John Keats wrote When I Have Fears That I May Cease to Be between January 22 and 31 of 1818, lkely on the Isle of Wight. The poem includes imagery of the narrator, who is presumably John Keats himself, standing on a shore, much like he would have on the Isle of Wight. Keats also writes about how while his impending death allows his imagination to run wilder than any other as he looks up at the starry sky, he cannot help but lament the fact that he will never learn any of the greater truths about these celestial bodies. The 19th Century is filled with major advances in astronomy, but Keats never gets to see the discoveries of the asteroid belt, Neptune, spectroscopy, or the Transit of Venus. He passes away only a year after the founding of the Royal Astronomical Society, and the world was robbed of his teeming brain, filled with the desires for knowledge and love.

Sources:

https://www.britannica.com/biography/John-Keats/The-year-1819

https://en.wikipedia.org/wiki/John_Keats

https://erling.yoga/john-keats-isle-of-wight/

https://www.christies.com/features/Joseph-Severn-portrait-of-Keats-11258-1.aspx