| 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
$$
M_a = (7.966 + 3.198\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
7.966 |
| n |
3.198 |
| gf |
0.800 |
| gb |
-0.500 |
| k |
1.000 |
| δ90 |
1.247 |
| 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 |
+67.7705 |
-8.668 |
| 1989-07-14 |
1989-09-11 |
-0.4609 |
-0.069 |
| 1989-09-12 |
2019-02-03 |
-6.3683 |
-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) |
| 2026-03-26 00:00 |
17:35:52.05 |
-38:05:45.7 |
HIP 86119 |
1.73 |
| 2026-03-26 12:00 |
17:35:51.40 |
-38:05:58.5 |
HIP 86119 |
1.82 |
| 2026-03-27 00:00 |
17:35:50.72 |
-38:06:11.3 |
HIP 86119 |
1.95 |
| 2026-03-27 12:00 |
17:35:49.99 |
-38:06:24.0 |
HIP 86119 |
2.11 |
| 2026-03-28 00:00 |
17:35:49.23 |
-38:06:36.7 |
HIP 86119 |
2.30 |
| 2026-03-28 12:00 |
17:35:48.43 |
-38:06:49.4 |
HIP 86119 |
2.50 |
| 2026-03-29 00:00 |
17:35:47.59 |
-38:07:02.0 |
HIP 86119 |
2.72 |
| 2026-03-29 12:00 |
17:35:46.71 |
-38:07:14.6 |
HIP 86119 |
2.96 |
| 2026-03-30 00:00 |
17:35:45.80 |
-38:07:27.1 |
HIP 86119 |
3.21 |
| 2026-03-30 12:00 |
17:35:44.84 |
-38:07:39.6 |
HIP 86119 |
3.47 |
| 2026-03-31 00:00 |
17:35:43.85 |
-38:07:52.1 |
HIP 86119 |
3.74 |
| 2026-03-31 12:00 |
17:35:42.82 |
-38:08:04.5 |
HIP 86119 |
4.01 |
| 2026-04-01 00:00 |
17:35:41.75 |
-38:08:16.9 |
HIP 86119 |
4.30 |
| 2026-04-01 12:00 |
17:35:40.64 |
-38:08:29.2 |
HIP 86119 |
4.59 |
| 2026-04-02 00:00 |
17:35:39.50 |
-38:08:41.5 |
HIP 86119 |
4.89 |
| 2026-04-02 12:00 |
17:35:38.31 |
-38:08:53.7 |
HIP 86119 |
5.19 |
| 2026-04-03 00:00 |
17:35:37.09 |
-38:09:05.9 |
HIP 86119 |
5.50 |
| 2026-04-03 12:00 |
17:35:35.84 |
-38:09:18.0 |
HIP 86119 |
5.82 |
| 2026-04-04 00:00 |
17:35:34.54 |
-38:09:30.1 |
HIP 86119 |
6.14 |
| 2026-04-04 12:00 |
17:35:33.21 |
-38:09:42.1 |
HIP 86119 |
6.47 |
| 2026-04-05 00:00 |
17:35:31.84 |
-38:09:54.1 |
HIP 86119 |
6.81 |
| 2026-04-05 12:00 |
17:35:30.43 |
-38:10:06.0 |
HIP 86119 |
7.15 |
| 2026-04-06 00:00 |
17:35:28.99 |
-38:10:17.8 |
HIP 86119 |
7.49 |
| 2026-04-06 12:00 |
17:35:27.50 |
-38:10:29.6 |
HIP 86119 |
7.85 |
| 2026-04-07 00:00 |
17:35:25.98 |
-38:10:41.4 |
HIP 86119 |
8.20 |
| 2026-04-07 12:00 |
17:35:24.43 |
-38:10:53.1 |
HIP 86119 |
8.56 |
| 2026-04-08 00:00 |
17:35:22.84 |
-38:11:04.7 |
HIP 86119 |
8.93 |
| 2026-04-08 12:00 |
17:35:21.21 |
-38:11:16.3 |
HIP 86119 |
9.31 |
| 2026-04-09 00:00 |
17:35:19.54 |
-38:11:27.8 |
HIP 86119 |
9.69 |
| 2026-04-09 12:00 |
17:35:17.84 |
-38:11:39.2 |
HIP 86119 |
10.07 |
| 2026-04-10 00:00 |
17:35:16.10 |
-38:11:50.6 |
HIP 86119 |
10.46 |
| 2026-04-10 12:00 |
17:35:14.32 |
-38:12:02.0 |
HIP 86119 |
10.86 |
| 2026-04-11 00:00 |
17:35:12.51 |
-38:12:13.2 |
HIP 86119 |
11.26 |
| 2026-04-11 12:00 |
17:35:10.66 |
-38:12:24.4 |
HIP 86119 |
11.66 |
| 2026-04-12 00:00 |
17:35:08.78 |
-38:12:35.5 |
HIP 86119 |
12.07 |
| 2026-04-12 12:00 |
17:35:06.86 |
-38:12:46.6 |
HIP 86119 |
12.49 |
| 2026-04-13 00:00 |
17:35:04.90 |
-38:12:57.6 |
HIP 86119 |
12.91 |
| 2026-04-13 12:00 |
17:35:02.91 |
-38:13:08.5 |
HIP 86119 |
13.34 |
| 2026-04-14 00:00 |
17:35:00.88 |
-38:13:19.3 |
HIP 86119 |
13.78 |
| 2026-04-14 12:00 |
17:34:58.82 |
-38:13:30.1 |
HIP 86119 |
14.22 |
| 2026-04-15 00:00 |
17:34:56.72 |
-38:13:40.8 |
HIP 86119 |
14.66 |
| 2026-04-15 12:00 |
17:34:54.59 |
-38:13:51.4 |
HIP 86119 |
15.11 |
| 2026-04-16 00:00 |
17:34:52.42 |
-38:14:02.0 |
HIP 86119 |
15.57 |