23P/Brorsen-Metcalf
| Parameter |
Value |
| Designation |
23P/Brorsen-Metcalf |
| Type |
P |
| Perihelion (tp_cal, UTC) |
1989-09-11T22:29:54.219840Z |
| Orbit solution date (soln_date, UTC) |
2002-03-01T13:24:57Z |
| Obs used |
223 |
| NEO |
Yes |
| M1 |
7.800 |
| K1 |
8.000 |
| PC |
0.030 |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1989-10-01.0000000 |
| e |
0.97195226 |
| q (au) |
0.478753 |
| a (au) |
17.069207 |
| i (deg) |
19.333940 |
| Ω (om, deg) |
311.585462 |
| ω (w, deg) |
129.610684 |
| M (ma, deg) |
0.266419 |
Magnitude
Scatter + Global Linear
$$
M_a = (7.965 + 3.198\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.965 |
| n |
3.198 |
| gf |
0.800 |
| gb |
-0.500 |
| k |
1.000 |
| δ90 |
1.248 |
| 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 |
| 1989-07-04 |
1989-07-14 |
+67.7843 |
-8.670 |
| 1989-07-14 |
1989-09-11 |
-0.4611 |
-0.069 |
| 1989-09-12 |
2019-02-03 |
-6.3680 |
-1.419 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
17:33:40.16 |
-37:43:57.0 |
HIP 85801 |
20.78 |
| 2026-02-03 12:00 |
17:33:43.18 |
-37:44:08.3 |
HIP 85801 |
21.40 |
| 2026-02-04 00:00 |
17:33:46.16 |
-37:44:19.6 |
HIP 86079 |
21.59 |
| 2026-02-04 12:00 |
17:33:49.12 |
-37:44:31.0 |
HIP 86079 |
20.97 |
| 2026-02-05 00:00 |
17:33:52.05 |
-37:44:42.5 |
HIP 86079 |
20.36 |
| 2026-02-05 12:00 |
17:33:54.95 |
-37:44:54.0 |
HIP 86079 |
19.76 |
| 2026-02-06 00:00 |
17:33:57.82 |
-37:45:05.6 |
HIP 86079 |
19.16 |
| 2026-02-06 12:00 |
17:34:00.66 |
-37:45:17.2 |
HIP 86079 |
18.57 |
| 2026-02-07 00:00 |
17:34:03.47 |
-37:45:28.8 |
HIP 86079 |
17.98 |
| 2026-02-07 12:00 |
17:34:06.25 |
-37:45:40.6 |
HIP 86079 |
17.40 |
| 2026-02-08 00:00 |
17:34:09.00 |
-37:45:52.4 |
HIP 86079 |
16.82 |
| 2026-02-08 12:00 |
17:34:11.72 |
-37:46:04.2 |
HIP 86079 |
16.25 |
| 2026-02-09 00:00 |
17:34:14.41 |
-37:46:16.1 |
HIP 86079 |
15.68 |
| 2026-02-09 12:00 |
17:34:17.07 |
-37:46:28.0 |
HIP 86079 |
15.12 |
| 2026-02-10 00:00 |
17:34:19.70 |
-37:46:40.0 |
HIP 86079 |
14.56 |
| 2026-02-10 12:00 |
17:34:22.30 |
-37:46:52.0 |
HIP 86079 |
14.01 |
| 2026-02-11 00:00 |
17:34:24.86 |
-37:47:04.1 |
HIP 86079 |
13.47 |
| 2026-02-11 12:00 |
17:34:27.40 |
-37:47:16.2 |
HIP 86079 |
12.93 |
| 2026-02-12 00:00 |
17:34:29.90 |
-37:47:28.4 |
HIP 86079 |
12.40 |
| 2026-02-12 12:00 |
17:34:32.37 |
-37:47:40.6 |
HIP 86079 |
11.88 |
| 2026-02-13 00:00 |
17:34:34.81 |
-37:47:52.8 |
HIP 86079 |
11.36 |
| 2026-02-13 12:00 |
17:34:37.22 |
-37:48:05.1 |
HIP 86079 |
10.85 |
| 2026-02-14 00:00 |
17:34:39.59 |
-37:48:17.5 |
HIP 86079 |
10.34 |
| 2026-02-14 12:00 |
17:34:41.93 |
-37:48:29.9 |
HIP 86079 |
9.84 |
| 2026-02-15 00:00 |
17:34:44.24 |
-37:48:42.3 |
HIP 86079 |
9.35 |
| 2026-02-15 12:00 |
17:34:46.51 |
-37:48:54.8 |
HIP 86079 |
8.87 |
| 2026-02-16 00:00 |
17:34:48.75 |
-37:49:07.3 |
HIP 86079 |
8.39 |
| 2026-02-16 12:00 |
17:34:50.96 |
-37:49:19.8 |
HIP 86079 |
7.92 |
| 2026-02-17 00:00 |
17:34:53.13 |
-37:49:32.4 |
HIP 86079 |
7.46 |
| 2026-02-17 12:00 |
17:34:55.27 |
-37:49:45.0 |
HIP 86079 |
7.01 |
| 2026-02-18 00:00 |
17:34:57.38 |
-37:49:57.7 |
HIP 86079 |
6.56 |
| 2026-02-18 12:00 |
17:34:59.45 |
-37:50:10.4 |
HIP 86079 |
6.13 |
| 2026-02-19 00:00 |
17:35:01.49 |
-37:50:23.1 |
HIP 86079 |
5.71 |
| 2026-02-19 12:00 |
17:35:03.49 |
-37:50:35.9 |
HIP 86079 |
5.30 |
| 2026-02-20 00:00 |
17:35:05.45 |
-37:50:48.7 |
HIP 86079 |
4.91 |
| 2026-02-20 12:00 |
17:35:07.39 |
-37:51:01.5 |
HIP 86079 |
4.53 |
| 2026-02-21 00:00 |
17:35:09.28 |
-37:51:14.3 |
HIP 86079 |
4.17 |
| 2026-02-21 12:00 |
17:35:11.14 |
-37:51:27.2 |
HIP 86079 |
3.83 |
| 2026-02-22 00:00 |
17:35:12.97 |
-37:51:40.2 |
HIP 86079 |
3.52 |
| 2026-02-22 12:00 |
17:35:14.76 |
-37:51:53.1 |
HIP 86079 |
3.23 |
| 2026-02-23 00:00 |
17:35:16.52 |
-37:52:06.1 |
HIP 86079 |
2.99 |
| 2026-02-23 12:00 |
17:35:18.24 |
-37:52:19.1 |
HIP 86079 |
2.79 |
| 2026-02-24 00:00 |
17:35:19.92 |
-37:52:32.1 |
HIP 86079 |
2.64 |