| Parameter |
Value |
| Designation |
C/2009 O4 (Hill) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2010-01-01T06:37:51.360960Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:32Z |
| Obs used |
764 |
| NEO |
- |
| M1 |
4.900 |
| K1 |
21.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2009-09-03.0000000 |
| e |
1.00133631 |
| q (au) |
2.563789 |
| a (au) |
-1918.552115 |
| i (deg) |
95.823277 |
| Ω (om, deg) |
172.936518 |
| ω (w, deg) |
223.731941 |
| M (ma, deg) |
-0.001411 |
Magnitude
Scatter + Global Linear
$$
M_a = (14.078 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.078 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.622 |
| k |
0.800 |
| 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) |
| 2026-09-20 00:00 |
11:48:55.65 |
+13:51:11.2 |
HIP 57606 |
26.19 |
| 2026-09-20 12:00 |
11:48:58.87 |
+13:50:55.2 |
HIP 57606 |
26.58 |
| 2026-09-21 00:00 |
11:49:02.09 |
+13:50:39.3 |
HIP 57606 |
27.00 |
| 2026-09-21 12:00 |
11:49:05.30 |
+13:50:23.6 |
HIP 57606 |
27.42 |
| 2026-09-22 00:00 |
11:49:08.51 |
+13:50:07.9 |
HIP 57606 |
27.87 |
| 2026-09-22 12:00 |
11:49:11.73 |
+13:49:52.3 |
HIP 57606 |
28.33 |
| 2026-09-23 00:00 |
11:49:14.94 |
+13:49:36.8 |
HIP 57777 |
27.89 |
| 2026-09-23 12:00 |
11:49:18.15 |
+13:49:21.4 |
HIP 57777 |
27.09 |
| 2026-09-24 00:00 |
11:49:21.36 |
+13:49:06.1 |
HIP 57777 |
26.29 |
| 2026-09-24 12:00 |
11:49:24.56 |
+13:48:50.9 |
HIP 57777 |
25.50 |
| 2026-09-25 00:00 |
11:49:27.77 |
+13:48:35.8 |
HIP 57777 |
24.71 |
| 2026-09-25 12:00 |
11:49:30.97 |
+13:48:20.9 |
HIP 57777 |
23.92 |
| 2026-09-26 00:00 |
11:49:34.17 |
+13:48:06.0 |
HIP 57777 |
23.14 |
| 2026-09-26 12:00 |
11:49:37.36 |
+13:47:51.2 |
HIP 57777 |
22.36 |
| 2026-09-27 00:00 |
11:49:40.55 |
+13:47:36.5 |
HIP 57777 |
21.58 |
| 2026-09-27 12:00 |
11:49:43.75 |
+13:47:22.0 |
HIP 57777 |
20.81 |
| 2026-09-28 00:00 |
11:49:46.93 |
+13:47:07.5 |
HIP 57777 |
20.04 |
| 2026-09-28 12:00 |
11:49:50.12 |
+13:46:53.2 |
HIP 57777 |
19.28 |
| 2026-09-29 00:00 |
11:49:53.30 |
+13:46:39.0 |
HIP 57777 |
18.52 |
| 2026-09-29 12:00 |
11:49:56.47 |
+13:46:24.9 |
HIP 57777 |
17.77 |
| 2026-09-30 00:00 |
11:49:59.64 |
+13:46:10.9 |
HIP 57777 |
17.03 |
| 2026-09-30 12:00 |
11:50:02.81 |
+13:45:57.0 |
HIP 57777 |
16.29 |
| 2026-10-01 00:00 |
11:50:05.97 |
+13:45:43.3 |
HIP 57777 |
15.57 |
| 2026-10-01 12:00 |
11:50:09.13 |
+13:45:29.6 |
HIP 57777 |
14.85 |
| 2026-10-02 00:00 |
11:50:12.28 |
+13:45:16.1 |
HIP 57777 |
14.14 |
| 2026-10-02 12:00 |
11:50:15.43 |
+13:45:02.7 |
HIP 57777 |
13.45 |
| 2026-10-03 00:00 |
11:50:18.58 |
+13:44:49.4 |
HIP 57777 |
12.77 |
| 2026-10-03 12:00 |
11:50:21.71 |
+13:44:36.3 |
HIP 57777 |
12.11 |
| 2026-10-04 00:00 |
11:50:24.85 |
+13:44:23.2 |
HIP 57777 |
11.47 |
| 2026-10-04 12:00 |
11:50:27.97 |
+13:44:10.3 |
HIP 57777 |
10.85 |
| 2026-10-05 00:00 |
11:50:31.09 |
+13:43:57.6 |
HIP 57777 |
10.26 |
| 2026-10-05 12:00 |
11:50:34.20 |
+13:43:44.9 |
HIP 57777 |
9.69 |
| 2026-10-06 00:00 |
11:50:37.31 |
+13:43:32.4 |
HIP 57777 |
9.17 |
| 2026-10-06 12:00 |
11:50:40.41 |
+13:43:20.0 |
HIP 57777 |
8.68 |
| 2026-10-07 00:00 |
11:50:43.50 |
+13:43:07.7 |
HIP 57777 |
8.24 |
| 2026-10-07 12:00 |
11:50:46.59 |
+13:42:55.6 |
HIP 57777 |
7.86 |
| 2026-10-08 00:00 |
11:50:49.67 |
+13:42:43.6 |
HIP 57777 |
7.54 |
| 2026-10-08 12:00 |
11:50:52.74 |
+13:42:31.8 |
HIP 57777 |
7.29 |
| 2026-10-09 00:00 |
11:50:55.80 |
+13:42:20.1 |
HIP 57777 |
7.12 |
| 2026-10-09 12:00 |
11:50:58.86 |
+13:42:08.5 |
HIP 57777 |
7.03 |
| 2026-10-10 00:00 |
11:51:01.90 |
+13:41:57.1 |
HIP 57777 |
7.02 |
| 2026-10-10 12:00 |
11:51:04.94 |
+13:41:45.8 |
HIP 57777 |
7.10 |
| 2026-10-11 00:00 |
11:51:07.97 |
+13:41:34.6 |
HIP 57777 |
7.26 |