| Parameter |
Value |
| Designation |
4P/Faye |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2021-09-05T16:51:28.051200Z |
| Orbit solution date (soln_date, UTC) |
2026-01-13T17:40:35Z |
| Obs used |
3565 |
| NEO |
- |
| M1 |
11.000 |
| K1 |
9.500 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2019-02-09.0000000 |
| e |
0.58445627 |
| q (au) |
1.578180 |
| a (au) |
3.797867 |
| i (deg) |
8.159059 |
| Ω (om, deg) |
194.793848 |
| ω (w, deg) |
205.996302 |
| M (ma, deg) |
234.863274 |
Magnitude
Scatter + Global Linear
$$
M_a = (9.888 + 3.879\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
9.888 |
| n |
3.879 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| 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 |
| 2021-03-26 |
2021-09-05 |
+0.9434 |
-0.816 |
| 2021-09-06 |
2023-03-25 |
+0.6989 |
-0.717 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-03-26 00:00 |
15:59:21.51 |
-14:41:28.4 |
HIP 78204 |
22.55 |
| 2026-03-26 12:00 |
15:59:15.77 |
-14:40:33.2 |
HIP 78204 |
20.89 |
| 2026-03-27 00:00 |
15:59:09.85 |
-14:39:37.5 |
HIP 78204 |
19.19 |
| 2026-03-27 12:00 |
15:59:03.74 |
-14:38:41.4 |
HIP 78204 |
17.45 |
| 2026-03-28 00:00 |
15:58:57.46 |
-14:37:44.8 |
HIP 78204 |
15.68 |
| 2026-03-28 12:00 |
15:58:51.00 |
-14:36:47.7 |
HIP 78204 |
13.88 |
| 2026-03-29 00:00 |
15:58:44.36 |
-14:35:50.1 |
HIP 78204 |
12.05 |
| 2026-03-29 12:00 |
15:58:37.55 |
-14:34:52.0 |
HIP 78204 |
10.19 |
| 2026-03-30 00:00 |
15:58:30.56 |
-14:33:53.5 |
HIP 78204 |
8.33 |
| 2026-03-30 12:00 |
15:58:23.39 |
-14:32:54.6 |
HIP 78204 |
6.48 |
| 2026-03-31 00:00 |
15:58:16.05 |
-14:31:55.2 |
HIP 78204 |
4.74 |
| 2026-03-31 12:00 |
15:58:08.53 |
-14:30:55.3 |
HIP 78204 |
3.34 |
| 2026-04-01 00:00 |
15:58:00.84 |
-14:29:55.0 |
HIP 78204 |
2.91 |
| 2026-04-01 12:00 |
15:57:52.97 |
-14:28:54.2 |
HIP 78204 |
3.89 |
| 2026-04-02 00:00 |
15:57:44.94 |
-14:27:53.1 |
HIP 78204 |
5.61 |
| 2026-04-02 12:00 |
15:57:36.73 |
-14:26:51.4 |
HIP 78204 |
7.63 |
| 2026-04-03 00:00 |
15:57:28.34 |
-14:25:49.4 |
HIP 78204 |
9.78 |
| 2026-04-03 12:00 |
15:57:19.79 |
-14:24:46.9 |
HIP 78204 |
12.02 |
| 2026-04-04 00:00 |
15:57:11.07 |
-14:23:44.0 |
HIP 78059 |
13.72 |
| 2026-04-04 12:00 |
15:57:02.18 |
-14:22:40.6 |
HIP 78059 |
11.64 |
| 2026-04-05 00:00 |
15:56:53.11 |
-14:21:36.9 |
HIP 78059 |
9.66 |
| 2026-04-05 12:00 |
15:56:43.88 |
-14:20:32.7 |
HIP 78059 |
7.91 |
| 2026-04-06 00:00 |
15:56:34.49 |
-14:19:28.1 |
HIP 78059 |
6.62 |
| 2026-04-06 12:00 |
15:56:24.93 |
-14:18:23.2 |
HIP 78059 |
6.12 |
| 2026-04-07 00:00 |
15:56:15.20 |
-14:17:17.8 |
HIP 78059 |
6.66 |
| 2026-04-07 12:00 |
15:56:05.30 |
-14:16:12.1 |
HIP 78059 |
8.06 |
| 2026-04-08 00:00 |
15:55:55.25 |
-14:15:05.9 |
HIP 78059 |
10.00 |
| 2026-04-08 12:00 |
15:55:45.03 |
-14:13:59.4 |
HIP 78059 |
12.24 |
| 2026-04-09 00:00 |
15:55:34.65 |
-14:12:52.5 |
HIP 78059 |
14.68 |
| 2026-04-09 12:00 |
15:55:24.11 |
-14:11:45.2 |
HIP 77894 |
14.77 |
| 2026-04-10 00:00 |
15:55:13.41 |
-14:10:37.6 |
HIP 77894 |
12.75 |
| 2026-04-10 12:00 |
15:55:02.55 |
-14:09:29.6 |
HIP 77894 |
11.05 |
| 2026-04-11 00:00 |
15:54:51.53 |
-14:08:21.2 |
HIP 77894 |
9.89 |
| 2026-04-11 12:00 |
15:54:40.36 |
-14:07:12.5 |
HIP 77894 |
9.50 |
| 2026-04-12 00:00 |
15:54:29.03 |
-14:06:03.4 |
HIP 77894 |
10.00 |
| 2026-04-12 12:00 |
15:54:17.55 |
-14:04:54.0 |
HIP 77894 |
11.30 |
| 2026-04-13 00:00 |
15:54:05.91 |
-14:03:44.3 |
HIP 77894 |
13.19 |
| 2026-04-13 12:00 |
15:53:54.13 |
-14:02:34.3 |
HIP 77894 |
15.48 |
| 2026-04-14 00:00 |
15:53:42.19 |
-14:01:23.9 |
HIP 77894 |
18.04 |
| 2026-04-14 12:00 |
15:53:30.11 |
-14:00:13.3 |
HIP 77894 |
20.78 |
| 2026-04-15 00:00 |
15:53:17.88 |
-13:59:02.3 |
HIP 77894 |
23.65 |
| 2026-04-15 12:00 |
15:53:05.50 |
-13:57:51.0 |
HIP 77689 |
23.44 |
| 2026-04-16 00:00 |
15:52:52.98 |
-13:56:39.4 |
HIP 77689 |
21.36 |