C/2021 D1 (SWAN)
| Parameter |
Value |
| Designation |
C/2021 D1 (SWAN) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-02-27T14:36:45.581760Z |
| Orbit solution date (soln_date, UTC) |
2021-07-06T18:29:33Z |
| Obs used |
342 |
| NEO |
- |
| M1 |
13.300 |
| K1 |
14.500 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2021-02-28T17:29:51.648000Z |
| Discovery magnitude (MPC) |
14.60 R |
| Discovery observatory (MPC) |
K88 · GINOP-KHK, Piszkéstető |
Osculating Elements
| Parameter |
Value |
| Epoch (epoch_cal, TDB) |
2021-03-19.0000000 |
| e |
0.99064883 |
| q (au) |
0.901798 |
| a (au) |
96.436853 |
| i (deg) |
31.460781 |
| Ω (om, deg) |
311.271222 |
| ω (w, deg) |
72.222962 |
| M (ma, deg) |
0.020181 |
Magnitude
Scatter + Global Linear
$$
M_a = (14.258 + 5.845\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
Model Parameters
| Parameter |
Value |
| H0 |
14.258 |
| n |
5.845 |
| gf |
0.994 |
| gb |
-0.610 |
| 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 |
| 2021-02-28 |
2021-05-11 |
-0.4219 |
-0.927 |
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 |
11:02:18.48 |
-18:39:12.7 |
HIP 53809 |
31.69 |
| 2026-02-03 12:00 |
11:02:11.98 |
-18:39:08.5 |
HIP 53809 |
30.45 |
| 2026-02-04 00:00 |
11:02:05.43 |
-18:39:03.8 |
HIP 53809 |
29.23 |
| 2026-02-04 12:00 |
11:01:58.85 |
-18:38:58.4 |
HIP 53809 |
28.03 |
| 2026-02-05 00:00 |
11:01:52.24 |
-18:38:52.5 |
HIP 53809 |
26.85 |
| 2026-02-05 12:00 |
11:01:45.59 |
-18:38:45.9 |
HIP 53809 |
25.70 |
| 2026-02-06 00:00 |
11:01:38.90 |
-18:38:38.8 |
HIP 53809 |
24.59 |
| 2026-02-06 12:00 |
11:01:32.18 |
-18:38:31.1 |
HIP 53809 |
23.52 |
| 2026-02-07 00:00 |
11:01:25.43 |
-18:38:22.7 |
HIP 53809 |
22.50 |
| 2026-02-07 12:00 |
11:01:18.64 |
-18:38:13.8 |
HIP 53809 |
21.54 |
| 2026-02-08 00:00 |
11:01:11.82 |
-18:38:04.3 |
HIP 53809 |
20.64 |
| 2026-02-08 12:00 |
11:01:04.97 |
-18:37:54.2 |
HIP 53809 |
19.83 |
| 2026-02-09 00:00 |
11:00:58.09 |
-18:37:43.5 |
HIP 53809 |
19.11 |
| 2026-02-09 12:00 |
11:00:51.18 |
-18:37:32.2 |
HIP 53809 |
18.50 |
| 2026-02-10 00:00 |
11:00:44.24 |
-18:37:20.3 |
HIP 53809 |
18.01 |
| 2026-02-10 12:00 |
11:00:37.26 |
-18:37:07.8 |
HIP 53809 |
17.66 |
| 2026-02-11 00:00 |
11:00:30.27 |
-18:36:54.8 |
HIP 53809 |
17.44 |
| 2026-02-11 12:00 |
11:00:23.24 |
-18:36:41.1 |
HIP 53809 |
17.38 |
| 2026-02-12 00:00 |
11:00:16.18 |
-18:36:26.9 |
HIP 53809 |
17.47 |
| 2026-02-12 12:00 |
11:00:09.10 |
-18:36:12.1 |
HIP 53809 |
17.71 |
| 2026-02-13 00:00 |
11:00:02.00 |
-18:35:56.7 |
HIP 53809 |
18.10 |
| 2026-02-13 12:00 |
10:59:54.87 |
-18:35:40.7 |
HIP 53740 |
17.84 |
| 2026-02-14 00:00 |
10:59:47.71 |
-18:35:24.1 |
HIP 53740 |
17.46 |
| 2026-02-14 12:00 |
10:59:40.53 |
-18:35:07.0 |
HIP 53740 |
17.23 |
| 2026-02-15 00:00 |
10:59:33.33 |
-18:34:49.3 |
HIP 53740 |
17.17 |
| 2026-02-15 12:00 |
10:59:26.11 |
-18:34:31.0 |
HIP 53740 |
17.28 |
| 2026-02-16 00:00 |
10:59:18.86 |
-18:34:12.1 |
HIP 53740 |
17.55 |
| 2026-02-16 12:00 |
10:59:11.60 |
-18:33:52.7 |
HIP 53740 |
17.98 |
| 2026-02-17 00:00 |
10:59:04.31 |
-18:33:32.7 |
HIP 53740 |
18.56 |
| 2026-02-17 12:00 |
10:58:57.01 |
-18:33:12.1 |
HIP 53740 |
19.29 |
| 2026-02-18 00:00 |
10:58:49.68 |
-18:32:51.0 |
HIP 53740 |
20.13 |
| 2026-02-18 12:00 |
10:58:42.34 |
-18:32:29.3 |
HIP 53740 |
21.09 |
| 2026-02-19 00:00 |
10:58:34.98 |
-18:32:07.1 |
HIP 53740 |
22.15 |
| 2026-02-19 12:00 |
10:58:27.61 |
-18:31:44.3 |
HIP 53518 |
22.52 |
| 2026-02-20 00:00 |
10:58:20.22 |
-18:31:20.9 |
HIP 53518 |
20.74 |
| 2026-02-20 12:00 |
10:58:12.82 |
-18:30:57.0 |
HIP 53518 |
18.96 |
| 2026-02-21 00:00 |
10:58:05.40 |
-18:30:32.6 |
HIP 53518 |
17.18 |
| 2026-02-21 12:00 |
10:57:57.97 |
-18:30:07.6 |
HIP 53518 |
15.40 |
| 2026-02-22 00:00 |
10:57:50.53 |
-18:29:42.1 |
HIP 53518 |
13.63 |
| 2026-02-22 12:00 |
10:57:43.08 |
-18:29:16.0 |
HIP 53518 |
11.86 |
| 2026-02-23 00:00 |
10:57:35.61 |
-18:28:49.4 |
HIP 53518 |
10.12 |
| 2026-02-23 12:00 |
10:57:28.14 |
-18:28:22.3 |
HIP 53518 |
8.40 |
| 2026-02-24 00:00 |
10:57:20.66 |
-18:27:54.6 |
HIP 53518 |
6.75 |