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Davidson's Comet
- Mackay's celestial
claim to fame 
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by Danielle Jesser

It’s Mackay's claim to celestial fame – 134 years ago the world had a new comet thanks to a discovery by an amateur astronomer at Walkerston.

 

Davidson’s Comet is one of 3743 known comets listed by NASA and as named after its finder, Scotsman and sugar pioneer John Ewen Davidson.

 

On a clear Friday night on 19 July 1889 Davidson walked from his house at Branscombe Sugar Estate on the banks of the Pioneer River to his observatory where he opened the retractable roof. Around 9pm he focused his telescope on the constellation Centaurus, adjacent to the familiar five stars of the Southern Cross, and spotted a comet as a bright but hazy star travelling in a north-westerly direction. 

 

He told the Mackay Standard newspaper the comet was easily visible. “I observed a comet visible to the naked eye as a hazy star, at present in the constellation Centaurus, in a region where there are no conspicuous fixed stars,” he said. The paper said while it was not yet known whether the comet had been noticed in southern observatories, it was at any rate an independent find. “Mr Davidson informs that provided the night is clear, the comet is visible from 7pm to 11pm in the western sky,” the paper wrote.

The next day Davidson travelled in his horse-drawn dogcart to the post office in Mackay to telegram news his discovery to the Sydney Observatory. Receipt of the telegram was reported in Sydney’s Daily Telegraph on Tuesday 23 July 1889 with the Government Astronomer also sighting the comet and telegraphing news of the discovery to Europe. News of the new comet rapidly spread with observatories around with the world tracking its progress. Sightings soon followed in Sydney, Melbourne, South Africa, Italy, Algeria, the United States, Switzerland, Rome, Germany, Austria, France and England.

 

In California, Lick Observatory astronomer Edward Emerson Barnard photographed the comet on 30 July 1889. “The comet was large and bright, with a bushy tail. It was easily visible to the naked eye, appearing as a large oblong nebulous mass as bright as a 6th magnitude star,” he wrote.

 

Davidson was soon confirmed as the discoverer of the new comet and the Mackay Standard reported the government astronomer had written to verify this. “Mr Ellery has communicated with Europe on the subject, and it appears that this starry visitor cannot be identified with any hitherto known comet … Mr Davidson will find his name immortalised in connection with this comet, the discovery of which would appear, beyond all doubt, to have been made at the observatory at Branscombe.”

By August the New York Times reported the Davidson comet had been increasing its distance from the earth and sun, and its brightness had diminished by half since its discovery. “The stellar tramp will not be visible to the naked eye by the time the present moon has gone,” the article said.

The Davidson comet was last seen on 21 November 1889 after having been officially observed on 92 occasions over 115 days.

Davidson’s success as an amateur astronomer was repeated three years later in November 1892 when he observed another comet, however as he was only the fourth independent observer, the find does not bear his name.

While his home and observatory are long gone, the area of the plantation is marked by a line of mango trees along Eungella Road near the intersection with Branscombe Road.  A Daily Mercury report of his death in London in 1923 says Davidson would retreat to his observatory after his evening meal. The author recalled lavish three and four course dinners of excellent food and wine served in cut-glass goblets by servants, followed by cigars and stories as they sat in lounge chairs on the veranda.

These nights were set to the background of a setting moon and the sing-song chatter of the South Sea Islander workers housed in their quarters. “And then Davidson would say to one or two of his favoured guests, ‘come along to my telescope’,” his friend wrote.

“He had quite a good instrument, of which he was justifiably proud. At that time there was no better in Queensland, or probably in Australia.”

Davidson and Thomas Henry Fitzgerald produced the first commercial crushing of sugar earlier in 1868, building his wealth at the expense of indentured South Sea Island labour. He built his observatory to house a 6-inch refractor equatorially mounted C

ooke telescope, one of two brought to Queensland by British astronomers in 1882 to observe the transit of Venus. By measuring the passing of the planet across the face of the sun astronomers were able to to calculate, for the first time, the distance of the Earth from the Sun.

After cloud cover thwarted observations of the transit on the Darling Downs, the two telescopes were purchased by a Townsville amateur astronomer who later sold one to Davidson. The fate of Davidson’s telescope is unknown however researchers suggest it is likely it returned to England with him.

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If you’re keen to see the Davidson comet with your own eyes, you’re out of luck.

The long-period comet is predicted to return in 9079 years, and while this seems an eternity, it’s not particularly long for a comet.

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Sydney Observatory Programs Coordinator Melissa Hulbert said some such as Comet Hyakutake had an orbital period of 70,000 years.

“A long-period comet is one with an orbital period of greater than 200 years so the return time of Davidson’s comet is not particularly long by comparison to others,” she said. Another strike against future generations seeing the comet is the possibility it has broken up after its nucleus split in two by August 1889, a sign it was more fragile due to thermal stress on its surface.

By the time Davidson spotted the comet it had already navigated a treacherous journey from the Oort Cloud, the home of long-period comets at the edge of the solar system. “Comets can also originate from the Kuiper Belt which extends from the orbit of Neptune, and it’s from here that short-period comets such as Comet Halley, which is seen every 76 years, originate,” Ms Hulbert said.

Comets are often described as a “dirty snowball” of rock, dust and ice, and now and again a new one is discovered after it is pushed by gravity into an orbit that brings it closer to the Sun. It’s not until the comet comes closer to the Sun that this icy conglomerate heats up, converting ice to gas, producing familiar features such as the glowing coma around the nucleus and two tails, a long one of gas and a shorter one of dust particles. Ms Hulbert said clear skies in Mackay that night favoured Davidson spotting the comet over other observatories.

 

“Finding a comet is all about looking in the right patch of sky at the right time. These days most new comets are discovered by survey telescopes rather than individuals, but amateur astronomers still do make discoveries. And when a new comet is found news of the discovery still spreads quickly around the world and around the time of closest approach/maximum brightness astronomers rush to observe and photograph it.”

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