491P/Spacewatch-PANSTARRS
| Parameter |
Value |
| Designation |
491P/Spacewatch-PANSTARRS |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2024-09-06T08:23:41.847360Z |
| Orbit solution date (soln_date, UTC) |
2025-11-21T13:43:12Z |
| Obs used |
455 |
| NEO |
- |
| M1 |
10.900 |
| K1 |
8.500 |
| PC |
0.030 |
| 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) |
2020-12-03.0000000 |
| e |
0.25975071 |
| q (au) |
3.709914 |
| a (au) |
5.011709 |
| i (deg) |
9.371310 |
| Ω (om, deg) |
311.733543 |
| ω (w, deg) |
299.086407 |
| M (ma, deg) |
239.355776 |
Magnitude
Scatter + Global Linear
$$
M_a = (12.229 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
12.229 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.963 |
| 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) |
| 2026-02-03 00:00 |
21:29:12.24 |
-13:25:04.8 |
HIP 106068 |
22.87 |
| 2026-02-03 12:00 |
21:29:44.41 |
-13:22:01.5 |
HIP 106068 |
27.63 |
| 2026-02-04 00:00 |
21:30:16.56 |
-13:18:57.8 |
HIP 106068 |
33.84 |
| 2026-02-04 12:00 |
21:30:48.69 |
-13:15:53.8 |
HIP 106380 |
31.08 |
| 2026-02-05 00:00 |
21:31:20.80 |
-13:12:49.5 |
HIP 106380 |
25.65 |
| 2026-02-05 12:00 |
21:31:52.90 |
-13:09:45.0 |
HIP 106380 |
22.16 |
| 2026-02-06 00:00 |
21:32:24.97 |
-13:06:40.2 |
HIP 106380 |
21.56 |
| 2026-02-06 12:00 |
21:32:57.03 |
-13:03:35.1 |
HIP 106380 |
24.08 |
| 2026-02-07 00:00 |
21:33:29.07 |
-13:00:29.8 |
HIP 106441 |
26.54 |
| 2026-02-07 12:00 |
21:34:01.08 |
-12:57:24.1 |
HIP 106441 |
30.31 |
| 2026-02-08 00:00 |
21:34:33.07 |
-12:54:18.2 |
HIP 106497 |
34.95 |
| 2026-02-08 12:00 |
21:35:05.05 |
-12:51:12.1 |
HIP 106497 |
39.62 |
| 2026-02-09 00:00 |
21:35:37.00 |
-12:48:05.7 |
HIP 106698 |
42.64 |
| 2026-02-09 12:00 |
21:36:08.92 |
-12:44:59.0 |
HIP 106698 |
43.39 |
| 2026-02-10 00:00 |
21:36:40.82 |
-12:41:52.1 |
HIP 106951 |
43.74 |
| 2026-02-10 12:00 |
21:37:12.70 |
-12:38:44.9 |
HIP 106951 |
35.76 |
| 2026-02-11 00:00 |
21:37:44.56 |
-12:35:37.5 |
HIP 106951 |
28.02 |
| 2026-02-11 12:00 |
21:38:16.39 |
-12:32:29.8 |
HIP 106951 |
20.77 |
| 2026-02-12 00:00 |
21:38:48.19 |
-12:29:21.9 |
HIP 106951 |
14.78 |
| 2026-02-12 12:00 |
21:39:19.96 |
-12:26:13.8 |
HIP 106951 |
12.06 |
| 2026-02-13 00:00 |
21:39:51.71 |
-12:23:05.4 |
HIP 106951 |
14.57 |
| 2026-02-13 12:00 |
21:40:23.43 |
-12:19:56.8 |
HIP 106951 |
20.47 |
| 2026-02-14 00:00 |
21:40:55.12 |
-12:16:48.0 |
HIP 107127 |
16.06 |
| 2026-02-14 12:00 |
21:41:26.79 |
-12:13:39.0 |
HIP 107127 |
8.33 |
| 2026-02-15 00:00 |
21:41:58.42 |
-12:10:29.8 |
HIP 107127 |
4.51 |
| 2026-02-15 12:00 |
21:42:30.02 |
-12:07:20.3 |
HIP 107182 |
5.07 |
| 2026-02-16 00:00 |
21:43:01.60 |
-12:04:10.7 |
HIP 107182 |
6.27 |
| 2026-02-16 12:00 |
21:43:33.14 |
-12:01:00.8 |
HIP 107182 |
13.85 |
| 2026-02-17 00:00 |
21:44:04.65 |
-11:57:50.8 |
HIP 107337 |
12.40 |
| 2026-02-17 12:00 |
21:44:36.12 |
-11:54:40.5 |
HIP 107337 |
8.82 |
| 2026-02-18 00:00 |
21:45:07.56 |
-11:51:30.1 |
HIP 107337 |
11.85 |
| 2026-02-18 12:00 |
21:45:38.97 |
-11:48:19.5 |
HIP 107527 |
16.75 |
| 2026-02-19 00:00 |
21:46:10.34 |
-11:45:08.7 |
HIP 107527 |
8.44 |
| 2026-02-19 12:00 |
21:46:41.68 |
-11:41:57.7 |
HIP 107527 |
0.15 |
| 2026-02-20 00:00 |
21:47:12.98 |
-11:38:46.6 |
HIP 107527 |
8.17 |
| 2026-02-20 12:00 |
21:47:44.24 |
-11:35:35.3 |
HIP 107527 |
16.46 |
| 2026-02-21 00:00 |
21:48:15.47 |
-11:32:23.9 |
HIP 107758 |
23.77 |
| 2026-02-21 12:00 |
21:48:46.66 |
-11:29:12.3 |
HIP 107758 |
18.68 |
| 2026-02-22 00:00 |
21:49:17.80 |
-11:26:00.5 |
HIP 107793 |
14.22 |
| 2026-02-22 12:00 |
21:49:48.91 |
-11:22:48.6 |
HIP 107793 |
5.96 |
| 2026-02-23 00:00 |
21:50:19.98 |
-11:19:36.5 |
HIP 107793 |
2.31 |
| 2026-02-23 12:00 |
21:50:51.01 |
-11:16:24.4 |
HIP 107793 |
10.56 |
| 2026-02-24 00:00 |
21:51:22.00 |
-11:13:12.1 |
HIP 107793 |
18.80 |