| 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) |
| 2026-06-01 00:00 |
17:29:34.71 |
-38:22:59.7 |
HIP 85589 |
8.22 |
| 2026-06-01 12:00 |
17:29:30.38 |
-38:23:00.0 |
HIP 85589 |
8.07 |
| 2026-06-02 00:00 |
17:29:26.04 |
-38:23:00.1 |
HIP 85589 |
8.02 |
| 2026-06-02 12:00 |
17:29:21.69 |
-38:23:00.1 |
HIP 85589 |
8.05 |
| 2026-06-03 00:00 |
17:29:17.33 |
-38:23:00.0 |
HIP 85589 |
8.18 |
| 2026-06-03 12:00 |
17:29:12.97 |
-38:22:59.7 |
HIP 85589 |
8.39 |
| 2026-06-04 00:00 |
17:29:08.59 |
-38:22:59.3 |
HIP 85589 |
8.69 |
| 2026-06-04 12:00 |
17:29:04.21 |
-38:22:58.8 |
HIP 85589 |
9.06 |
| 2026-06-05 00:00 |
17:28:59.83 |
-38:22:58.1 |
HIP 85589 |
9.50 |
| 2026-06-05 12:00 |
17:28:55.43 |
-38:22:57.3 |
HIP 85589 |
9.99 |
| 2026-06-06 00:00 |
17:28:51.03 |
-38:22:56.4 |
HIP 85589 |
10.54 |
| 2026-06-06 12:00 |
17:28:46.63 |
-38:22:55.3 |
HIP 85589 |
11.12 |
| 2026-06-07 00:00 |
17:28:42.22 |
-38:22:54.1 |
HIP 85589 |
11.75 |
| 2026-06-07 12:00 |
17:28:37.80 |
-38:22:52.8 |
HIP 85589 |
12.40 |
| 2026-06-08 00:00 |
17:28:33.38 |
-38:22:51.3 |
HIP 85589 |
13.08 |
| 2026-06-08 12:00 |
17:28:28.95 |
-38:22:49.7 |
HIP 85589 |
13.79 |
| 2026-06-09 00:00 |
17:28:24.52 |
-38:22:48.0 |
HIP 85589 |
14.51 |
| 2026-06-09 12:00 |
17:28:20.09 |
-38:22:46.2 |
HIP 85589 |
15.25 |
| 2026-06-10 00:00 |
17:28:15.65 |
-38:22:44.2 |
HIP 85589 |
16.00 |
| 2026-06-10 12:00 |
17:28:11.22 |
-38:22:42.1 |
HIP 85589 |
16.77 |
| 2026-06-11 00:00 |
17:28:06.77 |
-38:22:39.8 |
HIP 85589 |
17.55 |
| 2026-06-11 12:00 |
17:28:02.33 |
-38:22:37.4 |
HIP 85359 |
17.45 |
| 2026-06-12 00:00 |
17:27:57.88 |
-38:22:34.9 |
HIP 85359 |
16.58 |
| 2026-06-12 12:00 |
17:27:53.43 |
-38:22:32.3 |
HIP 85359 |
15.71 |
| 2026-06-13 00:00 |
17:27:48.98 |
-38:22:29.5 |
HIP 85359 |
14.85 |
| 2026-06-13 12:00 |
17:27:44.53 |
-38:22:26.6 |
HIP 85359 |
13.98 |
| 2026-06-14 00:00 |
17:27:40.08 |
-38:22:23.6 |
HIP 85359 |
13.12 |
| 2026-06-14 12:00 |
17:27:35.63 |
-38:22:20.4 |
HIP 85359 |
12.25 |
| 2026-06-15 00:00 |
17:27:31.18 |
-38:22:17.1 |
HIP 85359 |
11.39 |
| 2026-06-15 12:00 |
17:27:26.73 |
-38:22:13.7 |
HIP 85359 |
10.53 |
| 2026-06-16 00:00 |
17:27:22.29 |
-38:22:10.1 |
HIP 85359 |
9.67 |
| 2026-06-16 12:00 |
17:27:17.84 |
-38:22:06.4 |
HIP 85359 |
8.81 |
| 2026-06-17 00:00 |
17:27:13.39 |
-38:22:02.6 |
HIP 85359 |
7.96 |
| 2026-06-17 12:00 |
17:27:08.95 |
-38:21:58.7 |
HIP 85359 |
7.11 |
| 2026-06-18 00:00 |
17:27:04.51 |
-38:21:54.6 |
HIP 85359 |
6.26 |
| 2026-06-18 12:00 |
17:27:00.08 |
-38:21:50.4 |
HIP 85359 |
5.43 |
| 2026-06-19 00:00 |
17:26:55.64 |
-38:21:46.1 |
HIP 85359 |
4.61 |
| 2026-06-19 12:00 |
17:26:51.21 |
-38:21:41.6 |
HIP 85359 |
3.81 |
| 2026-06-20 00:00 |
17:26:46.79 |
-38:21:37.1 |
HIP 85359 |
3.05 |
| 2026-06-20 12:00 |
17:26:42.37 |
-38:21:32.4 |
HIP 85359 |
2.37 |
| 2026-06-21 00:00 |
17:26:37.95 |
-38:21:27.5 |
HIP 85359 |
1.85 |
| 2026-06-21 12:00 |
17:26:33.54 |
-38:21:22.6 |
HIP 85359 |
1.66 |
| 2026-06-22 00:00 |
17:26:29.14 |
-38:21:17.5 |
HIP 85359 |
1.89 |