| Parameter |
Value |
| Designation |
C/2008 N1 (Holmes) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2009-09-25T21:06:06.120000Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:31:21Z |
| Obs used |
1522 |
| NEO |
- |
| M1 |
12.800 |
| K1 |
4.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2009-06-22.0000000 |
| e |
0.99713966 |
| q (au) |
2.783511 |
| a (au) |
973.139852 |
| i (deg) |
115.521017 |
| Ω (om, deg) |
357.472211 |
| ω (w, deg) |
100.813452 |
| M (ma, deg) |
359.996887 |
Magnitude
Scatter + Global Linear
$$
M_a = (11.312 + 2.390\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
11.312 |
| n |
2.390 |
| gf |
1.000 |
| gb |
-0.883 |
| k |
0.999 |
| 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 |
| 2008-07-01 |
2009-05-02 |
+2.0960 |
-1.501 |
| 2009-05-02 |
2009-09-25 |
+0.0188 |
-0.150 |
| 2009-09-26 |
2010-02-20 |
+7.1027 |
-3.886 |
| 2010-02-20 |
2010-06-30 |
+5.8832 |
-3.022 |
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 |
07:48:05.48 |
-35:40:24.7 |
HIP 38128 |
9.75 |
| 2026-07-29 12:00 |
07:48:09.18 |
-35:40:39.1 |
HIP 38128 |
8.97 |
| 2026-07-30 00:00 |
07:48:12.87 |
-35:40:53.9 |
HIP 38128 |
8.18 |
| 2026-07-30 12:00 |
07:48:16.56 |
-35:41:08.9 |
HIP 38128 |
7.40 |
| 2026-07-31 00:00 |
07:48:20.24 |
-35:41:24.3 |
HIP 38128 |
6.62 |
| 2026-07-31 12:00 |
07:48:23.92 |
-35:41:40.0 |
HIP 38128 |
5.83 |
| 2026-08-01 00:00 |
07:48:27.58 |
-35:41:56.1 |
HIP 38128 |
5.05 |
| 2026-08-01 12:00 |
07:48:31.24 |
-35:42:12.5 |
HIP 38128 |
4.27 |
| 2026-08-02 00:00 |
07:48:34.89 |
-35:42:29.2 |
HIP 38128 |
3.49 |
| 2026-08-02 12:00 |
07:48:38.53 |
-35:42:46.2 |
HIP 38128 |
2.72 |
| 2026-08-03 00:00 |
07:48:42.17 |
-35:43:03.6 |
HIP 38128 |
1.97 |
| 2026-08-03 12:00 |
07:48:45.79 |
-35:43:21.2 |
HIP 38128 |
1.26 |
| 2026-08-04 00:00 |
07:48:49.41 |
-35:43:39.2 |
HIP 38128 |
0.73 |
| 2026-08-04 12:00 |
07:48:53.01 |
-35:43:57.6 |
HIP 38128 |
0.86 |
| 2026-08-05 00:00 |
07:48:56.61 |
-35:44:16.2 |
HIP 38128 |
1.48 |
| 2026-08-05 12:00 |
07:49:00.20 |
-35:44:35.2 |
HIP 38128 |
2.21 |
| 2026-08-06 00:00 |
07:49:03.78 |
-35:44:54.4 |
HIP 38128 |
2.97 |
| 2026-08-06 12:00 |
07:49:07.34 |
-35:45:14.0 |
HIP 38128 |
3.75 |
| 2026-08-07 00:00 |
07:49:10.90 |
-35:45:34.0 |
HIP 38128 |
4.53 |
| 2026-08-07 12:00 |
07:49:14.44 |
-35:45:54.2 |
HIP 38128 |
5.31 |
| 2026-08-08 00:00 |
07:49:17.98 |
-35:46:14.7 |
HIP 38128 |
6.10 |
| 2026-08-08 12:00 |
07:49:21.50 |
-35:46:35.6 |
HIP 38128 |
6.89 |
| 2026-08-09 00:00 |
07:49:25.02 |
-35:46:56.8 |
HIP 38128 |
7.68 |
| 2026-08-09 12:00 |
07:49:28.52 |
-35:47:18.3 |
HIP 38128 |
8.47 |
| 2026-08-10 00:00 |
07:49:32.00 |
-35:47:40.1 |
HIP 38128 |
9.26 |
| 2026-08-10 12:00 |
07:49:35.48 |
-35:48:02.2 |
HIP 38262 |
9.19 |
| 2026-08-11 00:00 |
07:49:38.94 |
-35:48:24.6 |
HIP 38262 |
8.52 |
| 2026-08-11 12:00 |
07:49:42.39 |
-35:48:47.4 |
HIP 38262 |
7.89 |
| 2026-08-12 00:00 |
07:49:45.83 |
-35:49:10.4 |
HIP 38262 |
7.28 |
| 2026-08-12 12:00 |
07:49:49.25 |
-35:49:33.7 |
HIP 38262 |
6.72 |
| 2026-08-13 00:00 |
07:49:52.66 |
-35:49:57.4 |
HIP 38262 |
6.22 |
| 2026-08-13 12:00 |
07:49:56.06 |
-35:50:21.3 |
HIP 38262 |
5.79 |
| 2026-08-14 00:00 |
07:49:59.44 |
-35:50:45.6 |
HIP 38262 |
5.44 |
| 2026-08-14 12:00 |
07:50:02.81 |
-35:51:10.1 |
HIP 38262 |
5.21 |
| 2026-08-15 00:00 |
07:50:06.16 |
-35:51:35.0 |
HIP 38262 |
5.09 |
| 2026-08-15 12:00 |
07:50:09.49 |
-35:52:00.1 |
HIP 38262 |
5.10 |
| 2026-08-16 00:00 |
07:50:12.82 |
-35:52:25.6 |
HIP 38262 |
5.24 |
| 2026-08-16 12:00 |
07:50:16.12 |
-35:52:51.3 |
HIP 38262 |
5.50 |
| 2026-08-17 00:00 |
07:50:19.41 |
-35:53:17.3 |
HIP 38262 |
5.86 |
| 2026-08-17 12:00 |
07:50:22.69 |
-35:53:43.6 |
HIP 38262 |
6.30 |
| 2026-08-18 00:00 |
07:50:25.94 |
-35:54:10.2 |
HIP 38262 |
6.82 |
| 2026-08-18 12:00 |
07:50:29.19 |
-35:54:37.1 |
HIP 38262 |
7.38 |
| 2026-08-19 00:00 |
07:50:32.41 |
-35:55:04.2 |
HIP 38262 |
7.99 |