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
$$ M_a = (8.983 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 8.983 |
| 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 | 2026-02-25 | +3.4128 | -1.197 |
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) |
|---|---|---|---|---|
| 2026-05-12 00:00 | 04:11:13.57 | -30:56:41.9 | HIP 19703 | 32.83 |
| 2026-05-12 12:00 | 04:12:12.48 | -31:03:00.8 | HIP 19703 | 19.22 |
| 2026-05-13 00:00 | 04:13:11.63 | -31:09:21.8 | HIP 19703 | 7.65 |
| 2026-05-13 12:00 | 04:14:11.02 | -31:15:44.9 | HIP 19703 | 12.22 |
| 2026-05-14 00:00 | 04:15:10.65 | -31:22:10.0 | HIP 19840 | 25.22 |
| 2026-05-14 12:00 | 04:16:10.53 | -31:28:37.2 | HIP 19840 | 22.45 |
| 2026-05-15 00:00 | 04:17:10.64 | -31:35:06.5 | HIP 19840 | 27.95 |
| 2026-05-15 12:00 | 04:18:11.00 | -31:41:38.0 | HIP 20140 | 24.78 |
| 2026-05-16 00:00 | 04:19:11.60 | -31:48:11.5 | HIP 20140 | 28.60 |
| 2026-05-16 12:00 | 04:20:12.44 | -31:54:47.1 | HIP 20383 | 26.98 |
| 2026-05-17 00:00 | 04:21:13.53 | -32:01:24.8 | HIP 20383 | 12.96 |
| 2026-05-17 12:00 | 04:22:14.86 | -32:08:04.7 | HIP 20383 | 5.59 |
| 2026-05-18 00:00 | 04:23:16.44 | -32:14:46.6 | HIP 20474 | 5.67 |
| 2026-05-18 12:00 | 04:24:18.27 | -32:21:30.6 | HIP 20536 | 17.01 |
| 2026-05-19 00:00 | 04:25:20.34 | -32:28:16.8 | HIP 20684 | 12.89 |
| 2026-05-19 12:00 | 04:26:22.66 | -32:35:05.1 | HIP 20727 | 13.99 |
| 2026-05-20 00:00 | 04:27:25.23 | -32:41:55.4 | HIP 20727 | 13.50 |
| 2026-05-20 12:00 | 04:28:28.05 | -32:48:47.9 | HIP 20888 | 20.93 |
| 2026-05-21 00:00 | 04:29:31.12 | -32:55:42.4 | HIP 20818 | 27.32 |
| 2026-05-21 12:00 | 04:30:34.44 | -33:02:39.0 | HIP 21207 | 30.07 |
| 2026-05-22 00:00 | 04:31:38.01 | -33:09:37.7 | HIP 21207 | 17.00 |
| 2026-05-22 12:00 | 04:32:41.83 | -33:16:38.5 | HIP 21207 | 11.28 |
| 2026-05-23 00:00 | 04:33:45.91 | -33:23:41.3 | HIP 21357 | 15.14 |
| 2026-05-23 12:00 | 04:34:50.24 | -33:30:46.2 | HIP 21322 | 8.47 |
| 2026-05-24 00:00 | 04:35:54.82 | -33:37:53.1 | HIP 21322 | 16.25 |
| 2026-05-24 12:00 | 04:36:59.66 | -33:45:02.1 | HIP 21592 | 26.03 |
| 2026-05-25 00:00 | 04:38:04.76 | -33:52:13.1 | HIP 21592 | 14.44 |
| 2026-05-25 12:00 | 04:39:10.12 | -33:59:26.1 | HIP 21694 | 3.73 |
| 2026-05-26 00:00 | 04:40:15.74 | -34:06:41.1 | HIP 21694 | 11.98 |
| 2026-05-26 12:00 | 04:41:21.62 | -34:13:58.1 | HIP 21922 | 18.61 |
| 2026-05-27 00:00 | 04:42:27.75 | -34:21:17.1 | HIP 21922 | 9.63 |
| 2026-05-27 12:00 | 04:43:34.16 | -34:28:38.0 | HIP 21922 | 17.94 |
| 2026-05-28 00:00 | 04:44:40.82 | -34:36:00.9 | HIP 21956 | 24.27 |
| 2026-05-28 12:00 | 04:45:47.75 | -34:43:25.8 | HIP 21956 | 33.75 |
| 2026-05-29 00:00 | 04:46:54.95 | -34:50:52.6 | HIP 22387 | 30.97 |
| 2026-05-29 12:00 | 04:48:02.41 | -34:58:21.3 | HIP 22387 | 15.25 |
| 2026-05-30 00:00 | 04:49:10.15 | -35:05:51.9 | HIP 22387 | 0.86 |
| 2026-05-30 12:00 | 04:50:18.15 | -35:13:24.4 | HIP 22451 | 8.74 |
| 2026-05-31 00:00 | 04:51:26.42 | -35:20:58.8 | HIP 22451 | 24.09 |
| 2026-05-31 12:00 | 04:52:34.97 | -35:28:35.1 | HIP 22787 | 18.66 |
| 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 |