Septuagenarian ‘Wizard’ Finds Bright Comet


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Comet 2004 F4 (Bradfield) in SOHO’s LASCO C3 field of view
on April 18, 2004, the day after perihelion.
(Image courtesy SOHO/LASCO consortium. SOHO is a project
of international cooperation between ESA and NASA.)


The 20th Century's most successful visual comet hunter, Australian amateur William Bradfield, “struck ice” for the first time this millennium on March 23, 2004. While searching comets low in the western evening sky, Bradfield came across an 8th magnitude comet in the constellation Cetus. He observed it again the following night, but although astronomers tried to confirm it for the next two weeks, it wasn't until April 8 that it was recovered. It had already brightened to nearly 3rd magnitude, but within a few days it was lost in bright twilight.

On April 15, Comet 2004 F4 (Bradfield) entered SOHO's LASCO C3 images, its head trailed by a dust tail that ultimately extended fully across the LASCO field of view (upwards of a dozen degrees); the first 5 degrees of tail were bright. The comet reached perihelion on April 17 and peaked in brightness a day later. Astronomers estimated that the comet was then about magnitude -3, as bright as Mars was when at its best in the summer of 2003 and fully 100 times brighter than most had predicted. Its increase in brightness was aided by the forward-scatter of sunlight due to the comet’s passing more-or-less between Earth and Sun, an effect that also produces the brilliance of a field of dew viewed in the direction of the Sun in early morning. (If Bradfield had missed finding the comet in late March, it’s likely it would have passed undiscovered until it emerged full-blown into the LASCO field of view, giving the community of SOHO comet hunters a collective heart attack.)

Before the comet entered LASCO, comet expert John Bortle was doubtful that Bradfield would even survive perihelion, but it became a fine object in the morning sky, as it passed from Pisces up through Andromeda in late April into early May. The first post-perihelion image of Bradfield, was taken on April 22 by Michael Jäger; the comet was then around magnitude 3. Although it quickly faded below 4th magnitude, it showed a long, straight tail well in binoculars and on photos. This shot by Wally Pacholka shows the comet near the Andromeda Galaxy.

For Bradfield, his most recent find was his 18th comet. He had found the others between 1972 and 1995. For his exceptional ability in finding comets, he earned the nickname “The Wizard of Dernancourt,” the town where he lived. In 1995, he moved to Yankalilla, a nearby town, but one with considerably cloudier skies. The late 1990s saw the rise of robotic sky surveys such as LINEAR, which greatly cut into the number of comets being found by amateurs (though the Southern Hemisphere has been less affected). At 76, Bradfield is probably the second oldest person to find a comet. (Albert Jones, a variable-star observer, co-discovered Comet Utsunomiya-Jones in 2000 at age 80. It was Jones’s second comet; he had found his first one 54 years earlier!)

The appearance of the very bright Comet Bennett in early 1970 sparked Bradfield’s desire to find a new comet. “I thought that if Bennett, an amateur astronomer in South Africa, could find a comet that eventually turned into a spectacular object, I could do the same,” Bradfield wrote to me in 1988. “Later that year, I was able to procure a 150-mm f/5.5 refractor that was very suitable for comet hunting.” He used that telescope for 14 of his discoveries; his latest find was with a 250-mm (10-inch) reflector.

Although none of Bradfield's finds have approached Bennett's majesty, many were respectable objects, and a few reached naked-eye visibility. Remarkably, while many comets are found by several hunters who each get co-credit for their discoveries, Bradfield has been the sole discoverer of all 18 of his comets.




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