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) |
|---|---|---|---|---|
| 2026-06-01 00:00 | 22:40:18.61 | -47:43:30.3 | HIP 111894 | 3.85 |
| 2026-06-01 12:00 | 22:40:01.85 | -47:58:40.5 | HIP 111894 | 14.04 |
| 2026-06-02 00:00 | 22:39:44.36 | -48:13:53.2 | HIP 112081 | 24.16 |
| 2026-06-02 12:00 | 22:39:26.12 | -48:29:08.5 | HIP 111784 | 14.79 |
| 2026-06-03 00:00 | 22:39:07.12 | -48:44:26.2 | HIP 111784 | 6.90 |
| 2026-06-03 12:00 | 22:38:47.34 | -48:59:46.2 | HIP 111737 | 15.92 |
| 2026-06-04 00:00 | 22:38:26.77 | -49:15:08.5 | HIP 111788 | 2.74 |
| 2026-06-04 12:00 | 22:38:05.40 | -49:30:32.8 | HIP 111788 | 13.66 |
| 2026-06-05 00:00 | 22:37:43.21 | -49:45:59.1 | HIP 111714 | 18.02 |
| 2026-06-05 12:00 | 22:37:20.19 | -50:01:27.3 | HIP 111714 | 4.93 |
| 2026-06-06 00:00 | 22:36:56.33 | -50:16:57.3 | HIP 111714 | 15.25 |
| 2026-06-06 12:00 | 22:36:31.62 | -50:32:28.9 | HIP 111511 | 9.92 |
| 2026-06-07 00:00 | 22:36:06.02 | -50:48:02.0 | HIP 111511 | 13.87 |
| 2026-06-07 12:00 | 22:35:39.54 | -51:03:36.6 | HIP 111412 | 19.97 |
| 2026-06-08 00:00 | 22:35:12.16 | -51:19:12.3 | HIP 111358 | 15.29 |
| 2026-06-08 12:00 | 22:34:43.86 | -51:34:49.3 | HIP 111512 | 7.78 |
| 2026-06-09 00:00 | 22:34:14.62 | -51:50:27.2 | HIP 111512 | 18.71 |
| 2026-06-09 12:00 | 22:33:44.43 | -52:06:05.9 | HIP 111512 | 34.26 |
| 2026-06-10 00:00 | 22:33:13.27 | -52:21:45.4 | HIP 111007 | 38.69 |
| 2026-06-10 12:00 | 22:32:41.13 | -52:37:25.5 | HIP 111114 | 25.97 |
| 2026-06-11 00:00 | 22:32:08.00 | -52:53:06.0 | HIP 111114 | 14.20 |
| 2026-06-11 12:00 | 22:31:33.84 | -53:08:46.7 | HIP 111190 | 14.17 |
| 2026-06-12 00:00 | 22:30:58.65 | -53:24:27.6 | HIP 111190 | 5.38 |
| 2026-06-12 12:00 | 22:30:22.40 | -53:40:08.4 | HIP 111190 | 20.16 |
| 2026-06-13 00:00 | 22:29:45.09 | -53:55:49.0 | HIP 111190 | 36.57 |
| 2026-06-13 12:00 | 22:29:06.69 | -54:11:29.2 | HIP 110794 | 33.05 |
| 2026-06-14 00:00 | 22:28:27.19 | -54:27:08.9 | HIP 110794 | 17.77 |
| 2026-06-14 12:00 | 22:27:46.57 | -54:42:47.9 | HIP 110797 | 8.57 |
| 2026-06-15 00:00 | 22:27:04.80 | -54:58:25.9 | HIP 110797 | 13.24 |
| 2026-06-15 12:00 | 22:26:21.88 | -55:14:02.9 | HIP 110797 | 28.96 |
| 2026-06-16 00:00 | 22:25:37.78 | -55:29:38.6 | HIP 110503 | 32.07 |
| 2026-06-16 12:00 | 22:24:52.49 | -55:45:12.9 | HIP 110503 | 17.07 |
| 2026-06-17 00:00 | 22:24:05.98 | -56:00:45.6 | HIP 110503 | 10.92 |
| 2026-06-17 12:00 | 22:23:18.25 | -56:16:16.4 | HIP 110470 | 9.20 |
| 2026-06-18 00:00 | 22:22:29.26 | -56:31:45.3 | HIP 110470 | 22.63 |
| 2026-06-18 12:00 | 22:21:39.01 | -56:47:11.9 | HIP 110534 | 30.24 |
| 2026-06-19 00:00 | 22:20:47.48 | -57:02:36.1 | HIP 110534 | 24.78 |
| 2026-06-19 12:00 | 22:19:54.64 | -57:17:57.7 | HIP 110311 | 13.81 |
| 2026-06-20 00:00 | 22:19:00.48 | -57:33:16.5 | HIP 110311 | 13.13 |
| 2026-06-20 12:00 | 22:18:04.98 | -57:48:32.4 | HIP 110051 | 5.47 |
| 2026-06-21 00:00 | 22:17:08.11 | -58:03:45.0 | HIP 110051 | 16.86 |
| 2026-06-21 12:00 | 22:16:09.88 | -58:18:54.2 | HIP 109792 | 22.95 |
| 2026-06-22 00:00 | 22:15:10.24 | -58:33:59.8 | HIP 109568 | 31.12 |