C/2025 Q3 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 Q3 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2026-02-25T15:15:55.886400Z |
| Orbit solution date (soln_date, UTC) | 2026-01-13T08:12:19Z |
| Obs used | 1191 |
| NEO | - |
| M1 | 9.100 |
| K1 | 17.500 |
| 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) | 2025-11-04.0000000 |
| e | 0.99731565 |
| q (au) | 2.112553 |
| a (au) | 786.987411 |
| i (deg) | 90.187544 |
| Ω (om, deg) | 233.144006 |
| ω (w, deg) | 218.453092 |
| M (ma, deg) | 359.994927 |
Magnitude
Scatter + Global Linear
$$ M_a = (9.152 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 9.152 |
| n | 6.000 |
| gf | 1.000 |
| gb | -0.898 |
| 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 | 2025-11-21 | +0.1797 | +0.107 |
| 2025-11-21 | 2026-02-06 | +15.2562 | -5.530 |
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 | 02:07:18.48 | -16:00:00.2 | HIP 9869 | 18.38 |
| 2026-02-03 12:00 | 02:07:33.11 | -16:05:42.7 | HIP 10010 | 20.40 |
| 2026-02-04 00:00 | 02:07:48.07 | -16:11:21.6 | HIP 10010 | 19.42 |
| 2026-02-04 12:00 | 02:08:03.36 | -16:16:57.2 | HIP 10037 | 16.49 |
| 2026-02-05 00:00 | 02:08:18.97 | -16:22:29.4 | HIP 10037 | 12.56 |
| 2026-02-05 12:00 | 02:08:34.90 | -16:27:58.3 | HIP 10037 | 11.44 |
| 2026-02-06 00:00 | 02:08:51.15 | -16:33:23.9 | HIP 10026 | 6.23 |
| 2026-02-06 12:00 | 02:09:07.72 | -16:38:46.5 | HIP 10026 | 1.08 |
| 2026-02-07 00:00 | 02:09:24.60 | -16:44:05.9 | HIP 10026 | 7.28 |
| 2026-02-07 12:00 | 02:09:41.80 | -16:49:22.3 | HIP 10063 | 8.71 |
| 2026-02-08 00:00 | 02:09:59.30 | -16:54:35.7 | HIP 10063 | 7.23 |
| 2026-02-08 12:00 | 02:10:17.11 | -16:59:46.2 | HIP 10063 | 10.94 |
| 2026-02-09 00:00 | 02:10:35.22 | -17:04:53.8 | HIP 10128 | 8.27 |
| 2026-02-09 12:00 | 02:10:53.64 | -17:09:58.7 | HIP 10128 | 9.17 |
| 2026-02-10 00:00 | 02:11:12.36 | -17:15:00.8 | HIP 10128 | 13.85 |
| 2026-02-10 12:00 | 02:11:31.37 | -17:20:00.3 | HIP 10128 | 19.79 |
| 2026-02-11 00:00 | 02:11:50.68 | -17:24:57.2 | HIP 10263 | 19.02 |
| 2026-02-11 12:00 | 02:12:10.29 | -17:29:51.5 | HIP 10263 | 13.93 |
| 2026-02-12 00:00 | 02:12:30.19 | -17:34:43.3 | HIP 10312 | 8.14 |
| 2026-02-12 12:00 | 02:12:50.37 | -17:39:32.7 | HIP 10312 | 1.69 |
| 2026-02-13 00:00 | 02:13:10.85 | -17:44:19.7 | HIP 10312 | 5.71 |
| 2026-02-13 12:00 | 02:13:31.61 | -17:49:04.4 | HIP 10392 | 10.20 |
| 2026-02-14 00:00 | 02:13:52.65 | -17:53:46.8 | HIP 10392 | 4.29 |
| 2026-02-14 12:00 | 02:14:13.98 | -17:58:27.0 | HIP 10392 | 5.28 |
| 2026-02-15 00:00 | 02:14:35.58 | -18:03:05.1 | HIP 10392 | 11.54 |
| 2026-02-15 12:00 | 02:14:57.47 | -18:07:41.0 | HIP 10542 | 13.31 |
| 2026-02-16 00:00 | 02:15:19.62 | -18:12:14.9 | HIP 10542 | 6.62 |
| 2026-02-16 12:00 | 02:15:42.06 | -18:16:46.8 | HIP 10542 | 2.69 |
| 2026-02-17 00:00 | 02:16:04.76 | -18:21:16.8 | HIP 10542 | 8.28 |
| 2026-02-17 12:00 | 02:16:27.73 | -18:25:44.9 | HIP 10542 | 15.13 |
| 2026-02-18 00:00 | 02:16:50.97 | -18:30:11.2 | HIP 10542 | 22.13 |
| 2026-02-18 12:00 | 02:17:14.48 | -18:34:35.6 | HIP 10759 | 28.01 |
| 2026-02-19 00:00 | 02:17:38.25 | -18:38:58.4 | HIP 10831 | 25.69 |
| 2026-02-19 12:00 | 02:18:02.28 | -18:43:19.4 | HIP 10831 | 21.56 |
| 2026-02-20 00:00 | 02:18:26.58 | -18:47:38.8 | HIP 10831 | 19.25 |
| 2026-02-20 12:00 | 02:18:51.13 | -18:51:56.7 | HIP 10831 | 19.44 |
| 2026-02-21 00:00 | 02:19:15.94 | -18:56:13.0 | HIP 10853 | 14.28 |
| 2026-02-21 12:00 | 02:19:41.00 | -19:00:27.8 | HIP 10853 | 8.80 |
| 2026-02-22 00:00 | 02:20:06.31 | -19:04:41.2 | HIP 10853 | 7.63 |
| 2026-02-22 12:00 | 02:20:31.88 | -19:08:53.2 | HIP 10853 | 12.14 |
| 2026-02-23 00:00 | 02:20:57.69 | -19:13:03.9 | HIP 10853 | 18.62 |
| 2026-02-23 12:00 | 02:21:23.75 | -19:17:13.2 | HIP 10853 | 25.64 |
| 2026-02-24 00:00 | 02:21:50.06 | -19:21:21.3 | HIP 10853 | 32.89 |