C/2010 A4 (Siding Spring)
| Parameter |
Value |
| Designation |
C/2010 A4 (Siding Spring) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2010-10-08T17:46:24.746880Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:39Z |
| Obs used |
140 |
| NEO |
- |
| M1 |
7.100 |
| K1 |
15.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2010-05-04.0000000 |
| e |
0.99062596 |
| q (au) |
2.737996 |
| a (au) |
292.082906 |
| i (deg) |
96.730138 |
| Ω (om, deg) |
346.685502 |
| ω (w, deg) |
271.685276 |
| M (ma, deg) |
359.968855 |
Magnitude
Scatter + Global Linear
$$
M_a = (7.590 + 5.685\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.590 |
| n |
5.685 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
0.998 |
| 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) |
| 2026-02-03 00:00 |
20:49:28.33 |
+42:07:11.5 |
HIP 102619 |
20.19 |
| 2026-02-03 12:00 |
20:49:32.91 |
+42:07:25.3 |
HIP 102885 |
19.82 |
| 2026-02-04 00:00 |
20:49:37.48 |
+42:07:39.6 |
HIP 102885 |
19.11 |
| 2026-02-04 12:00 |
20:49:42.04 |
+42:07:54.3 |
HIP 102885 |
18.41 |
| 2026-02-05 00:00 |
20:49:46.61 |
+42:08:09.3 |
HIP 102885 |
17.73 |
| 2026-02-05 12:00 |
20:49:51.16 |
+42:08:24.8 |
HIP 102885 |
17.06 |
| 2026-02-06 00:00 |
20:49:55.72 |
+42:08:40.6 |
HIP 102885 |
16.40 |
| 2026-02-06 12:00 |
20:50:00.26 |
+42:08:56.9 |
HIP 102885 |
15.76 |
| 2026-02-07 00:00 |
20:50:04.81 |
+42:09:13.5 |
HIP 102885 |
15.14 |
| 2026-02-07 12:00 |
20:50:09.34 |
+42:09:30.6 |
HIP 102885 |
14.54 |
| 2026-02-08 00:00 |
20:50:13.87 |
+42:09:48.0 |
HIP 102885 |
13.96 |
| 2026-02-08 12:00 |
20:50:18.40 |
+42:10:05.8 |
HIP 102885 |
13.41 |
| 2026-02-09 00:00 |
20:50:22.91 |
+42:10:24.0 |
HIP 102885 |
12.90 |
| 2026-02-09 12:00 |
20:50:27.42 |
+42:10:42.6 |
HIP 102885 |
12.42 |
| 2026-02-10 00:00 |
20:50:31.92 |
+42:11:01.6 |
HIP 102885 |
11.98 |
| 2026-02-10 12:00 |
20:50:36.42 |
+42:11:21.0 |
HIP 102885 |
11.59 |
| 2026-02-11 00:00 |
20:50:40.91 |
+42:11:40.7 |
HIP 102885 |
11.24 |
| 2026-02-11 12:00 |
20:50:45.38 |
+42:12:00.9 |
HIP 102885 |
10.96 |
| 2026-02-12 00:00 |
20:50:49.85 |
+42:12:21.4 |
HIP 102885 |
10.73 |
| 2026-02-12 12:00 |
20:50:54.31 |
+42:12:42.3 |
HIP 102885 |
10.57 |
| 2026-02-13 00:00 |
20:50:58.76 |
+42:13:03.6 |
HIP 102885 |
10.48 |
| 2026-02-13 12:00 |
20:51:03.21 |
+42:13:25.2 |
HIP 102885 |
10.45 |
| 2026-02-14 00:00 |
20:51:07.64 |
+42:13:47.3 |
HIP 102885 |
10.50 |
| 2026-02-14 12:00 |
20:51:12.06 |
+42:14:09.7 |
HIP 102885 |
10.61 |
| 2026-02-15 00:00 |
20:51:16.47 |
+42:14:32.5 |
HIP 102885 |
10.80 |
| 2026-02-15 12:00 |
20:51:20.87 |
+42:14:55.7 |
HIP 102885 |
11.04 |
| 2026-02-16 00:00 |
20:51:25.25 |
+42:15:19.2 |
HIP 102885 |
11.35 |
| 2026-02-16 12:00 |
20:51:29.63 |
+42:15:43.1 |
HIP 102885 |
11.71 |
| 2026-02-17 00:00 |
20:51:33.99 |
+42:16:07.4 |
HIP 102885 |
12.13 |
| 2026-02-17 12:00 |
20:51:38.34 |
+42:16:32.0 |
HIP 102885 |
12.59 |
| 2026-02-18 00:00 |
20:51:42.68 |
+42:16:57.1 |
HIP 102885 |
13.09 |
| 2026-02-18 12:00 |
20:51:47.01 |
+42:17:22.4 |
HIP 102885 |
13.63 |
| 2026-02-19 00:00 |
20:51:51.32 |
+42:17:48.2 |
HIP 102885 |
14.20 |
| 2026-02-19 12:00 |
20:51:55.62 |
+42:18:14.3 |
HIP 102885 |
14.80 |
| 2026-02-20 00:00 |
20:51:59.90 |
+42:18:40.7 |
HIP 103086 |
14.02 |
| 2026-02-20 12:00 |
20:52:04.17 |
+42:19:07.5 |
HIP 103086 |
13.15 |
| 2026-02-21 00:00 |
20:52:08.42 |
+42:19:34.7 |
HIP 103086 |
12.29 |
| 2026-02-21 12:00 |
20:52:12.66 |
+42:20:02.2 |
HIP 103086 |
11.44 |
| 2026-02-22 00:00 |
20:52:16.89 |
+42:20:30.1 |
HIP 103086 |
10.61 |
| 2026-02-22 12:00 |
20:52:21.09 |
+42:20:58.3 |
HIP 103086 |
9.78 |
| 2026-02-23 00:00 |
20:52:25.29 |
+42:21:26.8 |
HIP 103086 |
8.98 |
| 2026-02-23 12:00 |
20:52:29.46 |
+42:21:55.7 |
HIP 103086 |
8.20 |
| 2026-02-24 00:00 |
20:52:33.62 |
+42:22:25.0 |
HIP 103086 |
7.46 |