| Parameter |
Value |
| Designation |
C/1919 Q2 (Metcalf) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
1919-12-07T19:37:10.358400Z |
| Orbit solution date (soln_date, UTC) |
2021-04-15T23:29:02Z |
| Obs used |
18 |
| NEO |
- |
| M1 |
5.100 |
| K1 |
11.500 |
| PC |
- |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
1919-09-18.0000000 |
| e |
0.99977859 |
| q (au) |
1.115204 |
| a (au) |
5036.797426 |
| i (deg) |
46.383158 |
| Ω (om, deg) |
122.097279 |
| ω (w, deg) |
185.764445 |
| M (ma, deg) |
359.999777 |
Magnitude
Scatter + Global Linear
$$
M_a = (6.671 + 5.125\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
6.671 |
| n |
5.125 |
| gf |
0.999 |
| gb |
-1.000 |
| k |
0.800 |
| 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
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-05-12 00:00 |
07:58:11.81 |
+17:01:02.6 |
HIP 39046 |
19.75 |
| 2026-05-12 12:00 |
07:58:12.19 |
+17:01:02.5 |
HIP 39046 |
19.68 |
| 2026-05-13 00:00 |
07:58:12.59 |
+17:01:02.3 |
HIP 39046 |
19.60 |
| 2026-05-13 12:00 |
07:58:12.99 |
+17:01:02.1 |
HIP 39046 |
19.52 |
| 2026-05-14 00:00 |
07:58:13.39 |
+17:01:01.8 |
HIP 39046 |
19.44 |
| 2026-05-14 12:00 |
07:58:13.81 |
+17:01:01.6 |
HIP 39046 |
19.36 |
| 2026-05-15 00:00 |
07:58:14.23 |
+17:01:01.3 |
HIP 39046 |
19.28 |
| 2026-05-15 12:00 |
07:58:14.66 |
+17:01:01.0 |
HIP 39046 |
19.20 |
| 2026-05-16 00:00 |
07:58:15.10 |
+17:01:00.7 |
HIP 39046 |
19.11 |
| 2026-05-16 12:00 |
07:58:15.54 |
+17:01:00.3 |
HIP 39046 |
19.02 |
| 2026-05-17 00:00 |
07:58:15.99 |
+17:01:00.0 |
HIP 39046 |
18.94 |
| 2026-05-17 12:00 |
07:58:16.45 |
+17:00:59.6 |
HIP 39046 |
18.85 |
| 2026-05-18 00:00 |
07:58:16.91 |
+17:00:59.1 |
HIP 39046 |
18.76 |
| 2026-05-18 12:00 |
07:58:17.39 |
+17:00:58.7 |
HIP 39046 |
18.66 |
| 2026-05-19 00:00 |
07:58:17.87 |
+17:00:58.2 |
HIP 39046 |
18.57 |
| 2026-05-19 12:00 |
07:58:18.35 |
+17:00:57.7 |
HIP 39046 |
18.48 |
| 2026-05-20 00:00 |
07:58:18.85 |
+17:00:57.2 |
HIP 39046 |
18.38 |
| 2026-05-20 12:00 |
07:58:19.35 |
+17:00:56.7 |
HIP 39046 |
18.28 |
| 2026-05-21 00:00 |
07:58:19.85 |
+17:00:56.1 |
HIP 39046 |
18.18 |
| 2026-05-21 12:00 |
07:58:20.37 |
+17:00:55.5 |
HIP 39046 |
18.08 |
| 2026-05-22 00:00 |
07:58:20.89 |
+17:00:54.9 |
HIP 39046 |
17.98 |
| 2026-05-22 12:00 |
07:58:21.42 |
+17:00:54.2 |
HIP 39046 |
17.88 |
| 2026-05-23 00:00 |
07:58:21.95 |
+17:00:53.6 |
HIP 39046 |
17.78 |
| 2026-05-23 12:00 |
07:58:22.49 |
+17:00:52.9 |
HIP 39046 |
17.67 |
| 2026-05-24 00:00 |
07:58:23.04 |
+17:00:52.2 |
HIP 39046 |
17.57 |
| 2026-05-24 12:00 |
07:58:23.59 |
+17:00:51.4 |
HIP 39046 |
17.46 |
| 2026-05-25 00:00 |
07:58:24.15 |
+17:00:50.7 |
HIP 39046 |
17.35 |
| 2026-05-25 12:00 |
07:58:24.72 |
+17:00:49.9 |
HIP 39046 |
17.24 |
| 2026-05-26 00:00 |
07:58:25.29 |
+17:00:49.1 |
HIP 39046 |
17.13 |
| 2026-05-26 12:00 |
07:58:25.87 |
+17:00:48.3 |
HIP 39046 |
17.02 |
| 2026-05-27 00:00 |
07:58:26.46 |
+17:00:47.4 |
HIP 39046 |
16.91 |
| 2026-05-27 12:00 |
07:58:27.05 |
+17:00:46.6 |
HIP 39046 |
16.80 |
| 2026-05-28 00:00 |
07:58:27.65 |
+17:00:45.7 |
HIP 39046 |
16.69 |
| 2026-05-28 12:00 |
07:58:28.25 |
+17:00:44.7 |
HIP 39046 |
16.57 |
| 2026-05-29 00:00 |
07:58:28.87 |
+17:00:43.8 |
HIP 39046 |
16.46 |
| 2026-05-29 12:00 |
07:58:29.48 |
+17:00:42.8 |
HIP 39046 |
16.34 |
| 2026-05-30 00:00 |
07:58:30.11 |
+17:00:41.9 |
HIP 39046 |
16.22 |
| 2026-05-30 12:00 |
07:58:30.74 |
+17:00:40.8 |
HIP 39046 |
16.11 |
| 2026-05-31 00:00 |
07:58:31.37 |
+17:00:39.8 |
HIP 39046 |
15.99 |
| 2026-05-31 12:00 |
07:58:32.01 |
+17:00:38.8 |
HIP 39046 |
15.87 |
| 2026-06-01 00:00 |
07:58:32.66 |
+17:00:37.7 |
HIP 39046 |
15.75 |
| 2026-06-01 12:00 |
07:58:33.31 |
+17:00:36.6 |
HIP 39046 |
15.63 |
| 2026-06-02 00:00 |
07:58:33.97 |
+17:00:35.5 |
HIP 39046 |
15.51 |