 2026-05-30 12:00 |
19:42:25.78 |
+36:14:36.1 |
HIP 96949 |
2.00 |
| 2026-05-31 00:00 |
19:42:18.90 |
+36:15:40.7 |
HIP 96949 |
3.69 |
| 2026-05-31 12:00 |
19:42:11.95 |
+36:16:44.6 |
HIP 96906 |
4.36 |
| 2026-06-01 00:00 |
19:42:04.94 |
+36:17:47.7 |
HIP 96924 |
3.35 |
| 2026-06-01 12:00 |
19:41:57.86 |
+36:18:50.0 |
HIP 96924 |
3.08 |
| 2026-06-02 00:00 |
19:41:50.73 |
+36:19:51.6 |
HIP 96924 |
3.75 |