A photograph believed to be an extremely rare image of Emily Dickinson has surfaced in her home town of Amherst, Massachusetts, showing a young woman in old-fashioned clothes, a tiny smile on her lips and a hand extended solicitously towards her friend.

There is, currently, only one authenticated photograph of Dickinson in existence – the well-known image of the poet as a teenager in 1847. But Amherst College believes an 1859 daguerreotype may well also be an image of the reclusive, beloved poet, by now in her mid-20s and sitting with her recently widowed friend, Kate Scott Turner. If so, it will shed new light on the poet who, by the late 1850s, was withdrawing further and further from the world.

The college's archives and special collections department has subjected the 1859 daguerreotype, owned by a New England collector, to multiple tests, including an ophthalmological report, and says that all of the current evidence is in favour of the woman on the left of the image being Dickinson.

Comparing the 1859 picture with the 1847 photograph known to be of Dickinson, Professor Susan Pepin of Dartmouth Hitchcock Medical Centre measured eyelid and facial features of both women. "The two women have the same eye opening size with the right eye opening being slightly larger than the left. The left lower lid in both women sits lower than the right lower lid," she wrote in a report. "Other similar facial features are evident between the women in the daguerreotypes. The right earlobe is higher on both women. The inferonasal corneal light reflex suggests corneal curvature similarity, allowing us to speculate about similar astigmatism in the two women. Both women have a central hair cowlick. Finally, both women have a more prominent left nasolabial fold."

Pepin concluded that "after a thorough examination of both of these women's facial features as viewed from the 1847 and 1859 daguerreotypes, I believe strongly that these are the same people".

Amherst has also searched the Emily Dickinson Museum's textile collection and has found at least one fabric sample in a blue check it believes is a candidate for the dress the woman supposed to be Dickinson is wearing in the image. It is planning further work by a textile expert to determine whether the two are the same. The woman on the right, thought to be Kate Turner, is wearing widow's black, "as would have been appropriate following the May, 1857 death of her young husband, Campbell Ladd Turner", it said.

Amherst does admit that the dress worn in the photograph by "Dickinson" does seem to be out-of-date for the late 1850s, but it believes that "may be of less significance when one considers the 23-year-old Dickinson's comment to friend Abiah Root in 1854, 'I'm so old fashioned, Darling, that all your friends would stare'".

The college has released the image to the public in the hope that anyone with further information about the photograph will come forward, whether or not it is favourable to the college's proposed identification of the two women as Dickinson and Turner.

If the daguerreotype is eventually proved to be Dickinson, Amherst believes it will "change our idea" of the poet, showing her "as a mature woman showing striking presence, strength, and serenity", rather than as a teenager.

"She (whoever she is) seems to be the one in charge here, the one who decided that on a certain day in a certain year, she and her friend would have their likenesses preserved. In fact, even if this photograph is not of Dickinson and Turner, it has still been of use in forcing us to imagine Dickinson as an adult, past the age of the ethereal-looking 16-year-old we have known for so many years," the college added.

• This article was amended on 10 September 2012 to correct the spelling of Amherst College Archives in the photo caption, from Amhurst College Archives.