| 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 |
1.000 |
| 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) |
| 2026-07-29 00:00 |
10:49:38.26 |
-15:28:33.5 |
HIP 52990 |
25.08 |
| 2026-07-29 12:00 |
10:49:44.20 |
-15:28:47.8 |
HIP 52990 |
24.68 |
| 2026-07-30 00:00 |
10:49:50.17 |
-15:29:02.6 |
HIP 52990 |
24.36 |
| 2026-07-30 12:00 |
10:49:56.16 |
-15:29:17.7 |
HIP 52990 |
24.13 |
| 2026-07-31 00:00 |
10:50:02.18 |
-15:29:33.3 |
HIP 52990 |
24.00 |
| 2026-07-31 12:00 |
10:50:08.22 |
-15:29:49.3 |
HIP 52990 |
23.96 |
| 2026-08-01 00:00 |
10:50:14.29 |
-15:30:05.8 |
HIP 52990 |
24.02 |
| 2026-08-01 12:00 |
10:50:20.38 |
-15:30:22.6 |
HIP 52990 |
24.17 |
| 2026-08-02 00:00 |
10:50:26.50 |
-15:30:39.9 |
HIP 52990 |
24.43 |
| 2026-08-02 12:00 |
10:50:32.65 |
-15:30:57.6 |
HIP 52990 |
24.78 |
| 2026-08-03 00:00 |
10:50:38.81 |
-15:31:15.8 |
HIP 53088 |
24.43 |
| 2026-08-03 12:00 |
10:50:45.00 |
-15:31:34.3 |
HIP 53088 |
23.31 |
| 2026-08-04 00:00 |
10:50:51.22 |
-15:31:53.3 |
HIP 53088 |
22.23 |
| 2026-08-04 12:00 |
10:50:57.45 |
-15:32:12.7 |
HIP 53088 |
21.20 |
| 2026-08-05 00:00 |
10:51:03.71 |
-15:32:32.5 |
HIP 53088 |
20.22 |
| 2026-08-05 12:00 |
10:51:09.99 |
-15:32:52.8 |
HIP 53088 |
19.31 |
| 2026-08-06 00:00 |
10:51:16.29 |
-15:33:13.4 |
HIP 53088 |
18.47 |
| 2026-08-06 12:00 |
10:51:22.62 |
-15:33:34.5 |
HIP 53088 |
17.73 |
| 2026-08-07 00:00 |
10:51:28.96 |
-15:33:55.9 |
HIP 53088 |
17.08 |
| 2026-08-07 12:00 |
10:51:35.33 |
-15:34:17.8 |
HIP 53088 |
16.56 |
| 2026-08-08 00:00 |
10:51:41.71 |
-15:34:40.1 |
HIP 53088 |
16.16 |
| 2026-08-08 12:00 |
10:51:48.12 |
-15:35:02.8 |
HIP 53088 |
15.90 |
| 2026-08-09 00:00 |
10:51:54.54 |
-15:35:26.0 |
HIP 53088 |
15.80 |
| 2026-08-09 12:00 |
10:52:00.99 |
-15:35:49.5 |
HIP 53088 |
15.85 |
| 2026-08-10 00:00 |
10:52:07.45 |
-15:36:13.4 |
HIP 53088 |
16.06 |
| 2026-08-10 12:00 |
10:52:13.94 |
-15:36:37.8 |
HIP 53228 |
15.66 |
| 2026-08-11 00:00 |
10:52:20.44 |
-15:37:02.5 |
HIP 53228 |
14.35 |
| 2026-08-11 12:00 |
10:52:26.96 |
-15:37:27.7 |
HIP 53228 |
13.10 |
| 2026-08-12 00:00 |
10:52:33.49 |
-15:37:53.2 |
HIP 53228 |
11.94 |
| 2026-08-12 12:00 |
10:52:40.04 |
-15:38:19.2 |
HIP 53228 |
10.91 |
| 2026-08-13 00:00 |
10:52:46.61 |
-15:38:45.5 |
HIP 53228 |
10.04 |
| 2026-08-13 12:00 |
10:52:53.20 |
-15:39:12.3 |
HIP 53228 |
9.38 |
| 2026-08-14 00:00 |
10:52:59.80 |
-15:39:39.4 |
HIP 53228 |
8.99 |
| 2026-08-14 12:00 |
10:53:06.42 |
-15:40:06.9 |
HIP 53228 |
8.89 |
| 2026-08-15 00:00 |
10:53:13.05 |
-15:40:34.9 |
HIP 53228 |
9.11 |
| 2026-08-15 12:00 |
10:53:19.69 |
-15:41:03.2 |
HIP 53250 |
8.42 |
| 2026-08-16 00:00 |
10:53:26.35 |
-15:41:31.9 |
HIP 53250 |
7.71 |
| 2026-08-16 12:00 |
10:53:33.03 |
-15:42:01.0 |
HIP 53250 |
7.33 |
| 2026-08-17 00:00 |
10:53:39.71 |
-15:42:30.4 |
HIP 53250 |
7.31 |
| 2026-08-17 12:00 |
10:53:46.41 |
-15:43:00.3 |
HIP 53250 |
7.67 |
| 2026-08-18 00:00 |
10:53:53.13 |
-15:43:30.5 |
HIP 53250 |
8.36 |
| 2026-08-18 12:00 |
10:53:59.85 |
-15:44:01.1 |
HIP 53250 |
9.30 |
| 2026-08-19 00:00 |
10:54:06.58 |
-15:44:32.1 |
HIP 53250 |
10.44 |