C/2021 S3 (PANSTARRS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2021 S3 (PANSTARRS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2024-02-14T17:02:56.019840Z |
| Orbit solution date (soln_date, UTC) | 2026-07-28T14:12:16Z |
| Obs used | 4867 |
| NEO | - |
| M1 | 10.700 |
| K1 | 4.500 |
| PC | - |
| Discovery observation (MPC, UTC) | 2021-09-24T13:27:42.969600Z |
| Discovery magnitude (MPC) | 20.17 i |
| Discovery observatory (MPC) | F52 · Pan-STARRS 2, Haleakala |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2024-03-19.0000000 |
| e | 1.00024547 |
| q (au) | 1.320205 |
| a (au) | -5378.325711 |
| i (deg) | 58.532818 |
| Ω (om, deg) | 215.620806 |
| ω (w, deg) | 6.853898 |
| M (ma, deg) | 0.000083 |
Magnitude
Scatter + Global Linear
$$ M_a = (9.812 + 3.233\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 9.812 |
| n | 3.233 |
| gf | 0.991 |
| gb | -0.915 |
| k | 0.980 |
| δ90 | 9.884 |
| 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 |
|---|---|---|---|
| 2020-12-06 | 2023-05-02 | +6.6906 | -5.821 |
| 2023-05-02 | 2024-02-14 | -0.5527 | -1.219 |
| 2024-02-14 | 2024-11-13 | +1.6110 | -0.826 |
| 2024-11-13 | 2025-12-27 | +6.1193 | -3.554 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Finding Chart
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-07-29 00:00 | 00:16:50.42 | +37:56:22.7 | HIP 1411 | 26.06 |
| 2026-07-29 12:00 | 00:16:44.39 | +37:57:06.4 | HIP 1411 | 27.20 |
| 2026-07-30 00:00 | 00:16:38.25 | +37:57:49.1 | HIP 1411 | 28.35 |
| 2026-07-30 12:00 | 00:16:31.99 | +37:58:30.9 | HIP 1411 | 29.53 |
| 2026-07-31 00:00 | 00:16:25.62 | +37:59:11.7 | HIP 1411 | 30.72 |
| 2026-07-31 12:00 | 00:16:19.13 | +37:59:51.5 | HIP 1411 | 31.93 |
| 2026-08-01 00:00 | 00:16:12.52 | +38:00:30.4 | HIP 1411 | 33.15 |
| 2026-08-01 12:00 | 00:16:05.80 | +38:01:08.2 | HIP 1411 | 34.40 |
| 2026-08-02 00:00 | 00:15:58.97 | +38:01:45.0 | HIP 1411 | 35.65 |
| 2026-08-02 12:00 | 00:15:52.02 | +38:02:20.8 | HIP 1411 | 36.93 |
| 2026-08-03 00:00 | 00:15:44.96 | +38:02:55.7 | HIP 1411 | 38.22 |
| 2026-08-03 12:00 | 00:15:37.79 | +38:03:29.4 | HIP 1411 | 39.52 |
| 2026-08-04 00:00 | 00:15:30.50 | +38:04:02.2 | HIP 1030 | 38.76 |
| 2026-08-04 12:00 | 00:15:23.10 | +38:04:33.9 | HIP 1030 | 37.90 |
| 2026-08-05 00:00 | 00:15:15.60 | +38:05:04.6 | HIP 1030 | 37.05 |
| 2026-08-05 12:00 | 00:15:07.98 | +38:05:34.2 | HIP 1030 | 36.22 |
| 2026-08-06 00:00 | 00:15:00.25 | +38:06:02.8 | HIP 1030 | 35.42 |
| 2026-08-06 12:00 | 00:14:52.42 | +38:06:30.3 | HIP 1030 | 34.64 |
| 2026-08-07 00:00 | 00:14:44.48 | +38:06:56.8 | HIP 1030 | 33.90 |
| 2026-08-07 12:00 | 00:14:36.42 | +38:07:22.1 | HIP 1030 | 33.19 |
| 2026-08-08 00:00 | 00:14:28.27 | +38:07:46.4 | HIP 1030 | 32.52 |
| 2026-08-08 12:00 | 00:14:20.00 | +38:08:09.6 | HIP 1030 | 31.90 |
| 2026-08-09 00:00 | 00:14:11.63 | +38:08:31.7 | HIP 1030 | 31.33 |
| 2026-08-09 12:00 | 00:14:03.15 | +38:08:52.6 | HIP 1030 | 30.82 |
| 2026-08-10 00:00 | 00:13:54.58 | +38:09:12.5 | HIP 1030 | 30.37 |
| 2026-08-10 12:00 | 00:13:45.89 | +38:09:31.2 | HIP 1030 | 29.98 |
| 2026-08-11 00:00 | 00:13:37.11 | +38:09:48.9 | HIP 1030 | 29.67 |
| 2026-08-11 12:00 | 00:13:28.22 | +38:10:05.3 | HIP 1030 | 29.44 |
| 2026-08-12 00:00 | 00:13:19.23 | +38:10:20.7 | HIP 1030 | 29.29 |
| 2026-08-12 12:00 | 00:13:10.15 | +38:10:34.9 | HIP 1030 | 29.23 |
| 2026-08-13 00:00 | 00:13:00.96 | +38:10:47.9 | HIP 1030 | 29.26 |
| 2026-08-13 12:00 | 00:12:51.68 | +38:10:59.8 | HIP 1030 | 29.38 |
| 2026-08-14 00:00 | 00:12:42.30 | +38:11:10.6 | HIP 1030 | 29.60 |
| 2026-08-14 12:00 | 00:12:32.82 | +38:11:20.1 | HIP 1030 | 29.91 |
| 2026-08-15 00:00 | 00:12:23.25 | +38:11:28.5 | HIP 823 | 30.21 |
| 2026-08-15 12:00 | 00:12:13.58 | +38:11:35.7 | HIP 823 | 28.47 |
| 2026-08-16 00:00 | 00:12:03.83 | +38:11:41.8 | HIP 823 | 26.74 |
| 2026-08-16 12:00 | 00:11:53.98 | +38:11:46.6 | HIP 823 | 25.04 |
| 2026-08-17 00:00 | 00:11:44.04 | +38:11:50.3 | HIP 823 | 23.37 |
| 2026-08-17 12:00 | 00:11:34.01 | +38:11:52.8 | HIP 823 | 21.74 |
| 2026-08-18 00:00 | 00:11:23.90 | +38:11:54.1 | HIP 823 | 20.17 |
| 2026-08-18 12:00 | 00:11:13.69 | +38:11:54.1 | HIP 823 | 18.68 |
| 2026-08-19 00:00 | 00:11:03.40 | +38:11:53.0 | HIP 823 | 17.30 |