C/2025 T1 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2025 T1 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2025-12-02T09:02:14.170560Z |
| Orbit solution date (soln_date, UTC) | 2026-03-31T09:42:20Z |
| Obs used | 753 |
| NEO | - |
| M1 | 11.600 |
| K1 | 25.750 |
| 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) | 2025-11-22.0000000 |
| e | 0.99970816 |
| q (au) | 1.108812 |
| a (au) | 3799.344757 |
| i (deg) | 123.433363 |
| Ω (om, deg) | 140.494928 |
| ω (w, deg) | 114.142039 |
| M (ma, deg) | 359.999956 |
Magnitude
Scatter + Global Linear
$$ M_a = (11.665 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 11.665 |
| n | 6.000 |
| gf | 0.999 |
| gb | -1.000 |
| k | 0.800 |
| 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 | +40.3659 | -3.536 |
| 2025-12-02 | 2026-03-25 | +7.3748 | -2.039 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-03-26 00:00 | 22:16:30.90 | -23:41:31.6 | HIP 109838 | 30.25 |
| 2026-03-26 12:00 | 22:16:56.20 | -23:48:33.6 | HIP 109838 | 31.75 |
| 2026-03-27 00:00 | 22:17:21.38 | -23:55:37.6 | HIP 110210 | 29.73 |
| 2026-03-27 12:00 | 22:17:46.43 | -24:02:43.6 | HIP 110210 | 27.27 |
| 2026-03-28 00:00 | 22:18:11.35 | -24:09:51.6 | HIP 110210 | 27.79 |
| 2026-03-28 12:00 | 22:18:36.15 | -24:17:01.7 | HIP 110210 | 31.16 |
| 2026-03-29 00:00 | 22:19:00.82 | -24:24:13.8 | HIP 110210 | 36.59 |
| 2026-03-29 12:00 | 22:19:25.36 | -24:31:28.2 | HIP 110210 | 43.33 |
| 2026-03-30 00:00 | 22:19:49.78 | -24:38:44.7 | HIP 110529 | 50.68 |
| 2026-03-30 12:00 | 22:20:14.06 | -24:46:03.4 | HIP 110413 | 42.54 |
| 2026-03-31 00:00 | 22:20:38.21 | -24:53:24.4 | HIP 110413 | 33.40 |
| 2026-03-31 12:00 | 22:21:02.23 | -25:00:47.6 | HIP 110413 | 24.27 |
| 2026-04-01 00:00 | 22:21:26.12 | -25:08:13.2 | HIP 110413 | 15.18 |
| 2026-04-01 12:00 | 22:21:49.87 | -25:15:41.1 | HIP 110413 | 6.34 |
| 2026-04-02 00:00 | 22:22:13.48 | -25:23:11.5 | HIP 110413 | 4.35 |
| 2026-04-02 12:00 | 22:22:36.96 | -25:30:44.3 | HIP 110413 | 12.93 |
| 2026-04-03 00:00 | 22:23:00.30 | -25:38:19.5 | HIP 110512 | 12.59 |
| 2026-04-03 12:00 | 22:23:23.51 | -25:45:57.3 | HIP 110512 | 5.02 |
| 2026-04-04 00:00 | 22:23:46.57 | -25:53:37.6 | HIP 110512 | 7.91 |
| 2026-04-04 12:00 | 22:24:09.49 | -26:01:20.6 | HIP 110576 | 10.55 |
| 2026-04-05 00:00 | 22:24:32.26 | -26:09:06.1 | HIP 110576 | 6.89 |
| 2026-04-05 12:00 | 22:24:54.89 | -26:16:54.3 | HIP 110577 | 12.15 |
| 2026-04-06 00:00 | 22:25:17.38 | -26:24:45.3 | HIP 110577 | 16.04 |
| 2026-04-06 12:00 | 22:25:39.71 | -26:32:38.9 | HIP 110641 | 22.36 |
| 2026-04-07 00:00 | 22:26:01.90 | -26:40:35.4 | HIP 110641 | 20.11 |
| 2026-04-07 12:00 | 22:26:23.93 | -26:48:34.7 | HIP 110641 | 21.94 |
| 2026-04-08 00:00 | 22:26:45.81 | -26:56:36.8 | HIP 110908 | 24.75 |
| 2026-04-08 12:00 | 22:27:07.54 | -27:04:41.8 | HIP 110908 | 16.15 |
| 2026-04-09 00:00 | 22:27:29.11 | -27:12:49.8 | HIP 110908 | 9.37 |
| 2026-04-09 12:00 | 22:27:50.53 | -27:21:00.7 | HIP 110908 | 9.71 |
| 2026-04-10 00:00 | 22:28:11.78 | -27:29:14.7 | HIP 110908 | 16.79 |
| 2026-04-10 12:00 | 22:28:32.87 | -27:37:31.7 | HIP 110908 | 25.53 |
| 2026-04-11 00:00 | 22:28:53.79 | -27:45:51.8 | HIP 110908 | 34.71 |
| 2026-04-11 12:00 | 22:29:14.55 | -27:54:15.1 | HIP 111218 | 38.59 |
| 2026-04-12 00:00 | 22:29:35.14 | -28:02:41.5 | HIP 111218 | 31.95 |
| 2026-04-12 12:00 | 22:29:55.57 | -28:11:11.1 | HIP 111218 | 27.20 |
| 2026-04-13 00:00 | 22:30:15.81 | -28:19:43.9 | HIP 111015 | 22.67 |
| 2026-04-13 12:00 | 22:30:35.89 | -28:28:20.1 | HIP 111015 | 19.05 |
| 2026-04-14 00:00 | 22:30:55.78 | -28:36:59.5 | HIP 111015 | 19.90 |
| 2026-04-14 12:00 | 22:31:15.50 | -28:45:42.4 | HIP 111013 | 24.34 |
| 2026-04-15 00:00 | 22:31:35.04 | -28:54:28.6 | HIP 111311 | 19.18 |
| 2026-04-15 12:00 | 22:31:54.39 | -29:03:18.2 | HIP 111311 | 15.06 |
| 2026-04-16 00:00 | 22:32:13.55 | -29:12:11.3 | HIP 111311 | 16.74 |