3I = C/2025 N1 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 N1 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-10-29T11:53:10.705920Z |
| Orbit solution date (soln_date, UTC) | 2026-02-19T09:10:47Z |
| Obs used | 782 |
| 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) | 2026-02-19.0000000 |
| e | 6.14135145 |
| q (au) | 1.356481 |
| a (au) | -0.263837 |
| i (deg) | 175.116457 |
| Ω (om, deg) | 322.169609 |
| ω (w, deg) | 128.022870 |
| M (ma, deg) | 818.220246 |
Magnitude
Scatter + Global Linear
$$ M_a = (7.358 + 5.638\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 7.358 |
| n | 5.638 |
| gf | 0.999 |
| gb | -0.803 |
| k | 0.985 |
| 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 | 2025-10-02 | -1.6278 | +1.089 |
| 2025-11-03 | 2026-01-06 | -0.4756 | -0.427 |
| 2026-01-06 | 2026-04-13 | -6.1414 | +2.505 |
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 | 07:14:24.85 | +19:19:15.6 | HIP 35086 | 20.67 |
| 2026-09-20 12:00 | 07:14:23.74 | +19:19:07.0 | HIP 35086 | 20.74 |
| 2026-09-21 00:00 | 07:14:22.55 | +19:18:58.4 | HIP 35086 | 20.82 |
| 2026-09-21 12:00 | 07:14:21.28 | +19:18:50.0 | HIP 35086 | 20.93 |
| 2026-09-22 00:00 | 07:14:19.92 | +19:18:41.8 | HIP 35086 | 21.05 |
| 2026-09-22 12:00 | 07:14:18.48 | +19:18:33.7 | HIP 35086 | 21.20 |
| 2026-09-23 00:00 | 07:14:16.96 | +19:18:25.7 | HIP 35086 | 21.37 |
| 2026-09-23 12:00 | 07:14:15.35 | +19:18:17.9 | HIP 35086 | 21.56 |
| 2026-09-24 00:00 | 07:14:13.66 | +19:18:10.2 | HIP 35086 | 21.77 |
| 2026-09-24 12:00 | 07:14:11.89 | +19:18:02.7 | HIP 35086 | 22.00 |
| 2026-09-25 00:00 | 07:14:10.03 | +19:17:55.3 | HIP 35086 | 22.26 |
| 2026-09-25 12:00 | 07:14:08.09 | +19:17:48.1 | HIP 35086 | 22.54 |
| 2026-09-26 00:00 | 07:14:06.07 | +19:17:41.0 | HIP 35086 | 22.84 |
| 2026-09-26 12:00 | 07:14:03.97 | +19:17:34.0 | HIP 35086 | 23.16 |
| 2026-09-27 00:00 | 07:14:01.78 | +19:17:27.3 | HIP 35086 | 23.51 |
| 2026-09-27 12:00 | 07:13:59.51 | +19:17:20.6 | HIP 35086 | 23.89 |
| 2026-09-28 00:00 | 07:13:57.15 | +19:17:14.1 | HIP 34900 | 24.16 |
| 2026-09-28 12:00 | 07:13:54.71 | +19:17:07.7 | HIP 34900 | 23.82 |
| 2026-09-29 00:00 | 07:13:52.19 | +19:17:01.5 | HIP 34900 | 23.50 |
| 2026-09-29 12:00 | 07:13:49.59 | +19:16:55.5 | HIP 34900 | 23.18 |
| 2026-09-30 00:00 | 07:13:46.90 | +19:16:49.6 | HIP 34900 | 22.86 |
| 2026-09-30 12:00 | 07:13:44.13 | +19:16:43.8 | HIP 34900 | 22.56 |
| 2026-10-01 00:00 | 07:13:41.27 | +19:16:38.2 | HIP 34900 | 22.27 |
| 2026-10-01 12:00 | 07:13:38.33 | +19:16:32.7 | HIP 34900 | 22.00 |
| 2026-10-02 00:00 | 07:13:35.31 | +19:16:27.4 | HIP 34900 | 21.74 |
| 2026-10-02 12:00 | 07:13:32.20 | +19:16:22.3 | HIP 34900 | 21.50 |
| 2026-10-03 00:00 | 07:13:29.01 | +19:16:17.3 | HIP 34900 | 21.28 |
| 2026-10-03 12:00 | 07:13:25.74 | +19:16:12.4 | HIP 34900 | 21.09 |
| 2026-10-04 00:00 | 07:13:22.38 | +19:16:07.7 | HIP 34900 | 20.93 |
| 2026-10-04 12:00 | 07:13:18.94 | +19:16:03.1 | HIP 34900 | 20.80 |
| 2026-10-05 00:00 | 07:13:15.42 | +19:15:58.7 | HIP 34900 | 20.70 |
| 2026-10-05 12:00 | 07:13:11.81 | +19:15:54.5 | HIP 34900 | 20.63 |
| 2026-10-06 00:00 | 07:13:08.12 | +19:15:50.4 | HIP 34900 | 20.61 |
| 2026-10-06 12:00 | 07:13:04.35 | +19:15:46.4 | HIP 34900 | 20.63 |
| 2026-10-07 00:00 | 07:13:00.49 | +19:15:42.6 | HIP 34900 | 20.69 |
| 2026-10-07 12:00 | 07:12:56.54 | +19:15:39.0 | HIP 34900 | 20.80 |
| 2026-10-08 00:00 | 07:12:52.52 | +19:15:35.5 | HIP 34900 | 20.96 |
| 2026-10-08 12:00 | 07:12:48.41 | +19:15:32.1 | HIP 34900 | 21.17 |
| 2026-10-09 00:00 | 07:12:44.22 | +19:15:28.9 | HIP 34900 | 21.43 |
| 2026-10-09 12:00 | 07:12:39.94 | +19:15:25.9 | HIP 34900 | 21.74 |
| 2026-10-10 00:00 | 07:12:35.58 | +19:15:23.0 | HIP 34900 | 22.10 |
| 2026-10-10 12:00 | 07:12:31.14 | +19:15:20.3 | HIP 34900 | 22.52 |
| 2026-10-11 00:00 | 07:12:26.62 | +19:15:17.8 | HIP 34900 | 22.99 |