C/2019 Y4 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | C/2019 Y4 (ATLAS) |
| Type | C |
| Perihelion (tp_cal, UTC) | 2020-05-31T00:23:50.930880Z |
| Orbit solution date (soln_date, UTC) | 2024-01-05T08:08:32Z |
| Obs used | 1259 |
| NEO | - |
| M1 | 8.800 |
| K1 | 18.500 |
| PC | 0.030 |
| Discovery observation (MPC, UTC) | 2019-12-28T14:19:26.457600Z |
| Discovery magnitude (MPC) | 19.63 o |
| Discovery observatory (MPC) | T08 · ATLAS-MLO, Mauna Loa |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2020-02-24.0000000 |
| e | 0.99922493 |
| q (au) | 0.252854 |
| a (au) | 326.234163 |
| i (deg) | 45.380208 |
| Ω (om, deg) | 120.568599 |
| ω (w, deg) | 177.409813 |
| M (ma, deg) | 359.983772 |
Magnitude
Scatter + Global Linear
$$ M_a = (9.706 + 5.131\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 9.706 |
| n | 5.131 |
| gf | 0.800 |
| gb | -0.500 |
| k | 1.000 |
| δ90 | 1.000 |
| 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 |
|---|---|---|---|
| 2019-12-20 | 2020-03-20 | +13.7200 | -4.891 |
| 2020-03-20 | 2020-04-12 | -22.9056 | +3.035 |
| 2020-04-12 | 2020-04-27 | -8.4908 | +0.540 |
| 2020-04-27 | 2020-05-21 | -11.1661 | +1.086 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) | RA (J2000) | Dec (J2000) | Nearest HIP | Dist from HIP (arcmin) |
|---|---|---|---|---|
| 2026-09-20 00:00 | 07:28:47.66 | +10:49:41.4 | HIP 36385 | 13.95 |
| 2026-09-20 12:00 | 07:28:50.12 | +10:49:22.2 | HIP 36385 | 13.92 |
| 2026-09-21 00:00 | 07:28:52.54 | +10:49:02.9 | HIP 36385 | 13.92 |
| 2026-09-21 12:00 | 07:28:54.91 | +10:48:43.7 | HIP 36385 | 13.96 |
| 2026-09-22 00:00 | 07:28:57.24 | +10:48:24.5 | HIP 36385 | 14.03 |
| 2026-09-22 12:00 | 07:28:59.51 | +10:48:05.4 | HIP 36385 | 14.14 |
| 2026-09-23 00:00 | 07:29:01.74 | +10:47:46.3 | HIP 36385 | 14.28 |
| 2026-09-23 12:00 | 07:29:03.92 | +10:47:27.2 | HIP 36385 | 14.44 |
| 2026-09-24 00:00 | 07:29:06.05 | +10:47:08.2 | HIP 36385 | 14.64 |
| 2026-09-24 12:00 | 07:29:08.14 | +10:46:49.3 | HIP 36385 | 14.85 |
| 2026-09-25 00:00 | 07:29:10.17 | +10:46:30.4 | HIP 36385 | 15.09 |
| 2026-09-25 12:00 | 07:29:12.16 | +10:46:11.5 | HIP 36385 | 15.35 |
| 2026-09-26 00:00 | 07:29:14.10 | +10:45:52.7 | HIP 36385 | 15.62 |
| 2026-09-26 12:00 | 07:29:15.98 | +10:45:34.0 | HIP 36385 | 15.91 |
| 2026-09-27 00:00 | 07:29:17.82 | +10:45:15.3 | HIP 36385 | 16.22 |
| 2026-09-27 12:00 | 07:29:19.61 | +10:44:56.6 | HIP 36385 | 16.53 |
| 2026-09-28 00:00 | 07:29:21.35 | +10:44:38.0 | HIP 36385 | 16.86 |
| 2026-09-28 12:00 | 07:29:23.04 | +10:44:19.5 | HIP 36385 | 17.19 |
| 2026-09-29 00:00 | 07:29:24.68 | +10:44:01.1 | HIP 36385 | 17.53 |
| 2026-09-29 12:00 | 07:29:26.27 | +10:43:42.7 | HIP 36385 | 17.87 |
| 2026-09-30 00:00 | 07:29:27.81 | +10:43:24.3 | HIP 36385 | 18.22 |
| 2026-09-30 12:00 | 07:29:29.30 | +10:43:06.0 | HIP 36385 | 18.58 |
| 2026-10-01 00:00 | 07:29:30.73 | +10:42:47.8 | HIP 36385 | 18.93 |
| 2026-10-01 12:00 | 07:29:32.12 | +10:42:29.7 | HIP 36385 | 19.29 |
| 2026-10-02 00:00 | 07:29:33.46 | +10:42:11.6 | HIP 36385 | 19.64 |
| 2026-10-02 12:00 | 07:29:34.74 | +10:41:53.6 | HIP 36385 | 20.00 |
| 2026-10-03 00:00 | 07:29:35.97 | +10:41:35.7 | HIP 36385 | 20.36 |
| 2026-10-03 12:00 | 07:29:37.16 | +10:41:17.8 | HIP 36385 | 20.71 |
| 2026-10-04 00:00 | 07:29:38.29 | +10:41:00.0 | HIP 36385 | 21.06 |
| 2026-10-04 12:00 | 07:29:39.36 | +10:40:42.3 | HIP 36385 | 21.41 |
| 2026-10-05 00:00 | 07:29:40.39 | +10:40:24.7 | HIP 36385 | 21.76 |
| 2026-10-05 12:00 | 07:29:41.36 | +10:40:07.2 | HIP 36385 | 22.10 |
| 2026-10-06 00:00 | 07:29:42.28 | +10:39:49.7 | HIP 36385 | 22.44 |
| 2026-10-06 12:00 | 07:29:43.15 | +10:39:32.3 | HIP 36385 | 22.78 |
| 2026-10-07 00:00 | 07:29:43.97 | +10:39:15.0 | HIP 36385 | 23.11 |
| 2026-10-07 12:00 | 07:29:44.73 | +10:38:57.8 | HIP 36385 | 23.44 |
| 2026-10-08 00:00 | 07:29:45.44 | +10:38:40.7 | HIP 36385 | 23.76 |
| 2026-10-08 12:00 | 07:29:46.09 | +10:38:23.7 | HIP 36385 | 24.08 |
| 2026-10-09 00:00 | 07:29:46.70 | +10:38:06.8 | HIP 36385 | 24.39 |
| 2026-10-09 12:00 | 07:29:47.25 | +10:37:49.9 | HIP 36385 | 24.70 |
| 2026-10-10 00:00 | 07:29:47.74 | +10:37:33.2 | HIP 36385 | 25.00 |
| 2026-10-10 12:00 | 07:29:48.18 | +10:37:16.5 | HIP 36385 | 25.30 |
| 2026-10-11 00:00 | 07:29:48.57 | +10:37:00.0 | HIP 36385 | 25.59 |