P/2021 R8 (Sheppard)
| 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) |
| 2026-02-03 00:00 |
18:16:12.49 |
-21:36:42.6 |
HIP 89369 |
27.76 |
| 2026-02-03 12:00 |
18:17:02.19 |
-21:36:16.0 |
HIP 89687 |
26.57 |
| 2026-02-04 00:00 |
18:17:51.86 |
-21:35:48.5 |
HIP 89744 |
16.42 |
| 2026-02-04 12:00 |
18:18:41.50 |
-21:35:19.9 |
HIP 89744 |
8.14 |
| 2026-02-05 00:00 |
18:19:31.09 |
-21:34:50.3 |
HIP 89744 |
11.38 |
| 2026-02-05 12:00 |
18:20:20.66 |
-21:34:19.7 |
HIP 89744 |
21.42 |
| 2026-02-06 00:00 |
18:21:10.18 |
-21:33:48.1 |
HIP 89744 |
32.46 |
| 2026-02-06 12:00 |
18:21:59.66 |
-21:33:15.4 |
HIP 90130 |
23.10 |
| 2026-02-07 00:00 |
18:22:49.11 |
-21:32:41.7 |
HIP 90130 |
12.82 |
| 2026-02-07 12:00 |
18:23:38.51 |
-21:32:07.0 |
HIP 90130 |
7.77 |
| 2026-02-08 00:00 |
18:24:27.88 |
-21:31:31.3 |
HIP 90130 |
14.85 |
| 2026-02-08 12:00 |
18:25:17.20 |
-21:30:54.6 |
HIP 90145 |
24.85 |
| 2026-02-09 00:00 |
18:26:06.48 |
-21:30:16.8 |
HIP 90516 |
32.92 |
| 2026-02-09 12:00 |
18:26:55.71 |
-21:29:38.1 |
HIP 90516 |
23.13 |
| 2026-02-10 00:00 |
18:27:44.90 |
-21:28:58.4 |
HIP 90516 |
15.79 |
| 2026-02-10 12:00 |
18:28:34.04 |
-21:28:17.6 |
HIP 90516 |
15.04 |
| 2026-02-11 00:00 |
18:29:23.14 |
-21:27:35.9 |
HIP 90700 |
20.22 |
| 2026-02-11 12:00 |
18:30:12.19 |
-21:26:53.2 |
HIP 90700 |
15.00 |
| 2026-02-12 00:00 |
18:31:01.18 |
-21:26:09.4 |
HIP 90811 |
12.93 |
| 2026-02-12 12:00 |
18:31:50.13 |
-21:25:24.7 |
HIP 90811 |
11.55 |
| 2026-02-13 00:00 |
18:32:39.03 |
-21:24:39.1 |
HIP 90811 |
18.97 |
| 2026-02-13 12:00 |
18:33:27.88 |
-21:23:52.4 |
HIP 91046 |
15.44 |
| 2026-02-14 00:00 |
18:34:16.67 |
-21:23:04.8 |
HIP 91046 |
10.18 |
| 2026-02-14 12:00 |
18:35:05.41 |
-21:22:16.2 |
HIP 91046 |
15.11 |
| 2026-02-15 00:00 |
18:35:54.09 |
-21:21:26.6 |
HIP 91304 |
23.32 |
| 2026-02-15 12:00 |
18:36:42.72 |
-21:20:36.1 |
HIP 91304 |
13.91 |
| 2026-02-16 00:00 |
18:37:31.29 |
-21:19:44.6 |
HIP 91347 |
6.78 |
| 2026-02-16 12:00 |
18:38:19.80 |
-21:18:52.1 |
HIP 91347 |
7.73 |
| 2026-02-17 00:00 |
18:39:08.26 |
-21:17:58.7 |
HIP 91438 |
15.28 |
| 2026-02-17 12:00 |
18:39:56.65 |
-21:17:04.4 |
HIP 91438 |
20.31 |
| 2026-02-18 00:00 |
18:40:44.98 |
-21:16:09.1 |
HIP 91438 |
29.10 |
| 2026-02-18 12:00 |
18:41:33.25 |
-21:15:12.9 |
HIP 91849 |
34.36 |
| 2026-02-19 00:00 |
18:42:21.46 |
-21:14:15.8 |
HIP 91849 |
25.35 |
| 2026-02-19 12:00 |
18:43:09.60 |
-21:13:17.7 |
HIP 91849 |
18.95 |
| 2026-02-20 00:00 |
18:43:57.67 |
-21:12:18.7 |
HIP 91954 |
16.93 |
| 2026-02-20 12:00 |
18:44:45.68 |
-21:11:18.9 |
HIP 91954 |
13.16 |
| 2026-02-21 00:00 |
18:45:33.63 |
-21:10:18.0 |
HIP 92016 |
10.79 |
| 2026-02-21 12:00 |
18:46:21.50 |
-21:09:16.3 |
HIP 92016 |
17.30 |
| 2026-02-22 00:00 |
18:47:09.31 |
-21:08:13.7 |
HIP 92242 |
15.22 |
| 2026-02-22 12:00 |
18:47:57.04 |
-21:07:10.2 |
HIP 92242 |
9.38 |
| 2026-02-23 00:00 |
18:48:44.71 |
-21:06:05.8 |
HIP 92242 |
13.93 |
| 2026-02-23 12:00 |
18:49:32.30 |
-21:05:00.6 |
HIP 92242 |
23.43 |
| 2026-02-24 00:00 |
18:50:19.82 |
-21:03:54.4 |
HIP 92242 |
33.94 |