C/2025 K1 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 K1 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-10-08T10:33:21.035520Z |
| Orbit solution date (soln_date, UTC) | 2026-01-15T15:46:49Z |
| Obs used | 1899 |
| 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) | 2025-09-22.0000000 |
| e | 1.00025497 |
| q (au) | 0.334210 |
| a (au) | -1310.796536 |
| i (deg) | 147.865965 |
| Ω (om, deg) | 97.556143 |
| ω (w, deg) | 271.023548 |
| M (ma, deg) | -0.000341 |
Magnitude
Scatter + Global Linear
$$ M_a = (13.216 + 4.031\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 13.216 |
| n | 4.031 |
| gf | 1.000 |
| gb | -1.000 |
| k | 0.923 |
| 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 | +2.2234 | -0.992 |
| 2025-07-11 | 2025-09-06 | -1.0796 | +0.274 |
| 2025-09-06 | 2025-09-25 | +4.2485 | +0.396 |
| 2025-10-18 | 2025-11-19 | +1.3422 | -0.997 |
| 2025-11-19 | 2025-11-26 | -13.1361 | +0.218 |
| 2025-11-26 | 2026-01-22 | +7.9265 | -1.624 |
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) |
|---|---|---|---|---|
| 2026-02-03 00:00 | 01:12:45.38 | +32:12:14.0 | HIP 5645 | 3.20 |
| 2026-02-03 12:00 | 01:13:06.79 | +32:10:42.2 | HIP 5671 | 6.83 |
| 2026-02-04 00:00 | 01:13:28.30 | +32:09:14.3 | HIP 5671 | 8.84 |
| 2026-02-04 12:00 | 01:13:49.92 | +32:07:50.2 | HIP 5671 | 12.50 |
| 2026-02-05 00:00 | 01:14:11.64 | +32:06:29.9 | HIP 5671 | 16.78 |
| 2026-02-05 12:00 | 01:14:33.47 | +32:05:13.2 | HIP 5671 | 21.30 |
| 2026-02-06 00:00 | 01:14:55.40 | +32:04:00.2 | HIP 5911 | 21.57 |
| 2026-02-06 12:00 | 01:15:17.43 | +32:02:50.7 | HIP 5911 | 19.78 |
| 2026-02-07 00:00 | 01:15:39.56 | +32:01:44.7 | HIP 5911 | 19.00 |
| 2026-02-07 12:00 | 01:16:01.78 | +32:00:42.1 | HIP 5911 | 19.35 |
| 2026-02-08 00:00 | 01:16:24.09 | +31:59:42.9 | HIP 5989 | 16.57 |
| 2026-02-08 12:00 | 01:16:46.50 | +31:58:47.0 | HIP 5989 | 13.99 |
| 2026-02-09 00:00 | 01:17:08.99 | +31:57:54.3 | HIP 5989 | 12.85 |
| 2026-02-09 12:00 | 01:17:31.57 | +31:57:04.9 | HIP 6025 | 12.50 |
| 2026-02-10 00:00 | 01:17:54.24 | +31:56:18.5 | HIP 6025 | 13.27 |
| 2026-02-10 12:00 | 01:18:17.00 | +31:55:35.3 | HIP 6025 | 15.66 |
| 2026-02-11 00:00 | 01:18:39.83 | +31:54:55.1 | HIP 6025 | 19.06 |
| 2026-02-11 12:00 | 01:19:02.75 | +31:54:17.9 | HIP 6252 | 20.60 |
| 2026-02-12 00:00 | 01:19:25.74 | +31:53:43.7 | HIP 6252 | 16.96 |
| 2026-02-12 12:00 | 01:19:48.82 | +31:53:12.3 | HIP 6252 | 14.14 |
| 2026-02-13 00:00 | 01:20:11.97 | +31:52:43.8 | HIP 6252 | 12.74 |
| 2026-02-13 12:00 | 01:20:35.19 | +31:52:18.1 | HIP 6252 | 13.23 |
| 2026-02-14 00:00 | 01:20:58.48 | +31:51:55.2 | HIP 6252 | 15.43 |
| 2026-02-14 12:00 | 01:21:21.85 | +31:51:34.9 | HIP 6400 | 14.01 |
| 2026-02-15 00:00 | 01:21:45.29 | +31:51:17.3 | HIP 6400 | 10.52 |
| 2026-02-15 12:00 | 01:22:08.79 | +31:51:02.4 | HIP 6400 | 8.70 |
| 2026-02-16 00:00 | 01:22:32.36 | +31:50:50.0 | HIP 6453 | 5.12 |
| 2026-02-16 12:00 | 01:22:56.00 | +31:50:40.2 | HIP 6453 | 0.22 |
| 2026-02-17 00:00 | 01:23:19.70 | +31:50:32.9 | HIP 6453 | 4.94 |
| 2026-02-17 12:00 | 01:23:43.46 | +31:50:28.0 | HIP 6453 | 9.99 |
| 2026-02-18 00:00 | 01:24:07.28 | +31:50:25.6 | HIP 6453 | 15.05 |
| 2026-02-18 12:00 | 01:24:31.16 | +31:50:25.6 | HIP 6453 | 20.12 |
| 2026-02-19 00:00 | 01:24:55.10 | +31:50:27.9 | HIP 6668 | 19.31 |
| 2026-02-19 12:00 | 01:25:19.09 | +31:50:32.5 | HIP 6668 | 17.80 |
| 2026-02-20 00:00 | 01:25:43.14 | +31:50:39.4 | HIP 6668 | 17.73 |
| 2026-02-20 12:00 | 01:26:07.24 | +31:50:48.5 | HIP 6675 | 19.04 |
| 2026-02-21 00:00 | 01:26:31.39 | +31:50:59.9 | HIP 6819 | 16.68 |
| 2026-02-21 12:00 | 01:26:55.59 | +31:51:13.4 | HIP 6819 | 12.09 |
| 2026-02-22 00:00 | 01:27:19.83 | +31:51:29.1 | HIP 6819 | 8.13 |
| 2026-02-22 12:00 | 01:27:44.13 | +31:51:46.8 | HIP 6819 | 6.23 |
| 2026-02-23 00:00 | 01:28:08.47 | +31:52:06.6 | HIP 6819 | 8.04 |
| 2026-02-23 12:00 | 01:28:32.85 | +31:52:28.5 | HIP 6819 | 11.99 |
| 2026-02-24 00:00 | 01:28:57.27 | +31:52:52.4 | HIP 6890 | 16.44 |