C/2021 C5 (PANSTARRS)
| Parameter |
Value |
| Designation |
C/2021 C5 (PANSTARRS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2023-02-11T00:59:44.805120Z |
| Orbit solution date (soln_date, UTC) |
2024-07-08T10:14:37Z |
| Obs used |
456 |
| NEO |
- |
| M1 |
12.100 |
| K1 |
5.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-02-12T08:17:13.660800Z |
| Discovery magnitude (MPC) |
21.01 w |
| Discovery observatory (MPC) |
F51 · Pan-STARRS 1, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2022-03-02.0000000 |
| e |
0.99926635 |
| q (au) |
3.241820 |
| a (au) |
4418.763332 |
| i (deg) |
50.784623 |
| Ω (om, deg) |
323.689906 |
| ω (w, deg) |
270.917360 |
| M (ma, deg) |
359.998839 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.668 + 3.655\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.668 |
| n |
3.655 |
| gf |
1.000 |
| gb |
-0.758 |
| 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 |
| 2020-12-22 |
2022-01-01 |
+5.5972 |
-4.468 |
| 2022-01-01 |
2022-03-29 |
-7.2990 |
+4.715 |
| 2022-03-29 |
2022-07-02 |
+8.9265 |
-5.991 |
| 2022-07-02 |
2023-02-07 |
-26.0299 |
+14.598 |
| 2023-02-16 |
2024-07-03 |
+12.5302 |
-5.302 |
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 |
22:04:01.13 |
+02:32:27.4 |
HIP 108940 |
5.65 |
| 2026-02-03 12:00 |
22:04:12.76 |
+02:33:58.3 |
HIP 108940 |
2.66 |
| 2026-02-04 00:00 |
22:04:24.40 |
+02:35:29.5 |
HIP 108940 |
1.92 |
| 2026-02-04 12:00 |
22:04:36.05 |
+02:37:01.2 |
HIP 108940 |
4.68 |
| 2026-02-05 00:00 |
22:04:47.71 |
+02:38:33.2 |
HIP 108940 |
7.85 |
| 2026-02-05 12:00 |
22:04:59.38 |
+02:40:05.6 |
HIP 108940 |
11.10 |
| 2026-02-06 00:00 |
22:05:11.06 |
+02:41:38.4 |
HIP 108940 |
14.38 |
| 2026-02-06 12:00 |
22:05:22.74 |
+02:43:11.5 |
HIP 108940 |
17.67 |
| 2026-02-07 00:00 |
22:05:34.44 |
+02:44:45.0 |
HIP 108940 |
20.96 |
| 2026-02-07 12:00 |
22:05:46.14 |
+02:46:18.8 |
HIP 109155 |
23.90 |
| 2026-02-08 00:00 |
22:05:57.84 |
+02:47:53.1 |
HIP 109155 |
23.83 |
| 2026-02-08 12:00 |
22:06:09.56 |
+02:49:27.7 |
HIP 109155 |
24.22 |
| 2026-02-09 00:00 |
22:06:21.27 |
+02:51:02.6 |
HIP 109155 |
25.06 |
| 2026-02-09 12:00 |
22:06:33.00 |
+02:52:37.9 |
HIP 109155 |
26.30 |
| 2026-02-10 00:00 |
22:06:44.72 |
+02:54:13.5 |
HIP 109155 |
27.89 |
| 2026-02-10 12:00 |
22:06:56.45 |
+02:55:49.5 |
HIP 109155 |
29.78 |
| 2026-02-11 00:00 |
22:07:08.18 |
+02:57:25.9 |
HIP 109327 |
28.00 |
| 2026-02-11 12:00 |
22:07:19.92 |
+02:59:02.6 |
HIP 109327 |
24.75 |
| 2026-02-12 00:00 |
22:07:31.66 |
+03:00:39.6 |
HIP 109327 |
21.54 |
| 2026-02-12 12:00 |
22:07:43.39 |
+03:02:16.9 |
HIP 109327 |
18.37 |
| 2026-02-13 00:00 |
22:07:55.13 |
+03:03:54.6 |
HIP 109327 |
15.28 |
| 2026-02-13 12:00 |
22:08:06.87 |
+03:05:32.7 |
HIP 109327 |
12.33 |
| 2026-02-14 00:00 |
22:08:18.61 |
+03:07:11.0 |
HIP 109327 |
9.65 |
| 2026-02-14 12:00 |
22:08:30.34 |
+03:08:49.7 |
HIP 109327 |
7.53 |
| 2026-02-15 00:00 |
22:08:42.07 |
+03:10:28.7 |
HIP 109327 |
6.56 |
| 2026-02-15 12:00 |
22:08:53.80 |
+03:12:08.1 |
HIP 109327 |
7.21 |
| 2026-02-16 00:00 |
22:09:05.53 |
+03:13:47.7 |
HIP 109327 |
9.15 |
| 2026-02-16 12:00 |
22:09:17.25 |
+03:15:27.7 |
HIP 109327 |
11.75 |
| 2026-02-17 00:00 |
22:09:28.97 |
+03:17:08.0 |
HIP 109327 |
14.67 |
| 2026-02-17 12:00 |
22:09:40.69 |
+03:18:48.5 |
HIP 109327 |
17.76 |
| 2026-02-18 00:00 |
22:09:52.39 |
+03:20:29.4 |
HIP 109327 |
20.93 |
| 2026-02-18 12:00 |
22:10:04.10 |
+03:22:10.6 |
HIP 109327 |
24.16 |
| 2026-02-19 00:00 |
22:10:15.79 |
+03:23:52.1 |
HIP 109327 |
27.43 |
| 2026-02-19 12:00 |
22:10:27.48 |
+03:25:33.9 |
HIP 109327 |
30.72 |
| 2026-02-20 00:00 |
22:10:39.15 |
+03:27:15.9 |
HIP 109327 |
34.03 |
| 2026-02-20 12:00 |
22:10:50.82 |
+03:28:58.3 |
HIP 109678 |
34.02 |
| 2026-02-21 00:00 |
22:11:02.48 |
+03:30:40.9 |
HIP 109678 |
31.68 |
| 2026-02-21 12:00 |
22:11:14.13 |
+03:32:23.9 |
HIP 109678 |
29.55 |
| 2026-02-22 00:00 |
22:11:25.77 |
+03:34:07.1 |
HIP 109678 |
27.67 |
| 2026-02-22 12:00 |
22:11:37.40 |
+03:35:50.5 |
HIP 109678 |
26.10 |
| 2026-02-23 00:00 |
22:11:49.01 |
+03:37:34.3 |
HIP 109678 |
24.90 |
| 2026-02-23 12:00 |
22:12:00.61 |
+03:39:18.3 |
HIP 109570 |
23.77 |
| 2026-02-24 00:00 |
22:12:12.20 |
+03:41:02.6 |
HIP 109570 |
22.75 |