| 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) |
| 2026-07-29 00:00 |
17:22:54.20 |
+29:11:18.9 |
HIP 85057 |
9.42 |
| 2026-07-29 12:00 |
17:22:25.26 |
+28:58:53.8 |
HIP 85047 |
12.00 |
| 2026-07-30 00:00 |
17:21:56.89 |
+28:46:29.6 |
HIP 84934 |
5.71 |
| 2026-07-30 12:00 |
17:21:29.08 |
+28:34:06.2 |
HIP 84934 |
11.39 |
| 2026-07-31 00:00 |
17:21:01.82 |
+28:21:43.7 |
HIP 84872 |
4.71 |
| 2026-07-31 12:00 |
17:20:35.10 |
+28:09:22.2 |
HIP 84872 |
15.57 |
| 2026-08-01 00:00 |
17:20:08.93 |
+27:57:01.8 |
HIP 84743 |
10.93 |
| 2026-08-01 12:00 |
17:19:43.31 |
+27:44:42.5 |
HIP 84743 |
17.39 |
| 2026-08-02 00:00 |
17:19:18.21 |
+27:32:24.4 |
HIP 84744 |
15.43 |
| 2026-08-02 12:00 |
17:18:53.65 |
+27:20:07.6 |
HIP 84744 |
7.43 |
| 2026-08-03 00:00 |
17:18:29.62 |
+27:07:52.1 |
HIP 84659 |
11.71 |
| 2026-08-03 12:00 |
17:18:06.11 |
+26:55:38.0 |
HIP 84659 |
4.15 |
| 2026-08-04 00:00 |
17:17:43.11 |
+26:43:25.4 |
HIP 84548 |
9.24 |
| 2026-08-04 12:00 |
17:17:20.64 |
+26:31:14.3 |
HIP 84512 |
10.41 |
| 2026-08-05 00:00 |
17:16:58.67 |
+26:19:04.8 |
HIP 84512 |
16.20 |
| 2026-08-05 12:00 |
17:16:37.21 |
+26:06:56.9 |
HIP 84561 |
16.37 |
| 2026-08-06 00:00 |
17:16:16.26 |
+25:54:50.7 |
HIP 84561 |
12.51 |
| 2026-08-06 12:00 |
17:15:55.80 |
+25:42:46.2 |
HIP 84561 |
19.45 |
| 2026-08-07 00:00 |
17:15:35.83 |
+25:30:43.6 |
HIP 84574 |
24.64 |
| 2026-08-07 12:00 |
17:15:16.36 |
+25:18:42.8 |
HIP 84574 |
28.49 |
| 2026-08-08 00:00 |
17:14:57.37 |
+25:06:43.9 |
HIP 84379 |
16.39 |
| 2026-08-08 12:00 |
17:14:38.87 |
+24:54:47.0 |
HIP 84379 |
6.84 |
| 2026-08-09 00:00 |
17:14:20.84 |
+24:42:52.0 |
HIP 84379 |
11.97 |
| 2026-08-09 12:00 |
17:14:03.29 |
+24:30:59.2 |
HIP 84281 |
16.07 |
| 2026-08-10 00:00 |
17:13:46.21 |
+24:19:08.4 |
HIP 84281 |
3.67 |
| 2026-08-10 12:00 |
17:13:29.59 |
+24:07:19.7 |
HIP 84281 |
8.84 |
| 2026-08-11 00:00 |
17:13:13.44 |
+23:55:33.3 |
HIP 84281 |
21.16 |
| 2026-08-11 12:00 |
17:12:57.75 |
+23:43:49.0 |
HIP 84109 |
19.10 |
| 2026-08-12 00:00 |
17:12:42.51 |
+23:32:07.1 |
HIP 84215 |
23.68 |
| 2026-08-12 12:00 |
17:12:27.72 |
+23:20:27.5 |
HIP 84215 |
13.26 |
| 2026-08-13 00:00 |
17:12:13.38 |
+23:08:50.2 |
HIP 84215 |
9.16 |
| 2026-08-13 12:00 |
17:11:59.48 |
+22:57:15.4 |
HIP 84095 |
15.04 |
| 2026-08-14 00:00 |
17:11:46.02 |
+22:45:42.9 |
HIP 84095 |
3.70 |
| 2026-08-14 12:00 |
17:11:32.99 |
+22:34:13.0 |
HIP 84095 |
9.28 |
| 2026-08-15 00:00 |
17:11:20.40 |
+22:22:45.6 |
HIP 84095 |
20.95 |
| 2026-08-15 12:00 |
17:11:08.23 |
+22:11:20.7 |
HIP 83974 |
16.73 |
| 2026-08-16 00:00 |
17:10:56.48 |
+21:59:58.4 |
HIP 83974 |
16.68 |
| 2026-08-16 12:00 |
17:10:45.15 |
+21:48:38.7 |
HIP 84000 |
22.42 |
| 2026-08-17 00:00 |
17:10:34.23 |
+21:37:21.7 |
HIP 84000 |
10.95 |
| 2026-08-17 12:00 |
17:10:23.72 |
+21:26:07.3 |
HIP 84000 |
2.21 |
| 2026-08-18 00:00 |
17:10:13.62 |
+21:14:55.6 |
HIP 84020 |
4.43 |
| 2026-08-18 12:00 |
17:10:03.92 |
+21:03:46.7 |
HIP 84020 |
11.07 |
| 2026-08-19 00:00 |
17:09:54.62 |
+20:52:40.5 |
HIP 84020 |
21.93 |