メタデータ
| 項目 |
値 |
| Designation |
C/2021 A4 (NEOWISE) |
| Type |
C |
| Perihelion (tp_cal, UTC) |
2021-03-20T00:53:23.712000Z |
| Orbit solution date (soln_date, UTC) |
2022-03-08T19:43:19Z |
| Obs used |
683 |
| NEO |
- |
| M1 |
13.600 |
| K1 |
28.500 |
| PC |
0.030 |
| Discovery observation (MPC, UTC) |
2021-01-03T22:02:49.632000Z |
| Discovery magnitude (MPC) |
20.00 R |
| Discovery observatory (MPC) |
C51 · WISE |
オスキュレーティング軌道要素
| 項目 |
値 |
| Epoch (epoch_cal, TDB) |
2021-02-16.0000000 |
| e |
0.97324748 |
| q (au) |
1.145476 |
| a (au) |
42.817518 |
| i (deg) |
111.569834 |
| Ω (om, deg) |
307.084762 |
| ω (w, deg) |
204.665566 |
| M (ma, deg) |
359.887300 |
等級
散乱 + 全体線形
$$
M_a = (14.236 + 6.000\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta
$$
$$
\theta = 180^\circ - \alpha
$$
$$
\Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b)
$$
$$
\Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1
$$
モデル定数
| 項目 |
値 |
| H0 |
14.236 |
| n |
6.000 |
| 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 |
| 2021-01-03 |
2021-03-19 |
+14.1648 |
-1.643 |
| 2021-03-21 |
2021-07-07 |
-3.2765 |
-1.725 |
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) |
| 2026-05-12 00:00 |
21:05:18.85 |
-21:05:45.2 |
HIP 103967 |
28.92 |
| 2026-05-12 12:00 |
21:05:17.22 |
-21:05:49.5 |
HIP 103967 |
28.71 |
| 2026-05-13 00:00 |
21:05:15.51 |
-21:05:54.1 |
HIP 103967 |
28.50 |
| 2026-05-13 12:00 |
21:05:13.74 |
-21:05:58.9 |
HIP 103967 |
28.28 |
| 2026-05-14 00:00 |
21:05:11.89 |
-21:06:04.1 |
HIP 103967 |
28.06 |
| 2026-05-14 12:00 |
21:05:09.98 |
-21:06:09.5 |
HIP 103967 |
27.83 |
| 2026-05-15 00:00 |
21:05:07.99 |
-21:06:15.1 |
HIP 103967 |
27.61 |
| 2026-05-15 12:00 |
21:05:05.94 |
-21:06:21.1 |
HIP 103967 |
27.39 |
| 2026-05-16 00:00 |
21:05:03.82 |
-21:06:27.3 |
HIP 103967 |
27.16 |
| 2026-05-16 12:00 |
21:05:01.62 |
-21:06:33.9 |
HIP 103967 |
26.94 |
| 2026-05-17 00:00 |
21:04:59.36 |
-21:06:40.6 |
HIP 103967 |
26.72 |
| 2026-05-17 12:00 |
21:04:57.02 |
-21:06:47.7 |
HIP 103967 |
26.51 |
| 2026-05-18 00:00 |
21:04:54.62 |
-21:06:55.0 |
HIP 103967 |
26.30 |
| 2026-05-18 12:00 |
21:04:52.15 |
-21:07:02.6 |
HIP 103967 |
26.10 |
| 2026-05-19 00:00 |
21:04:49.60 |
-21:07:10.5 |
HIP 103967 |
25.90 |
| 2026-05-19 12:00 |
21:04:46.99 |
-21:07:18.6 |
HIP 103967 |
25.71 |
| 2026-05-20 00:00 |
21:04:44.31 |
-21:07:27.0 |
HIP 103967 |
25.53 |
| 2026-05-20 12:00 |
21:04:41.56 |
-21:07:35.7 |
HIP 103967 |
25.37 |
| 2026-05-21 00:00 |
21:04:38.74 |
-21:07:44.6 |
HIP 103967 |
25.22 |
| 2026-05-21 12:00 |
21:04:35.85 |
-21:07:53.8 |
HIP 103967 |
25.08 |
| 2026-05-22 00:00 |
21:04:32.89 |
-21:08:03.2 |
HIP 103967 |
24.96 |
| 2026-05-22 12:00 |
21:04:29.86 |
-21:08:13.0 |
HIP 103967 |
24.86 |
| 2026-05-23 00:00 |
21:04:26.77 |
-21:08:22.9 |
HIP 103967 |
24.77 |
| 2026-05-23 12:00 |
21:04:23.60 |
-21:08:33.1 |
HIP 103967 |
24.71 |
| 2026-05-24 00:00 |
21:04:20.37 |
-21:08:43.6 |
HIP 103967 |
24.67 |
| 2026-05-24 12:00 |
21:04:17.07 |
-21:08:54.3 |
HIP 103967 |
24.66 |
| 2026-05-25 00:00 |
21:04:13.70 |
-21:09:05.3 |
HIP 103967 |
24.67 |
| 2026-05-25 12:00 |
21:04:10.27 |
-21:09:16.5 |
HIP 103967 |
24.71 |
| 2026-05-26 00:00 |
21:04:06.77 |
-21:09:28.0 |
HIP 103967 |
24.78 |
| 2026-05-26 12:00 |
21:04:03.20 |
-21:09:39.7 |
HIP 103927 |
24.33 |
| 2026-05-27 00:00 |
21:03:59.56 |
-21:09:51.6 |
HIP 103927 |
23.84 |
| 2026-05-27 12:00 |
21:03:55.86 |
-21:10:03.8 |
HIP 103927 |
23.36 |
| 2026-05-28 00:00 |
21:03:52.09 |
-21:10:16.2 |
HIP 103927 |
22.90 |
| 2026-05-28 12:00 |
21:03:48.25 |
-21:10:28.9 |
HIP 103927 |
22.45 |
| 2026-05-29 00:00 |
21:03:44.35 |
-21:10:41.8 |
HIP 103927 |
22.03 |
| 2026-05-29 12:00 |
21:03:40.38 |
-21:10:54.9 |
HIP 103927 |
21.64 |
| 2026-05-30 00:00 |
21:03:36.34 |
-21:11:08.3 |
HIP 103927 |
21.27 |
| 2026-05-30 12:00 |
21:03:32.24 |
-21:11:21.9 |
HIP 103927 |
20.94 |
| 2026-05-31 00:00 |
21:03:28.07 |
-21:11:35.7 |
HIP 103808 |
20.49 |
| 2026-05-31 12:00 |
21:03:23.84 |
-21:11:49.8 |
HIP 103808 |
19.50 |
| 2026-06-01 00:00 |
21:03:19.54 |
-21:12:04.1 |
HIP 103808 |
18.49 |
| 2026-06-01 12:00 |
21:03:15.18 |
-21:12:18.6 |
HIP 103808 |
17.47 |
| 2026-06-02 00:00 |
21:03:10.76 |
-21:12:33.3 |
HIP 103808 |
16.43 |