P/2021 Q5 (ATLAS)
Metadata
| Parameter | Value |
|---|---|
| Designation | P/2021 Q5 (ATLAS) |
| Type | P |
| Perihelion (tp_cal, UTC) | 2021-08-30T10:00:46.546560Z |
| Orbit solution date (soln_date, UTC) | 2025-01-14T17:42:18Z |
| Obs used | 274 |
| NEO | Yes |
| M1 | 15.800 |
| K1 | 4.500 |
| PC | 0.030 |
| Discovery observation (MPC, UTC) | 2021-08-29T14:33:45.619200Z |
| Discovery magnitude (MPC) | 17.59 o |
| Discovery observatory (MPC) | T05 · ATLAS-HKO, Haleakala |
Osculating Elements
| Parameter | Value |
|---|---|
| Epoch (epoch_cal, TDB) | 2021-09-20.0000000 |
| e | 0.62395172 |
| q (au) | 1.234397 |
| a (au) | 3.282550 |
| i (deg) | 10.733839 |
| Ω (om, deg) | 239.770616 |
| ω (w, deg) | 180.879852 |
| M (ma, deg) | 3.411076 |
Magnitude
Scatter + Global Linear
$$ M_a = (14.774 + 2.320\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$
Model Parameters
| Parameter | Value |
|---|---|
| H0 | 14.774 |
| n | 2.320 |
| gf | 0.999 |
| gb | -0.998 |
| 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 |
|---|---|---|---|
| 2021-08-30 | 2021-11-02 | -1.8955 | -0.495 |
| 2021-11-02 | 2022-01-25 | +11.5758 | -1.923 |
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) |
|---|---|---|---|---|
| 2026-02-03 00:00 | 18:31:35.32 | -18:35:54.1 | HIP 90806 | 11.94 |
| 2026-02-03 12:00 | 18:32:03.48 | -18:34:59.6 | HIP 90806 | 13.97 |
| 2026-02-04 00:00 | 18:32:31.59 | -18:34:04.6 | HIP 90950 | 15.06 |
| 2026-02-04 12:00 | 18:32:59.64 | -18:33:09.1 | HIP 90950 | 11.32 |
| 2026-02-05 00:00 | 18:33:27.63 | -18:32:13.1 | HIP 90950 | 10.94 |
| 2026-02-05 12:00 | 18:33:55.56 | -18:31:16.6 | HIP 90950 | 14.16 |
| 2026-02-06 00:00 | 18:34:23.42 | -18:30:19.6 | HIP 91143 | 17.59 |
| 2026-02-06 12:00 | 18:34:51.22 | -18:29:22.1 | HIP 91143 | 11.40 |
| 2026-02-07 00:00 | 18:35:18.96 | -18:28:24.1 | HIP 91143 | 6.27 |
| 2026-02-07 12:00 | 18:35:46.63 | -18:27:25.7 | HIP 91143 | 6.08 |
| 2026-02-08 00:00 | 18:36:14.23 | -18:26:26.7 | HIP 91143 | 11.06 |
| 2026-02-08 12:00 | 18:36:41.77 | -18:25:27.3 | HIP 91143 | 17.18 |
| 2026-02-09 00:00 | 18:37:09.24 | -18:24:27.4 | HIP 91143 | 23.55 |
| 2026-02-09 12:00 | 18:37:36.64 | -18:23:27.0 | HIP 91143 | 30.00 |
| 2026-02-10 00:00 | 18:38:03.97 | -18:22:26.2 | HIP 91486 | 27.00 |
| 2026-02-10 12:00 | 18:38:31.23 | -18:21:24.8 | HIP 91486 | 23.39 |
| 2026-02-11 00:00 | 18:38:58.41 | -18:20:23.0 | HIP 91486 | 21.25 |
| 2026-02-11 12:00 | 18:39:25.53 | -18:19:20.7 | HIP 91486 | 21.02 |
| 2026-02-12 00:00 | 18:39:52.57 | -18:18:18.0 | HIP 91486 | 22.74 |
| 2026-02-12 12:00 | 18:40:19.53 | -18:17:14.8 | HIP 91667 | 25.61 |
| 2026-02-13 00:00 | 18:40:46.41 | -18:16:11.1 | HIP 91667 | 20.66 |
| 2026-02-13 12:00 | 18:41:13.22 | -18:15:07.0 | HIP 91667 | 16.77 |
| 2026-02-14 00:00 | 18:41:39.95 | -18:14:02.4 | HIP 91667 | 14.80 |
| 2026-02-14 12:00 | 18:42:06.60 | -18:12:57.3 | HIP 91806 | 15.34 |
| 2026-02-15 00:00 | 18:42:33.17 | -18:11:51.8 | HIP 91806 | 8.95 |
| 2026-02-15 12:00 | 18:42:59.66 | -18:10:45.9 | HIP 91806 | 2.64 |
| 2026-02-16 00:00 | 18:43:26.07 | -18:09:39.5 | HIP 91806 | 3.91 |
| 2026-02-16 12:00 | 18:43:52.39 | -18:08:32.6 | HIP 91806 | 10.22 |
| 2026-02-17 00:00 | 18:44:18.63 | -18:07:25.3 | HIP 91806 | 16.54 |
| 2026-02-17 12:00 | 18:44:44.78 | -18:06:17.6 | HIP 92066 | 22.49 |
| 2026-02-18 00:00 | 18:45:10.84 | -18:05:09.5 | HIP 92066 | 19.49 |
| 2026-02-18 12:00 | 18:45:36.81 | -18:04:00.9 | HIP 92066 | 18.25 |
| 2026-02-19 00:00 | 18:46:02.70 | -18:02:51.9 | HIP 92066 | 19.11 |
| 2026-02-19 12:00 | 18:46:28.49 | -18:01:42.4 | HIP 92066 | 21.81 |
| 2026-02-20 00:00 | 18:46:54.20 | -18:00:32.5 | HIP 92245 | 20.16 |
| 2026-02-20 12:00 | 18:47:19.81 | -17:59:22.3 | HIP 92245 | 17.03 |
| 2026-02-21 00:00 | 18:47:45.33 | -17:58:11.6 | HIP 92245 | 15.84 |
| 2026-02-21 12:00 | 18:48:10.75 | -17:57:00.5 | HIP 92245 | 16.97 |
| 2026-02-22 00:00 | 18:48:36.08 | -17:55:48.9 | HIP 92245 | 20.02 |
| 2026-02-22 12:00 | 18:49:01.31 | -17:54:37.0 | HIP 92360 | 22.98 |
| 2026-02-23 00:00 | 18:49:26.44 | -17:53:24.7 | HIP 92492 | 23.21 |
| 2026-02-23 12:00 | 18:49:51.48 | -17:52:12.0 | HIP 92492 | 17.16 |
| 2026-02-24 00:00 | 18:50:16.42 | -17:50:58.8 | HIP 92492 | 11.16 |