C/2021 A1 (Leonard)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2021 A1 (Leonard) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2022-01-03T07:01:27.517440Z |
| Orbit solution date (soln_date, UTC) | 2025-01-02T20:12:26Z |
| Obs used | 2422 |
| NEO | - |
| M1 | 12.500 |
| K1 | 4.500 |
| PC | - |
| Discovery observation (MPC, UTC) | 2021-01-03T13:00:51.696000Z |
| Discovery magnitude (MPC) | 19.00 G |
| Discovery observatory (MPC) | G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2021-07-11.0000000 |
| e | 1.00010048 |
| q (au) | 0.615230 |
| a (au) | -6122.881779 |
| i (deg) | 132.685813 |
| Ω (om, deg) | 255.889104 |
| ω (w, deg) | 225.087713 |
| M (ma, deg) | -0.000363 |
Magnitude
Scatter + Global Linear
$$ M_a = (11.026 + 5.173\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.026 |
| n | 5.173 |
| gf | 0.800 |
| gb | -0.921 |
| k | 0.832 |
| 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 |
|---|---|---|---|
| 2020-04-11 | 2021-10-30 | +1.4929 | -0.909 |
| 2021-10-30 | 2021-12-06 | -9.8712 | +0.200 |
| 2021-12-06 | 2022-01-03 | +28.1721 | +3.535 |
| 2022-01-03 | 2022-05-28 | +0.7525 | -1.273 |
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 | 16:24:32.64 | -06:43:08.8 | HIP 80402 | 10.86 |
| 2026-02-03 12:00 | 16:24:35.55 | -06:42:37.8 | HIP 80402 | 10.23 |
| 2026-02-04 00:00 | 16:24:38.39 | -06:42:06.5 | HIP 80402 | 9.63 |
| 2026-02-04 12:00 | 16:24:41.16 | -06:41:35.0 | HIP 80402 | 9.08 |
| 2026-02-05 00:00 | 16:24:43.87 | -06:41:03.1 | HIP 80402 | 8.58 |
| 2026-02-05 12:00 | 16:24:46.52 | -06:40:31.0 | HIP 80402 | 8.12 |
| 2026-02-06 00:00 | 16:24:49.09 | -06:39:58.5 | HIP 80402 | 7.73 |
| 2026-02-06 12:00 | 16:24:51.60 | -06:39:25.8 | HIP 80402 | 7.39 |
| 2026-02-07 00:00 | 16:24:54.05 | -06:38:52.8 | HIP 80402 | 7.13 |
| 2026-02-07 12:00 | 16:24:56.42 | -06:38:19.5 | HIP 80402 | 6.94 |
| 2026-02-08 00:00 | 16:24:58.73 | -06:37:45.9 | HIP 80402 | 6.83 |
| 2026-02-08 12:00 | 16:25:00.97 | -06:37:12.1 | HIP 80402 | 6.79 |
| 2026-02-09 00:00 | 16:25:03.14 | -06:36:37.9 | HIP 80402 | 6.83 |
| 2026-02-09 12:00 | 16:25:05.24 | -06:36:03.5 | HIP 80402 | 6.95 |
| 2026-02-10 00:00 | 16:25:07.27 | -06:35:28.8 | HIP 80402 | 7.12 |
| 2026-02-10 12:00 | 16:25:09.23 | -06:34:53.8 | HIP 80402 | 7.36 |
| 2026-02-11 00:00 | 16:25:11.13 | -06:34:18.6 | HIP 80402 | 7.65 |
| 2026-02-11 12:00 | 16:25:12.95 | -06:33:43.0 | HIP 80402 | 7.98 |
| 2026-02-12 00:00 | 16:25:14.70 | -06:33:07.2 | HIP 80402 | 8.34 |
| 2026-02-12 12:00 | 16:25:16.39 | -06:32:31.2 | HIP 80402 | 8.74 |
| 2026-02-13 00:00 | 16:25:18.00 | -06:31:54.8 | HIP 80402 | 9.15 |
| 2026-02-13 12:00 | 16:25:19.54 | -06:31:18.2 | HIP 80402 | 9.59 |
| 2026-02-14 00:00 | 16:25:21.01 | -06:30:41.3 | HIP 80402 | 10.05 |
| 2026-02-14 12:00 | 16:25:22.41 | -06:30:04.2 | HIP 80402 | 10.52 |
| 2026-02-15 00:00 | 16:25:23.74 | -06:29:26.8 | HIP 80402 | 10.99 |
| 2026-02-15 12:00 | 16:25:24.99 | -06:28:49.1 | HIP 80402 | 11.48 |
| 2026-02-16 00:00 | 16:25:26.18 | -06:28:11.2 | HIP 80402 | 11.97 |
| 2026-02-16 12:00 | 16:25:27.29 | -06:27:33.0 | HIP 80402 | 12.47 |
| 2026-02-17 00:00 | 16:25:28.33 | -06:26:54.6 | HIP 80402 | 12.97 |
| 2026-02-17 12:00 | 16:25:29.29 | -06:26:15.9 | HIP 80402 | 13.47 |
| 2026-02-18 00:00 | 16:25:30.19 | -06:25:37.0 | HIP 80402 | 13.98 |
| 2026-02-18 12:00 | 16:25:31.01 | -06:24:57.8 | HIP 80402 | 14.48 |
| 2026-02-19 00:00 | 16:25:31.75 | -06:24:18.4 | HIP 80402 | 14.99 |
| 2026-02-19 12:00 | 16:25:32.43 | -06:23:38.7 | HIP 80402 | 15.50 |
| 2026-02-20 00:00 | 16:25:33.03 | -06:22:58.8 | HIP 80402 | 16.01 |
| 2026-02-20 12:00 | 16:25:33.55 | -06:22:18.7 | HIP 80402 | 16.52 |
| 2026-02-21 00:00 | 16:25:34.01 | -06:21:38.3 | HIP 80494 | 16.47 |
| 2026-02-21 12:00 | 16:25:34.38 | -06:20:57.7 | HIP 80494 | 15.79 |
| 2026-02-22 00:00 | 16:25:34.69 | -06:20:16.8 | HIP 80494 | 15.11 |
| 2026-02-22 12:00 | 16:25:34.92 | -06:19:35.8 | HIP 80494 | 14.44 |
| 2026-02-23 00:00 | 16:25:35.08 | -06:18:54.5 | HIP 80494 | 13.77 |
| 2026-02-23 12:00 | 16:25:35.16 | -06:18:12.9 | HIP 80494 | 13.10 |
| 2026-02-24 00:00 | 16:25:35.17 | -06:17:31.2 | HIP 80494 | 12.44 |