メタデータ
| 項目 |
値 |
| Designation |
C/2020 A2 (Iwamoto) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2020-01-08T07:41:43.028160Z |
| Orbit solution date (soln_date, UTC) |
2022-12-31T16:12:34Z |
| Obs used |
529 |
| NEO |
- |
| M1 |
15.100 |
| K1 |
10.750 |
| PC |
0.030 |
オスキュレーティング軌道要素
| 項目 |
値 |
| Epoch (epoch_cal, TDB) |
2020-02-23.0000000 |
| e |
0.99907770 |
| q (au) |
0.978012 |
| a (au) |
1060.410619 |
| i (deg) |
120.750132 |
| Ω (om, deg) |
286.379413 |
| ω (w, deg) |
68.209203 |
| M (ma, deg) |
0.001304 |
等級
散乱 + 全体線形
$$
M_a = (11.896 + 2.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
モデル定数
| 項目 |
値 |
| H0 |
11.896 |
| n |
2.000 |
| gf |
1.000 |
| gb |
-0.500 |
| k |
1.000 |
| δ90 |
10.000 |
| パラメータ |
記号 |
範囲 |
説明 |
| 太陽・地球距離が1 AUのときの絶対等級 |
H0 |
-5 to 20 |
彗星の固有の明るさ |
| 測光スロープパラメータ |
n |
2 to 6 |
太陽距離に対する明るさ変化率 |
| 前方散乱非対称係数 |
gf |
0.8 to 1 |
前方散乱の強さ |
| 後方散乱非対称係数 |
gb |
-1 to -0.5 |
後方散乱の強さ |
| 分配係数 |
k |
0.8 to 1 |
前方/後方散乱の寄与比 |
| ダスト/ガス明るさ比 |
δ90 |
1 to 10 |
ダスト散乱とガス放射の相対寄与 |
参考: EPSC-DPS2025-160
残差 (区間線形)
$$\epsilon = a \log_{10} r_{\mathrm{au}} + b$$
| 開始日 (UTC) |
終了日 (UTC) |
a |
b |
| 2020-01-08 |
2020-03-22 |
-3.5046 |
-0.515 |
| 2020-03-22 |
2020-04-15 |
+14.5888 |
-2.691 |
log10 r = log10(太陽距離/AU)、Δ = 地球距離(AU)
天体暦
| Date/Time (UTC) |
RA (J2000) |
Dec (J2000) |
Nearest HIP |
Dist from HIP (arcmin) |
| 2026-07-29 00:00 |
05:40:45.28 |
-10:24:19.6 |
HIP 26728 |
0.30 |
| 2026-07-29 12:00 |
05:40:49.59 |
-10:24:56.7 |
HIP 26728 |
0.94 |
| 2026-07-30 00:00 |
05:40:53.87 |
-10:25:34.1 |
HIP 26728 |
2.16 |
| 2026-07-30 12:00 |
05:40:58.12 |
-10:26:11.9 |
HIP 26728 |
3.38 |
| 2026-07-31 00:00 |
05:41:02.34 |
-10:26:50.0 |
HIP 26728 |
4.60 |
| 2026-07-31 12:00 |
05:41:06.53 |
-10:27:28.4 |
HIP 26728 |
5.81 |
| 2026-08-01 00:00 |
05:41:10.68 |
-10:28:07.2 |
HIP 26728 |
7.01 |
| 2026-08-01 12:00 |
05:41:14.79 |
-10:28:46.3 |
HIP 26728 |
8.22 |
| 2026-08-02 00:00 |
05:41:18.88 |
-10:29:25.8 |
HIP 26728 |
9.42 |
| 2026-08-02 12:00 |
05:41:22.93 |
-10:30:05.5 |
HIP 26728 |
10.61 |
| 2026-08-03 00:00 |
05:41:26.94 |
-10:30:45.6 |
HIP 26728 |
11.80 |
| 2026-08-03 12:00 |
05:41:30.92 |
-10:31:26.0 |
HIP 26728 |
12.99 |
| 2026-08-04 00:00 |
05:41:34.86 |
-10:32:06.8 |
HIP 26728 |
14.17 |
| 2026-08-04 12:00 |
05:41:38.77 |
-10:32:47.9 |
HIP 26894 |
14.39 |
| 2026-08-05 00:00 |
05:41:42.64 |
-10:33:29.3 |
HIP 26894 |
13.26 |
| 2026-08-05 12:00 |
05:41:46.48 |
-10:34:11.0 |
HIP 26894 |
12.15 |
| 2026-08-06 00:00 |
05:41:50.28 |
-10:34:53.0 |
HIP 26894 |
11.06 |
| 2026-08-06 12:00 |
05:41:54.04 |
-10:35:35.3 |
HIP 26894 |
9.99 |
| 2026-08-07 00:00 |
05:41:57.77 |
-10:36:18.0 |
HIP 26894 |
8.96 |
| 2026-08-07 12:00 |
05:42:01.46 |
-10:37:01.0 |
HIP 26894 |
7.97 |
| 2026-08-08 00:00 |
05:42:05.11 |
-10:37:44.2 |
HIP 26894 |
7.04 |
| 2026-08-08 12:00 |
05:42:08.72 |
-10:38:27.8 |
HIP 26894 |
6.20 |
| 2026-08-09 00:00 |
05:42:12.30 |
-10:39:11.7 |
HIP 26894 |
5.47 |
| 2026-08-09 12:00 |
05:42:15.83 |
-10:39:55.9 |
HIP 26894 |
4.92 |
| 2026-08-10 00:00 |
05:42:19.33 |
-10:40:40.4 |
HIP 26894 |
4.61 |
| 2026-08-10 12:00 |
05:42:22.79 |
-10:41:25.3 |
HIP 26894 |
4.57 |
| 2026-08-11 00:00 |
05:42:26.20 |
-10:42:10.4 |
HIP 26894 |
4.82 |
| 2026-08-11 12:00 |
05:42:29.58 |
-10:42:55.8 |
HIP 26894 |
5.30 |
| 2026-08-12 00:00 |
05:42:32.92 |
-10:43:41.4 |
HIP 26894 |
5.96 |
| 2026-08-12 12:00 |
05:42:36.22 |
-10:44:27.4 |
HIP 26894 |
6.75 |
| 2026-08-13 00:00 |
05:42:39.47 |
-10:45:13.7 |
HIP 26894 |
7.63 |
| 2026-08-13 12:00 |
05:42:42.69 |
-10:46:00.3 |
HIP 26894 |
8.56 |
| 2026-08-14 00:00 |
05:42:45.86 |
-10:46:47.1 |
HIP 26962 |
8.92 |
| 2026-08-14 12:00 |
05:42:48.99 |
-10:47:34.2 |
HIP 26962 |
8.66 |
| 2026-08-15 00:00 |
05:42:52.08 |
-10:48:21.6 |
HIP 26962 |
8.54 |
| 2026-08-15 12:00 |
05:42:55.13 |
-10:49:09.3 |
HIP 26962 |
8.57 |
| 2026-08-16 00:00 |
05:42:58.13 |
-10:49:57.2 |
HIP 26962 |
8.74 |
| 2026-08-16 12:00 |
05:43:01.09 |
-10:50:45.4 |
HIP 26962 |
9.06 |
| 2026-08-17 00:00 |
05:43:04.01 |
-10:51:33.9 |
HIP 26962 |
9.49 |
| 2026-08-17 12:00 |
05:43:06.88 |
-10:52:22.6 |
HIP 26962 |
10.04 |
| 2026-08-18 00:00 |
05:43:09.72 |
-10:53:11.6 |
HIP 26962 |
10.66 |
| 2026-08-18 12:00 |
05:43:12.50 |
-10:54:00.9 |
HIP 26962 |
11.37 |
| 2026-08-19 00:00 |
05:43:15.25 |
-10:54:50.4 |
HIP 26962 |
12.13 |