C/2025 Q3 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 Q3 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2026-02-25T15:17:27.098880Z |
| Orbit solution date (soln_date, UTC) | 2026-05-05T09:12:15Z |
| Obs used | 1432 |
| NEO | - |
| M1 | 8.100 |
| K1 | 19.750 |
| PC | 0.030 |
| Discovery observation (MPC, UTC) | 2025-08-20T13:35:03.868800Z |
| Discovery magnitude (MPC) | 19.53 o |
| Discovery observatory (MPC) | T05 · ATLAS-HKO, Haleakala |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-11-18.0000000 |
| e | 0.99730694 |
| q (au) | 2.112541 |
| a (au) | 784.439913 |
| i (deg) | 90.187003 |
| Ω (om, deg) | 233.144051 |
| ω (w, deg) | 218.453690 |
| M (ma, deg) | 359.995530 |
Magnitude
Scatter + Global Linear
$$ M_a = (8.934 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 8.934 |
| n | 6.000 |
| gf | 1.000 |
| gb | -0.500 |
| k | 1.000 |
| 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 |
|---|---|---|---|
| 2025-08-20 | 2025-10-05 | -6.1885 | +3.201 |
| 2025-10-05 | 2025-11-24 | +11.2220 | -4.247 |
| 2025-11-24 | 2026-02-25 | +7.9374 | -2.741 |
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) |
|---|---|---|---|---|
| 2026-06-01 00:00 | 04:53:43.79 | -35:36:13.2 | HIP 22787 | 12.62 |
| 2026-06-01 12:00 | 04:54:52.88 | -35:43:53.2 | HIP 22895 | 9.73 |
| 2026-06-02 00:00 | 04:56:02.25 | -35:51:35.0 | HIP 22895 | 15.82 |
| 2026-06-02 12:00 | 04:57:11.90 | -35:59:18.6 | HIP 22895 | 30.39 |
| 2026-06-03 00:00 | 04:58:21.83 | -36:07:04.0 | HIP 23267 | 32.60 |
| 2026-06-03 12:00 | 04:59:32.03 | -36:14:51.2 | HIP 23224 | 22.95 |
| 2026-06-04 00:00 | 05:00:42.52 | -36:22:40.1 | HIP 23224 | 18.02 |
| 2026-06-04 12:00 | 05:01:53.29 | -36:30:30.8 | HIP 23224 | 25.44 |
| 2026-06-05 00:00 | 05:03:04.34 | -36:38:23.2 | HIP 23412 | 24.68 |
| 2026-06-05 12:00 | 05:04:15.67 | -36:46:17.3 | HIP 23412 | 30.86 |
| 2026-06-06 00:00 | 05:05:27.30 | -36:54:13.1 | HIP 23800 | 23.98 |
| 2026-06-06 12:00 | 05:06:39.20 | -37:02:10.6 | HIP 23800 | 9.40 |
| 2026-06-07 00:00 | 05:07:51.40 | -37:10:09.8 | HIP 23800 | 11.88 |
| 2026-06-07 12:00 | 05:09:03.88 | -37:18:10.6 | HIP 23800 | 27.15 |
| 2026-06-08 00:00 | 05:10:16.66 | -37:26:13.0 | HIP 24189 | 15.92 |
| 2026-06-08 12:00 | 05:11:29.72 | -37:34:17.0 | HIP 24189 | 10.63 |
| 2026-06-09 00:00 | 05:12:43.08 | -37:42:22.6 | HIP 24291 | 13.98 |
| 2026-06-09 12:00 | 05:13:56.73 | -37:50:29.7 | HIP 24291 | 15.01 |
| 2026-06-10 00:00 | 05:15:10.67 | -37:58:38.4 | HIP 24517 | 23.39 |
| 2026-06-10 12:00 | 05:16:24.91 | -38:06:48.6 | HIP 24697 | 16.53 |
| 2026-06-11 00:00 | 05:17:39.44 | -38:15:00.4 | HIP 24697 | 6.13 |
| 2026-06-11 12:00 | 05:18:54.27 | -38:23:13.6 | HIP 24697 | 19.17 |
| 2026-06-12 00:00 | 05:20:09.39 | -38:31:28.2 | HIP 25067 | 21.44 |
| 2026-06-12 12:00 | 05:21:24.82 | -38:39:44.3 | HIP 25067 | 12.32 |
| 2026-06-13 00:00 | 05:22:40.54 | -38:48:01.8 | HIP 25067 | 20.44 |
| 2026-06-13 12:00 | 05:23:56.56 | -38:56:20.6 | HIP 25283 | 6.78 |
| 2026-06-14 00:00 | 05:25:12.88 | -39:04:40.9 | HIP 25283 | 10.55 |
| 2026-06-14 12:00 | 05:26:29.50 | -39:13:02.4 | HIP 25553 | 14.60 |
| 2026-06-15 00:00 | 05:27:46.42 | -39:21:25.3 | HIP 25627 | 8.08 |
| 2026-06-15 12:00 | 05:29:03.64 | -39:29:49.4 | HIP 25627 | 10.22 |
| 2026-06-16 00:00 | 05:30:21.17 | -39:38:14.8 | HIP 25757 | 8.50 |
| 2026-06-16 12:00 | 05:31:38.99 | -39:46:41.4 | HIP 25935 | 17.08 |
| 2026-06-17 00:00 | 05:32:57.12 | -39:55:09.1 | HIP 25935 | 12.57 |
| 2026-06-17 12:00 | 05:34:15.55 | -40:03:38.0 | HIP 25935 | 24.84 |
| 2026-06-18 00:00 | 05:35:34.28 | -40:12:08.1 | HIP 26193 | 24.92 |
| 2026-06-18 12:00 | 05:36:53.31 | -40:20:39.2 | HIP 26193 | 26.64 |
| 2026-06-19 00:00 | 05:38:12.65 | -40:29:11.3 | HIP 26545 | 14.49 |
| 2026-06-19 12:00 | 05:39:32.29 | -40:37:44.5 | HIP 26621 | 3.32 |
| 2026-06-20 00:00 | 05:40:52.24 | -40:46:18.6 | HIP 26621 | 16.36 |
| 2026-06-20 12:00 | 05:42:12.49 | -40:54:53.7 | HIP 27048 | 24.82 |
| 2026-06-21 00:00 | 05:43:33.05 | -41:03:29.6 | HIP 27048 | 7.39 |
| 2026-06-21 12:00 | 05:44:53.91 | -41:12:06.4 | HIP 27085 | 8.25 |
| 2026-06-22 00:00 | 05:46:15.08 | -41:20:44.0 | HIP 27085 | 19.05 |