| 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) |
| 2026-05-12 00:00 |
15:39:30.86 |
-12:51:13.6 |
HIP 76622 |
13.34 |
| 2026-05-12 12:00 |
15:39:13.54 |
-12:49:58.2 |
HIP 76622 |
11.81 |
| 2026-05-13 00:00 |
15:38:56.19 |
-12:48:42.9 |
HIP 76622 |
11.81 |
| 2026-05-13 12:00 |
15:38:38.81 |
-12:47:27.9 |
HIP 76622 |
13.36 |
| 2026-05-14 00:00 |
15:38:21.41 |
-12:46:13.0 |
HIP 76622 |
16.01 |
| 2026-05-14 12:00 |
15:38:03.99 |
-12:44:58.3 |
HIP 76622 |
19.32 |
| 2026-05-15 00:00 |
15:37:46.55 |
-12:43:43.9 |
HIP 76622 |
23.01 |
| 2026-05-15 12:00 |
15:37:29.09 |
-12:42:29.6 |
HIP 76363 |
26.39 |
| 2026-05-16 00:00 |
15:37:11.62 |
-12:41:15.6 |
HIP 76363 |
22.96 |
| 2026-05-16 12:00 |
15:36:54.14 |
-12:40:01.8 |
HIP 76363 |
19.93 |
| 2026-05-17 00:00 |
15:36:36.64 |
-12:38:48.3 |
HIP 76363 |
17.50 |
| 2026-05-17 12:00 |
15:36:19.15 |
-12:37:35.1 |
HIP 76363 |
15.96 |
| 2026-05-18 00:00 |
15:36:01.65 |
-12:36:22.1 |
HIP 76314 |
11.98 |
| 2026-05-18 12:00 |
15:35:44.15 |
-12:35:09.4 |
HIP 76314 |
7.75 |
| 2026-05-19 00:00 |
15:35:26.65 |
-12:33:57.0 |
HIP 76314 |
3.98 |
| 2026-05-19 12:00 |
15:35:09.16 |
-12:32:45.0 |
HIP 76314 |
3.33 |
| 2026-05-20 00:00 |
15:34:51.67 |
-12:31:33.2 |
HIP 76314 |
6.75 |
| 2026-05-20 12:00 |
15:34:34.20 |
-12:30:21.7 |
HIP 76314 |
10.93 |
| 2026-05-21 00:00 |
15:34:16.74 |
-12:29:10.6 |
HIP 76314 |
15.24 |
| 2026-05-21 12:00 |
15:33:59.30 |
-12:27:59.9 |
HIP 76314 |
19.60 |
| 2026-05-22 00:00 |
15:33:41.87 |
-12:26:49.4 |
HIP 76314 |
23.97 |
| 2026-05-22 12:00 |
15:33:24.47 |
-12:25:39.4 |
HIP 76314 |
28.36 |
| 2026-05-23 00:00 |
15:33:07.09 |
-12:24:29.7 |
HIP 76314 |
32.74 |
| 2026-05-23 12:00 |
15:32:49.73 |
-12:23:20.4 |
HIP 76314 |
37.12 |
| 2026-05-24 00:00 |
15:32:32.41 |
-12:22:11.5 |
HIP 75935 |
36.24 |
| 2026-05-24 12:00 |
15:32:15.11 |
-12:21:03.0 |
HIP 75935 |
33.79 |
| 2026-05-25 00:00 |
15:31:57.85 |
-12:19:54.9 |
HIP 75935 |
31.75 |
| 2026-05-25 12:00 |
15:31:40.62 |
-12:18:47.2 |
HIP 75935 |
30.22 |
| 2026-05-26 00:00 |
15:31:23.44 |
-12:17:39.9 |
HIP 75935 |
29.24 |
| 2026-05-26 12:00 |
15:31:06.29 |
-12:16:33.1 |
HIP 75935 |
28.90 |
| 2026-05-27 00:00 |
15:30:49.19 |
-12:15:26.7 |
HIP 75935 |
29.19 |
| 2026-05-27 12:00 |
15:30:32.13 |
-12:14:20.7 |
HIP 75935 |
30.09 |
| 2026-05-28 00:00 |
15:30:15.12 |
-12:13:15.2 |
HIP 75935 |
31.56 |
| 2026-05-28 12:00 |
15:29:58.16 |
-12:12:10.2 |
HIP 75832 |
29.46 |
| 2026-05-29 00:00 |
15:29:41.25 |
-12:11:05.6 |
HIP 75832 |
27.55 |
| 2026-05-29 12:00 |
15:29:24.39 |
-12:10:01.6 |
HIP 75832 |
26.21 |
| 2026-05-30 00:00 |
15:29:07.60 |
-12:08:58.0 |
HIP 75669 |
24.22 |
| 2026-05-30 12:00 |
15:28:50.86 |
-12:07:54.9 |
HIP 75669 |
20.99 |
| 2026-05-31 00:00 |
15:28:34.18 |
-12:06:52.3 |
HIP 75669 |
18.17 |
| 2026-05-31 12:00 |
15:28:17.57 |
-12:05:50.2 |
HIP 75669 |
15.98 |
| 2026-06-01 00:00 |
15:28:01.02 |
-12:04:48.7 |
HIP 75669 |
14.69 |
| 2026-06-01 12:00 |
15:27:44.54 |
-12:03:47.7 |
HIP 75669 |
14.52 |
| 2026-06-02 00:00 |
15:27:28.13 |
-12:02:47.2 |
HIP 75669 |
15.49 |