C/2025 L1 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 L1 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2026-01-12T17:37:31.797120Z |
| Orbit solution date (soln_date, UTC) | 2026-06-09T11:12:30Z |
| Obs used | 135 |
| NEO | - |
| M1 | 14.300 |
| K1 | 4.500 |
| PC | - |
| Discovery observation (MPC, UTC) | 2025-06-06T09:16:16.579200Z |
| Discovery magnitude (MPC) | 18.22 c |
| Discovery observatory (MPC) | W68 · ATLAS Chile, Rio Hurtado |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-10-24.0000000 |
| e | 1.00148102 |
| q (au) | 1.679668 |
| a (au) | -1134.130676 |
| i (deg) | 114.136813 |
| Ω (om, deg) | 208.109329 |
| ω (w, deg) | 341.249896 |
| M (ma, deg) | -0.002083 |
Magnitude
Scatter + Global Linear
$$ M_a = (16.166 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 16.166 |
| n | 2.000 |
| gf | 1.000 |
| gb | -0.845 |
| k | 0.800 |
| 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 |
|---|---|---|---|
| 2024-10-01 | 2026-01-02 | +6.9278 | -3.538 |
| 2026-01-13 | 2026-05-21 | +25.2169 | -6.250 |
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) |
|---|---|---|---|---|
| 2026-07-29 00:00 | 11:49:29.50 | +49:58:03.6 | HIP 57556 | 18.22 |
| 2026-07-29 12:00 | 11:49:53.01 | +49:57:00.3 | HIP 57556 | 21.23 |
| 2026-07-30 00:00 | 11:50:16.71 | +49:55:58.0 | HIP 57876 | 18.94 |
| 2026-07-30 12:00 | 11:50:40.59 | +49:54:56.7 | HIP 57876 | 15.13 |
| 2026-07-31 00:00 | 11:51:04.64 | +49:53:56.5 | HIP 57876 | 11.40 |
| 2026-07-31 12:00 | 11:51:28.88 | +49:52:57.3 | HIP 57876 | 7.90 |
| 2026-08-01 00:00 | 11:51:53.29 | +49:51:59.2 | HIP 57876 | 5.18 |
| 2026-08-01 12:00 | 11:52:17.87 | +49:51:02.2 | HIP 57876 | 4.89 |
| 2026-08-02 00:00 | 11:52:42.62 | +49:50:06.2 | HIP 57876 | 7.36 |
| 2026-08-02 12:00 | 11:53:07.55 | +49:49:11.3 | HIP 57876 | 10.88 |
| 2026-08-03 00:00 | 11:53:32.64 | +49:48:17.5 | HIP 57984 | 12.29 |
| 2026-08-03 12:00 | 11:53:57.90 | +49:47:24.8 | HIP 57984 | 11.86 |
| 2026-08-04 00:00 | 11:54:23.33 | +49:46:33.2 | HIP 57984 | 12.89 |
| 2026-08-04 12:00 | 11:54:48.92 | +49:45:42.6 | HIP 57984 | 15.10 |
| 2026-08-05 00:00 | 11:55:14.68 | +49:44:53.2 | HIP 57984 | 18.07 |
| 2026-08-05 12:00 | 11:55:40.60 | +49:44:04.9 | HIP 57984 | 21.51 |
| 2026-08-06 00:00 | 11:56:06.67 | +49:43:17.7 | HIP 58355 | 21.53 |
| 2026-08-06 12:00 | 11:56:32.91 | +49:42:31.6 | HIP 58355 | 18.58 |
| 2026-08-07 00:00 | 11:56:59.31 | +49:41:46.7 | HIP 58355 | 16.20 |
| 2026-08-07 12:00 | 11:57:25.86 | +49:41:03.0 | HIP 58355 | 14.71 |
| 2026-08-08 00:00 | 11:57:52.57 | +49:40:20.3 | HIP 58355 | 14.40 |
| 2026-08-08 12:00 | 11:58:19.43 | +49:39:38.9 | HIP 58355 | 15.37 |
| 2026-08-09 00:00 | 11:58:46.45 | +49:38:58.6 | HIP 58555 | 16.67 |
| 2026-08-09 12:00 | 11:59:13.62 | +49:38:19.5 | HIP 58555 | 12.25 |
| 2026-08-10 00:00 | 11:59:40.94 | +49:37:41.6 | HIP 58555 | 7.84 |
| 2026-08-10 12:00 | 12:00:08.40 | +49:37:04.9 | HIP 58555 | 3.55 |
| 2026-08-11 00:00 | 12:00:36.02 | +49:36:29.4 | HIP 58555 | 2.07 |
| 2026-08-11 12:00 | 12:01:03.78 | +49:35:55.2 | HIP 58555 | 6.09 |
| 2026-08-12 00:00 | 12:01:31.68 | +49:35:22.2 | HIP 58555 | 10.56 |
| 2026-08-12 12:00 | 12:01:59.73 | +49:34:50.4 | HIP 58555 | 15.10 |
| 2026-08-13 00:00 | 12:02:27.92 | +49:34:19.8 | HIP 58555 | 19.69 |
| 2026-08-13 12:00 | 12:02:56.25 | +49:33:50.6 | HIP 58555 | 24.30 |
| 2026-08-14 00:00 | 12:03:24.72 | +49:33:22.6 | HIP 58992 | 23.69 |
| 2026-08-14 12:00 | 12:03:53.33 | +49:32:55.9 | HIP 58992 | 19.54 |
| 2026-08-15 00:00 | 12:04:22.07 | +49:32:30.4 | HIP 58992 | 15.63 |
| 2026-08-15 12:00 | 12:04:50.95 | +49:32:06.3 | HIP 58992 | 12.25 |
| 2026-08-16 00:00 | 12:05:19.96 | +49:31:43.5 | HIP 58992 | 9.96 |
| 2026-08-16 12:00 | 12:05:49.11 | +49:31:22.0 | HIP 58992 | 9.61 |
| 2026-08-17 00:00 | 12:06:18.38 | +49:31:01.8 | HIP 58992 | 11.41 |
| 2026-08-17 12:00 | 12:06:47.79 | +49:30:42.9 | HIP 58992 | 14.61 |
| 2026-08-18 00:00 | 12:07:17.32 | +49:30:25.4 | HIP 58992 | 18.50 |
| 2026-08-18 12:00 | 12:07:46.98 | +49:30:09.2 | HIP 59228 | 21.91 |
| 2026-08-19 00:00 | 12:08:16.76 | +49:29:54.4 | HIP 59228 | 19.72 |