| Parameter |
Value |
| Designation |
491P/Spacewatch-PANSTARRS |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2024-09-07T03:51:41.734080Z |
| Orbit solution date (soln_date, UTC) |
2026-09-21T07:12:14Z |
| Obs used |
673 |
| NEO |
- |
| M1 |
13.200 |
| K1 |
4.750 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2024-05-30T08:01:15.830400Z |
| Discovery magnitude (MPC) |
21.20 w |
| Discovery observatory (MPC) |
F51 · Pan-STARRS 1, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2022-10-02.0000000 |
| e |
0.25897755 |
| q (au) |
3.714649 |
| a (au) |
5.012870 |
| i (deg) |
9.367374 |
| Ω (om, deg) |
311.729881 |
| ω (w, deg) |
299.042627 |
| M (ma, deg) |
297.987658 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.212 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.212 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.965 |
| 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
Finding Chart
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
22:44:23.81 |
-00:55:42.8 |
HIP 112255 |
3.33 |
| 2026-09-20 12:00 |
22:44:08.95 |
-00:56:58.7 |
HIP 112255 |
0.78 |
| 2026-09-21 00:00 |
22:43:54.18 |
-00:58:14.4 |
HIP 112255 |
4.55 |
| 2026-09-21 12:00 |
22:43:39.52 |
-00:59:30.0 |
HIP 112255 |
8.42 |
| 2026-09-22 00:00 |
22:43:24.96 |
-01:00:45.5 |
HIP 112255 |
12.27 |
| 2026-09-22 12:00 |
22:43:10.50 |
-01:02:00.7 |
HIP 112255 |
16.09 |
| 2026-09-23 00:00 |
22:42:56.16 |
-01:03:15.8 |
HIP 112104 |
17.70 |
| 2026-09-23 12:00 |
22:42:41.92 |
-01:04:30.7 |
HIP 112104 |
17.60 |
| 2026-09-24 00:00 |
22:42:27.80 |
-01:05:45.3 |
HIP 112104 |
18.28 |
| 2026-09-24 12:00 |
22:42:13.80 |
-01:06:59.8 |
HIP 112104 |
19.66 |
| 2026-09-25 00:00 |
22:41:59.91 |
-01:08:13.9 |
HIP 112030 |
19.49 |
| 2026-09-25 12:00 |
22:41:46.15 |
-01:09:27.8 |
HIP 112030 |
17.18 |
| 2026-09-26 00:00 |
22:41:32.50 |
-01:10:41.4 |
HIP 112030 |
15.40 |
| 2026-09-26 12:00 |
22:41:18.98 |
-01:11:54.7 |
HIP 112030 |
14.34 |
| 2026-09-27 00:00 |
22:41:05.59 |
-01:13:07.8 |
HIP 112030 |
14.13 |
| 2026-09-27 12:00 |
22:40:52.33 |
-01:14:20.4 |
HIP 112030 |
14.78 |
| 2026-09-28 00:00 |
22:40:39.19 |
-01:15:32.8 |
HIP 112030 |
16.18 |
| 2026-09-28 12:00 |
22:40:26.19 |
-01:16:44.7 |
HIP 112030 |
18.12 |
| 2026-09-29 00:00 |
22:40:13.33 |
-01:17:56.3 |
HIP 112030 |
20.44 |
| 2026-09-29 12:00 |
22:40:00.60 |
-01:19:07.6 |
HIP 112030 |
23.01 |
| 2026-09-30 00:00 |
22:39:48.01 |
-01:20:18.4 |
HIP 112030 |
25.74 |
| 2026-09-30 12:00 |
22:39:35.56 |
-01:21:28.8 |
HIP 112030 |
28.57 |
| 2026-10-01 00:00 |
22:39:23.25 |
-01:22:38.8 |
HIP 112030 |
31.46 |
| 2026-10-01 12:00 |
22:39:11.09 |
-01:23:48.3 |
HIP 112030 |
34.39 |
| 2026-10-02 00:00 |
22:38:59.07 |
-01:24:57.4 |
HIP 112030 |
37.33 |
| 2026-10-02 12:00 |
22:38:47.20 |
-01:26:06.0 |
HIP 112030 |
40.28 |
| 2026-10-03 00:00 |
22:38:35.49 |
-01:27:14.2 |
HIP 112030 |
43.23 |
| 2026-10-03 12:00 |
22:38:23.92 |
-01:28:21.8 |
HIP 112030 |
46.16 |
| 2026-10-04 00:00 |
22:38:12.51 |
-01:29:28.9 |
HIP 111474 |
46.62 |
| 2026-10-04 12:00 |
22:38:01.25 |
-01:30:35.5 |
HIP 111474 |
43.77 |
| 2026-10-05 00:00 |
22:37:50.15 |
-01:31:41.6 |
HIP 111474 |
40.99 |
| 2026-10-05 12:00 |
22:37:39.21 |
-01:32:47.1 |
HIP 111474 |
38.27 |
| 2026-10-06 00:00 |
22:37:28.43 |
-01:33:52.0 |
HIP 111474 |
35.64 |
| 2026-10-06 12:00 |
22:37:17.81 |
-01:34:56.3 |
HIP 111474 |
33.09 |
| 2026-10-07 00:00 |
22:37:07.36 |
-01:36:00.1 |
HIP 111474 |
30.63 |
| 2026-10-07 12:00 |
22:36:57.08 |
-01:37:03.2 |
HIP 111474 |
28.28 |
| 2026-10-08 00:00 |
22:36:46.96 |
-01:38:05.7 |
HIP 111474 |
26.05 |
| 2026-10-08 12:00 |
22:36:37.01 |
-01:39:07.6 |
HIP 111474 |
23.96 |
| 2026-10-09 00:00 |
22:36:27.23 |
-01:40:08.8 |
HIP 111474 |
22.04 |
| 2026-10-09 12:00 |
22:36:17.63 |
-01:41:09.3 |
HIP 111474 |
20.31 |
| 2026-10-10 00:00 |
22:36:08.20 |
-01:42:09.2 |
HIP 111474 |
18.82 |
| 2026-10-10 12:00 |
22:35:58.94 |
-01:43:08.4 |
HIP 111474 |
17.61 |
| 2026-10-11 00:00 |
22:35:49.87 |
-01:44:06.8 |
HIP 111474 |
16.70 |