Another Comet

From S&T mailshot.

Cheers,
~Al

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This Is SKY & TELESCOPE's AstroAlert for Comets
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COMET BRADFIELD, C/2004 F4

William A. Bradfield of Yankalilla, South Australia, has discovered a comet in the constellation Cetus. He first spotted it low in the western evening sky with his 10-inch reflector on March 23rd and 24th, then lost sight of it until April 8th. The find was announced this morning by Daniel W. E. Green of the Central Bureau for Astronomical Telegrams ( cfa-www.harvard.edu/iau/cbat.html ) on IAU Circular 8319.

Green's calculations show that the comet will move even closer to the Sun, both in space and as seen from Earth, until the third week of April. It reaches perihelion on the 17th, when it will be a scant 0.17 astronomical unit (about 25 million kilometers) from the Sun, well inside Mercury's orbit. Even though perhaps brightening to 2nd magnitude, it will be totally impossible to observe for a week or more except via the SOHO Web site ( sohowww.nascom.nasa.gov/data/realtime-images.html ), primarily in the LASCO C3 images. It passes 2.6 degrees from the Sun's center on April 18th. Toward the end of the month Comet Bradfield emerges in the predawn sky for skywatchers in midnorthern latitudes. While rapidly fading, it may become visible in binoculars then.

Indefatigable comet hunter Bradfield, now age 76, is credited with numerous other discoveries dating back to 1972. All 18 of these comets bear his name alone, which means he spotted and reported them well ahead of any other observer. But it's been nine years since his last discovery, C/1995 Q1. Born in New Zealand, Bradfield worked many years for the Australian government as a research scientist on rocket-propulsion systems before retiring in the late 1980s.

The following ephemeris is based on Green's very preliminary orbital elements. For 0 hours UT on each date, it lists the comet's right ascension and declination (equinox 2000.0), distance from Earth (Delta) and the Sun (r) in astronomical units, elongation angle from the Sun, approximate visual magnitude, and constellation. The last column, "optimum latitude" for viewing, indicates the comet is only visible from the Southern Hemisphere before the mid-April invisibility period. Thereafter, those in the Northern Hemisphere are favored.


Roger W. Sinnott
Senior Editor
SKY & TELESCOPE

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COMET BRADFIELD, C/2004 F4

2004 RA (2000) Dec Delta r Elong Mag Const OpLat
h m o ' au au o o
Apr 12 2 08.0 -00 41 1.046 0.265 15 3.8 Cet 40S
Apr 13 2 06.6 -00 07 1.005 0.237 14 3.3 Cet 43S
Apr 14 2 04.1 +00 41 0.963 0.212 12 2.9 Cet 46S
Apr 15 2 00.3 +01 52 0.923 0.190 10 2.4 Cet 50S
Apr 16 1 54.9 +03 31 0.886 0.175 8 2.1 Psc 57S
Apr 17 1 48.0 +05 43 0.856 0.169 5 1.9 Psc 70S
Apr 18 1 40.2 +08 23 0.837 0.173 3 1.9 Psc 64S
Apr 19 1 32.3 +11 18 0.830 0.186 4 2.1 Psc 02S
Apr 20 1 25.0 +14 12 0.833 0.206 7 2.5 Psc 17N
Apr 21 1 18.9 +16 57 0.845 0.231 10 2.9 Psc 24N
Apr 22 1 13.8 +19 28 0.862 0.258 13 3.3 Psc 28N
Apr 23 1 09.7 +21 44 0.883 0.287 16 3.7 Psc 30N
Apr 24 1 06.5 +23 47 0.905 0.316 18 4.0 Psc 31N
Apr 25 1 04.0 +25 37 0.930 0.346 20 4.4 Psc 32N
Apr 26 1 02.1 +27 16 0.955 0.375 22 4.7 Psc 33N
Apr 27 1 00.6 +28 46 0.980 0.405 24 5.0 Psc 33N
Apr 28 0 59.6 +30 08 1.005 0.434 25 5.3 Psc 34N
Apr 29 0 58.9 +31 24 1.031 0.462 26 5.6 Psc 34N
Apr 30 0 58.4 +32 33 1.056 0.491 27 5.8 Psc 34N
May 01 0 58.2 +33 37 1.081 0.519 28 6.0 Psc 35N
May 02 0 58.2 +34 37 1.106 0.546 30 6.2 And 35N
May 03 0 58.3 +35 33 1.130 0.573 30 6.5 And 35N

(If the columns of the table don't line up properly, switch to
a fixed-space font like Courier.)

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Fair play to Mr. Bradfield, still keeping the human side of Comet Discovery alive. One of his advantages over us 'northerners' is that southern observers still have a better chance of finding a comet than you or I, this is because of the LINEAR and NEAT asteroid search programs that operate from most of the earth's northern hemisphere. However, not for long more, I think they have just been set up in the southern hemisphere as well!
Still, we keep trying.....
Keith..
:roll:

Unfortunately, this comet is likely to fizzle out within days.

Gordon

John Bortle says:
"Although Bill Bradfield's new bright comet could potentially become
visible from mid-northern latitudes toward the end of the month,
there is already a fly in the ointment.

Based on the preliminary orbital elements and reported magnitudes,
the comet seems to be an intrinsically faint one. Some years ago I
published a study of the post-perihelion survival of comets with
small perihelion distances. The study demonstrated that there was a
very definite relationship between perihelion distance, intrinsic
brightness, and a comet's post-T survival or non-survival.

As things stand right now, Comet Bradfield's brightness seems to
place it below the survival threshold. If this is so, we may well
actually be able to witness its demise via SOHO images as it rounds
the Sun next week.