The black and white photograph featured a familiar face that had apparently been on a library wall in the Sarah Orne Jewett House in South Berwick for years until a University of Southern Maine graduate student discovered the valuable artifact.

Robin Whitham Acker, a graduate student in USM’s American and New England Studies program, was just another visitor to the historic home of the well-known Maine author when she spotted the portrait of Alfred, Lord Tennyson, the British poet laureate, hanging near a fireplace.

But it wasn’t so much the subject as it was the photographer that caught Acker’s attention.

Acker recognized the portrait as the work of British photographer Julia Margaret Cameron. Cameron, who died in 1879, established a reputation as one of England’s most famous Victorian photographic artists. Cameron photographed celebrities such as American poet Henry Wadsworth Longfellow, who was born in Portland; English naturalist Charles Darwin, who became known after publishing his theories on human evolution; and Tennyson.

“I was thrilled when I saw the portrait,” said Acker, who lives in the Portland area with her fiance, Stratton McCrady. Acker and McCrady were familiar with Cameron’s work – McCrady taught photographic history at Boston University for several years and Acker has been studying Cameron since 2004 – and approached the owners of the historic home about authenticating the photograph.

The Sarah Orne Jewett House at 5 Portland St. in South Berwick is owned by Historic New England, a historic preservation organization based in Boston.

Jewett, who died in 1909, is regarded as one of America’s premier regional writers.

Cameron’s work is considered rare and is highly sought after, with her photographs valued in the thousands of dollars. One of her portraits sold at auction in 2011 for almost $90,000.

Acker said officials from Historic New England invited her to their offices on June 10, when they removed the portrait from the frame and looked at it under a microscope.

An impression stamp on the back of the portrait confirmed it was an authentic 1867 Cameron photograph of Tennyson – one of about a dozen that she took of the poet.

The team also discovered that the photograph, which was framed by Doll and Richards Gallery and Framing of Boston, was backed by a newspaper dated August 1882 – the same summer of Jewett’s first trip to England.

Historic New England said the organization took possession of the photograph when Theodore Jewett Eastman – Jewett’s nephew – bequeathed the home to it in 1931.

Acker said she is still trying to figure out how Jewett obtained the portrait. She issued a statement through the university on Monday.

“The Cameron photographic portrait teaches us about the friending and trending activities of the Victorians,” Acker said.

“It teaches us that just like on Facebook, they were sharing image of themselves and others, exchanging letters with each other and keeping journals with updates from their daily lives. This is something we still do today, only we do it in a technologically advanced medium, which at times lacks a contemplative and reflective experience. Facebook is filled with some of the same activities the Victorians loved.”

Historic New England officials issued an email stating that they are “delighted that a photograph in its collection is being authenticated as the work of Julia Margaret Cameron and extends thanks to Robin Acker for all her hard work.”

“Robin has made a terrific discovery here,” Kent Ryden, a professor and director of USM’s American and New England Studies program, said in a prepared statement.

“Her work not only indicates the high quality of student research that is done at USM, but also shows how that research can illuminate important, little known aspects of Maine and New England culture and history.”