C/2022 U2 (ATLAS)
| Parameter |
Value |
| Designation |
C/2022 U2 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2023-01-14T05:16:42.461760Z |
| Orbit solution date (soln_date, UTC) |
2023-11-04T19:42:53Z |
| Obs used |
996 |
| NEO |
- |
| M1 |
13.600 |
| K1 |
19.750 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2022-10-25T05:05:57.926400Z |
| Discovery magnitude (MPC) |
19.13 o |
| Discovery observatory (MPC) |
T08 · ATLAS-MLO, Mauna Loa |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2023-01-07.0000000 |
| e |
0.98612019 |
| q (au) |
1.328023 |
| a (au) |
95.680211 |
| i (deg) |
48.249781 |
| Ω (om, deg) |
304.475901 |
| ω (w, deg) |
147.908535 |
| M (ma, deg) |
359.992397 |
Magnitude
Scatter + Global Linear
$$
M_a = (13.414 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
13.414 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-0.998 |
| k |
1.000 |
| 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 |
| 2022-10-25 |
2023-01-13 |
+20.1792 |
-4.155 |
| 2023-01-14 |
2023-05-19 |
+3.5650 |
-2.036 |
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 |
15:16:08.89 |
-64:18:25.7 |
HIP 74398 |
28.44 |
| 2026-02-03 12:00 |
15:16:15.32 |
-64:20:28.0 |
HIP 74398 |
28.11 |
| 2026-02-04 00:00 |
15:16:21.56 |
-64:22:30.3 |
HIP 75082 |
27.71 |
| 2026-02-04 12:00 |
15:16:27.60 |
-64:24:32.4 |
HIP 75082 |
26.73 |
| 2026-02-05 00:00 |
15:16:33.45 |
-64:26:34.4 |
HIP 75082 |
25.92 |
| 2026-02-05 12:00 |
15:16:39.09 |
-64:28:36.3 |
HIP 75082 |
25.29 |
| 2026-02-06 00:00 |
15:16:44.53 |
-64:30:38.1 |
HIP 75082 |
24.84 |
| 2026-02-06 12:00 |
15:16:49.78 |
-64:32:39.7 |
HIP 75082 |
24.60 |
| 2026-02-07 00:00 |
15:16:54.81 |
-64:34:41.2 |
HIP 75082 |
24.55 |
| 2026-02-07 12:00 |
15:16:59.65 |
-64:36:42.6 |
HIP 75082 |
24.70 |
| 2026-02-08 00:00 |
15:17:04.28 |
-64:38:43.8 |
HIP 75082 |
25.04 |
| 2026-02-08 12:00 |
15:17:08.71 |
-64:40:44.9 |
HIP 75082 |
25.57 |
| 2026-02-09 00:00 |
15:17:12.93 |
-64:42:45.8 |
HIP 75082 |
26.27 |
| 2026-02-09 12:00 |
15:17:16.94 |
-64:44:46.5 |
HIP 75052 |
26.99 |
| 2026-02-10 00:00 |
15:17:20.74 |
-64:46:47.0 |
HIP 75052 |
25.26 |
| 2026-02-10 12:00 |
15:17:24.33 |
-64:48:47.4 |
HIP 75052 |
23.60 |
| 2026-02-11 00:00 |
15:17:27.71 |
-64:50:47.5 |
HIP 75052 |
22.02 |
| 2026-02-11 12:00 |
15:17:30.88 |
-64:52:47.5 |
HIP 75052 |
20.54 |
| 2026-02-12 00:00 |
15:17:33.84 |
-64:54:47.2 |
HIP 75052 |
19.18 |
| 2026-02-12 12:00 |
15:17:36.58 |
-64:56:46.7 |
HIP 75052 |
17.98 |
| 2026-02-13 00:00 |
15:17:39.11 |
-64:58:46.0 |
HIP 75052 |
16.95 |
| 2026-02-13 12:00 |
15:17:41.42 |
-65:00:45.0 |
HIP 75052 |
16.12 |
| 2026-02-14 00:00 |
15:17:43.51 |
-65:02:43.8 |
HIP 75052 |
15.54 |
| 2026-02-14 12:00 |
15:17:45.39 |
-65:04:42.3 |
HIP 74712 |
14.37 |
| 2026-02-15 00:00 |
15:17:47.05 |
-65:06:40.6 |
HIP 74712 |
13.20 |
| 2026-02-15 12:00 |
15:17:48.48 |
-65:08:38.6 |
HIP 74712 |
12.21 |
| 2026-02-16 00:00 |
15:17:49.70 |
-65:10:36.3 |
HIP 74712 |
11.46 |
| 2026-02-16 12:00 |
15:17:50.70 |
-65:12:33.7 |
HIP 74712 |
11.00 |
| 2026-02-17 00:00 |
15:17:51.47 |
-65:14:30.7 |
HIP 74712 |
10.84 |
| 2026-02-17 12:00 |
15:17:52.02 |
-65:16:27.5 |
HIP 74712 |
11.02 |
| 2026-02-18 00:00 |
15:17:52.35 |
-65:18:24.0 |
HIP 74712 |
11.50 |
| 2026-02-18 12:00 |
15:17:52.45 |
-65:20:20.1 |
HIP 74712 |
12.25 |
| 2026-02-19 00:00 |
15:17:52.33 |
-65:22:15.9 |
HIP 74712 |
13.22 |
| 2026-02-19 12:00 |
15:17:51.99 |
-65:24:11.3 |
HIP 74898 |
12.53 |
| 2026-02-20 00:00 |
15:17:51.41 |
-65:26:06.3 |
HIP 74898 |
10.72 |
| 2026-02-20 12:00 |
15:17:50.61 |
-65:28:01.0 |
HIP 74898 |
8.97 |
| 2026-02-21 00:00 |
15:17:49.59 |
-65:29:55.3 |
HIP 74898 |
7.32 |
| 2026-02-21 12:00 |
15:17:48.33 |
-65:31:49.2 |
HIP 74898 |
5.84 |
| 2026-02-22 00:00 |
15:17:46.85 |
-65:33:42.7 |
HIP 74898 |
4.70 |
| 2026-02-22 12:00 |
15:17:45.14 |
-65:35:35.8 |
HIP 74898 |
4.19 |
| 2026-02-23 00:00 |
15:17:43.20 |
-65:37:28.5 |
HIP 74898 |
4.51 |
| 2026-02-23 12:00 |
15:17:41.03 |
-65:39:20.8 |
HIP 74898 |
5.52 |
| 2026-02-24 00:00 |
15:17:38.63 |
-65:41:12.6 |
HIP 74852 |
5.44 |