| Parameter |
Value |
| Designation |
P/2021 R8 (Sheppard) |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2021-10-07T12:21:16.145280Z |
| Orbit solution date (soln_date, UTC) |
2021-12-07T11:12:02Z |
| Obs used |
26 |
| NEO |
- |
| M1 |
18.600 |
| K1 |
10.000 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2021-09-05T13:08:45.772800Z |
| Discovery magnitude (MPC) |
21.69 G |
| Discovery observatory (MPC) |
T09 · Subaru Telescope, Maunakea |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-09-16.0000000 |
| e |
0.29404210 |
| q (au) |
2.130978 |
| a (au) |
3.018562 |
| i (deg) |
2.203054 |
| Ω (om, deg) |
167.025325 |
| ω (w, deg) |
190.793883 |
| M (ma, deg) |
355.956657 |
Magnitude
Scatter + Global Linear
$$
M_a = (16.419 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
16.419 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.900 |
| k |
1.000 |
| 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) |
| 2026-03-26 00:00 |
19:35:06.09 |
-19:34:41.1 |
HIP 96238 |
13.36 |
| 2026-03-26 12:00 |
19:35:47.45 |
-19:32:53.4 |
HIP 96238 |
23.13 |
| 2026-03-27 00:00 |
19:36:28.68 |
-19:31:05.3 |
HIP 96238 |
32.96 |
| 2026-03-27 12:00 |
19:37:09.77 |
-19:29:16.7 |
HIP 96424 |
37.08 |
| 2026-03-28 00:00 |
19:37:50.72 |
-19:27:27.8 |
HIP 96726 |
30.63 |
| 2026-03-28 12:00 |
19:38:31.54 |
-19:25:38.4 |
HIP 96726 |
21.36 |
| 2026-03-29 00:00 |
19:39:12.22 |
-19:23:48.6 |
HIP 96726 |
12.92 |
| 2026-03-29 12:00 |
19:39:52.76 |
-19:21:58.5 |
HIP 96726 |
8.25 |
| 2026-03-30 00:00 |
19:40:33.16 |
-19:20:07.9 |
HIP 96726 |
12.58 |
| 2026-03-30 12:00 |
19:41:13.43 |
-19:18:17.0 |
HIP 96726 |
20.87 |
| 2026-03-31 00:00 |
19:41:53.55 |
-19:16:25.8 |
HIP 97031 |
20.97 |
| 2026-03-31 12:00 |
19:42:33.52 |
-19:14:34.2 |
HIP 97031 |
12.05 |
| 2026-04-01 00:00 |
19:43:13.36 |
-19:12:42.2 |
HIP 97031 |
5.98 |
| 2026-04-01 12:00 |
19:43:53.04 |
-19:10:49.9 |
HIP 97031 |
10.47 |
| 2026-04-02 00:00 |
19:44:32.59 |
-19:08:57.3 |
HIP 97031 |
19.10 |
| 2026-04-02 12:00 |
19:45:11.98 |
-19:07:04.4 |
HIP 97031 |
28.28 |
| 2026-04-03 00:00 |
19:45:51.23 |
-19:05:11.1 |
HIP 97358 |
28.96 |
| 2026-04-03 12:00 |
19:46:30.33 |
-19:03:17.6 |
HIP 97358 |
21.69 |
| 2026-04-04 00:00 |
19:47:09.27 |
-19:01:23.8 |
HIP 97358 |
16.75 |
| 2026-04-04 12:00 |
19:47:48.07 |
-18:59:29.7 |
HIP 97358 |
16.33 |
| 2026-04-05 00:00 |
19:48:26.71 |
-18:57:35.4 |
HIP 97358 |
20.67 |
| 2026-04-05 12:00 |
19:49:05.19 |
-18:55:40.8 |
HIP 97358 |
27.57 |
| 2026-04-06 00:00 |
19:49:43.52 |
-18:53:46.0 |
HIP 97727 |
32.59 |
| 2026-04-06 12:00 |
19:50:21.69 |
-18:51:50.9 |
HIP 97727 |
27.22 |
| 2026-04-07 00:00 |
19:50:59.71 |
-18:49:55.6 |
HIP 97783 |
21.34 |
| 2026-04-07 12:00 |
19:51:37.56 |
-18:48:00.1 |
HIP 97783 |
16.80 |
| 2026-04-08 00:00 |
19:52:15.25 |
-18:46:04.5 |
HIP 97783 |
16.64 |
| 2026-04-08 12:00 |
19:52:52.78 |
-18:44:08.6 |
HIP 97783 |
20.91 |
| 2026-04-09 00:00 |
19:53:30.14 |
-18:42:12.5 |
HIP 98005 |
21.80 |
| 2026-04-09 12:00 |
19:54:07.33 |
-18:40:16.3 |
HIP 98005 |
13.91 |
| 2026-04-10 00:00 |
19:54:44.36 |
-18:38:20.0 |
HIP 98005 |
8.64 |
| 2026-04-10 12:00 |
19:55:21.22 |
-18:36:23.5 |
HIP 98005 |
10.81 |
| 2026-04-11 00:00 |
19:55:57.90 |
-18:34:26.9 |
HIP 98005 |
17.83 |
| 2026-04-11 12:00 |
19:56:34.42 |
-18:32:30.2 |
HIP 98078 |
21.89 |
| 2026-04-12 00:00 |
19:57:10.75 |
-18:30:33.3 |
HIP 98078 |
28.08 |
| 2026-04-12 12:00 |
19:57:46.92 |
-18:28:36.4 |
HIP 98339 |
22.19 |
| 2026-04-13 00:00 |
19:58:22.90 |
-18:26:39.4 |
HIP 98339 |
15.82 |
| 2026-04-13 12:00 |
19:58:58.71 |
-18:24:42.4 |
HIP 98339 |
12.71 |
| 2026-04-14 00:00 |
19:59:34.34 |
-18:22:45.3 |
HIP 98339 |
14.97 |
| 2026-04-14 12:00 |
20:00:09.78 |
-18:20:48.1 |
HIP 98502 |
8.43 |
| 2026-04-15 00:00 |
20:00:45.04 |
-18:18:51.0 |
HIP 98502 |
1.62 |
| 2026-04-15 12:00 |
20:01:20.11 |
-18:16:53.8 |
HIP 98502 |
9.00 |
| 2026-04-16 00:00 |
20:01:55.00 |
-18:14:56.7 |
HIP 98502 |
17.44 |