Gore was born at Athlone on 1845, June 1. The eldest son of the Venerable John Ribton Gore, Archdeacon of Athenry. He was educated privately and at Trinity College, Dublin, where he took an engineering degree in 1865, being first in his year. In 1868, he gained second place in the open competition for the Indian Public Works Department. He was posted to the Punjab, as Assistant Engineer in connection with the construction of the Sirhind Canal. His career in India was relatively short - about eleven years. It did appear that he did not get on too well with his Chief and as he is reputed to have been an outspoken young man, there was trouble. It is understood that one of the reasons for his early retirement was his action in writing to an Indian newspaper, criticizing the policy of the Department. At any rate, he returned to Ireland on two years furlough in 1877 but he never returned to India. In 1879, he retired from the Indian service and drew a pension for the remainder of his life.
Gore was an amateur astronomer and prolific author of popular astronomy books. His main observational interest was variable stars, of which he discovered several, and he served as the first Director of the British Astronomical Association Variable Star Section. He was also interested in binary stars, leading him to calculate orbital elements of many such systems. He demonstrated that the companion of Sirius, thought by many to be a dark body, was in fact self luminous. In doing so he provided the first indication of the immense density of what later became known as white dwarfs.
His variable star discoveries included:
- W Cyg (1884)
- S Sge (1885)
- U Ori (1885)
- X Her (1890)
- Nova Per 1901 (independent discovery)
Gore died on 18th July, 1910, his death being the result of a street accident.
At the meeting of 1891-08-12 a lengthy letter from Mr. Gore on the subject of his studies with opera-glasses was read out, and he continued to correspond with the Society. At the meeting of 1891-11-16, on motion of Mr. G.E. Lumsden, seconded by Mr. J.G. Ridout, Mr. J. Ellard Gore was elected a Corresponding Member of the Astronomical and Physical Society of Toronto. This was followed by the reading of Gore's paper on the Pleiades.
Gore is a lunar impact crater located on the lunar near side near the northern pole. The crater was adopted and named after John Ellard Gore by the IAU in 2009.