メタデータ

項目	値
Designation	C/2025 R2 (SWAN)
Type	C
Perihelion (tp_cal, UTC)	2025-09-12T20:18:10.952640Z
Orbit solution date (soln_date, UTC)	2026-07-06T12:12:28Z
Obs used	2441
NEO	-
M1	13.900
K1	9.500
PC	-
Discovery observation (MPC, UTC)	2025-09-11T23:33:15.552000Z
Discovery magnitude (MPC)	7.50 V
Discovery observatory (MPC)	247 · Roving Observer

オスキュレーティング軌道要素

項目	値
Epoch (epoch_cal, TDB)	2025-11-12.0000000
e	0.99419572
q (au)	0.504085
a (au)	86.846983
i (deg)	4.472975
Ω (om, deg)	335.326008
ω (w, deg)	308.358635
M (ma, deg)	0.073255

等級

散乱 + 全体線形

$$ M_a = (12.783 + 5.090\cdot 2.5\log_{10} r) + \epsilon - 2.5\log_{10}\Phi(\theta) + 5\log_{10}\Delta $$ $$ \theta = 180^\circ - \alpha $$ $$ \Phi(\theta) = \frac{\delta_{90} D(\theta) + 1}{\delta_{90} + 1},\quad D(\theta) = k\cdot \Phi_{HG}(\theta; g_f) + (1-k)\cdot \Phi_{HG}(\theta; g_b) $$ $$ \Phi_{HG}(\theta; g) = \left(\frac{1+g^2}{1+g^2-2g\cos\theta}\right)^{3/2},\quad \Phi_{HG}(90^\circ)=1 $$

モデル定数

項目	値
H0	12.783
n	5.090
gf	1.000
gb	-0.999
k	0.936
δ90	9.997

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
2025-09-12	2026-03-09	-1.8779	-0.979

log10 r = log10(太陽距離/AU)、Δ = 地球距離(AU)

ファインディングチャート

天体暦

Date/Time (UTC)	RA (J2000)	Dec (J2000)	Nearest HIP	Dist from HIP (arcmin)
2026-09-25 00:00	05:09:50.38	+27:42:26.0	HIP 24035	4.46
2026-09-25 12:00	05:09:45.91	+27:42:47.8	HIP 24035	5.32
2026-09-26 00:00	05:09:41.21	+27:43:09.2	HIP 24035	6.28
2026-09-26 12:00	05:09:36.28	+27:43:30.4	HIP 24035	7.30
2026-09-27 00:00	05:09:31.13	+27:43:51.2	HIP 24035	8.40
2026-09-27 12:00	05:09:25.75	+27:44:11.8	HIP 24035	9.55
2026-09-28 00:00	05:09:20.14	+27:44:32.0	HIP 24035	10.77
2026-09-28 12:00	05:09:14.30	+27:44:51.9	HIP 24035	12.04
2026-09-29 00:00	05:09:08.24	+27:45:11.5	HIP 24035	13.36
2026-09-29 12:00	05:09:01.94	+27:45:30.7	HIP 24035	14.73
2026-09-30 00:00	05:08:55.42	+27:45:49.6	HIP 24035	16.16
2026-09-30 12:00	05:08:48.67	+27:46:08.2	HIP 24035	17.64
2026-10-01 00:00	05:08:41.70	+27:46:26.5	HIP 24035	19.17
2026-10-01 12:00	05:08:34.50	+27:46:44.4	HIP 24035	20.75
2026-10-02 00:00	05:08:27.07	+27:47:02.0	HIP 24035	22.38
2026-10-02 12:00	05:08:19.41	+27:47:19.2	HIP 24019	23.85
2026-10-03 00:00	05:08:11.53	+27:47:36.0	HIP 24019	25.09
2026-10-03 12:00	05:08:03.41	+27:47:52.5	HIP 24019	26.44
2026-10-04 00:00	05:07:55.08	+27:48:08.6	HIP 24019	27.89
2026-10-04 12:00	05:07:46.51	+27:48:24.4	HIP 24019	29.43
2026-10-05 00:00	05:07:37.72	+27:48:39.8	HIP 23721	28.56
2026-10-05 12:00	05:07:28.71	+27:48:54.7	HIP 23721	26.91
2026-10-06 00:00	05:07:19.47	+27:49:09.3	HIP 23721	25.28
2026-10-06 12:00	05:07:10.01	+27:49:23.6	HIP 23721	23.69
2026-10-07 00:00	05:07:00.32	+27:49:37.4	HIP 23721	22.17
2026-10-07 12:00	05:06:50.40	+27:49:50.8	HIP 23721	20.73
2026-10-08 00:00	05:06:40.27	+27:50:03.8	HIP 23721	19.42
2026-10-08 12:00	05:06:29.91	+27:50:16.4	HIP 23721	18.28
2026-10-09 00:00	05:06:19.33	+27:50:28.6	HIP 23721	17.36
2026-10-09 12:00	05:06:08.53	+27:50:40.3	HIP 23721	16.73
2026-10-10 00:00	05:05:57.51	+27:50:51.7	HIP 23721	16.43
2026-10-10 12:00	05:05:46.27	+27:51:02.6	HIP 23721	16.51
2026-10-11 00:00	05:05:34.81	+27:51:13.0	HIP 23614	15.73
2026-10-11 12:00	05:05:23.14	+27:51:23.1	HIP 23614	13.87
2026-10-12 00:00	05:05:11.25	+27:51:32.6	HIP 23614	12.24
2026-10-12 12:00	05:04:59.14	+27:51:41.8	HIP 23614	10.98
2026-10-13 00:00	05:04:46.82	+27:51:50.4	HIP 23614	10.26
2026-10-13 12:00	05:04:34.29	+27:51:58.6	HIP 23614	10.24
2026-10-14 00:00	05:04:21.55	+27:52:06.4	HIP 23614	10.96
2026-10-14 12:00	05:04:08.59	+27:52:13.7	HIP 23614	12.31
2026-10-15 00:00	05:03:55.43	+27:52:20.5	HIP 23614	14.15
2026-10-15 12:00	05:03:42.06	+27:52:26.8	HIP 23614	16.33
2026-10-16 00:00	05:03:28.48	+27:52:32.6	HIP 23614	18.77