| Parameter |
Value |
| Designation |
17P/Holmes |
| Type |
P |
| Perihelion (tp_cal, UTC) |
2014-03-26T17:17:14.196480Z |
| Orbit solution date (soln_date, UTC) |
2023-10-10T13:05:23Z |
| Obs used |
2211 |
| NEO |
- |
| M1 |
9.400 |
| K1 |
14.750 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2016-10-19.0000000 |
| e |
0.43015482 |
| q (au) |
2.066329 |
| a (au) |
3.626124 |
| i (deg) |
19.070359 |
| Ω (om, deg) |
326.773810 |
| ω (w, deg) |
24.738506 |
| M (ma, deg) |
133.785581 |
Magnitude
Scatter + Global Linear
$$
M_a = (8.460 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
8.460 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-1.000 |
| 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 |
| 2019-01-17 |
2021-07-29 |
-14.8750 |
+4.940 |
| 2021-07-29 |
2021-10-22 |
+35.1628 |
-14.605 |
| 2021-10-22 |
2022-01-30 |
-23.8751 |
+11.231 |
| 2022-01-30 |
2023-01-22 |
+4.5697 |
-3.280 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
13:19:08.10 |
-28:38:32.3 |
HIP 64942 |
5.44 |
| 2026-07-29 12:00 |
13:19:26.61 |
-28:38:14.7 |
HIP 64942 |
9.43 |
| 2026-07-30 00:00 |
13:19:45.32 |
-28:37:58.7 |
HIP 64942 |
13.50 |
| 2026-07-30 12:00 |
13:20:04.22 |
-28:37:44.0 |
HIP 64967 |
17.24 |
| 2026-07-31 00:00 |
13:20:23.32 |
-28:37:30.8 |
HIP 64967 |
20.99 |
| 2026-07-31 12:00 |
13:20:42.61 |
-28:37:19.1 |
HIP 64967 |
24.90 |
| 2026-08-01 00:00 |
13:21:02.10 |
-28:37:08.8 |
HIP 65222 |
23.26 |
| 2026-08-01 12:00 |
13:21:21.78 |
-28:36:59.9 |
HIP 65222 |
21.39 |
| 2026-08-02 00:00 |
13:21:41.66 |
-28:36:52.4 |
HIP 65222 |
20.25 |
| 2026-08-02 12:00 |
13:22:01.72 |
-28:36:46.4 |
HIP 65222 |
19.99 |
| 2026-08-03 00:00 |
13:22:21.98 |
-28:36:41.7 |
HIP 65222 |
20.67 |
| 2026-08-03 12:00 |
13:22:42.43 |
-28:36:38.5 |
HIP 65382 |
21.86 |
| 2026-08-04 00:00 |
13:23:03.06 |
-28:36:36.7 |
HIP 65382 |
18.67 |
| 2026-08-04 12:00 |
13:23:23.88 |
-28:36:36.3 |
HIP 65382 |
16.13 |
| 2026-08-05 00:00 |
13:23:44.89 |
-28:36:37.3 |
HIP 65382 |
14.63 |
| 2026-08-05 12:00 |
13:24:06.09 |
-28:36:39.6 |
HIP 65382 |
14.55 |
| 2026-08-06 00:00 |
13:24:27.47 |
-28:36:43.4 |
HIP 65382 |
15.92 |
| 2026-08-06 12:00 |
13:24:49.04 |
-28:36:48.6 |
HIP 65382 |
18.48 |
| 2026-08-07 00:00 |
13:25:10.79 |
-28:36:55.1 |
HIP 65520 |
16.77 |
| 2026-08-07 12:00 |
13:25:32.72 |
-28:37:03.0 |
HIP 65520 |
15.06 |
| 2026-08-08 00:00 |
13:25:54.84 |
-28:37:12.3 |
HIP 65520 |
14.83 |
| 2026-08-08 12:00 |
13:26:17.13 |
-28:37:22.9 |
HIP 65520 |
16.17 |
| 2026-08-09 00:00 |
13:26:39.61 |
-28:37:35.0 |
HIP 65520 |
18.78 |
| 2026-08-09 12:00 |
13:27:02.27 |
-28:37:48.3 |
HIP 65520 |
22.24 |
| 2026-08-10 00:00 |
13:27:25.11 |
-28:38:03.1 |
HIP 65730 |
19.45 |
| 2026-08-10 12:00 |
13:27:48.13 |
-28:38:19.1 |
HIP 65730 |
16.51 |
| 2026-08-11 00:00 |
13:28:11.32 |
-28:38:36.5 |
HIP 65730 |
14.79 |
| 2026-08-11 12:00 |
13:28:34.69 |
-28:38:55.3 |
HIP 65730 |
14.75 |
| 2026-08-12 00:00 |
13:28:58.23 |
-28:39:15.4 |
HIP 65730 |
16.45 |
| 2026-08-12 12:00 |
13:29:21.95 |
-28:39:36.8 |
HIP 65847 |
18.37 |
| 2026-08-13 00:00 |
13:29:45.85 |
-28:39:59.5 |
HIP 65847 |
16.76 |
| 2026-08-13 12:00 |
13:30:09.91 |
-28:40:23.6 |
HIP 65847 |
16.71 |
| 2026-08-14 00:00 |
13:30:34.15 |
-28:40:48.9 |
HIP 65847 |
18.25 |
| 2026-08-14 12:00 |
13:30:58.56 |
-28:41:15.6 |
HIP 65847 |
21.08 |
| 2026-08-15 00:00 |
13:31:23.14 |
-28:41:43.5 |
HIP 66065 |
15.97 |
| 2026-08-15 12:00 |
13:31:47.89 |
-28:42:12.8 |
HIP 66065 |
10.56 |
| 2026-08-16 00:00 |
13:32:12.80 |
-28:42:43.3 |
HIP 66065 |
5.21 |
| 2026-08-16 12:00 |
13:32:37.89 |
-28:43:15.1 |
HIP 66065 |
1.74 |
| 2026-08-17 00:00 |
13:33:03.13 |
-28:43:48.1 |
HIP 66065 |
6.36 |
| 2026-08-17 12:00 |
13:33:28.55 |
-28:44:22.4 |
HIP 66065 |
11.87 |
| 2026-08-18 00:00 |
13:33:54.12 |
-28:44:58.0 |
HIP 66118 |
15.99 |
| 2026-08-18 12:00 |
13:34:19.86 |
-28:45:34.7 |
HIP 66118 |
19.27 |
| 2026-08-19 00:00 |
13:34:45.76 |
-28:46:12.8 |
HIP 66118 |
23.49 |