| 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) |
| 2026-06-01 00:00 |
14:58:26.69 |
-08:19:46.0 |
HIP 73255 |
22.02 |
| 2026-06-01 12:00 |
14:58:17.19 |
-08:19:04.1 |
HIP 73255 |
22.60 |
| 2026-06-02 00:00 |
14:58:07.73 |
-08:18:22.6 |
HIP 73255 |
23.42 |
| 2026-06-02 12:00 |
14:57:58.31 |
-08:17:41.3 |
HIP 73255 |
24.45 |
| 2026-06-03 00:00 |
14:57:48.94 |
-08:17:00.4 |
HIP 73255 |
25.65 |
| 2026-06-03 12:00 |
14:57:39.61 |
-08:16:19.9 |
HIP 73255 |
27.01 |
| 2026-06-04 00:00 |
14:57:30.33 |
-08:15:39.6 |
HIP 73255 |
28.50 |
| 2026-06-04 12:00 |
14:57:21.09 |
-08:14:59.8 |
HIP 73255 |
30.10 |
| 2026-06-05 00:00 |
14:57:11.89 |
-08:14:20.2 |
HIP 73255 |
31.78 |
| 2026-06-05 12:00 |
14:57:02.75 |
-08:13:41.1 |
HIP 73255 |
33.54 |
| 2026-06-06 00:00 |
14:56:53.65 |
-08:13:02.2 |
HIP 73255 |
35.35 |
| 2026-06-06 12:00 |
14:56:44.60 |
-08:12:23.7 |
HIP 72943 |
35.32 |
| 2026-06-07 00:00 |
14:56:35.59 |
-08:11:45.6 |
HIP 72943 |
33.42 |
| 2026-06-07 12:00 |
14:56:26.64 |
-08:11:07.8 |
HIP 72943 |
31.59 |
| 2026-06-08 00:00 |
14:56:17.73 |
-08:10:30.4 |
HIP 72943 |
29.83 |
| 2026-06-08 12:00 |
14:56:08.88 |
-08:09:53.4 |
HIP 72943 |
28.16 |
| 2026-06-09 00:00 |
14:56:00.08 |
-08:09:16.7 |
HIP 72943 |
26.58 |
| 2026-06-09 12:00 |
14:55:51.32 |
-08:08:40.3 |
HIP 72943 |
25.12 |
| 2026-06-10 00:00 |
14:55:42.62 |
-08:08:04.4 |
HIP 72943 |
23.78 |
| 2026-06-10 12:00 |
14:55:33.97 |
-08:07:28.8 |
HIP 72943 |
22.59 |
| 2026-06-11 00:00 |
14:55:25.38 |
-08:06:53.6 |
HIP 72943 |
21.57 |
| 2026-06-11 12:00 |
14:55:16.84 |
-08:06:18.7 |
HIP 72943 |
20.74 |
| 2026-06-12 00:00 |
14:55:08.35 |
-08:05:44.2 |
HIP 72943 |
20.11 |
| 2026-06-12 12:00 |
14:54:59.92 |
-08:05:10.1 |
HIP 72943 |
19.70 |
| 2026-06-13 00:00 |
14:54:51.54 |
-08:04:36.4 |
HIP 72943 |
19.53 |
| 2026-06-13 12:00 |
14:54:43.22 |
-08:04:03.1 |
HIP 72943 |
19.58 |
| 2026-06-14 00:00 |
14:54:34.96 |
-08:03:30.1 |
HIP 72943 |
19.86 |
| 2026-06-14 12:00 |
14:54:26.75 |
-08:02:57.5 |
HIP 72844 |
19.02 |
| 2026-06-15 00:00 |
14:54:18.60 |
-08:02:25.3 |
HIP 72844 |
17.05 |
| 2026-06-15 12:00 |
14:54:10.51 |
-08:01:53.5 |
HIP 72844 |
15.14 |
| 2026-06-16 00:00 |
14:54:02.48 |
-08:01:22.0 |
HIP 72844 |
13.28 |
| 2026-06-16 12:00 |
14:53:54.51 |
-08:00:51.0 |
HIP 72844 |
11.51 |
| 2026-06-17 00:00 |
14:53:46.60 |
-08:00:20.3 |
HIP 72844 |
9.86 |
| 2026-06-17 12:00 |
14:53:38.75 |
-07:59:50.1 |
HIP 72844 |
8.38 |
| 2026-06-18 00:00 |
14:53:30.96 |
-07:59:20.2 |
HIP 72844 |
7.18 |
| 2026-06-18 12:00 |
14:53:23.23 |
-07:58:50.7 |
HIP 72844 |
6.39 |
| 2026-06-19 00:00 |
14:53:15.56 |
-07:58:21.6 |
HIP 72844 |
6.16 |
| 2026-06-19 12:00 |
14:53:07.96 |
-07:57:52.9 |
HIP 72844 |
6.54 |
| 2026-06-20 00:00 |
14:53:00.42 |
-07:57:24.6 |
HIP 72844 |
7.42 |
| 2026-06-20 12:00 |
14:52:52.94 |
-07:56:56.7 |
HIP 72844 |
8.63 |
| 2026-06-21 00:00 |
14:52:45.52 |
-07:56:29.2 |
HIP 72844 |
10.05 |
| 2026-06-21 12:00 |
14:52:38.17 |
-07:56:02.0 |
HIP 72844 |
11.59 |
| 2026-06-22 00:00 |
14:52:30.89 |
-07:55:35.3 |
HIP 72844 |
13.21 |