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 · University of Arizona 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 | -9.8456 | +0.200 |
| 2021-12-06 | 2022-01-03 | +28.4757 | +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) |
|---|---|---|---|---|
| 2026-06-01 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 |
| 2026-06-02 12:00 | 16:06:00.36 | -03:53:24.5 | HIP 78949 | 15.17 |
| 2026-06-03 00:00 | 16:05:51.65 | -03:52:59.1 | HIP 78949 | 17.33 |
| 2026-06-03 12:00 | 16:05:42.95 | -03:52:34.2 | HIP 78949 | 19.50 |
| 2026-06-04 00:00 | 16:05:34.27 | -03:52:09.6 | HIP 78792 | 21.49 |
| 2026-06-04 12:00 | 16:05:25.61 | -03:51:45.3 | HIP 78792 | 20.55 |
| 2026-06-05 00:00 | 16:05:16.97 | -03:51:21.4 | HIP 78792 | 19.81 |
| 2026-06-05 12:00 | 16:05:08.35 | -03:50:57.8 | HIP 78792 | 19.31 |
| 2026-06-06 00:00 | 16:04:59.75 | -03:50:34.7 | HIP 78792 | 19.05 |
| 2026-06-06 12:00 | 16:04:51.17 | -03:50:11.8 | HIP 78792 | 19.04 |
| 2026-06-07 00:00 | 16:04:42.61 | -03:49:49.4 | HIP 78792 | 19.28 |
| 2026-06-07 12:00 | 16:04:34.07 | -03:49:27.3 | HIP 78792 | 19.76 |
| 2026-06-08 00:00 | 16:04:25.55 | -03:49:05.6 | HIP 78792 | 20.46 |
| 2026-06-08 12:00 | 16:04:17.06 | -03:48:44.2 | HIP 78792 | 21.36 |
| 2026-06-09 00:00 | 16:04:08.59 | -03:48:23.2 | HIP 78792 | 22.43 |
| 2026-06-09 12:00 | 16:04:00.15 | -03:48:02.6 | HIP 78577 | 21.20 |
| 2026-06-10 00:00 | 16:03:51.73 | -03:47:42.4 | HIP 78577 | 19.15 |
| 2026-06-10 12:00 | 16:03:43.34 | -03:47:22.5 | HIP 78577 | 17.13 |
| 2026-06-11 00:00 | 16:03:34.98 | -03:47:03.0 | HIP 78577 | 15.14 |
| 2026-06-11 12:00 | 16:03:26.64 | -03:46:43.8 | HIP 78577 | 13.20 |
| 2026-06-12 00:00 | 16:03:18.33 | -03:46:25.1 | HIP 78577 | 11.33 |
| 2026-06-12 12:00 | 16:03:10.05 | -03:46:06.7 | HIP 78577 | 9.57 |
| 2026-06-13 00:00 | 16:03:01.80 | -03:45:48.7 | HIP 78577 | 7.97 |
| 2026-06-13 12:00 | 16:02:53.58 | -03:45:31.0 | HIP 78577 | 6.65 |
| 2026-06-14 00:00 | 16:02:45.40 | -03:45:13.8 | HIP 78577 | 5.80 |
| 2026-06-14 12:00 | 16:02:37.24 | -03:44:56.9 | HIP 78577 | 5.62 |
| 2026-06-15 00:00 | 16:02:29.11 | -03:44:40.4 | HIP 78577 | 6.17 |
| 2026-06-15 12:00 | 16:02:21.02 | -03:44:24.3 | HIP 78577 | 7.27 |
| 2026-06-16 00:00 | 16:02:12.97 | -03:44:08.6 | HIP 78513 | 8.09 |
| 2026-06-16 12:00 | 16:02:04.94 | -03:43:53.2 | HIP 78513 | 6.22 |
| 2026-06-17 00:00 | 16:01:56.95 | -03:43:38.2 | HIP 78513 | 4.49 |
| 2026-06-17 12:00 | 16:01:49.00 | -03:43:23.6 | HIP 78513 | 3.10 |
| 2026-06-18 00:00 | 16:01:41.08 | -03:43:09.4 | HIP 78513 | 2.65 |
| 2026-06-18 12:00 | 16:01:33.20 | -03:42:55.6 | HIP 78513 | 3.51 |
| 2026-06-19 00:00 | 16:01:25.36 | -03:42:42.1 | HIP 78513 | 5.03 |
| 2026-06-19 12:00 | 16:01:17.56 | -03:42:29.0 | HIP 78513 | 6.78 |
| 2026-06-20 00:00 | 16:01:09.79 | -03:42:16.3 | HIP 78513 | 8.60 |
| 2026-06-20 12:00 | 16:01:02.07 | -03:42:04.0 | HIP 78513 | 10.46 |
| 2026-06-21 00:00 | 16:00:54.38 | -03:41:52.1 | HIP 78513 | 12.33 |
| 2026-06-21 12:00 | 16:00:46.74 | -03:41:40.5 | HIP 78513 | 14.21 |
| 2026-06-22 00:00 | 16:00:39.13 | -03:41:29.3 | HIP 78513 | 16.08 |