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) |
|---|---|---|---|---|
| 2026-07-29 00:00 | 15:53:39.92 | -03:44:18.7 | HIP 77899 | 34.75 |
| 2026-07-29 12:00 | 15:53:36.51 | -03:44:33.3 | HIP 77899 | 34.84 |
| 2026-07-30 00:00 | 15:53:33.17 | -03:44:48.1 | HIP 77899 | 34.93 |
| 2026-07-30 12:00 | 15:53:29.89 | -03:45:03.2 | HIP 77899 | 35.04 |
| 2026-07-31 00:00 | 15:53:26.68 | -03:45:18.6 | HIP 77899 | 35.16 |
| 2026-07-31 12:00 | 15:53:23.53 | -03:45:34.3 | HIP 77899 | 35.28 |
| 2026-08-01 00:00 | 15:53:20.45 | -03:45:50.3 | HIP 77899 | 35.41 |
| 2026-08-01 12:00 | 15:53:17.44 | -03:46:06.5 | HIP 77899 | 35.55 |
| 2026-08-02 00:00 | 15:53:14.49 | -03:46:23.0 | HIP 77899 | 35.69 |
| 2026-08-02 12:00 | 15:53:11.60 | -03:46:39.7 | HIP 77899 | 35.83 |
| 2026-08-03 00:00 | 15:53:08.79 | -03:46:56.8 | HIP 77899 | 35.98 |
| 2026-08-03 12:00 | 15:53:06.03 | -03:47:14.0 | HIP 77899 | 36.13 |
| 2026-08-04 00:00 | 15:53:03.35 | -03:47:31.6 | HIP 77899 | 36.28 |
| 2026-08-04 12:00 | 15:53:00.73 | -03:47:49.4 | HIP 77899 | 36.44 |
| 2026-08-05 00:00 | 15:52:58.18 | -03:48:07.5 | HIP 77899 | 36.59 |
| 2026-08-05 12:00 | 15:52:55.69 | -03:48:25.8 | HIP 77899 | 36.74 |
| 2026-08-06 00:00 | 15:52:53.27 | -03:48:44.4 | HIP 77899 | 36.89 |
| 2026-08-06 12:00 | 15:52:50.92 | -03:49:03.2 | HIP 77899 | 37.04 |
| 2026-08-07 00:00 | 15:52:48.63 | -03:49:22.3 | HIP 77899 | 37.18 |
| 2026-08-07 12:00 | 15:52:46.41 | -03:49:41.6 | HIP 77899 | 37.32 |
| 2026-08-08 00:00 | 15:52:44.26 | -03:50:01.2 | HIP 77899 | 37.46 |
| 2026-08-08 12:00 | 15:52:42.17 | -03:50:21.0 | HIP 77899 | 37.59 |
| 2026-08-09 00:00 | 15:52:40.15 | -03:50:41.1 | HIP 77899 | 37.72 |
| 2026-08-09 12:00 | 15:52:38.20 | -03:51:01.4 | HIP 77899 | 37.84 |
| 2026-08-10 00:00 | 15:52:36.32 | -03:51:21.9 | HIP 77899 | 37.96 |
| 2026-08-10 12:00 | 15:52:34.50 | -03:51:42.7 | HIP 77899 | 38.06 |
| 2026-08-11 00:00 | 15:52:32.75 | -03:52:03.7 | HIP 77899 | 38.17 |
| 2026-08-11 12:00 | 15:52:31.06 | -03:52:24.9 | HIP 77899 | 38.26 |
| 2026-08-12 00:00 | 15:52:29.44 | -03:52:46.3 | HIP 77542 | 37.92 |
| 2026-08-12 12:00 | 15:52:27.89 | -03:53:08.0 | HIP 77542 | 37.51 |
| 2026-08-13 00:00 | 15:52:26.41 | -03:53:29.9 | HIP 77542 | 37.12 |
| 2026-08-13 12:00 | 15:52:25.00 | -03:53:52.0 | HIP 77542 | 36.75 |
| 2026-08-14 00:00 | 15:52:23.65 | -03:54:14.4 | HIP 77542 | 36.40 |
| 2026-08-14 12:00 | 15:52:22.36 | -03:54:36.9 | HIP 77542 | 36.07 |
| 2026-08-15 00:00 | 15:52:21.15 | -03:54:59.6 | HIP 77542 | 35.76 |
| 2026-08-15 12:00 | 15:52:20.00 | -03:55:22.6 | HIP 77542 | 35.48 |
| 2026-08-16 00:00 | 15:52:18.92 | -03:55:45.8 | HIP 77542 | 35.21 |
| 2026-08-16 12:00 | 15:52:17.90 | -03:56:09.1 | HIP 77542 | 34.97 |
| 2026-08-17 00:00 | 15:52:16.96 | -03:56:32.7 | HIP 77542 | 34.74 |
| 2026-08-17 12:00 | 15:52:16.07 | -03:56:56.4 | HIP 77542 | 34.54 |
| 2026-08-18 00:00 | 15:52:15.26 | -03:57:20.4 | HIP 77542 | 34.36 |
| 2026-08-18 12:00 | 15:52:14.51 | -03:57:44.5 | HIP 77542 | 34.20 |
| 2026-08-19 00:00 | 15:52:13.83 | -03:58:08.8 | HIP 77542 | 34.06 |