C/2025 K1 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 K1 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-10-08T10:33:17.674560Z |
| Orbit solution date (soln_date, UTC) | 2026-07-28T14:17:42Z |
| Obs used | 2410 |
| NEO | - |
| M1 | 14.200 |
| K1 | 4.500 |
| PC | - |
| Discovery observation (MPC, UTC) | 2025-05-24T08:29:05.942400Z |
| Discovery magnitude (MPC) | 18.66 c |
| Discovery observatory (MPC) | W68 · ATLAS Chile, Rio Hurtado |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-09-23.0000000 |
| e | 1.00025724 |
| q (au) | 0.334212 |
| a (au) | -1299.233883 |
| i (deg) | 147.864796 |
| Ω (om, deg) | 97.556975 |
| ω (w, deg) | 271.023897 |
| M (ma, deg) | -0.000325 |
Magnitude
Scatter + Global Linear
$$ M_a = (13.136 + 4.041\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 13.136 |
| n | 4.041 |
| gf | 1.000 |
| gb | -1.000 |
| k | 0.929 |
| 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 |
|---|---|---|---|
| 2025-04-08 | 2025-07-11 | +2.3077 | -1.022 |
| 2025-07-11 | 2025-09-05 | -1.3041 | +0.312 |
| 2025-09-05 | 2025-09-25 | +3.9477 | +0.374 |
| 2025-10-18 | 2025-11-19 | +0.3698 | -1.067 |
| 2025-11-19 | 2025-12-04 | -0.9694 | -0.624 |
| 2025-12-04 | 2026-01-22 | +7.1345 | -1.242 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Finding Chart
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-09-20 00:00 | 02:24:51.94 | +48:07:13.4 | HIP 11197 | 20.59 |
| 2026-09-20 12:00 | 02:24:14.92 | +48:07:48.1 | HIP 11197 | 18.92 |
| 2026-09-21 00:00 | 02:23:37.67 | +48:08:20.1 | HIP 11197 | 19.24 |
| 2026-09-21 12:00 | 02:23:00.19 | +48:08:49.4 | HIP 11048 | 17.76 |
| 2026-09-22 00:00 | 02:22:22.50 | +48:09:15.9 | HIP 11048 | 16.52 |
| 2026-09-22 12:00 | 02:21:44.58 | +48:09:39.7 | HIP 11048 | 17.59 |
| 2026-09-23 00:00 | 02:21:06.45 | +48:10:00.7 | HIP 11048 | 20.63 |
| 2026-09-23 12:00 | 02:20:28.11 | +48:10:18.8 | HIP 10736 | 22.85 |
| 2026-09-24 00:00 | 02:19:49.56 | +48:10:34.2 | HIP 10736 | 16.46 |
| 2026-09-24 12:00 | 02:19:10.82 | +48:10:46.8 | HIP 10736 | 10.09 |
| 2026-09-25 00:00 | 02:18:31.88 | +48:10:56.5 | HIP 10736 | 3.99 |
| 2026-09-25 12:00 | 02:17:52.76 | +48:11:03.3 | HIP 10736 | 3.78 |
| 2026-09-26 00:00 | 02:17:13.44 | +48:11:07.3 | HIP 10736 | 9.91 |
| 2026-09-26 12:00 | 02:16:33.95 | +48:11:08.4 | HIP 10736 | 16.39 |
| 2026-09-27 00:00 | 02:15:54.29 | +48:11:06.5 | HIP 10562 | 22.39 |
| 2026-09-27 12:00 | 02:15:14.45 | +48:11:01.8 | HIP 10562 | 23.45 |
| 2026-09-28 00:00 | 02:14:34.45 | +48:10:54.1 | HIP 10562 | 26.19 |
| 2026-09-28 12:00 | 02:13:54.29 | +48:10:43.5 | HIP 10317 | 25.64 |
| 2026-09-29 00:00 | 02:13:13.98 | +48:10:29.9 | HIP 10317 | 24.04 |
| 2026-09-29 12:00 | 02:12:33.52 | +48:10:13.3 | HIP 10317 | 24.31 |
| 2026-09-30 00:00 | 02:11:52.91 | +48:09:53.7 | HIP 10317 | 26.40 |
| 2026-09-30 12:00 | 02:11:12.17 | +48:09:31.2 | HIP 10317 | 29.96 |
| 2026-10-01 00:00 | 02:10:31.29 | +48:09:05.6 | HIP 9890 | 32.88 |
| 2026-10-01 12:00 | 02:09:50.29 | +48:08:37.1 | HIP 9890 | 26.02 |
| 2026-10-02 00:00 | 02:09:09.16 | +48:08:05.5 | HIP 9890 | 19.14 |
| 2026-10-02 12:00 | 02:08:27.92 | +48:07:30.8 | HIP 9890 | 12.24 |
| 2026-10-03 00:00 | 02:07:46.57 | +48:06:53.2 | HIP 9890 | 5.32 |
| 2026-10-03 12:00 | 02:07:05.12 | +48:06:12.5 | HIP 9890 | 1.68 |
| 2026-10-04 00:00 | 02:06:23.56 | +48:05:28.7 | HIP 9890 | 8.63 |
| 2026-10-04 12:00 | 02:05:41.92 | +48:04:41.8 | HIP 9890 | 15.62 |
| 2026-10-05 00:00 | 02:05:00.19 | +48:03:51.9 | HIP 9890 | 22.64 |
| 2026-10-05 12:00 | 02:04:18.37 | +48:02:59.0 | HIP 9890 | 29.68 |
| 2026-10-06 00:00 | 02:03:36.49 | +48:02:02.9 | HIP 9441 | 24.31 |
| 2026-10-06 12:00 | 02:02:54.53 | +48:01:03.8 | HIP 9441 | 17.26 |
| 2026-10-07 00:00 | 02:02:12.52 | +48:00:01.6 | HIP 9441 | 10.23 |
| 2026-10-07 12:00 | 02:01:30.45 | +47:58:56.3 | HIP 9441 | 3.49 |
| 2026-10-08 00:00 | 02:00:48.33 | +47:57:47.9 | HIP 9441 | 4.60 |
| 2026-10-08 12:00 | 02:00:06.17 | +47:56:36.5 | HIP 9441 | 11.50 |
| 2026-10-09 00:00 | 01:59:23.97 | +47:55:22.0 | HIP 9441 | 18.62 |
| 2026-10-09 12:00 | 01:58:41.74 | +47:54:04.4 | HIP 9150 | 21.67 |
| 2026-10-10 00:00 | 01:57:59.49 | +47:52:43.8 | HIP 9150 | 18.86 |
| 2026-10-10 12:00 | 01:57:17.22 | +47:51:20.1 | HIP 9150 | 18.57 |
| 2026-10-11 00:00 | 01:56:34.94 | +47:49:53.4 | HIP 8898 | 20.26 |