The Minneapolis Institute of Arts has promised weekly surprises throughout its 2015 centennial celebration, and it delivered a big one Friday, unveiling "Woman in Blue Reading a Letter," one of only 34 surviving works by 17th-century Dutch painter Johannes Vermeer.

The oil painting — an enigmatic gem about 18 inches high and 15 inches wide — will be on view through May 3 in the museum's Cargill Gallery, just off the main lobby. There is no charge for admission.

On loan from Amsterdam's Rijksmuseum, the picture is a prime example of Vermeer's intimate studies of women in contemplative moments.

"I'm not good at verbalizing beauty, but it's really beautiful," said Brenda Freier, a recently retired defense contract analyst from Apple Valley who was visiting the museum Friday morning and unexpectedly got swept up in the hoopla. "We've been wanting to come here for a long time and this was just a nice surprise."

Even the museum's staff gasped and applauded when director Kaywin Feldman unveiled the picture Friday morning.

"This is the first Vermeer I've ever seen, so it's extremely exciting," said Aubrey Mozer, the museum's corporate relations specialist. "I work with our sponsors and even they didn't know" what they were paying to bring to Minneapolis, she said.

The painting is the first of three promised masterpieces on loan that the MIA will unveil at unannounced times throughout its centennial year.

The identity of the woman in blue is unknown, but the picture contains details that help experts interpret the scene. Like many of Vermeer's subjects, the woman faces a window from which morning light floods the room. That she is still wearing her bed jacket, a pearl necklace on the table beside her, hints that the letter's arrival interrupted her as she dressed for the day.

"Perhaps Vermeer is giving us clues," said Feldman, an expert in Dutch art who negotiated the loan. "The map in the background may suggest that the letter is from a husband or lover who is traveling abroad."

Other experts note that the Dutch were famous map makers and, like other artists of the time, Vermeer frequently included maps in his paintings. Some have speculated that the artist used lenses and other newfangled optical equipment to help create the mesmerizing detail, light and space in his work.

Vermeer (1632-75) spent his whole career in his hometown of Delft. He joined the St. Luke's Guild, a fraternity of master painters, at age 21. A Protestant of modest means, he married a Catholic girl from a prosperous family and had at least 11 children. His impoverished widow sold 26 paintings to an Amsterdam dealer just months after his death. Even now scholars squabble about how many pictures he painted and how many have survived.

Largely forgotten until the late 19th century, Vermeer has become a popular favorite in recent years thanks to novels and films inspired by his seductive images, especially "Girl With a Pearl Earring," a 1999 historical novel by Tracy Chevalier that became a film starring Scarlett Johansson.

"Woman in Blue" is on something of a birthday tour this year. Following its Minneapolis appearance, it will go to the Timken Museum in San Diego, which is celebrating its 50th anniversary.

It is the second Vermeer shown at the institute in the past six years. "The Astronomer" was in a 2009 show of paintings on loan from the Louvre museum in Paris.