3I = C/2025 N1 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 N1 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-10-29T11:34:39.437760Z |
| Orbit solution date (soln_date, UTC) | 2026-01-26T14:41:19Z |
| Obs used | 795 |
| NEO | - |
| M1 | 12.500 |
| K1 | 4.500 |
| PC | - |
| Discovery observation (MPC, UTC) | 2025-07-01T05:15:11.232000Z |
| Discovery magnitude (MPC) | 17.72 o |
| Discovery observatory (MPC) | W68 · ATLAS Chile, Rio Hurtado |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-08-21.0000000 |
| e | 6.13940821 |
| q (au) | 1.356425 |
| a (au) | -0.263926 |
| i (deg) | 175.113113 |
| Ω (om, deg) | 322.156941 |
| ω (w, deg) | 128.009868 |
| M (ma, deg) | -505.073640 |
Magnitude
Scatter + Global Linear
$$ M_a = (6.403 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 6.403 |
| n | 6.000 |
| gf | 1.000 |
| gb | -0.871 |
| k | 0.997 |
| 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 |
|---|---|---|---|
| 2025-05-08 | 2025-09-09 | -2.1678 | +1.307 |
| 2025-09-09 | 2025-10-02 | +3.1020 | -0.222 |
| 2025-11-03 | 2026-01-07 | -4.1366 | -0.632 |
| 2026-01-07 | 2026-02-07 | +4.5207 | -4.140 |
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 | 07:42:50.38 | +18:45:27.8 | HIP 37745 | 25.31 |
| 2026-02-03 12:00 | 07:41:38.93 | +18:48:07.8 | HIP 37387 | 20.91 |
| 2026-02-04 00:00 | 07:40:28.60 | +18:50:43.7 | HIP 37387 | 15.34 |
| 2026-02-04 12:00 | 07:39:19.36 | +18:53:15.7 | HIP 37246 | 20.37 |
| 2026-02-05 00:00 | 07:38:11.21 | +18:55:43.9 | HIP 37107 | 9.65 |
| 2026-02-05 12:00 | 07:37:04.13 | +18:58:08.3 | HIP 37107 | 6.94 |
| 2026-02-06 00:00 | 07:35:58.12 | +19:00:29.1 | HIP 37011 | 15.14 |
| 2026-02-06 12:00 | 07:34:53.15 | +19:02:46.4 | HIP 36831 | 14.92 |
| 2026-02-07 00:00 | 07:33:49.23 | +19:05:00.2 | HIP 36831 | 18.37 |
| 2026-02-07 12:00 | 07:32:46.33 | +19:07:10.6 | HIP 36831 | 30.09 |
| 2026-02-08 00:00 | 07:31:44.46 | +19:09:17.7 | HIP 36491 | 21.25 |
| 2026-02-08 12:00 | 07:30:43.59 | +19:11:21.7 | HIP 36491 | 14.05 |
| 2026-02-09 00:00 | 07:29:43.71 | +19:13:22.5 | HIP 36491 | 18.94 |
| 2026-02-09 12:00 | 07:28:44.82 | +19:15:20.2 | HIP 36249 | 17.97 |
| 2026-02-10 00:00 | 07:27:46.90 | +19:17:15.0 | HIP 36249 | 14.58 |
| 2026-02-10 12:00 | 07:26:49.94 | +19:19:07.0 | HIP 36135 | 2.85 |
| 2026-02-11 00:00 | 07:25:53.93 | +19:20:56.1 | HIP 36135 | 10.82 |
| 2026-02-11 12:00 | 07:24:58.86 | +19:22:42.4 | HIP 36000 | 22.52 |
| 2026-02-12 00:00 | 07:24:04.71 | +19:24:26.1 | HIP 36000 | 28.58 |
| 2026-02-12 12:00 | 07:23:11.48 | +19:26:07.2 | HIP 35693 | 23.76 |
| 2026-02-13 00:00 | 07:22:19.16 | +19:27:45.8 | HIP 35693 | 17.54 |
| 2026-02-13 12:00 | 07:21:27.73 | +19:29:21.9 | HIP 35575 | 14.48 |
| 2026-02-14 00:00 | 07:20:37.18 | +19:30:55.5 | HIP 35575 | 7.25 |
| 2026-02-14 12:00 | 07:19:47.51 | +19:32:26.9 | HIP 35537 | 3.74 |
| 2026-02-15 00:00 | 07:18:58.69 | +19:33:55.9 | HIP 35537 | 15.28 |
| 2026-02-15 12:00 | 07:18:10.72 | +19:35:22.8 | HIP 35331 | 4.95 |
| 2026-02-16 00:00 | 07:17:23.60 | +19:36:47.5 | HIP 35331 | 7.92 |
| 2026-02-16 12:00 | 07:16:37.30 | +19:38:10.0 | HIP 35126 | 18.03 |
| 2026-02-17 00:00 | 07:15:51.82 | +19:39:30.5 | HIP 35126 | 11.53 |
| 2026-02-17 12:00 | 07:15:07.15 | +19:40:49.0 | HIP 35019 | 7.05 |
| 2026-02-18 00:00 | 07:14:23.27 | +19:42:05.6 | HIP 35019 | 3.40 |
| 2026-02-18 12:00 | 07:13:40.18 | +19:43:20.2 | HIP 35019 | 13.59 |
| 2026-02-19 00:00 | 07:12:57.86 | +19:44:33.0 | HIP 34764 | 18.34 |
| 2026-02-19 12:00 | 07:12:16.31 | +19:45:44.0 | HIP 34764 | 9.81 |
| 2026-02-20 00:00 | 07:11:35.52 | +19:46:53.3 | HIP 34764 | 7.00 |
| 2026-02-20 12:00 | 07:10:55.47 | +19:48:00.8 | HIP 34650 | 5.08 |
| 2026-02-21 00:00 | 07:10:16.16 | +19:49:06.7 | HIP 34650 | 4.27 |
| 2026-02-21 12:00 | 07:09:37.57 | +19:50:10.9 | HIP 34650 | 13.39 |
| 2026-02-22 00:00 | 07:08:59.70 | +19:51:13.6 | HIP 34520 | 18.55 |
| 2026-02-22 12:00 | 07:08:22.53 | +19:52:14.7 | HIP 34520 | 22.28 |
| 2026-02-23 00:00 | 07:07:46.06 | +19:53:14.4 | HIP 34243 | 26.89 |
| 2026-02-23 12:00 | 07:07:10.28 | +19:54:12.5 | HIP 34243 | 19.46 |
| 2026-02-24 00:00 | 07:06:35.17 | +19:55:09.3 | HIP 34243 | 13.42 |