| Parameter |
Value |
| Designation |
4P/Faye |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2021-09-05T16:51:28.051200Z |
| Orbit solution date (soln_date, UTC) |
2026-07-20T21:56:13Z |
| 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) |
| 2026-09-20 00:00 |
15:26:22.98 |
-13:05:19.5 |
HIP 75517 |
16.68 |
| 2026-09-20 12:00 |
15:26:39.17 |
-13:06:34.7 |
HIP 75517 |
20.24 |
| 2026-09-21 00:00 |
15:26:55.47 |
-13:07:50.1 |
HIP 75670 |
19.44 |
| 2026-09-21 12:00 |
15:27:11.88 |
-13:09:05.6 |
HIP 75670 |
18.93 |
| 2026-09-22 00:00 |
15:27:28.41 |
-13:10:21.3 |
HIP 75670 |
19.34 |
| 2026-09-22 12:00 |
15:27:45.04 |
-13:11:37.2 |
HIP 75715 |
20.15 |
| 2026-09-23 00:00 |
15:28:01.78 |
-13:12:53.3 |
HIP 75715 |
18.25 |
| 2026-09-23 12:00 |
15:28:18.63 |
-13:14:09.4 |
HIP 75715 |
17.21 |
| 2026-09-24 00:00 |
15:28:35.58 |
-13:15:25.8 |
HIP 75715 |
17.22 |
| 2026-09-24 12:00 |
15:28:52.65 |
-13:16:42.2 |
HIP 75715 |
18.30 |
| 2026-09-25 00:00 |
15:29:09.81 |
-13:17:58.8 |
HIP 75715 |
20.28 |
| 2026-09-25 12:00 |
15:29:27.09 |
-13:19:15.6 |
HIP 75715 |
22.96 |
| 2026-09-26 00:00 |
15:29:44.46 |
-13:20:32.4 |
HIP 75931 |
23.57 |
| 2026-09-26 12:00 |
15:30:01.94 |
-13:21:49.4 |
HIP 75931 |
20.59 |
| 2026-09-27 00:00 |
15:30:19.53 |
-13:23:06.5 |
HIP 75931 |
18.22 |
| 2026-09-27 12:00 |
15:30:37.22 |
-13:24:23.7 |
HIP 75931 |
16.71 |
| 2026-09-28 00:00 |
15:30:55.00 |
-13:25:41.0 |
HIP 75931 |
16.35 |
| 2026-09-28 12:00 |
15:31:12.89 |
-13:26:58.4 |
HIP 75931 |
17.22 |
| 2026-09-29 00:00 |
15:31:30.89 |
-13:28:15.9 |
HIP 75931 |
19.17 |
| 2026-09-29 12:00 |
15:31:48.98 |
-13:29:33.6 |
HIP 75931 |
21.93 |
| 2026-09-30 00:00 |
15:32:07.17 |
-13:30:51.3 |
HIP 75931 |
25.25 |
| 2026-09-30 12:00 |
15:32:25.46 |
-13:32:09.0 |
HIP 75931 |
28.94 |
| 2026-10-01 00:00 |
15:32:43.84 |
-13:33:26.9 |
HIP 75931 |
32.89 |
| 2026-10-01 12:00 |
15:33:02.33 |
-13:34:44.8 |
HIP 76153 |
34.13 |
| 2026-10-02 00:00 |
15:33:20.91 |
-13:36:02.9 |
HIP 76323 |
34.33 |
| 2026-10-02 12:00 |
15:33:39.59 |
-13:37:20.9 |
HIP 76323 |
31.19 |
| 2026-10-03 00:00 |
15:33:58.37 |
-13:38:39.1 |
HIP 76323 |
28.48 |
| 2026-10-03 12:00 |
15:34:17.24 |
-13:39:57.3 |
HIP 76323 |
26.34 |
| 2026-10-04 00:00 |
15:34:36.21 |
-13:41:15.5 |
HIP 76323 |
24.93 |
| 2026-10-04 12:00 |
15:34:55.27 |
-13:42:33.8 |
HIP 76323 |
24.39 |
| 2026-10-05 00:00 |
15:35:14.42 |
-13:43:52.2 |
HIP 76323 |
24.78 |
| 2026-10-05 12:00 |
15:35:33.67 |
-13:45:10.5 |
HIP 76323 |
26.09 |
| 2026-10-06 00:00 |
15:35:53.01 |
-13:46:28.9 |
HIP 76323 |
28.19 |
| 2026-10-06 12:00 |
15:36:12.44 |
-13:47:47.4 |
HIP 76484 |
29.66 |
| 2026-10-07 00:00 |
15:36:31.97 |
-13:49:05.8 |
HIP 76484 |
28.71 |
| 2026-10-07 12:00 |
15:36:51.58 |
-13:50:24.3 |
HIP 76562 |
25.02 |
| 2026-10-08 00:00 |
15:37:11.28 |
-13:51:42.8 |
HIP 76562 |
20.56 |
| 2026-10-08 12:00 |
15:37:31.08 |
-13:53:01.3 |
HIP 76562 |
16.39 |
| 2026-10-09 00:00 |
15:37:50.96 |
-13:54:19.8 |
HIP 76562 |
12.80 |
| 2026-10-09 12:00 |
15:38:10.93 |
-13:55:38.3 |
HIP 76562 |
10.43 |
| 2026-10-10 00:00 |
15:38:30.98 |
-13:56:56.8 |
HIP 76562 |
10.22 |
| 2026-10-10 12:00 |
15:38:51.12 |
-13:58:15.3 |
HIP 76676 |
9.30 |
| 2026-10-11 00:00 |
15:39:11.35 |
-13:59:33.7 |
HIP 76676 |
6.13 |