James Dunlop

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James Dunlop (31 October 1793 – 22 September 1848) was an astronomer and superintendent of the New South Wales (Australia) government observatory.

1 Early life
2 Career in Australia
3 Back to Scotland
4 Return to Australia
5 Publications
6 References
7 External links

Early life

Dunlop was the son of John Dunlop, a weaver; he was born in Dalry, Ayrshire, Scotland. He was educated at a school in Dalry and went to work at a thread factory in Beith when he was 14. He also attended a night-school kept by a man named Gardiner. He became interested in astronomy at an early age and was constructing telescopes in 1810. In 1820 he made the acquaintance of Sir Thomas Brisbane, who appointed him as second scientific assistant when he went to Sydney as governor in 1821.

Career in Australia

Soon after his arrival, Brisbane built an observatory at Parramatta, and Dunlop was employed there. Karl Rümker, who had been first assistant, left the observatory in 1823, and Dunlop was put in charge of it. He was not a trained astronomer, but he had learned much from Rümker and his employer, and between June 1823 and February 1826 he made 40,000 observations and catalogued 7385 stars. At the beginning of March, he left the observatory and continued working at his own home, Thomas Brisbane having sold his instruments to the government when he left Australia in December 1825. In May 1826, Rümker returned to the observatory, and seven months later he was appointed government astronomer.

Back to Scotland

Dunlop left Sydney for Scotland in February 1827 and was employed for four years at the observatory of Sir Thomas Brisbane. He had done very good work as an observer in New South Wales, and was associated with Rümker in the discovery of Encke's comet at Parramatta in June 1822. He was later to be the first in Great Britain to rediscover this comet on 26 October 1829. He had been awarded the Gold Medal of the Royal Astronomical Society of London on 8 February 1828. Sir John Herschel, when making the presentation, spoke in the highest terms of the value of the work done by Dunlop in New South Wales.

Return to Australia

In April 1831 Dunlop was appointed superintendent of the government observatory at Parramatta in succession to Rümker at a salary of £300 a year. He arrived at Sydney on 6 November 1831 and found the observatory in a deplorable condition; rain had come in, plaster from the roof had fallen down, and many records were destroyed. Dunlop succeeded in getting the building repaired and started on his work with energy, but around 1835 his health began to fail; he had no assistant, and the building, having been attacked by white ants, fell gradually into decay. In August 1847, he resigned his position, and went to live on his farm on Brisbane Water, an arm of Broken Bay. He died on 22 September 1848. In 1816 he'd married his cousin Jean Service, who survived him. In addition to the medal of the Royal Astronomical Society Dunlop was awarded medals for his work by the King of Denmark in 1833, and the Institut Royal de France in 1835. He was elected a fellow of the Royal Society of Edinburgh in 1832. Papers on, and references to, the work of Dunlop will be found in the Monthly Notices of the Royal Astronomical Society, in the Edinburgh Journal of Science, and in the Transactions of the Royal Society between the years 1823 and 1839.

He made several noteworthy discoveries in the Southern Hemisphere sky and wrote A Catalogue of Nebulae and Clusters of Stars in the Southern Hemisphere observed in New South Wales, which listed 629 objects. That said, a little more than half the objects he discovered proved to be real, most being small nebulous objects being probably artificially created from the handmade reflecting telescope he had constructed himself. His most famous discovery is likely the radio galaxy NGC 5128, though he found many new open star clusters, globular clusters, bright nebulae and planetary nebulae, most previously unknown to visual observers.

His other major observational work was of 256 southern double stars or "pairs" below the declination of about -30^o South. These were listed in Approximate Places of Double Stars in the Southern Hemisphere, observed at Paramatta in New South Wales published in 1829. Many of them were new discoveries, though the most northerly of them had been earlier discoveries by other observers. These double star observations were made roughly between December 1827 and December 1828, being observed through his homemade 9-foot 23cm (9-inch) speculum Newtonian reflector, or by measuring the separated distances and angles of selected double stars using the small 8.0 cm. (3¼-inch) equatorial mounted refracting telescope.^[1] Most of these pairs proved to be uninteresting to astronomers as many of the double stars were too wide for the indication of orbital motion as binary stars. It seems these observations were made when the atmospheric conditions were quite unsuitable for looking for deep sky objects, either under unsteady astronomical seeing or when the sky was illuminated by a bright moon. ^[2] John Herschel immediately on arrival in South Africa in 1834 and 1835 re-observed all of the James Dunlop's double stars, but had troubles identifying them or finding significant differences in the measured positions of the stars . He first began with Alpha Crucis / Acrux, the brightest star in the constellation of Crux also commonly known as the Southern Cross, then systematically searched for all the others. Herschel also was first to designated all the Dunlop double stars to begin with the Greek letter "Δ", which persists in many amateur observational references. Hence, bright southern doubles like p Eridani is Δ5, Gamma Crucis / Gacrux is Δ124, etc. Modern double star observers have since discarded this designation and prefer the observer abbreviation "DUN", as first adopted in the Washington Double Star Catalog (WDS) as maintained by the US Naval Observatory in Washington D.C.. Hence, p Eridani is DUN 5, Gamma Crucis / Gacrux is DUN 124, etc.

James Dunlop is currently buried in St. Paul's Anglican Church in Kincumber, New South Wales.

Publications

"A catalogue of nebulae and clusters of stars in the southern hemisphere, observed at Parramatta in New South Wales. Philosophical Transactions of the Royal Society, Vol. 118, p. 113--151, 1828. This catalogue with descriptions contains 629 southern deep-sky objects.
He also discovered and catalogued 256 southern double stars in "Approximate Places of Double Stars in the Southern Hemisphere, observed at Paramatta in New South Wales.", which was published in the Memoirs of the Royal Astronomical Society Mem.Ast.Soc.London, Vol. 3, 257, 1829.
Only five other papers were published by James Dunlop between 1829 and 1839, the most significant being on comets; “Places of Encke’s comet, from 30 observations. Monthly Notices of the Royal Astronomical Society (MNRAS)., Vol. 1, 120 (1829) and “Observation of a small comet at Paramatta. Monthly Notices of the Royal Astronomical Society (MNRAS)., Vol. 1, 130 (1829)

References

^ Andrew James. "Dunlop's Double Star Catalogue". Retrieved on 2008-01-11.
^ Andrew James. "The Double Stars of Dunlop and Rumker". Retrieved on 2008-01-11.

Serle, Percival (1949). "Dunlop, James". Dictionary of Australian Biography. Sydney: Angus and Robertson.

This article incorporates text from the public domain 1949 edition of Dictionary of Australian Biography from Project Gutenberg of Australia, which is in the public domain in Australia and the United States of America.