NEW COMET SWAN (C/2004 H6)

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This Is SKY & TELESCOPE's AstroAlert for Comets
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NEW COMET SWAN (C/2004 H6)

Michael Mattiazzo, Andrew Pearce, and Colin Drescher -- all in Australia -- have now sighted a comet that was first suspected on low-resolution images taken with the SOHO spacecraft's SWAN ultraviolet camera.

Mattiazzo's CCD astrometry on May 16th, 21st, and 25th allowed the IAU Central Bureau for Astronomical Telegrams, cfa-www.harvard.edu/iau/cbat.html , to calculate a preliminary orbit. According to IAU Circulars 8346 and 8347, Comet SWAN (C/2004 H6) passed perihelion on May 12th at 0.776 astronomical unit from the Sun (between the orbits of Earth and Venus). It is heading on a high-inclination, parabolic trajectory through the inner solar system.

As Comet SWAN draws steadily away from the Sun, it will probably stay visible in telescopes as an 8th-magnitude glow for at least two months. During June, Southern Hemisphere observers can follow its trek in the predawn sky from Eridanus into Cetus. By July, Comet SWAN should be visible from anywhere in the world.

The following ephemeris, based on Daniel W. E. Green's preliminary orbit, gives the comet's right ascension and declination at 0 hours Universal Time on each date, followed by its distance from Earth (Delta) and the Sun (r) in astronomical units (one a.u. is about 149,600,000 kilometers). Included are the comet's elongation angle in degrees from the Sun, its predicted visual magnitude, and the constellation it is in. The last column, "optimum latitude," tells which geographical locations on Earth can view the comet highest in a dark sky.

Keep in mind that future observations will allow the comet's predicted path and magnitude to be improved. So it could drift slightly off the ephemeris below, especially after June.


Roger W. Sinnott
Senior Editor
SKY & TELESCOPE

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Comet SWAN (C/2004 H6)

2004 RA (2000) Dec Delta r Elong Mag Const OpLat
h m o ' (au) (au) o o

May 29 3 21.4 -13 09 1.356 0.838 38 7.6 Eri 66S
May 30 3 19.6 -13 11 1.346 0.845 39 7.6 Eri 64S
May 31 3 17.8 -13 14 1.336 0.853 40 7.6 Eri 62S

Jun 01 3 15.9 -13 16 1.325 0.861 40 7.6 Eri 60S
Jun 02 3 14.1 -13 18 1.314 0.870 41 7.6 Eri 59S
Jun 03 3 12.2 -13 20 1.303 0.878 42 7.7 Eri 57S
Jun 04 3 10.3 -13 22 1.291 0.887 43 7.7 Eri 56S
Jun 05 3 08.4 -13 23 1.279 0.897 44 7.7 Eri 54S
Jun 06 3 06.4 -13 24 1.266 0.906 45 7.7 Eri 53S
Jun 07 3 04.4 -13 25 1.254 0.916 46 7.7 Eri 51S
Jun 08 3 02.4 -13 25 1.241 0.926 47 7.7 Eri 50S
Jun 09 3 00.4 -13 26 1.227 0.936 48 7.7 Eri 48S
Jun 10 2 58.3 -13 26 1.213 0.947 49 7.7 Eri 47S
Jun 11 2 56.1 -13 26 1.199 0.957 50 7.8 Eri 46S
Jun 12 2 54.0 -13 26 1.185 0.968 52 7.8 Eri 45S
Jun 13 2 51.7 -13 26 1.170 0.979 53 7.8 Eri 43S
Jun 14 2 49.5 -13 25 1.156 0.991 54 7.8 Eri 42S
Jun 15 2 47.1 -13 25 1.141 1.002 55 7.8 Eri 41S
Jun 16 2 44.7 -13 24 1.125 1.014 56 7.8 Cet 40S
Jun 17 2 42.3 -13 23 1.110 1.026 58 7.8 Cet 39S
Jun 18 2 39.7 -13 22 1.094 1.038 59 7.8 Cet 38S
Jun 19 2 37.1 -13 21 1.079 1.050 60 7.8 Cet 36S
Jun 20 2 34.4 -13 20 1.063 1.062 61 7.8 Cet 35S
Jun 21 2 31.7 -13 19 1.047 1.074 63 7.8 Cet 34S
Jun 22 2 28.8 -13 18 1.030 1.087 64 7.8 Cet 33S
Jun 23 2 25.8 -13 17 1.014 1.099 66 7.8 Cet 32S
Jun 24 2 22.7 -13 16 0.998 1.112 67 7.8 Cet 31S
Jun 25 2 19.5 -13 14 0.981 1.124 68 7.8 Cet 30S
Jun 26 2 16.2 -13 13 0.965 1.137 70 7.8 Cet 29S
Jun 27 2 12.8 -13 11 0.948 1.150 72 7.8 Cet 28S
Jun 28 2 09.2 -13 10 0.932 1.163 73 7.8 Cet 28S
Jun 29 2 05.4 -13 08 0.915 1.176 75 7.8 Cet 27S
Jun 30 2 01.5 -13 06 0.899 1.189 76 7.8 Cet 26S

Jul 01 1 57.5 -13 04 0.882 1.202 78 7.8 Cet 25S
Jul 03 1 48.8 -13 00 0.850 1.229 82 7.8 Cet 23S
Jul 05 1 39.3 -12 55 0.818 1.256 86 7.8 Cet 21S
Jul 07 1 29.0 -12 49 0.787 1.283 90 7.8 Cet 19S
Jul 09 1 17.6 -12 42 0.758 1.310 94 7.8 Cet 18S
Jul 11 1 05.2 -12 34 0.730 1.337 99 7.8 Cet 16S
Jul 13 0 51.7 -12 23 0.704 1.364 103 7.7 Cet 14S
Jul 15 0 36.9 -12 10 0.680 1.392 109 7.7 Cet 12S
Jul 17 0 21.0 -11 54 0.659 1.419 114 7.7 Cet 10S
Jul 19 0 04.0 -11 35 0.642 1.447 120 7.7 Cet 08S
Jul 21 23 45.9 -11 11 0.628 1.474 126 7.8 Aqr 06S
Jul 23 23 26.9 -10 44 0.619 1.502 132 7.8 Aqr 03S
Jul 25 23 07.3 -10 12 0.614 1.529 138 7.8 Aqr 00N
Jul 27 22 47.5 -09 36 0.614 1.557 145 7.9 Aqr 04N
Jul 29 22 27.8 -08 58 0.619 1.584 151 8.0 Aqr 08N
Jul 31 22 08.4 -08 17 0.629 1.612 157 8.0 Aqr 14N

Aug 01 21 59.0 -07 56 0.636 1.626 160 8.1 Aqr 18N
Aug 03 21 40.8 -07 15 0.653 1.653 165 8.2 Aqr 30N
Aug 05 21 23.6 -06 34 0.675 1.681 168 8.3 Aqr 45N
Aug 07 21 07.7 -05 55 0.701 1.709 170 8.5 Aqr 56N
Aug 09 20 53.0 -05 18 0.732 1.736 168 8.6 Aqr 45N
Aug 11 20 39.6 -04 44 0.765 1.763 165 8.8 Aqr 33N
Aug 13 20 27.4 -04 13 0.802 1.791 161 8.9 Aql 24N
Aug 15 20 16.5 -03 44 0.842 1.818 157 9.1 Aql 18N
Aug 17 20 06.6 -03 19 0.884 1.845 153 9.2 Aql 14N
Aug 19 19 57.8 -02 56 0.928 1.873 150 9.4 Aql 11N
Aug 21 19 49.9 -02 36 0.975 1.900 146 9.5 Aql 09N
Aug 23 19 42.9 -02 18 1.023 1.927 143 9.7 Aql 07N
Aug 25 19 36.6 -02 02 1.072 1.954 139 9.8 Aql 06N

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