Comet C/2019 K5 (Young) David Young (天体物理学研究センター, Queen's大学, Belfast)の通報によると、5月25.6日UT、 Mauna Loaにある小惑星地球衝突最終警報システム Asteroid Terrestrial-impact Last Alert System (ATLAS)調査プログラムのコースに0.5-m 反射望遠鏡で得たCCD画像から彗星を発見した。 30秒露出4枚のスタックでは、コマのFWHM (半値全幅)は近傍の恒星の5".7より大きく8".2であった。 南西に約19" かすかに拡張している。 小惑星センターのPCCP webpageに公表後、佐藤英貴氏(東京都文京区, iTelescope 天文台, 0.51- m f/6.8 アストログラフ, Siding Spring, 遠隔操作: 5月25.8日UT、60秒露出8枚のスタックで、 強く集光した15"のコマと、p.a. 250°に向かって35" の尾が見える。6".6の円形範囲で測定した 光度は16.7等であった)らCCD位置観測者によって彗星状と観測された。 発見位置は次のとおり、 2019 UT R.A. (2000) Decl. Mag. May 25.59037 0 09 43.68 + 5 34 19.9 17.1 25.59314 0 09 44.03 + 5 34 20.5 17.1 25.59881 0 09 44.81 + 5 34 23.6 16.9 25.60923 0 09 46.19 + 5 34 29.7 17.0 楕円軌道要素と位置推算表は次のとおり、 Orbital elements: C/2019 K5 Epoch 2019 June 6.0 TT = JDT 2458640.5 T 2019 June 22.70604 TT MPCLINUX q 2.0363680 (2000.0) P Q z +0.0044568 Peri. 174.89267 +0.99066989 +0.13567593 +/-0.001065 Node 177.21009 -0.13251440 +0.98100576 e 0.9909243 Incl. 15.31198 -0.03182931 +0.13863529 From 161 observations 2019 May 17-June 27, mean residual 0".6. C/2019 K5 Epoch 2019 Apr. 27.0 TT = JDT 2458600.5 T 2019 June 22.70308 TT MPCLINUX q 2.0363763 (2000.0) P Q z +0.0044592 Peri. 174.89121 +0.99066640 +0.13570142 +/-0.001065 Node 177.21008 -0.13253964 +0.98100237 e 0.9909194 Incl. 15.31199 -0.03183291 +0.13863433 From 161 observations 2019 May 17-June 27, mean residual 0".6. Ephemeris: Date TT R. A. (2000) Decl. Delta r Elong. Phase m1 2019 05 28 00 15 13.5 +05 55 48 2.3627 2.0596 60.4 25.3 19.5 ... 2019 06 12 00 49 16.7 +07 57 20 2.2282 2.0404 66.1 27.1 19.3 ... 2019 06 20 01 07 09.7 +08 51 33 2.1604 2.0366 69.3 27.8 19.3 ... 2019 06 26 01 20 22.3 +09 26 28 2.1112 2.0367 71.8 28.3 19.2 2019 06 27 01 22 33.2 +09 31 46 2.1032 2.0370 72.2 28.4 19.2 2019 06 28 01 24 43.6 +09 36 54 2.0951 2.0374 72.6 28.4 19.2 ... 2019 07 04 01 37 36.6 +10 04 25 2.0478 2.0409 75.2 28.8 19.2 ... 2019 07 12 01 54 17.0 +10 31 38 1.9868 2.0495 78.9 29.1 19.1 ... 2019 07 27 02 23 30.4 +10 51 22 1.8789 2.0774 86.3 29.2 19.0 This object was reported as cometary by D. Young (T08) in discovery images obtained on 2019 May 25 UT: "A median combined image of 4x30 second exposures gives a FWHM of 8.2 arcsec as opposed to 5.7 arcsec for nearby field stars. A faint extension ~19 arcsec to the South West was visible in the combined image." Other reports of cometary features are summarized below: OC Date Reporter Coma Tail Q62 May 25 H. Sato 15" 35" in P.A. 250 (8 x 60s) N55 May 25 D. W. E. Green 8" ~25" in P.A. 267 (20 x 40s) G40 May 26 M. Suzuki 18" (6 x 50s) I47 May 27 M. Masek 12" in P.A. 240 (40 x 60s) N55 May 26 D. W. E. Green 8" ~1' in P.A. 235-263 (42 x 40s) Q62 May 27 R. Ligustri 27" (10 x 60s) N55 May 27 D. W. E. Green 7" ~20" in P.A. ~264 (29 x 40s) 850 May 28 D. Durig 8" 10" in P.A. ~270 (100 x 10s) N55 May 29 D. W. E. Green 7" ~30" in 245,257,309 (28 x 40s) Q62 May 29 H. Sato 9" 14" in P.A. 246 (15 x 60s) N55 May 30 D. W. E. Green 8" ~25" in P.A. 258 (38 x 40s) G40 May 31 G. Gasparovic 8" 20" in P.A. 248 (8 x 50s) N55 June 1 D. W. E. Green 6/16" in P.A. 260 (24 x 40s) N55 June 2 D. W. E. Green 4-5" ~12" in P.A. 255 (19 x 40s) I47 June 4 M. Masek 14" in P.A. 245 (24 x 60s) N55 June 4 D. W. E. Green 8" in P.A. 160 (12 x 40s) N55 June 5 D. W. E. Green 9/30" in P.A. 150-240 (20 x 40s) N55 June 6 D. W. E. Green 8" 35" in P.A. 250 (20 x 40s) N55 June 7 D. W. E. Green 6" 8" in 274,24" in 250 (17 x 40s) 691 June 8 A. F. Tubbiolo 30-40" in P.A. 260 Q62 June 9 H. Sato 12" 20" in P.A. 255 (6 x 60s) N55 June 13 D. W. E. Green 7" 10" in P.A. ~250 (10 x 40s) N55 June 14 D. W. E. Green 8" 12" in P.A. ~260 (20 x 40s) 691 June 23 R. S. McMillan 8" in P.A. 260 691 June 24 R. S. McMillan 7" in P.A. 250 691 June 25 R. S. McMillan 7" in P.A. 250 G96 June 25 R. A. Kowalski ~20" ~1' in P.A. 260 (CBET 4637、MPEC 2019-M86)