| Parameter |
Value |
| Designation |
C/2009 G1 (STEREO) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2009-04-16T12:08:09.119040Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:30Z |
| Obs used |
119 |
| NEO |
- |
| M1 |
9.100 |
| K1 |
17.250 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2009-05-09.0000000 |
| e |
0.99767848 |
| q (au) |
1.128742 |
| a (au) |
486.208569 |
| i (deg) |
108.310256 |
| Ω (om, deg) |
120.634994 |
| ω (w, deg) |
175.444080 |
| M (ma, deg) |
0.002068 |
Magnitude
Scatter + Global Linear
$$
M_a = (9.287 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
9.287 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
0.965 |
| 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 |
08:26:05.73 |
-04:12:53.5 |
HIP 41316 |
4.81 |
| 2026-09-20 12:00 |
08:26:07.54 |
-04:13:13.0 |
HIP 41316 |
5.36 |
| 2026-09-21 00:00 |
08:26:09.33 |
-04:13:32.6 |
HIP 41316 |
5.91 |
| 2026-09-21 12:00 |
08:26:11.09 |
-04:13:52.1 |
HIP 41316 |
6.45 |
| 2026-09-22 00:00 |
08:26:12.84 |
-04:14:11.7 |
HIP 41316 |
7.00 |
| 2026-09-22 12:00 |
08:26:14.57 |
-04:14:31.3 |
HIP 41316 |
7.53 |
| 2026-09-23 00:00 |
08:26:16.27 |
-04:14:50.9 |
HIP 41316 |
8.06 |
| 2026-09-23 12:00 |
08:26:17.96 |
-04:15:10.6 |
HIP 41316 |
8.59 |
| 2026-09-24 00:00 |
08:26:19.62 |
-04:15:30.2 |
HIP 41316 |
9.12 |
| 2026-09-24 12:00 |
08:26:21.26 |
-04:15:49.9 |
HIP 41316 |
9.64 |
| 2026-09-25 00:00 |
08:26:22.88 |
-04:16:09.6 |
HIP 41316 |
10.16 |
| 2026-09-25 12:00 |
08:26:24.47 |
-04:16:29.4 |
HIP 41316 |
10.67 |
| 2026-09-26 00:00 |
08:26:26.05 |
-04:16:49.1 |
HIP 41316 |
11.18 |
| 2026-09-26 12:00 |
08:26:27.60 |
-04:17:08.9 |
HIP 41316 |
11.68 |
| 2026-09-27 00:00 |
08:26:29.13 |
-04:17:28.6 |
HIP 41316 |
12.18 |
| 2026-09-27 12:00 |
08:26:30.64 |
-04:17:48.4 |
HIP 41316 |
12.68 |
| 2026-09-28 00:00 |
08:26:32.12 |
-04:18:08.2 |
HIP 41316 |
13.17 |
| 2026-09-28 12:00 |
08:26:33.58 |
-04:18:28.0 |
HIP 41316 |
13.66 |
| 2026-09-29 00:00 |
08:26:35.02 |
-04:18:47.8 |
HIP 41316 |
14.14 |
| 2026-09-29 12:00 |
08:26:36.44 |
-04:19:07.6 |
HIP 41316 |
14.62 |
| 2026-09-30 00:00 |
08:26:37.83 |
-04:19:27.5 |
HIP 41316 |
15.09 |
| 2026-09-30 12:00 |
08:26:39.20 |
-04:19:47.3 |
HIP 41316 |
15.56 |
| 2026-10-01 00:00 |
08:26:40.55 |
-04:20:07.1 |
HIP 41489 |
15.76 |
| 2026-10-01 12:00 |
08:26:41.87 |
-04:20:26.9 |
HIP 41489 |
15.35 |
| 2026-10-02 00:00 |
08:26:43.17 |
-04:20:46.8 |
HIP 41489 |
14.94 |
| 2026-10-02 12:00 |
08:26:44.45 |
-04:21:06.6 |
HIP 41489 |
14.55 |
| 2026-10-03 00:00 |
08:26:45.70 |
-04:21:26.4 |
HIP 41489 |
14.16 |
| 2026-10-03 12:00 |
08:26:46.93 |
-04:21:46.2 |
HIP 41489 |
13.79 |
| 2026-10-04 00:00 |
08:26:48.13 |
-04:22:06.0 |
HIP 41489 |
13.42 |
| 2026-10-04 12:00 |
08:26:49.31 |
-04:22:25.8 |
HIP 41489 |
13.07 |
| 2026-10-05 00:00 |
08:26:50.47 |
-04:22:45.6 |
HIP 41489 |
12.73 |
| 2026-10-05 12:00 |
08:26:51.60 |
-04:23:05.4 |
HIP 41489 |
12.40 |
| 2026-10-06 00:00 |
08:26:52.71 |
-04:23:25.1 |
HIP 41489 |
12.08 |
| 2026-10-06 12:00 |
08:26:53.79 |
-04:23:44.9 |
HIP 41489 |
11.78 |
| 2026-10-07 00:00 |
08:26:54.85 |
-04:24:04.6 |
HIP 41489 |
11.49 |
| 2026-10-07 12:00 |
08:26:55.88 |
-04:24:24.3 |
HIP 41489 |
11.21 |
| 2026-10-08 00:00 |
08:26:56.89 |
-04:24:44.0 |
HIP 41489 |
10.95 |
| 2026-10-08 12:00 |
08:26:57.87 |
-04:25:03.7 |
HIP 41489 |
10.71 |
| 2026-10-09 00:00 |
08:26:58.83 |
-04:25:23.3 |
HIP 41489 |
10.48 |
| 2026-10-09 12:00 |
08:26:59.76 |
-04:25:42.9 |
HIP 41489 |
10.27 |
| 2026-10-10 00:00 |
08:27:00.67 |
-04:26:02.5 |
HIP 41489 |
10.07 |
| 2026-10-10 12:00 |
08:27:01.55 |
-04:26:22.1 |
HIP 41489 |
9.90 |
| 2026-10-11 00:00 |
08:27:02.41 |
-04:26:41.6 |
HIP 41489 |
9.74 |