C/2025 T1 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 T1 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-12-02T09:03:18.529920Z |
| Orbit solution date (soln_date, UTC) | 2026-05-22T14:12:20Z |
| Obs used | 821 |
| NEO | - |
| M1 | 12.100 |
| K1 | 19.000 |
| PC | 0.030 |
| Discovery observation (MPC, UTC) | 2025-10-11T14:54:27.014400Z |
| Discovery magnitude (MPC) | 17.50 o |
| Discovery observatory (MPC) | T08 · ATLAS-MLO, Mauna Loa |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2025-11-29.0000000 |
| e | 0.99965815 |
| q (au) | 1.108807 |
| a (au) | 3243.581968 |
| i (deg) | 123.433643 |
| Ω (om, deg) | 140.494892 |
| ω (w, deg) | 114.142738 |
| M (ma, deg) | 359.999982 |
Magnitude
Scatter + Global Linear
$$ M_a = (11.672 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.672 |
| n | 6.000 |
| gf | 1.000 |
| gb | -0.900 |
| k | 0.860 |
| 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 |
|---|---|---|---|
| 2025-10-11 | 2025-12-02 | +38.7971 | -3.630 |
| 2025-12-02 | 2026-05-17 | +7.6302 | -2.206 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-07-29 00:00 | 19:52:16.14 | -70:28:52.4 | HIP 97621 | 19.36 |
| 2026-07-29 12:00 | 19:49:48.01 | -70:30:56.9 | HIP 97335 | 16.07 |
| 2026-07-30 00:00 | 19:47:20.47 | -70:32:49.1 | HIP 97335 | 6.04 |
| 2026-07-30 12:00 | 19:44:53.59 | -70:34:29.3 | HIP 97226 | 4.88 |
| 2026-07-31 00:00 | 19:42:27.45 | -70:35:57.6 | HIP 97226 | 15.98 |
| 2026-07-31 12:00 | 19:40:02.11 | -70:37:14.2 | HIP 96705 | 14.43 |
| 2026-08-01 00:00 | 19:37:37.64 | -70:38:19.3 | HIP 96276 | 16.97 |
| 2026-08-01 12:00 | 19:35:14.09 | -70:39:13.0 | HIP 96276 | 9.12 |
| 2026-08-02 00:00 | 19:32:51.53 | -70:39:55.6 | HIP 96276 | 12.64 |
| 2026-08-02 12:00 | 19:30:30.03 | -70:40:27.2 | HIP 95800 | 22.56 |
| 2026-08-03 00:00 | 19:28:09.63 | -70:40:48.1 | HIP 95800 | 22.47 |
| 2026-08-03 12:00 | 19:25:50.39 | -70:40:58.5 | HIP 95210 | 22.23 |
| 2026-08-04 00:00 | 19:23:32.36 | -70:40:58.5 | HIP 95208 | 14.15 |
| 2026-08-04 12:00 | 19:21:15.60 | -70:40:48.4 | HIP 95208 | 12.78 |
| 2026-08-05 00:00 | 19:19:00.15 | -70:40:28.4 | HIP 95208 | 19.44 |
| 2026-08-05 12:00 | 19:16:46.07 | -70:39:58.8 | HIP 94318 | 25.81 |
| 2026-08-06 00:00 | 19:14:33.38 | -70:39:19.7 | HIP 94318 | 16.23 |
| 2026-08-06 12:00 | 19:12:22.14 | -70:38:31.4 | HIP 94318 | 10.23 |
| 2026-08-07 00:00 | 19:10:12.38 | -70:37:34.0 | HIP 94318 | 13.52 |
| 2026-08-07 12:00 | 19:08:04.15 | -70:36:28.0 | HIP 94318 | 22.17 |
| 2026-08-08 00:00 | 19:05:57.46 | -70:35:13.3 | HIP 93370 | 24.45 |
| 2026-08-08 12:00 | 19:03:52.36 | -70:33:50.4 | HIP 93370 | 14.00 |
| 2026-08-09 00:00 | 19:01:48.88 | -70:32:19.4 | HIP 93370 | 3.95 |
| 2026-08-09 12:00 | 18:59:47.04 | -70:30:40.6 | HIP 93238 | 2.97 |
| 2026-08-10 00:00 | 18:57:46.87 | -70:28:54.1 | HIP 92939 | 8.25 |
| 2026-08-10 12:00 | 18:55:48.38 | -70:27:00.2 | HIP 92939 | 2.76 |
| 2026-08-11 00:00 | 18:53:51.61 | -70:24:59.2 | HIP 92939 | 12.18 |
| 2026-08-11 12:00 | 18:51:56.56 | -70:22:51.3 | HIP 92939 | 22.00 |
| 2026-08-12 00:00 | 18:50:03.25 | -70:20:36.6 | HIP 92192 | 25.58 |
| 2026-08-12 12:00 | 18:48:11.70 | -70:18:15.5 | HIP 92192 | 19.66 |
| 2026-08-13 00:00 | 18:46:21.92 | -70:15:48.1 | HIP 92192 | 17.45 |
| 2026-08-13 12:00 | 18:44:33.91 | -70:13:14.7 | HIP 91744 | 11.57 |
| 2026-08-14 00:00 | 18:42:47.68 | -70:10:35.5 | HIP 91744 | 7.74 |
| 2026-08-14 12:00 | 18:41:03.25 | -70:07:50.7 | HIP 91744 | 12.68 |
| 2026-08-15 00:00 | 18:39:20.60 | -70:05:00.5 | HIP 91425 | 9.68 |
| 2026-08-15 12:00 | 18:37:39.75 | -70:02:05.2 | HIP 91146 | 11.95 |
| 2026-08-16 00:00 | 18:36:00.70 | -69:59:04.9 | HIP 91146 | 3.40 |
| 2026-08-16 12:00 | 18:34:23.43 | -69:55:59.9 | HIP 91146 | 6.34 |
| 2026-08-17 00:00 | 18:32:47.95 | -69:52:50.3 | HIP 90922 | 13.37 |
| 2026-08-17 12:00 | 18:31:14.26 | -69:49:36.3 | HIP 90922 | 18.51 |
| 2026-08-18 00:00 | 18:29:42.34 | -69:46:18.2 | HIP 90374 | 23.13 |
| 2026-08-18 12:00 | 18:28:12.19 | -69:42:56.2 | HIP 90374 | 15.38 |
| 2026-08-19 00:00 | 18:26:43.80 | -69:39:30.4 | HIP 90374 | 9.06 |