A stunning landscape that has spent much of its life unloved in a Norwegian attic has been revealed as a newly discovered masterpiece by Vincent Van Gogh.

Academics are nothing short of astonished, not least because it comes from the artist's greatest period when he lived in Arles, southern France, and created works such as The Yellow House and The Sunflowers.

Writing in the Burlington Magazine, the three Dutch experts from the Van Gogh Museum in Amsterdam responsible for the discovery call the work "absolutely sensational".

Sunset at Montmajour was unveiled at a ceremony in the Dutch city. Axel Rüger, director of the museum, called it a "once in a lifetime experience".

The picture was painted in 1888 and shows the wild and beautiful countryside near Arles with a ruined abbey on the hill of Montmajour.

The painting, new research suggests, was bought by a Norwegian industrialist, Christian Nicolai Mustad, in 1908 on the advice of art historian and conservator Jens Thiis, who that year became director of the National Museum in Oslo.

All was fine but a family story suggests that the French ambassador to Sweden visited Mustad and suggested it was either a fake or wrongly attributed. Furious, the industrialist banished it to the attic.

"The art world was jittery at the time, possibly because of a rise in the number of forgeries in circulation, and as a result owners felt uncertain," the three Dutch experts, Louis van Tilborg, Teio Meedendorp and Oda van Maanen, write in the Burlington.

What is not likely is that it was the ambassador. More likely it was the Norwegian consul in Paris, Auguste Pellerin, a collector who would have been considered an authority. Bizarrely, he was also the owner of Astra Margarine, the direct competitor with Mustad in Norway.

Putting all this together, that Mustad was a young fledgling collector, that Pellerin was both a greater authority and a business rival, then it is possible to see how upset Mustad might be. Better to get it off the wall and quickly move on to better acquisitions.

Mustad died in 1970 and the painting has twice been rejected as a Van Gogh – including once in 1991 by the Van Gogh Museum.

All the evidence now suggests the art experts were wrong and the museum has even found reference to the painting by the artist.

The magazine article quotes a moving description of a newly discovered landscape that an excited Van Gogh described in a letter to his brother Theo. He talked of the amazing sunlight – "absolutely a shower of gold" – and the beautiful lines. He wrote: "You wouldn't have been at all surprised to see knights and ladies suddenly appear, returning from hunting with hawks, or to hear the voice of an old provençal troubadour. The fields seem purple, the distances blue."

In the letter Van Gogh talks of a study that he made which has always been associated with a painting that hangs in the Museum of Fine Arts in Houston, The Rocks. The new research says that association is wrong, but the references do make sense when linked to Sunset at Montmajour.

There is ample evidence of it being his hand, says the article, not least "the diversity of the brushstrokes and the creaminess of the paint, as well as in the rapidity and liveliness with which it was applied".

The newly attributed painting is in the hands of a no doubt thrilled, but anonymous, owner but will be on display in Amsterdam from 24 September.