| Parameter |
Value |
| Designation |
C/2025 W2 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2025-12-07T20:01:40.048320Z |
| Orbit solution date (soln_date, UTC) |
2026-01-07T15:42:51Z |
| Obs used |
54 |
| NEO |
- |
| M1 |
15.400 |
| K1 |
23.250 |
| PC |
- |
| Discovery observation (MPC, UTC) |
2025-11-28T14:38:51.734400Z |
| Discovery magnitude (MPC) |
19.16 o |
| Discovery observatory (MPC) |
T08 · ATLAS-MLO, Mauna Loa |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2025-12-01.0000000 |
| e |
0.94608895 |
| q (au) |
1.453281 |
| a (au) |
26.957020 |
| i (deg) |
94.710549 |
| Ω (om, deg) |
90.844949 |
| ω (w, deg) |
41.034555 |
| M (ma, deg) |
359.951871 |
Magnitude
Scatter + Global Linear
$$
M_a = (16.538 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
16.538 |
| n |
6.000 |
| gf |
1.000 |
| gb |
-1.000 |
| k |
0.948 |
| 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) |
| 2026-09-20 00:00 |
17:11:03.02 |
+10:45:31.4 |
HIP 84060 |
10.17 |
| 2026-09-20 12:00 |
17:11:12.33 |
+10:37:40.0 |
HIP 84060 |
18.01 |
| 2026-09-21 00:00 |
17:11:21.84 |
+10:29:51.5 |
HIP 84177 |
17.04 |
| 2026-09-21 12:00 |
17:11:31.55 |
+10:22:05.8 |
HIP 84177 |
18.99 |
| 2026-09-22 00:00 |
17:11:41.45 |
+10:14:23.1 |
HIP 84177 |
23.66 |
| 2026-09-22 12:00 |
17:11:51.53 |
+10:06:43.2 |
HIP 84177 |
29.76 |
| 2026-09-23 00:00 |
17:12:01.81 |
+09:59:06.2 |
HIP 83994 |
34.61 |
| 2026-09-23 12:00 |
17:12:12.27 |
+09:51:32.0 |
HIP 83994 |
32.81 |
| 2026-09-24 00:00 |
17:12:22.91 |
+09:44:00.7 |
HIP 83994 |
32.97 |
| 2026-09-24 12:00 |
17:12:33.73 |
+09:36:32.2 |
HIP 83994 |
35.04 |
| 2026-09-25 00:00 |
17:12:44.74 |
+09:29:06.5 |
HIP 84199 |
37.91 |
| 2026-09-25 12:00 |
17:12:55.92 |
+09:21:43.6 |
HIP 84199 |
30.74 |
| 2026-09-26 00:00 |
17:13:07.27 |
+09:14:23.5 |
HIP 84199 |
24.07 |
| 2026-09-26 12:00 |
17:13:18.80 |
+09:07:06.2 |
HIP 84199 |
18.41 |
| 2026-09-27 00:00 |
17:13:30.50 |
+08:59:51.6 |
HIP 84199 |
14.94 |
| 2026-09-27 12:00 |
17:13:42.36 |
+08:52:39.8 |
HIP 84199 |
15.19 |
| 2026-09-28 00:00 |
17:13:54.40 |
+08:45:30.8 |
HIP 84199 |
18.97 |
| 2026-09-28 12:00 |
17:14:06.60 |
+08:38:24.5 |
HIP 84199 |
24.68 |
| 2026-09-29 00:00 |
17:14:18.96 |
+08:31:20.9 |
HIP 84199 |
31.28 |
| 2026-09-29 12:00 |
17:14:31.48 |
+08:24:20.0 |
HIP 84549 |
37.87 |
| 2026-09-30 00:00 |
17:14:44.17 |
+08:17:21.8 |
HIP 84521 |
32.09 |
| 2026-09-30 12:00 |
17:14:57.01 |
+08:10:26.3 |
HIP 84521 |
26.69 |
| 2026-10-01 00:00 |
17:15:10.01 |
+08:03:33.4 |
HIP 84521 |
22.56 |
| 2026-10-01 12:00 |
17:15:23.17 |
+07:56:43.2 |
HIP 84521 |
20.47 |
| 2026-10-02 00:00 |
17:15:36.47 |
+07:49:55.7 |
HIP 84521 |
21.00 |
| 2026-10-02 12:00 |
17:15:49.93 |
+07:43:10.8 |
HIP 84448 |
15.87 |
| 2026-10-03 00:00 |
17:16:03.54 |
+07:36:28.5 |
HIP 84448 |
9.43 |
| 2026-10-03 12:00 |
17:16:17.30 |
+07:29:48.9 |
HIP 84448 |
6.29 |
| 2026-10-04 00:00 |
17:16:31.21 |
+07:23:11.8 |
HIP 84448 |
10.12 |
| 2026-10-04 12:00 |
17:16:45.26 |
+07:16:37.4 |
HIP 84448 |
16.63 |
| 2026-10-05 00:00 |
17:16:59.46 |
+07:10:05.5 |
HIP 84418 |
22.82 |
| 2026-10-05 12:00 |
17:17:13.80 |
+07:03:36.2 |
HIP 84592 |
18.57 |
| 2026-10-06 00:00 |
17:17:28.28 |
+06:57:09.5 |
HIP 84592 |
11.54 |
| 2026-10-06 12:00 |
17:17:42.90 |
+06:50:45.3 |
HIP 84592 |
5.56 |
| 2026-10-07 00:00 |
17:17:57.65 |
+06:44:23.7 |
HIP 84592 |
6.11 |
| 2026-10-07 12:00 |
17:18:12.55 |
+06:38:04.6 |
HIP 84592 |
12.31 |
| 2026-10-08 00:00 |
17:18:27.57 |
+06:31:48.1 |
HIP 84592 |
19.31 |
| 2026-10-08 12:00 |
17:18:42.74 |
+06:25:34.0 |
HIP 84781 |
17.60 |
| 2026-10-09 00:00 |
17:18:58.03 |
+06:19:22.5 |
HIP 84704 |
14.31 |
| 2026-10-09 12:00 |
17:19:13.45 |
+06:13:13.5 |
HIP 84704 |
9.59 |
| 2026-10-10 00:00 |
17:19:29.00 |
+06:07:06.9 |
HIP 84704 |
9.22 |
| 2026-10-10 12:00 |
17:19:44.68 |
+06:01:02.8 |
HIP 84704 |
13.53 |
| 2026-10-11 00:00 |
17:20:00.48 |
+05:55:01.2 |
HIP 84704 |
19.63 |