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
$$ M_a = (11.021 + 5.164\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.021 |
| n | 5.164 |
| gf | 0.800 |
| gb | -0.920 |
| k | 0.834 |
| 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 | +1.5118 | -0.912 |
| 2021-10-30 | 2021-12-06 | -9.8457 | +0.200 |
| 2021-12-06 | 2022-01-03 | +28.4756 | +3.588 |
| 2022-01-03 | 2022-05-28 | +0.7618 | -1.274 |
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 | 16:12:20.84 | -04:16:47.8 | HIP 79463 | 9.60 |
| 2026-05-12 12:00 | 16:12:12.08 | -04:16:08.7 | HIP 79463 | 11.47 |
| 2026-05-13 00:00 | 16:12:03.32 | -04:15:30.0 | HIP 79463 | 13.47 |
| 2026-05-13 12:00 | 16:11:54.54 | -04:14:51.5 | HIP 79463 | 15.56 |
| 2026-05-14 00:00 | 16:11:45.74 | -04:14:13.3 | HIP 79316 | 16.83 |
| 2026-05-14 12:00 | 16:11:36.93 | -04:13:35.3 | HIP 79316 | 15.33 |
| 2026-05-15 00:00 | 16:11:28.11 | -04:12:57.7 | HIP 79316 | 14.06 |
| 2026-05-15 12:00 | 16:11:19.28 | -04:12:20.3 | HIP 79316 | 13.06 |
| 2026-05-16 00:00 | 16:11:10.44 | -04:11:43.2 | HIP 79316 | 12.41 |
| 2026-05-16 12:00 | 16:11:01.59 | -04:11:06.5 | HIP 79316 | 12.18 |
| 2026-05-17 00:00 | 16:10:52.73 | -04:10:30.0 | HIP 79316 | 12.37 |
| 2026-05-17 12:00 | 16:10:43.86 | -04:09:53.8 | HIP 79316 | 12.98 |
| 2026-05-18 00:00 | 16:10:34.98 | -04:09:17.9 | HIP 79316 | 13.95 |
| 2026-05-18 12:00 | 16:10:26.10 | -04:08:42.3 | HIP 79316 | 15.21 |
| 2026-05-19 00:00 | 16:10:17.21 | -04:08:07.0 | HIP 79316 | 16.70 |
| 2026-05-19 12:00 | 16:10:08.31 | -04:07:32.0 | HIP 79316 | 18.35 |
| 2026-05-20 00:00 | 16:09:59.42 | -04:06:57.3 | HIP 79316 | 20.14 |
| 2026-05-20 12:00 | 16:09:50.51 | -04:06:23.0 | HIP 79316 | 22.02 |
| 2026-05-21 00:00 | 16:09:41.61 | -04:05:48.9 | HIP 79132 | 23.70 |
| 2026-05-21 12:00 | 16:09:32.70 | -04:05:15.2 | HIP 79132 | 23.56 |
| 2026-05-22 00:00 | 16:09:23.80 | -04:04:41.8 | HIP 79132 | 23.64 |
| 2026-05-22 12:00 | 16:09:14.89 | -04:04:08.7 | HIP 79132 | 23.94 |
| 2026-05-23 00:00 | 16:09:05.98 | -04:03:35.9 | HIP 79132 | 24.45 |
| 2026-05-23 12:00 | 16:08:57.08 | -04:03:03.4 | HIP 79132 | 25.14 |
| 2026-05-24 00:00 | 16:08:48.18 | -04:02:31.3 | HIP 79132 | 26.02 |
| 2026-05-24 12:00 | 16:08:39.28 | -04:01:59.5 | HIP 78949 | 26.20 |
| 2026-05-25 00:00 | 16:08:30.38 | -04:01:28.0 | HIP 78949 | 23.94 |
| 2026-05-25 12:00 | 16:08:21.49 | -04:00:56.9 | HIP 78949 | 21.69 |
| 2026-05-26 00:00 | 16:08:12.60 | -04:00:26.1 | HIP 78949 | 19.45 |
| 2026-05-26 12:00 | 16:08:03.72 | -03:59:55.6 | HIP 78949 | 17.22 |
| 2026-05-27 00:00 | 16:07:54.84 | -03:59:25.4 | HIP 78949 | 15.01 |
| 2026-05-27 12:00 | 16:07:45.97 | -03:58:55.6 | HIP 78949 | 12.82 |
| 2026-05-28 00:00 | 16:07:37.11 | -03:58:26.1 | HIP 78949 | 10.67 |
| 2026-05-28 12:00 | 16:07:28.26 | -03:57:57.0 | HIP 78949 | 8.59 |
| 2026-05-29 00:00 | 16:07:19.42 | -03:57:28.2 | HIP 78949 | 6.62 |
| 2026-05-29 12:00 | 16:07:10.58 | -03:56:59.7 | HIP 78949 | 4.93 |
| 2026-05-30 00:00 | 16:07:01.76 | -03:56:31.6 | HIP 78949 | 3.86 |
| 2026-05-30 12:00 | 16:06:52.95 | -03:56:03.8 | HIP 78949 | 3.96 |
| 2026-05-31 00:00 | 16:06:44.15 | -03:55:36.4 | HIP 78949 | 5.15 |
| 2026-05-31 12:00 | 16:06:35.37 | -03:55:09.3 | HIP 78949 | 6.89 |
| 2026-06-01 00:00 | 16:06:26.59 | -03:54:42.6 | HIP 78949 | 8.85 |
| 2026-06-01 12:00 | 16:06:17.83 | -03:54:16.2 | HIP 78949 | 10.91 |
| 2026-06-02 00:00 | 16:06:09.09 | -03:53:50.2 | HIP 78949 | 13.03 |