C/2025 Q3 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 Q3 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2026-02-25T15:17:11.676480Z |
| Orbit solution date (soln_date, UTC) | 2026-07-28T14:12:17Z |
| Obs used | 1443 |
| 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) | 2025-11-20.0000000 |
| e | 0.99731001 |
| q (au) | 2.112542 |
| a (au) | 785.333373 |
| i (deg) | 90.186983 |
| Ω (om, deg) | 233.144049 |
| ω (w, deg) | 218.453616 |
| M (ma, deg) | 359.995627 |
Magnitude
Scatter + Global Linear
$$ M_a = (8.972 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 8.972 |
| n | 6.000 |
| gf | 0.998 |
| gb | -0.939 |
| 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 | -5.9389 | +3.051 |
| 2025-10-05 | 2025-11-24 | +8.2138 | -3.009 |
| 2025-11-24 | 2026-02-25 | +10.0171 | -3.487 |
| 2026-02-25 | 2026-07-25 | +9.6902 | -4.264 |
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 | 07:40:31.03 | -51:48:34.8 | HIP 37161 | 23.71 |
| 2026-07-29 12:00 | 07:42:14.20 | -51:56:15.4 | HIP 37635 | 17.10 |
| 2026-07-30 00:00 | 07:43:57.60 | -52:03:53.6 | HIP 37635 | 8.15 |
| 2026-07-30 12:00 | 07:45:41.23 | -52:11:29.6 | HIP 37966 | 14.85 |
| 2026-07-31 00:00 | 07:47:25.09 | -52:19:03.2 | HIP 37966 | 4.69 |
| 2026-07-31 12:00 | 07:49:09.16 | -52:26:34.4 | HIP 38107 | 15.45 |
| 2026-08-01 00:00 | 07:50:53.46 | -52:34:03.2 | HIP 38504 | 21.06 |
| 2026-08-01 12:00 | 07:52:37.97 | -52:41:29.5 | HIP 38504 | 4.31 |
| 2026-08-02 00:00 | 07:54:22.69 | -52:48:53.4 | HIP 38690 | 9.58 |
| 2026-08-02 12:00 | 07:56:07.62 | -52:56:14.9 | HIP 38827 | 6.48 |
| 2026-08-03 00:00 | 07:57:52.75 | -53:03:33.8 | HIP 38827 | 10.95 |
| 2026-08-03 12:00 | 07:59:38.09 | -53:10:50.1 | HIP 38827 | 28.35 |
| 2026-08-04 00:00 | 08:01:23.62 | -53:18:03.9 | HIP 39368 | 13.52 |
| 2026-08-04 12:00 | 08:03:09.35 | -53:25:15.1 | HIP 39368 | 6.44 |
| 2026-08-05 00:00 | 08:04:55.27 | -53:32:23.8 | HIP 39368 | 22.36 |
| 2026-08-05 12:00 | 08:06:41.38 | -53:39:29.8 | HIP 39665 | 23.48 |
| 2026-08-06 00:00 | 08:08:27.67 | -53:46:33.1 | HIP 39956 | 17.05 |
| 2026-08-06 12:00 | 08:10:14.14 | -53:53:33.9 | HIP 40153 | 16.75 |
| 2026-08-07 00:00 | 08:12:00.78 | -54:00:31.9 | HIP 40188 | 9.50 |
| 2026-08-07 12:00 | 08:13:47.60 | -54:07:27.2 | HIP 40188 | 11.05 |
| 2026-08-08 00:00 | 08:15:34.58 | -54:14:19.9 | HIP 40606 | 21.96 |
| 2026-08-08 12:00 | 08:17:21.72 | -54:21:09.8 | HIP 40606 | 7.98 |
| 2026-08-09 00:00 | 08:19:09.03 | -54:27:57.0 | HIP 40757 | 4.44 |
| 2026-08-09 12:00 | 08:20:56.48 | -54:34:41.4 | HIP 40757 | 15.63 |
| 2026-08-10 00:00 | 08:22:44.09 | -54:41:23.0 | HIP 41077 | 12.51 |
| 2026-08-10 12:00 | 08:24:31.83 | -54:48:01.9 | HIP 41327 | 12.06 |
| 2026-08-11 00:00 | 08:26:19.72 | -54:54:38.0 | HIP 41327 | 7.92 |
| 2026-08-11 12:00 | 08:28:07.74 | -55:01:11.2 | HIP 41464 | 5.78 |
| 2026-08-12 00:00 | 08:29:55.90 | -55:07:41.7 | HIP 41653 | 4.68 |
| 2026-08-12 12:00 | 08:31:44.17 | -55:14:09.3 | HIP 41897 | 9.97 |
| 2026-08-13 00:00 | 08:33:32.57 | -55:20:34.0 | HIP 41887 | 9.93 |
| 2026-08-13 12:00 | 08:35:21.08 | -55:26:55.9 | HIP 42152 | 20.81 |
| 2026-08-14 00:00 | 08:37:09.71 | -55:33:14.9 | HIP 42424 | 28.31 |
| 2026-08-14 12:00 | 08:38:58.43 | -55:39:31.1 | HIP 42424 | 17.05 |
| 2026-08-15 00:00 | 08:40:47.26 | -55:45:44.3 | HIP 42717 | 13.19 |
| 2026-08-15 12:00 | 08:42:36.19 | -55:51:54.7 | HIP 42717 | 5.84 |
| 2026-08-16 00:00 | 08:44:25.20 | -55:58:02.1 | HIP 42989 | 12.93 |
| 2026-08-16 12:00 | 08:46:14.30 | -56:04:06.6 | HIP 43009 | 3.88 |
| 2026-08-17 00:00 | 08:48:03.49 | -56:10:08.1 | HIP 43374 | 17.20 |
| 2026-08-17 12:00 | 08:49:52.74 | -56:16:06.7 | HIP 43374 | 6.47 |
| 2026-08-18 00:00 | 08:51:42.07 | -56:22:02.4 | HIP 43566 | 9.32 |
| 2026-08-18 12:00 | 08:53:31.47 | -56:27:55.1 | HIP 43620 | 11.69 |
| 2026-08-19 00:00 | 08:55:20.93 | -56:33:44.9 | HIP 43620 | 19.58 |