| 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) |
| 2026-05-12 00:00 |
10:43:00.24 |
-16:20:53.3 |
HIP 52364 |
19.81 |
| 2026-05-12 12:00 |
10:42:58.47 |
-16:20:03.4 |
HIP 52364 |
18.90 |
| 2026-05-13 00:00 |
10:42:56.76 |
-16:19:13.8 |
HIP 52364 |
18.00 |
| 2026-05-13 12:00 |
10:42:55.11 |
-16:18:24.5 |
HIP 52364 |
17.12 |
| 2026-05-14 00:00 |
10:42:53.53 |
-16:17:35.4 |
HIP 52364 |
16.26 |
| 2026-05-14 12:00 |
10:42:52.01 |
-16:16:46.6 |
HIP 52364 |
15.41 |
| 2026-05-15 00:00 |
10:42:50.55 |
-16:15:58.1 |
HIP 52364 |
14.58 |
| 2026-05-15 12:00 |
10:42:49.15 |
-16:15:09.8 |
HIP 52364 |
13.78 |
| 2026-05-16 00:00 |
10:42:47.82 |
-16:14:21.9 |
HIP 52364 |
12.99 |
| 2026-05-16 12:00 |
10:42:46.55 |
-16:13:34.2 |
HIP 52364 |
12.23 |
| 2026-05-17 00:00 |
10:42:45.34 |
-16:12:46.8 |
HIP 52364 |
11.50 |
| 2026-05-17 12:00 |
10:42:44.20 |
-16:11:59.7 |
HIP 52364 |
10.80 |
| 2026-05-18 00:00 |
10:42:43.12 |
-16:11:12.9 |
HIP 52364 |
10.14 |
| 2026-05-18 12:00 |
10:42:42.10 |
-16:10:26.4 |
HIP 52364 |
9.51 |
| 2026-05-19 00:00 |
10:42:41.14 |
-16:09:40.2 |
HIP 52364 |
8.93 |
| 2026-05-19 12:00 |
10:42:40.25 |
-16:08:54.3 |
HIP 52364 |
8.41 |
| 2026-05-20 00:00 |
10:42:39.42 |
-16:08:08.7 |
HIP 52364 |
7.94 |
| 2026-05-20 12:00 |
10:42:38.65 |
-16:07:23.5 |
HIP 52364 |
7.55 |
| 2026-05-21 00:00 |
10:42:37.95 |
-16:06:38.5 |
HIP 52364 |
7.23 |
| 2026-05-21 12:00 |
10:42:37.30 |
-16:05:53.9 |
HIP 52364 |
6.99 |
| 2026-05-22 00:00 |
10:42:36.72 |
-16:05:09.6 |
HIP 52364 |
6.85 |
| 2026-05-22 12:00 |
10:42:36.20 |
-16:04:25.7 |
HIP 52364 |
6.80 |
| 2026-05-23 00:00 |
10:42:35.75 |
-16:03:42.0 |
HIP 52364 |
6.85 |
| 2026-05-23 12:00 |
10:42:35.35 |
-16:02:58.7 |
HIP 52364 |
6.99 |
| 2026-05-24 00:00 |
10:42:35.02 |
-16:02:15.8 |
HIP 52364 |
7.21 |
| 2026-05-24 12:00 |
10:42:34.75 |
-16:01:33.2 |
HIP 52364 |
7.50 |
| 2026-05-25 00:00 |
10:42:34.54 |
-16:00:50.9 |
HIP 52364 |
7.85 |
| 2026-05-25 12:00 |
10:42:34.39 |
-16:00:09.0 |
HIP 52364 |
8.26 |
| 2026-05-26 00:00 |
10:42:34.31 |
-15:59:27.4 |
HIP 52364 |
8.71 |
| 2026-05-26 12:00 |
10:42:34.28 |
-15:58:46.2 |
HIP 52364 |
9.19 |
| 2026-05-27 00:00 |
10:42:34.32 |
-15:58:05.3 |
HIP 52364 |
9.71 |
| 2026-05-27 12:00 |
10:42:34.41 |
-15:57:24.8 |
HIP 52364 |
10.25 |
| 2026-05-28 00:00 |
10:42:34.57 |
-15:56:44.6 |
HIP 52364 |
10.81 |
| 2026-05-28 12:00 |
10:42:34.79 |
-15:56:04.8 |
HIP 52364 |
11.38 |
| 2026-05-29 00:00 |
10:42:35.07 |
-15:55:25.4 |
HIP 52364 |
11.97 |
| 2026-05-29 12:00 |
10:42:35.41 |
-15:54:46.3 |
HIP 52364 |
12.56 |
| 2026-05-30 00:00 |
10:42:35.80 |
-15:54:07.6 |
HIP 52364 |
13.17 |
| 2026-05-30 12:00 |
10:42:36.26 |
-15:53:29.3 |
HIP 52364 |
13.78 |
| 2026-05-31 00:00 |
10:42:36.78 |
-15:52:51.3 |
HIP 52364 |
14.39 |
| 2026-05-31 12:00 |
10:42:37.36 |
-15:52:13.7 |
HIP 52364 |
15.01 |
| 2026-06-01 00:00 |
10:42:38.00 |
-15:51:36.5 |
HIP 52364 |
15.63 |
| 2026-06-01 12:00 |
10:42:38.70 |
-15:50:59.7 |
HIP 52364 |
16.25 |
| 2026-06-02 00:00 |
10:42:39.46 |
-15:50:23.2 |
HIP 52364 |
16.88 |