| Parameter |
Value |
| Designation |
C/2021 U4 (Leonard) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-12-21T23:21:30.078720Z |
| Orbit solution date (soln_date, UTC) |
2025-01-14T17:42:12Z |
| Obs used |
37 |
| NEO |
- |
| M1 |
18.800 |
| K1 |
4.500 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-10-31T07:11:48.940800Z |
| Discovery magnitude (MPC) |
19.87 G |
| Discovery observatory (MPC) |
G96 · University of Arizona Mt. Lemmon Survey |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-10-27.0000000 |
| e |
0.95934634 |
| q (au) |
1.787292 |
| a (au) |
43.963864 |
| i (deg) |
152.875238 |
| Ω (om, deg) |
241.798913 |
| ω (w, deg) |
237.287717 |
| M (ma, deg) |
359.810748 |
Magnitude
Scatter + Global Linear
$$
M_a = (19.361 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
19.361 |
| n |
2.000 |
| gf |
0.977 |
| gb |
-0.500 |
| k |
0.800 |
| δ90 |
5.683 |
| 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) |
| 2026-07-29 00:00 |
14:46:47.11 |
-07:40:45.7 |
HIP 72218 |
10.91 |
| 2026-07-29 12:00 |
14:46:45.23 |
-07:40:47.8 |
HIP 72218 |
10.54 |
| 2026-07-30 00:00 |
14:46:43.43 |
-07:40:50.1 |
HIP 72218 |
10.18 |
| 2026-07-30 12:00 |
14:46:41.70 |
-07:40:52.9 |
HIP 72218 |
9.84 |
| 2026-07-31 00:00 |
14:46:40.04 |
-07:40:55.9 |
HIP 72218 |
9.52 |
| 2026-07-31 12:00 |
14:46:38.45 |
-07:40:59.3 |
HIP 72218 |
9.21 |
| 2026-08-01 00:00 |
14:46:36.94 |
-07:41:03.0 |
HIP 72218 |
8.91 |
| 2026-08-01 12:00 |
14:46:35.50 |
-07:41:07.1 |
HIP 72218 |
8.63 |
| 2026-08-02 00:00 |
14:46:34.13 |
-07:41:11.5 |
HIP 72218 |
8.37 |
| 2026-08-02 12:00 |
14:46:32.84 |
-07:41:16.2 |
HIP 72218 |
8.11 |
| 2026-08-03 00:00 |
14:46:31.62 |
-07:41:21.2 |
HIP 72218 |
7.87 |
| 2026-08-03 12:00 |
14:46:30.47 |
-07:41:26.6 |
HIP 72218 |
7.63 |
| 2026-08-04 00:00 |
14:46:29.40 |
-07:41:32.3 |
HIP 72218 |
7.41 |
| 2026-08-04 12:00 |
14:46:28.39 |
-07:41:38.3 |
HIP 72218 |
7.19 |
| 2026-08-05 00:00 |
14:46:27.46 |
-07:41:44.7 |
HIP 72218 |
6.99 |
| 2026-08-05 12:00 |
14:46:26.61 |
-07:41:51.3 |
HIP 72218 |
6.79 |
| 2026-08-06 00:00 |
14:46:25.82 |
-07:41:58.3 |
HIP 72218 |
6.59 |
| 2026-08-06 12:00 |
14:46:25.11 |
-07:42:05.6 |
HIP 72218 |
6.40 |
| 2026-08-07 00:00 |
14:46:24.46 |
-07:42:13.2 |
HIP 72218 |
6.22 |
| 2026-08-07 12:00 |
14:46:23.89 |
-07:42:21.2 |
HIP 72218 |
6.04 |
| 2026-08-08 00:00 |
14:46:23.40 |
-07:42:29.4 |
HIP 72218 |
5.86 |
| 2026-08-08 12:00 |
14:46:22.97 |
-07:42:37.9 |
HIP 72218 |
5.69 |
| 2026-08-09 00:00 |
14:46:22.61 |
-07:42:46.8 |
HIP 72218 |
5.52 |
| 2026-08-09 12:00 |
14:46:22.33 |
-07:42:55.9 |
HIP 72218 |
5.35 |
| 2026-08-10 00:00 |
14:46:22.12 |
-07:43:05.4 |
HIP 72218 |
5.18 |
| 2026-08-10 12:00 |
14:46:21.98 |
-07:43:15.2 |
HIP 72218 |
5.02 |
| 2026-08-11 00:00 |
14:46:21.91 |
-07:43:25.2 |
HIP 72218 |
4.86 |
| 2026-08-11 12:00 |
14:46:21.91 |
-07:43:35.6 |
HIP 72218 |
4.71 |
| 2026-08-12 00:00 |
14:46:21.98 |
-07:43:46.2 |
HIP 72218 |
4.56 |
| 2026-08-12 12:00 |
14:46:22.12 |
-07:43:57.2 |
HIP 72218 |
4.41 |
| 2026-08-13 00:00 |
14:46:22.33 |
-07:44:08.4 |
HIP 72218 |
4.28 |
| 2026-08-13 12:00 |
14:46:22.61 |
-07:44:19.9 |
HIP 72218 |
4.15 |
| 2026-08-14 00:00 |
14:46:22.96 |
-07:44:31.7 |
HIP 72218 |
4.04 |
| 2026-08-14 12:00 |
14:46:23.38 |
-07:44:43.8 |
HIP 72218 |
3.94 |
| 2026-08-15 00:00 |
14:46:23.87 |
-07:44:56.2 |
HIP 72218 |
3.86 |
| 2026-08-15 12:00 |
14:46:24.42 |
-07:45:08.8 |
HIP 72218 |
3.80 |
| 2026-08-16 00:00 |
14:46:25.05 |
-07:45:21.7 |
HIP 72218 |
3.77 |
| 2026-08-16 12:00 |
14:46:25.74 |
-07:45:34.9 |
HIP 72218 |
3.77 |
| 2026-08-17 00:00 |
14:46:26.51 |
-07:45:48.4 |
HIP 72218 |
3.80 |
| 2026-08-17 12:00 |
14:46:27.34 |
-07:46:02.1 |
HIP 72218 |
3.86 |
| 2026-08-18 00:00 |
14:46:28.23 |
-07:46:16.1 |
HIP 72218 |
3.96 |
| 2026-08-18 12:00 |
14:46:29.20 |
-07:46:30.3 |
HIP 72218 |
4.10 |
| 2026-08-19 00:00 |
14:46:30.23 |
-07:46:44.8 |
HIP 72218 |
4.28 |