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) |
|---|---|---|---|---|
| 2026-07-29 00:00 | 07:09:17.49 | +19:45:02.2 | HIP 34520 | 12.41 |
| 2026-07-29 12:00 | 07:09:23.73 | +19:44:43.9 | HIP 34520 | 12.44 |
| 2026-07-30 00:00 | 07:09:29.92 | +19:44:25.6 | HIP 34520 | 12.65 |
| 2026-07-30 12:00 | 07:09:36.07 | +19:44:07.3 | HIP 34520 | 13.02 |
| 2026-07-31 00:00 | 07:09:42.16 | +19:43:49.1 | HIP 34650 | 12.93 |
| 2026-07-31 12:00 | 07:09:48.20 | +19:43:30.9 | HIP 34650 | 11.72 |
| 2026-08-01 00:00 | 07:09:54.18 | +19:43:12.7 | HIP 34650 | 10.58 |
| 2026-08-01 12:00 | 07:10:00.12 | +19:42:54.5 | HIP 34650 | 9.54 |
| 2026-08-02 00:00 | 07:10:06.00 | +19:42:36.4 | HIP 34650 | 8.61 |
| 2026-08-02 12:00 | 07:10:11.83 | +19:42:18.4 | HIP 34650 | 7.84 |
| 2026-08-03 00:00 | 07:10:17.61 | +19:42:00.3 | HIP 34650 | 7.27 |
| 2026-08-03 12:00 | 07:10:23.33 | +19:41:42.4 | HIP 34650 | 6.94 |
| 2026-08-04 00:00 | 07:10:29.00 | +19:41:24.4 | HIP 34650 | 6.87 |
| 2026-08-04 12:00 | 07:10:34.62 | +19:41:06.5 | HIP 34650 | 7.08 |
| 2026-08-05 00:00 | 07:10:40.18 | +19:40:48.6 | HIP 34650 | 7.52 |
| 2026-08-05 12:00 | 07:10:45.68 | +19:40:30.8 | HIP 34650 | 8.16 |
| 2026-08-06 00:00 | 07:10:51.13 | +19:40:13.0 | HIP 34650 | 8.94 |
| 2026-08-06 12:00 | 07:10:56.52 | +19:39:55.3 | HIP 34650 | 9.83 |
| 2026-08-07 00:00 | 07:11:01.85 | +19:39:37.6 | HIP 34650 | 10.80 |
| 2026-08-07 12:00 | 07:11:07.13 | +19:39:20.0 | HIP 34650 | 11.81 |
| 2026-08-08 00:00 | 07:11:12.35 | +19:39:02.4 | HIP 34650 | 12.87 |
| 2026-08-08 12:00 | 07:11:17.51 | +19:38:44.9 | HIP 34650 | 13.94 |
| 2026-08-09 00:00 | 07:11:22.62 | +19:38:27.4 | HIP 34650 | 15.04 |
| 2026-08-09 12:00 | 07:11:27.66 | +19:38:10.0 | HIP 34764 | 15.79 |
| 2026-08-10 00:00 | 07:11:32.65 | +19:37:52.6 | HIP 34764 | 15.74 |
| 2026-08-10 12:00 | 07:11:37.57 | +19:37:35.3 | HIP 34764 | 15.78 |
| 2026-08-11 00:00 | 07:11:42.44 | +19:37:18.0 | HIP 34764 | 15.91 |
| 2026-08-11 12:00 | 07:11:47.24 | +19:37:00.8 | HIP 34764 | 16.13 |
| 2026-08-12 00:00 | 07:11:51.98 | +19:36:43.7 | HIP 34764 | 16.42 |
| 2026-08-12 12:00 | 07:11:56.66 | +19:36:26.6 | HIP 34764 | 16.79 |
| 2026-08-13 00:00 | 07:12:01.28 | +19:36:09.6 | HIP 34764 | 17.22 |
| 2026-08-13 12:00 | 07:12:05.83 | +19:35:52.7 | HIP 34764 | 17.71 |
| 2026-08-14 00:00 | 07:12:10.32 | +19:35:35.8 | HIP 34764 | 18.25 |
| 2026-08-14 12:00 | 07:12:14.75 | +19:35:19.0 | HIP 34764 | 18.82 |
| 2026-08-15 00:00 | 07:12:19.12 | +19:35:02.3 | HIP 34764 | 19.44 |
| 2026-08-15 12:00 | 07:12:23.41 | +19:34:45.6 | HIP 34764 | 20.08 |
| 2026-08-16 00:00 | 07:12:27.65 | +19:34:29.1 | HIP 34764 | 20.76 |
| 2026-08-16 12:00 | 07:12:31.82 | +19:34:12.6 | HIP 34764 | 21.45 |
| 2026-08-17 00:00 | 07:12:35.92 | +19:33:56.1 | HIP 34764 | 22.15 |
| 2026-08-17 12:00 | 07:12:39.96 | +19:33:39.8 | HIP 34764 | 22.87 |
| 2026-08-18 00:00 | 07:12:43.93 | +19:33:23.5 | HIP 34764 | 23.60 |
| 2026-08-18 12:00 | 07:12:47.83 | +19:33:07.3 | HIP 34764 | 24.34 |
| 2026-08-19 00:00 | 07:12:51.67 | +19:32:51.2 | HIP 34764 | 25.08 |