| 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) |
| 2026-05-12 00:00 |
07:39:50.86 |
-36:11:44.0 |
HIP 37223 |
22.55 |
| 2026-05-12 12:00 |
07:39:52.53 |
-36:11:08.7 |
HIP 37223 |
23.22 |
| 2026-05-13 00:00 |
07:39:54.23 |
-36:10:33.6 |
HIP 37223 |
23.90 |
| 2026-05-13 12:00 |
07:39:55.96 |
-36:09:58.7 |
HIP 37223 |
24.57 |
| 2026-05-14 00:00 |
07:39:57.72 |
-36:09:24.0 |
HIP 37223 |
25.25 |
| 2026-05-14 12:00 |
07:39:59.51 |
-36:08:49.6 |
HIP 37227 |
25.36 |
| 2026-05-15 00:00 |
07:40:01.33 |
-36:08:15.4 |
HIP 37227 |
25.12 |
| 2026-05-15 12:00 |
07:40:03.18 |
-36:07:41.4 |
HIP 37227 |
24.90 |
| 2026-05-16 00:00 |
07:40:05.06 |
-36:07:07.7 |
HIP 37227 |
24.71 |
| 2026-05-16 12:00 |
07:40:06.97 |
-36:06:34.2 |
HIP 37227 |
24.54 |
| 2026-05-17 00:00 |
07:40:08.91 |
-36:06:01.0 |
HIP 37227 |
24.39 |
| 2026-05-17 12:00 |
07:40:10.88 |
-36:05:28.0 |
HIP 37227 |
24.27 |
| 2026-05-18 00:00 |
07:40:12.88 |
-36:04:55.2 |
HIP 37227 |
24.17 |
| 2026-05-18 12:00 |
07:40:14.90 |
-36:04:22.7 |
HIP 37317 |
23.89 |
| 2026-05-19 00:00 |
07:40:16.96 |
-36:03:50.5 |
HIP 37317 |
23.50 |
| 2026-05-19 12:00 |
07:40:19.04 |
-36:03:18.5 |
HIP 37317 |
23.14 |
| 2026-05-20 00:00 |
07:40:21.15 |
-36:02:46.7 |
HIP 37317 |
22.79 |
| 2026-05-20 12:00 |
07:40:23.28 |
-36:02:15.2 |
HIP 37317 |
22.46 |
| 2026-05-21 00:00 |
07:40:25.45 |
-36:01:44.0 |
HIP 37317 |
22.16 |
| 2026-05-21 12:00 |
07:40:27.64 |
-36:01:13.0 |
HIP 37317 |
21.88 |
| 2026-05-22 00:00 |
07:40:29.86 |
-36:00:42.3 |
HIP 37317 |
21.62 |
| 2026-05-22 12:00 |
07:40:32.10 |
-36:00:11.9 |
HIP 37317 |
21.39 |
| 2026-05-23 00:00 |
07:40:34.38 |
-35:59:41.7 |
HIP 37317 |
21.19 |
| 2026-05-23 12:00 |
07:40:36.67 |
-35:59:11.8 |
HIP 37317 |
21.01 |
| 2026-05-24 00:00 |
07:40:39.00 |
-35:58:42.2 |
HIP 37317 |
20.86 |
| 2026-05-24 12:00 |
07:40:41.35 |
-35:58:12.8 |
HIP 37317 |
20.73 |
| 2026-05-25 00:00 |
07:40:43.73 |
-35:57:43.7 |
HIP 37317 |
20.64 |
| 2026-05-25 12:00 |
07:40:46.13 |
-35:57:14.9 |
HIP 37317 |
20.58 |
| 2026-05-26 00:00 |
07:40:48.55 |
-35:56:46.4 |
HIP 37317 |
20.54 |
| 2026-05-26 12:00 |
07:40:51.01 |
-35:56:18.1 |
HIP 37317 |
20.54 |
| 2026-05-27 00:00 |
07:40:53.48 |
-35:55:50.2 |
HIP 37317 |
20.56 |
| 2026-05-27 12:00 |
07:40:55.99 |
-35:55:22.5 |
HIP 37317 |
20.61 |
| 2026-05-28 00:00 |
07:40:58.51 |
-35:54:55.0 |
HIP 37317 |
20.70 |
| 2026-05-28 12:00 |
07:41:01.06 |
-35:54:27.9 |
HIP 37317 |
20.81 |
| 2026-05-29 00:00 |
07:41:03.64 |
-35:54:01.1 |
HIP 37317 |
20.95 |
| 2026-05-29 12:00 |
07:41:06.23 |
-35:53:34.5 |
HIP 37317 |
21.12 |
| 2026-05-30 00:00 |
07:41:08.85 |
-35:53:08.2 |
HIP 37317 |
21.32 |
| 2026-05-30 12:00 |
07:41:11.50 |
-35:52:42.3 |
HIP 37317 |
21.54 |
| 2026-05-31 00:00 |
07:41:14.17 |
-35:52:16.6 |
HIP 37317 |
21.79 |
| 2026-05-31 12:00 |
07:41:16.86 |
-35:51:51.2 |
HIP 37317 |
22.07 |
| 2026-06-01 00:00 |
07:41:19.57 |
-35:51:26.1 |
HIP 37317 |
22.37 |
| 2026-06-01 12:00 |
07:41:22.31 |
-35:51:01.3 |
HIP 37317 |
22.69 |
| 2026-06-02 00:00 |
07:41:25.07 |
-35:50:36.8 |
HIP 37317 |
23.04 |