C/2021 K1 (ATLAS)
| Parameter |
Value |
| Designation |
C/2021 K1 (ATLAS) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-05-04T13:50:34.362240Z |
| Orbit solution date (soln_date, UTC) |
2022-07-19T01:12:51Z |
| Obs used |
676 |
| NEO |
- |
| M1 |
6.600 |
| K1 |
19.000 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2021-05-24T14:32:49.718400Z |
| Discovery magnitude (MPC) |
16.39 o |
| Discovery observatory (MPC) |
T05 · ATLAS-HKO, Haleakala |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-08-19.0000000 |
| e |
0.80399384 |
| q (au) |
2.497832 |
| a (au) |
12.743639 |
| i (deg) |
16.276067 |
| Ω (om, deg) |
140.905656 |
| ω (w, deg) |
184.303821 |
| M (ma, deg) |
2.305686 |
Magnitude
Scatter + Global Linear
$$
M_a = (8.271 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
8.271 |
| n |
6.000 |
| gf |
0.800 |
| gb |
-0.840 |
| k |
0.995 |
| 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 |
| 2020-04-20 |
2020-08-12 |
-4.6047 |
+5.290 |
| 2021-05-14 |
2021-11-24 |
-4.0011 |
+1.844 |
| 2021-11-24 |
2022-01-31 |
-10.7283 |
+4.958 |
log10 r = log10(heliocentric distance / AU), Δ = geocentric distance (AU)
Ephemeris
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-02-03 00:00 |
06:53:16.67 |
+12:31:11.2 |
HIP 33204 |
20.61 |
| 2026-02-03 12:00 |
06:53:09.08 |
+12:31:44.2 |
HIP 33204 |
22.53 |
| 2026-02-04 00:00 |
06:53:01.56 |
+12:32:17.3 |
HIP 32969 |
23.10 |
| 2026-02-04 12:00 |
06:52:54.10 |
+12:32:50.4 |
HIP 32969 |
22.44 |
| 2026-02-05 00:00 |
06:52:46.70 |
+12:33:23.7 |
HIP 32969 |
21.93 |
| 2026-02-05 12:00 |
06:52:39.36 |
+12:33:57.0 |
HIP 32969 |
21.58 |
| 2026-02-06 00:00 |
06:52:32.09 |
+12:34:30.5 |
HIP 32969 |
21.40 |
| 2026-02-06 12:00 |
06:52:24.88 |
+12:35:04.0 |
HIP 32969 |
21.39 |
| 2026-02-07 00:00 |
06:52:17.74 |
+12:35:37.6 |
HIP 32969 |
21.54 |
| 2026-02-07 12:00 |
06:52:10.66 |
+12:36:11.3 |
HIP 32969 |
21.85 |
| 2026-02-08 00:00 |
06:52:03.65 |
+12:36:45.1 |
HIP 32969 |
22.30 |
| 2026-02-08 12:00 |
06:51:56.71 |
+12:37:18.9 |
HIP 32969 |
22.89 |
| 2026-02-09 00:00 |
06:51:49.84 |
+12:37:52.8 |
HIP 32969 |
23.59 |
| 2026-02-09 12:00 |
06:51:43.03 |
+12:38:26.8 |
HIP 32969 |
24.41 |
| 2026-02-10 00:00 |
06:51:36.30 |
+12:39:00.9 |
HIP 32969 |
25.31 |
| 2026-02-10 12:00 |
06:51:29.64 |
+12:39:35.0 |
HIP 32969 |
26.30 |
| 2026-02-11 00:00 |
06:51:23.04 |
+12:40:09.2 |
HIP 32969 |
27.35 |
| 2026-02-11 12:00 |
06:51:16.52 |
+12:40:43.5 |
HIP 32969 |
28.46 |
| 2026-02-12 00:00 |
06:51:10.07 |
+12:41:17.8 |
HIP 32969 |
29.62 |
| 2026-02-12 12:00 |
06:51:03.70 |
+12:41:52.2 |
HIP 32969 |
30.82 |
| 2026-02-13 00:00 |
06:50:57.39 |
+12:42:26.6 |
HIP 32969 |
32.05 |
| 2026-02-13 12:00 |
06:50:51.16 |
+12:43:01.1 |
HIP 32660 |
32.23 |
| 2026-02-14 00:00 |
06:50:45.01 |
+12:43:35.6 |
HIP 32660 |
30.97 |
| 2026-02-14 12:00 |
06:50:38.93 |
+12:44:10.2 |
HIP 32660 |
29.76 |
| 2026-02-15 00:00 |
06:50:32.93 |
+12:44:44.8 |
HIP 32660 |
28.61 |
| 2026-02-15 12:00 |
06:50:27.01 |
+12:45:19.5 |
HIP 32660 |
27.52 |
| 2026-02-16 00:00 |
06:50:21.16 |
+12:45:54.1 |
HIP 32660 |
26.49 |
| 2026-02-16 12:00 |
06:50:15.39 |
+12:46:28.9 |
HIP 32660 |
25.52 |
| 2026-02-17 00:00 |
06:50:09.70 |
+12:47:03.6 |
HIP 32660 |
24.63 |
| 2026-02-17 12:00 |
06:50:04.09 |
+12:47:38.4 |
HIP 32660 |
23.82 |
| 2026-02-18 00:00 |
06:49:58.55 |
+12:48:13.2 |
HIP 32660 |
23.09 |
| 2026-02-18 12:00 |
06:49:53.10 |
+12:48:48.0 |
HIP 32660 |
22.45 |
| 2026-02-19 00:00 |
06:49:47.73 |
+12:49:22.9 |
HIP 32660 |
21.90 |
| 2026-02-19 12:00 |
06:49:42.44 |
+12:49:57.7 |
HIP 32660 |
21.45 |
| 2026-02-20 00:00 |
06:49:37.23 |
+12:50:32.6 |
HIP 32726 |
20.89 |
| 2026-02-20 12:00 |
06:49:32.10 |
+12:51:07.5 |
HIP 32726 |
20.33 |
| 2026-02-21 00:00 |
06:49:27.06 |
+12:51:42.4 |
HIP 32726 |
19.85 |
| 2026-02-21 12:00 |
06:49:22.10 |
+12:52:17.3 |
HIP 32726 |
19.45 |
| 2026-02-22 00:00 |
06:49:17.22 |
+12:52:52.2 |
HIP 32726 |
19.13 |
| 2026-02-22 12:00 |
06:49:12.42 |
+12:53:27.1 |
HIP 32726 |
18.90 |
| 2026-02-23 00:00 |
06:49:07.71 |
+12:54:02.0 |
HIP 32726 |
18.74 |
| 2026-02-23 12:00 |
06:49:03.08 |
+12:54:36.9 |
HIP 32726 |
18.66 |
| 2026-02-24 00:00 |
06:48:58.54 |
+12:55:11.7 |
HIP 32726 |
18.66 |