James Dunlop

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James Dunlop (31 October 1793 – 22 September 1848) was an astronomer assistant hired by Sir Thomas Brisbane at his private observatory located in Parramatta, New South Wales, about 23 kilometres west of Sydney, Australia during the 1820's and '30's. Dunlop was essentially a visual observer, doing stellar astrometry work for Brisbane, and independently discovering and cataloguing many telescopic southern double stars and deep-sky objects. He later became the Superintendent of the observatory when it was finally sold to the New South Wales Government.

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[edit] Early life

James Dunlop was the son of John Dunlop, a weaver; who 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.

[edit] Career in Australia

Soon after his arrival, Brisbane built an observatory at Paramatta, now named Parramatta, and it was Dunlop was employed there to do observations of the then poorly known southern skies. German born Carl Ludwig Christian Rümker (or sometimes as Charles Karl Ludwig Rümker) (28 May 1788 - 21 December 1862), or simply Karl Rümker, who had been first assistant, soon left the observatory in 1823, leaving Dunlop charge of the astrometric observations and maintenance of the Observatory and instruments. He was not a trained astronomer and lacked the necessary mathematical skills to do reductions. He learned the necessary observational skills from the more able Rümker and his employer. Between June 1823 and February 1826 he made 40,000 observations and catalogued some 7385 stars, of which included 166 double stars and references to several bright deep-sky objects near the bright stars he catalogued. By the beginning of March, 1826, he left the Paramatta Observatory and continued working at his own home in Hunter Street, Paramatta. For there he began organising his own observations of double stars and deep-sky objects for the next 18 months, in which he constructed telescope and other equipment for his dedicated southern sky survey.

Sir Thomas Brisbane, before finally departing Sydney for the last time in December 1825, arranged to sell all of his instruments to the Government so the observatory could continue to function. Some of the equipment he gave to Dunlop, which he used at his home, especially the useful small equatorial mounted 8.0 cm. (3¼-inch) refracting telescope that Rümker, and later Dunlop, both used for doing the important double stars measures as their own personal projects.

By May 1826, Rümker returned to the observatory, and seven months later he was appointed as the first New South Wales Government Astronomer, though this officially did not happen until a few years later, much to Rümker's disgust, due to delays from his employes in Britain.

[edit] 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. On arrival, he also reduced his southern double stars and deep-sky observations for publication, which was believed to have taken about one month, and these were published also in the first half of 1828.

These two detailed astronomical papers were received with many accolades from his peers, which lasted until about 1834, when his observations were able to be scrutinised by John Herschel and Thomas Maclear in South Africa. Only then were the various flaws of his observations became revealed, and the time spent in the zenith of popularly, then dwindled to fierce criticism and personal rejection especially from the British astronomical community.

[edit] Return to Australia

In April 1831, Dunlop was appointed superintendent of the Government observatory at Parramatta. He was selected mainly from his good knowledge of Colony and the observatory site, but the real reason for his selection was more because even though such an astronomical position was formally advertised, nobody applied for the astronomical tenure. Here he was to succeed Rümker with the reasonable good 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 important 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 Waters, 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.

[edit] Observations and Discoveries in Australia

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 contains 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 -30o South. These were listed in Approximate Places of Double Stars in the Southern Hemisphere, observed at Paramatta in New South Wales, being published in 1829. Many of these pairs were actual new discoveries, though the most northerly of them had been earlier discoveries made by other observers. These double star observations were all 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 position angles of selected double stars using the small 8.0 cm. (3¼-inch) equatorial mounted refracting telescope.[1] Most of these pairs have proved to be uninteresting to astronomers, and many of the double stars selected 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 at deep sky objects, either being made under unsteady astronomical seeing or when the sky was illuminated by the 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 known as 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.

[edit] Publications

[edit] References

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

[edit] External links