| Parameter |
Value |
| Designation |
C/2007 K3 (Siding Spring) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2008-04-21T17:04:30.377280Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:08Z |
| Obs used |
94 |
| NEO |
- |
| M1 |
13.300 |
| K1 |
13.000 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2008-02-09.0000000 |
| e |
1.00124061 |
| q (au) |
2.050740 |
| a (au) |
-1653.004343 |
| i (deg) |
16.300560 |
| Ω (om, deg) |
263.252666 |
| ω (w, deg) |
23.593153 |
| M (ma, deg) |
-0.001066 |
Magnitude
Scatter + Global Linear
$$
M_a = (15.559 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
15.559 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.529 |
| 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
Residuals (Piecewise)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| Start (UTC) |
End (UTC) |
a |
b |
| 2007-04-18 |
2007-07-18 |
-5.6530 |
+2.025 |
| 2008-06-09 |
2008-09-30 |
+25.5862 |
-9.589 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-09-20 00:00 |
05:22:05.52 |
+24:09:35.9 |
HIP 24994 |
13.30 |
| 2026-09-20 12:00 |
05:22:05.29 |
+24:09:35.8 |
HIP 24994 |
13.25 |
| 2026-09-21 00:00 |
05:22:05.03 |
+24:09:35.6 |
HIP 24994 |
13.20 |
| 2026-09-21 12:00 |
05:22:04.73 |
+24:09:35.5 |
HIP 24994 |
13.13 |
| 2026-09-22 00:00 |
05:22:04.41 |
+24:09:35.3 |
HIP 24994 |
13.06 |
| 2026-09-22 12:00 |
05:22:04.06 |
+24:09:35.1 |
HIP 24994 |
12.99 |
| 2026-09-23 00:00 |
05:22:03.68 |
+24:09:34.8 |
HIP 24994 |
12.91 |
| 2026-09-23 12:00 |
05:22:03.27 |
+24:09:34.6 |
HIP 24994 |
12.82 |
| 2026-09-24 00:00 |
05:22:02.83 |
+24:09:34.3 |
HIP 24994 |
12.72 |
| 2026-09-24 12:00 |
05:22:02.36 |
+24:09:33.9 |
HIP 24994 |
12.62 |
| 2026-09-25 00:00 |
05:22:01.86 |
+24:09:33.6 |
HIP 24994 |
12.52 |
| 2026-09-25 12:00 |
05:22:01.34 |
+24:09:33.2 |
HIP 24994 |
12.40 |
| 2026-09-26 00:00 |
05:22:00.78 |
+24:09:32.8 |
HIP 24994 |
12.28 |
| 2026-09-26 12:00 |
05:22:00.19 |
+24:09:32.4 |
HIP 24994 |
12.16 |
| 2026-09-27 00:00 |
05:21:59.58 |
+24:09:31.9 |
HIP 24994 |
12.03 |
| 2026-09-27 12:00 |
05:21:58.93 |
+24:09:31.4 |
HIP 24994 |
11.89 |
| 2026-09-28 00:00 |
05:21:58.26 |
+24:09:30.9 |
HIP 24994 |
11.75 |
| 2026-09-28 12:00 |
05:21:57.55 |
+24:09:30.3 |
HIP 24994 |
11.60 |
| 2026-09-29 00:00 |
05:21:56.82 |
+24:09:29.7 |
HIP 24994 |
11.45 |
| 2026-09-29 12:00 |
05:21:56.06 |
+24:09:29.1 |
HIP 24994 |
11.29 |
| 2026-09-30 00:00 |
05:21:55.27 |
+24:09:28.5 |
HIP 24994 |
11.12 |
| 2026-09-30 12:00 |
05:21:54.45 |
+24:09:27.8 |
HIP 24994 |
10.95 |
| 2026-10-01 00:00 |
05:21:53.60 |
+24:09:27.1 |
HIP 24994 |
10.77 |
| 2026-10-01 12:00 |
05:21:52.72 |
+24:09:26.4 |
HIP 24994 |
10.59 |
| 2026-10-02 00:00 |
05:21:51.81 |
+24:09:25.7 |
HIP 24994 |
10.40 |
| 2026-10-02 12:00 |
05:21:50.87 |
+24:09:24.9 |
HIP 24994 |
10.21 |
| 2026-10-03 00:00 |
05:21:49.91 |
+24:09:24.1 |
HIP 24994 |
10.01 |
| 2026-10-03 12:00 |
05:21:48.91 |
+24:09:23.2 |
HIP 24994 |
9.81 |
| 2026-10-04 00:00 |
05:21:47.89 |
+24:09:22.4 |
HIP 24994 |
9.60 |
| 2026-10-04 12:00 |
05:21:46.84 |
+24:09:21.5 |
HIP 24994 |
9.39 |
| 2026-10-05 00:00 |
05:21:45.76 |
+24:09:20.6 |
HIP 24994 |
9.17 |
| 2026-10-05 12:00 |
05:21:44.65 |
+24:09:19.6 |
HIP 24994 |
8.95 |
| 2026-10-06 00:00 |
05:21:43.51 |
+24:09:18.6 |
HIP 24994 |
8.73 |
| 2026-10-06 12:00 |
05:21:42.34 |
+24:09:17.6 |
HIP 24994 |
8.50 |
| 2026-10-07 00:00 |
05:21:41.15 |
+24:09:16.6 |
HIP 24994 |
8.27 |
| 2026-10-07 12:00 |
05:21:39.92 |
+24:09:15.5 |
HIP 24994 |
8.03 |
| 2026-10-08 00:00 |
05:21:38.67 |
+24:09:14.4 |
HIP 24994 |
7.80 |
| 2026-10-08 12:00 |
05:21:37.39 |
+24:09:13.3 |
HIP 24994 |
7.56 |
| 2026-10-09 00:00 |
05:21:36.08 |
+24:09:12.1 |
HIP 24994 |
7.32 |
| 2026-10-09 12:00 |
05:21:34.74 |
+24:09:10.9 |
HIP 24994 |
7.08 |
| 2026-10-10 00:00 |
05:21:33.38 |
+24:09:09.7 |
HIP 24994 |
6.84 |
| 2026-10-10 12:00 |
05:21:31.98 |
+24:09:08.5 |
HIP 24994 |
6.61 |
| 2026-10-11 00:00 |
05:21:30.56 |
+24:09:07.2 |
HIP 24994 |
6.37 |