C/2021 G1 (Leonard)
| Parameter |
Value |
| Designation |
C/2021 G1 (Leonard) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-07-22T06:47:31.761600Z |
| Orbit solution date (soln_date, UTC) |
2025-01-14T17:42:12Z |
| Obs used |
54 |
| NEO |
- |
| M1 |
13.700 |
| K1 |
10.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-04-11T07:50:24.892800Z |
| Discovery magnitude (MPC) |
21.72 G |
| Discovery observatory (MPC) |
G96 · Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-04-21.0000000 |
| e |
0.95490157 |
| q (au) |
3.423704 |
| a (au) |
75.916250 |
| i (deg) |
131.566251 |
| Ω (om, deg) |
270.695657 |
| ω (w, deg) |
107.498712 |
| M (ma, deg) |
359.862493 |
Magnitude
Scatter + Global Linear
$$
M_a = (19.995 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
19.995 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
0.800 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
03:46:18.55 |
-14:22:38.8 |
HIP 17659 |
10.93 |
| 2026-02-03 12:00 |
03:46:14.90 |
-14:21:48.3 |
HIP 17659 |
12.13 |
| 2026-02-04 00:00 |
03:46:11.35 |
-14:20:57.4 |
HIP 17659 |
13.33 |
| 2026-02-04 12:00 |
03:46:07.88 |
-14:20:06.3 |
HIP 17659 |
14.51 |
| 2026-02-05 00:00 |
03:46:04.50 |
-14:19:14.8 |
HIP 17659 |
15.68 |
| 2026-02-05 12:00 |
03:46:01.20 |
-14:18:23.0 |
HIP 17659 |
16.83 |
| 2026-02-06 00:00 |
03:45:58.00 |
-14:17:30.9 |
HIP 17659 |
17.98 |
| 2026-02-06 12:00 |
03:45:54.88 |
-14:16:38.6 |
HIP 17659 |
19.11 |
| 2026-02-07 00:00 |
03:45:51.86 |
-14:15:45.9 |
HIP 17659 |
20.24 |
| 2026-02-07 12:00 |
03:45:48.92 |
-14:14:53.0 |
HIP 17659 |
21.35 |
| 2026-02-08 00:00 |
03:45:46.07 |
-14:13:59.8 |
HIP 17659 |
22.45 |
| 2026-02-08 12:00 |
03:45:43.30 |
-14:13:06.4 |
HIP 17659 |
23.54 |
| 2026-02-09 00:00 |
03:45:40.63 |
-14:12:12.7 |
HIP 17659 |
24.62 |
| 2026-02-09 12:00 |
03:45:38.04 |
-14:11:18.7 |
HIP 17659 |
25.69 |
| 2026-02-10 00:00 |
03:45:35.54 |
-14:10:24.5 |
HIP 17659 |
26.75 |
| 2026-02-10 12:00 |
03:45:33.13 |
-14:09:30.1 |
HIP 17659 |
27.80 |
| 2026-02-11 00:00 |
03:45:30.81 |
-14:08:35.4 |
HIP 17659 |
28.84 |
| 2026-02-11 12:00 |
03:45:28.57 |
-14:07:40.5 |
HIP 17659 |
29.87 |
| 2026-02-12 00:00 |
03:45:26.42 |
-14:06:45.4 |
HIP 17659 |
30.88 |
| 2026-02-12 12:00 |
03:45:24.36 |
-14:05:50.0 |
HIP 17659 |
31.89 |
| 2026-02-13 00:00 |
03:45:22.38 |
-14:04:54.5 |
HIP 17659 |
32.89 |
| 2026-02-13 12:00 |
03:45:20.49 |
-14:03:58.8 |
HIP 17659 |
33.88 |
| 2026-02-14 00:00 |
03:45:18.69 |
-14:03:02.8 |
HIP 17659 |
34.86 |
| 2026-02-14 12:00 |
03:45:16.98 |
-14:02:06.7 |
HIP 17484 |
34.89 |
| 2026-02-15 00:00 |
03:45:15.35 |
-14:01:10.4 |
HIP 17484 |
33.89 |
| 2026-02-15 12:00 |
03:45:13.81 |
-14:00:14.0 |
HIP 17484 |
32.89 |
| 2026-02-16 00:00 |
03:45:12.35 |
-13:59:17.3 |
HIP 17484 |
31.89 |
| 2026-02-16 12:00 |
03:45:10.98 |
-13:58:20.6 |
HIP 17484 |
30.90 |
| 2026-02-17 00:00 |
03:45:09.70 |
-13:57:23.6 |
HIP 17484 |
29.91 |
| 2026-02-17 12:00 |
03:45:08.50 |
-13:56:26.5 |
HIP 17484 |
28.92 |
| 2026-02-18 00:00 |
03:45:07.38 |
-13:55:29.3 |
HIP 17484 |
27.93 |
| 2026-02-18 12:00 |
03:45:06.35 |
-13:54:32.0 |
HIP 17484 |
26.94 |
| 2026-02-19 00:00 |
03:45:05.41 |
-13:53:34.5 |
HIP 17484 |
25.96 |
| 2026-02-19 12:00 |
03:45:04.55 |
-13:52:36.9 |
HIP 17484 |
24.98 |
| 2026-02-20 00:00 |
03:45:03.78 |
-13:51:39.2 |
HIP 17484 |
24.00 |
| 2026-02-20 12:00 |
03:45:03.08 |
-13:50:41.4 |
HIP 17484 |
23.02 |
| 2026-02-21 00:00 |
03:45:02.48 |
-13:49:43.5 |
HIP 17484 |
22.04 |
| 2026-02-21 12:00 |
03:45:01.95 |
-13:48:45.5 |
HIP 17484 |
21.07 |
| 2026-02-22 00:00 |
03:45:01.51 |
-13:47:47.4 |
HIP 17484 |
20.10 |
| 2026-02-22 12:00 |
03:45:01.15 |
-13:46:49.3 |
HIP 17484 |
19.13 |
| 2026-02-23 00:00 |
03:45:00.88 |
-13:45:51.0 |
HIP 17484 |
18.17 |
| 2026-02-23 12:00 |
03:45:00.68 |
-13:44:52.8 |
HIP 17484 |
17.21 |
| 2026-02-24 00:00 |
03:45:00.57 |
-13:43:54.4 |
HIP 17484 |
16.25 |