| Parameter |
Value |
| Designation |
C/2009 U3 (Hill) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2010-03-20T06:06:49.440960Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:36Z |
| Obs used |
602 |
| NEO |
- |
| M1 |
15.400 |
| K1 |
6.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2010-01-01.0000000 |
| e |
0.99157651 |
| q (au) |
1.414425 |
| a (au) |
167.914294 |
| i (deg) |
51.260767 |
| Ω (om, deg) |
49.322883 |
| ω (w, deg) |
77.701400 |
| M (ma, deg) |
359.964553 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.668 + 5.161\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.668 |
| n |
5.161 |
| gf |
1.000 |
| gb |
-0.772 |
| k |
0.984 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2009-10-20 |
2009-11-16 |
-11.6924 |
+4.120 |
| 2009-11-16 |
2009-12-24 |
+7.8024 |
-2.354 |
| 2009-12-24 |
2010-01-26 |
-15.1069 |
+3.691 |
| 2010-01-26 |
2010-03-19 |
+34.3839 |
-6.645 |
| 2010-03-24 |
2010-05-14 |
+6.6087 |
-1.956 |
| 2010-05-14 |
2010-06-18 |
-14.3862 |
+3.611 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
18:19:59.93 |
-64:04:28.4 |
HIP 89805 |
11.53 |
| 2026-05-12 12:00 |
18:19:54.45 |
-64:04:54.6 |
HIP 89805 |
11.86 |
| 2026-05-13 00:00 |
18:19:48.92 |
-64:05:20.7 |
HIP 89805 |
12.23 |
| 2026-05-13 12:00 |
18:19:43.34 |
-64:05:46.5 |
HIP 89805 |
12.63 |
| 2026-05-14 00:00 |
18:19:37.71 |
-64:06:12.2 |
HIP 89805 |
13.05 |
| 2026-05-14 12:00 |
18:19:32.03 |
-64:06:37.6 |
HIP 89805 |
13.50 |
| 2026-05-15 00:00 |
18:19:26.30 |
-64:07:02.7 |
HIP 89805 |
13.97 |
| 2026-05-15 12:00 |
18:19:20.52 |
-64:07:27.7 |
HIP 89805 |
14.47 |
| 2026-05-16 00:00 |
18:19:14.70 |
-64:07:52.4 |
HIP 89805 |
14.98 |
| 2026-05-16 12:00 |
18:19:08.82 |
-64:08:16.9 |
HIP 89805 |
15.51 |
| 2026-05-17 00:00 |
18:19:02.90 |
-64:08:41.1 |
HIP 89805 |
16.06 |
| 2026-05-17 12:00 |
18:18:56.93 |
-64:09:05.2 |
HIP 89805 |
16.62 |
| 2026-05-18 00:00 |
18:18:50.92 |
-64:09:28.9 |
HIP 89805 |
17.19 |
| 2026-05-18 12:00 |
18:18:44.86 |
-64:09:52.5 |
HIP 89805 |
17.78 |
| 2026-05-19 00:00 |
18:18:38.75 |
-64:10:15.8 |
HIP 89805 |
18.38 |
| 2026-05-19 12:00 |
18:18:32.60 |
-64:10:38.8 |
HIP 89805 |
18.99 |
| 2026-05-20 00:00 |
18:18:26.41 |
-64:11:01.6 |
HIP 89805 |
19.61 |
| 2026-05-20 12:00 |
18:18:20.17 |
-64:11:24.2 |
HIP 89805 |
20.24 |
| 2026-05-21 00:00 |
18:18:13.89 |
-64:11:46.5 |
HIP 89805 |
20.87 |
| 2026-05-21 12:00 |
18:18:07.57 |
-64:12:08.5 |
HIP 89805 |
21.52 |
| 2026-05-22 00:00 |
18:18:01.21 |
-64:12:30.3 |
HIP 89805 |
22.17 |
| 2026-05-22 12:00 |
18:17:54.80 |
-64:12:51.9 |
HIP 89805 |
22.83 |
| 2026-05-23 00:00 |
18:17:48.36 |
-64:13:13.2 |
HIP 89758 |
23.41 |
| 2026-05-23 12:00 |
18:17:41.87 |
-64:13:34.2 |
HIP 89758 |
23.99 |
| 2026-05-24 00:00 |
18:17:35.35 |
-64:13:55.0 |
HIP 89758 |
24.57 |
| 2026-05-24 12:00 |
18:17:28.78 |
-64:14:15.5 |
HIP 89758 |
25.17 |
| 2026-05-25 00:00 |
18:17:22.18 |
-64:14:35.7 |
HIP 89758 |
25.77 |
| 2026-05-25 12:00 |
18:17:15.54 |
-64:14:55.7 |
HIP 89758 |
26.38 |
| 2026-05-26 00:00 |
18:17:08.86 |
-64:15:15.4 |
HIP 89758 |
27.00 |
| 2026-05-26 12:00 |
18:17:02.15 |
-64:15:34.8 |
HIP 89758 |
27.63 |
| 2026-05-27 00:00 |
18:16:55.40 |
-64:15:54.0 |
HIP 89758 |
28.26 |
| 2026-05-27 12:00 |
18:16:48.62 |
-64:16:12.9 |
HIP 89758 |
28.90 |
| 2026-05-28 00:00 |
18:16:41.80 |
-64:16:31.5 |
HIP 89758 |
29.55 |
| 2026-05-28 12:00 |
18:16:34.94 |
-64:16:49.9 |
HIP 89758 |
30.20 |
| 2026-05-29 00:00 |
18:16:28.05 |
-64:17:08.0 |
HIP 89758 |
30.86 |
| 2026-05-29 12:00 |
18:16:21.13 |
-64:17:25.8 |
HIP 89758 |
31.52 |
| 2026-05-30 00:00 |
18:16:14.18 |
-64:17:43.3 |
HIP 89200 |
32.11 |
| 2026-05-30 12:00 |
18:16:07.19 |
-64:18:00.5 |
HIP 89200 |
31.66 |
| 2026-05-31 00:00 |
18:16:00.17 |
-64:18:17.5 |
HIP 89200 |
31.22 |
| 2026-05-31 12:00 |
18:15:53.13 |
-64:18:34.2 |
HIP 89200 |
30.79 |
| 2026-06-01 00:00 |
18:15:46.05 |
-64:18:50.6 |
HIP 89200 |
30.37 |
| 2026-06-01 12:00 |
18:15:38.94 |
-64:19:06.7 |
HIP 89200 |
29.95 |
| 2026-06-02 00:00 |
18:15:31.80 |
-64:19:22.5 |
HIP 89200 |
29.56 |