| 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
$$
M_a = (12.212 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
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) |
| 2026-05-12 00:00 |
22:57:15.11 |
-03:17:48.6 |
HIP 113331 |
3.72 |
| 2026-05-12 12:00 |
22:57:33.10 |
-03:15:09.8 |
HIP 113355 |
6.01 |
| 2026-05-13 00:00 |
22:57:50.95 |
-03:12:31.6 |
HIP 113355 |
6.98 |
| 2026-05-13 12:00 |
22:58:08.67 |
-03:09:54.1 |
HIP 113355 |
10.69 |
| 2026-05-14 00:00 |
22:58:26.26 |
-03:07:17.1 |
HIP 113355 |
15.22 |
| 2026-05-14 12:00 |
22:58:43.71 |
-03:04:40.8 |
HIP 113523 |
16.20 |
| 2026-05-15 00:00 |
22:59:01.02 |
-03:02:05.2 |
HIP 113523 |
11.39 |
| 2026-05-15 12:00 |
22:59:18.19 |
-02:59:30.2 |
HIP 113523 |
6.94 |
| 2026-05-16 00:00 |
22:59:35.23 |
-02:56:55.8 |
HIP 113523 |
4.08 |
| 2026-05-16 12:00 |
22:59:52.13 |
-02:54:22.1 |
HIP 113555 |
3.42 |
| 2026-05-17 00:00 |
23:00:08.88 |
-02:51:49.1 |
HIP 113555 |
2.52 |
| 2026-05-17 12:00 |
23:00:25.50 |
-02:49:16.7 |
HIP 113555 |
6.97 |
| 2026-05-18 00:00 |
23:00:41.97 |
-02:46:45.0 |
HIP 113555 |
11.71 |
| 2026-05-18 12:00 |
23:00:58.30 |
-02:44:14.0 |
HIP 113727 |
14.59 |
| 2026-05-19 00:00 |
23:01:14.48 |
-02:41:43.7 |
HIP 113727 |
10.23 |
| 2026-05-19 12:00 |
23:01:30.53 |
-02:39:14.1 |
HIP 113727 |
6.50 |
| 2026-05-20 00:00 |
23:01:46.42 |
-02:36:45.2 |
HIP 113727 |
4.95 |
| 2026-05-20 12:00 |
23:02:02.18 |
-02:34:17.0 |
HIP 113727 |
7.08 |
| 2026-05-21 00:00 |
23:02:17.78 |
-02:31:49.5 |
HIP 113727 |
10.88 |
| 2026-05-21 12:00 |
23:02:33.24 |
-02:29:22.7 |
HIP 113727 |
15.10 |
| 2026-05-22 00:00 |
23:02:48.55 |
-02:26:56.7 |
HIP 113727 |
19.45 |
| 2026-05-22 12:00 |
23:03:03.72 |
-02:24:31.4 |
HIP 113727 |
23.83 |
| 2026-05-23 00:00 |
23:03:18.73 |
-02:22:06.8 |
HIP 113727 |
28.21 |
| 2026-05-23 12:00 |
23:03:33.60 |
-02:19:42.9 |
HIP 113931 |
28.06 |
| 2026-05-24 00:00 |
23:03:48.31 |
-02:17:19.8 |
HIP 113931 |
24.52 |
| 2026-05-24 12:00 |
23:04:02.88 |
-02:14:57.4 |
HIP 113931 |
21.32 |
| 2026-05-25 00:00 |
23:04:17.29 |
-02:12:35.8 |
HIP 113931 |
18.61 |
| 2026-05-25 12:00 |
23:04:31.55 |
-02:10:15.0 |
HIP 113931 |
16.58 |
| 2026-05-26 00:00 |
23:04:45.66 |
-02:07:54.9 |
HIP 113931 |
15.49 |
| 2026-05-26 12:00 |
23:04:59.62 |
-02:05:35.5 |
HIP 113931 |
15.50 |
| 2026-05-27 00:00 |
23:05:13.42 |
-02:03:17.0 |
HIP 113931 |
16.58 |
| 2026-05-27 12:00 |
23:05:27.06 |
-02:00:59.2 |
HIP 113931 |
18.51 |
| 2026-05-28 00:00 |
23:05:40.56 |
-01:58:42.2 |
HIP 113931 |
21.04 |
| 2026-05-28 12:00 |
23:05:53.89 |
-01:56:26.0 |
HIP 113931 |
23.97 |
| 2026-05-29 00:00 |
23:06:07.07 |
-01:54:10.6 |
HIP 114202 |
26.32 |
| 2026-05-29 12:00 |
23:06:20.09 |
-01:51:55.9 |
HIP 114202 |
24.72 |
| 2026-05-30 00:00 |
23:06:32.96 |
-01:49:42.1 |
HIP 114202 |
23.69 |
| 2026-05-30 12:00 |
23:06:45.66 |
-01:47:29.1 |
HIP 114202 |
23.30 |
| 2026-05-31 00:00 |
23:06:58.21 |
-01:45:16.9 |
HIP 114202 |
23.55 |
| 2026-05-31 12:00 |
23:07:10.60 |
-01:43:05.5 |
HIP 114202 |
24.41 |
| 2026-06-01 00:00 |
23:07:22.82 |
-01:40:55.0 |
HIP 114202 |
25.79 |
| 2026-06-01 12:00 |
23:07:34.89 |
-01:38:45.3 |
HIP 114202 |
27.61 |
| 2026-06-02 00:00 |
23:07:46.79 |
-01:36:36.4 |
HIP 114202 |
29.76 |