C/2009 G1 (STEREO)
| 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) |
| 2026-02-03 00:00 |
08:20:05.92 |
-05:10:33.5 |
HIP 40859 |
9.63 |
| 2026-02-03 12:00 |
08:20:02.58 |
-05:10:16.6 |
HIP 40859 |
10.17 |
| 2026-02-04 00:00 |
08:19:59.24 |
-05:09:59.4 |
HIP 40859 |
10.75 |
| 2026-02-04 12:00 |
08:19:55.92 |
-05:09:42.1 |
HIP 40859 |
11.37 |
| 2026-02-05 00:00 |
08:19:52.60 |
-05:09:24.7 |
HIP 40859 |
12.03 |
| 2026-02-05 12:00 |
08:19:49.28 |
-05:09:07.1 |
HIP 40859 |
12.71 |
| 2026-02-06 00:00 |
08:19:45.98 |
-05:08:49.3 |
HIP 40859 |
13.42 |
| 2026-02-06 12:00 |
08:19:42.68 |
-05:08:31.4 |
HIP 40859 |
14.14 |
| 2026-02-07 00:00 |
08:19:39.39 |
-05:08:13.3 |
HIP 40859 |
14.89 |
| 2026-02-07 12:00 |
08:19:36.10 |
-05:07:55.0 |
HIP 40859 |
15.64 |
| 2026-02-08 00:00 |
08:19:32.83 |
-05:07:36.6 |
HIP 40859 |
16.41 |
| 2026-02-08 12:00 |
08:19:29.57 |
-05:07:18.0 |
HIP 40859 |
17.19 |
| 2026-02-09 00:00 |
08:19:26.31 |
-05:06:59.3 |
HIP 40859 |
17.98 |
| 2026-02-09 12:00 |
08:19:23.06 |
-05:06:40.4 |
HIP 40859 |
18.77 |
| 2026-02-10 00:00 |
08:19:19.83 |
-05:06:21.4 |
HIP 40859 |
19.57 |
| 2026-02-10 12:00 |
08:19:16.60 |
-05:06:02.3 |
HIP 40859 |
20.38 |
| 2026-02-11 00:00 |
08:19:13.38 |
-05:05:43.0 |
HIP 40859 |
21.19 |
| 2026-02-11 12:00 |
08:19:10.18 |
-05:05:23.5 |
HIP 40859 |
22.00 |
| 2026-02-12 00:00 |
08:19:06.98 |
-05:05:03.9 |
HIP 40859 |
22.82 |
| 2026-02-12 12:00 |
08:19:03.80 |
-05:04:44.2 |
HIP 40859 |
23.64 |
| 2026-02-13 00:00 |
08:19:00.63 |
-05:04:24.3 |
HIP 40859 |
24.46 |
| 2026-02-13 12:00 |
08:18:57.46 |
-05:04:04.3 |
HIP 40859 |
25.28 |
| 2026-02-14 00:00 |
08:18:54.31 |
-05:03:44.1 |
HIP 40859 |
26.11 |
| 2026-02-14 12:00 |
08:18:51.18 |
-05:03:23.8 |
HIP 40859 |
26.93 |
| 2026-02-15 00:00 |
08:18:48.05 |
-05:03:03.4 |
HIP 40859 |
27.76 |
| 2026-02-15 12:00 |
08:18:44.94 |
-05:02:42.8 |
HIP 40859 |
28.59 |
| 2026-02-16 00:00 |
08:18:41.84 |
-05:02:22.1 |
HIP 40592 |
29.18 |
| 2026-02-16 12:00 |
08:18:38.75 |
-05:02:01.3 |
HIP 40592 |
28.86 |
| 2026-02-17 00:00 |
08:18:35.67 |
-05:01:40.3 |
HIP 40592 |
28.56 |
| 2026-02-17 12:00 |
08:18:32.61 |
-05:01:19.3 |
HIP 40592 |
28.29 |
| 2026-02-18 00:00 |
08:18:29.57 |
-05:00:58.1 |
HIP 40592 |
28.05 |
| 2026-02-18 12:00 |
08:18:26.53 |
-05:00:36.7 |
HIP 40592 |
27.84 |
| 2026-02-19 00:00 |
08:18:23.52 |
-05:00:15.3 |
HIP 40592 |
27.65 |
| 2026-02-19 12:00 |
08:18:20.51 |
-04:59:53.7 |
HIP 40592 |
27.49 |
| 2026-02-20 00:00 |
08:18:17.52 |
-04:59:32.1 |
HIP 40592 |
27.36 |
| 2026-02-20 12:00 |
08:18:14.55 |
-04:59:10.3 |
HIP 40592 |
27.25 |
| 2026-02-21 00:00 |
08:18:11.59 |
-04:58:48.4 |
HIP 40592 |
27.18 |
| 2026-02-21 12:00 |
08:18:08.65 |
-04:58:26.3 |
HIP 40592 |
27.13 |
| 2026-02-22 00:00 |
08:18:05.72 |
-04:58:04.2 |
HIP 40592 |
27.11 |
| 2026-02-22 12:00 |
08:18:02.81 |
-04:57:42.0 |
HIP 40592 |
27.12 |
| 2026-02-23 00:00 |
08:17:59.92 |
-04:57:19.6 |
HIP 40592 |
27.16 |
| 2026-02-23 12:00 |
08:17:57.04 |
-04:56:57.2 |
HIP 40592 |
27.22 |
| 2026-02-24 00:00 |
08:17:54.18 |
-04:56:34.7 |
HIP 40592 |
27.31 |