We stood in Van Gogh's spot and saw exactly this lighting effect on the house in the last hour before sunset

Professor Donald Olsen

It hangs in the Hermitage Museum in St Petersburg, where it was kept hidden for half a century.

Astronomers at Southwest Texas State University in San Marcos calculated that the star is Venus, which was bright in the evening sky in June 1890.

They started by tracing the house, which still stands in the town.

Researchers Donald Olson and Russell Doescher say the canvas was painted from the bottom up during the course of an afternoon and early evening.

Astonished

"You can see it's about 7:00 pm from the sunlight on the house, but as the sun sets, Venus becomes bright and obvious," said Mr Doescher, who added that he was astonished by the accuracy of the star's position in the picture.

Professor Olsen added: "In the painting, the light is coming from right to left, with the front of the house lit up, the left side of the house in shadow and the women near the gate casting shadows to the left.

"We stood in Van Gogh's spot and saw exactly this lighting effect on the house in the last hour before sunset."

A computer program calculated that Venus was in the position shown in the painting at around 8:00pm on 16 June 1890, just six weeks before the artist killed himself.

They knew the painting was completed before 17 June because the artist wrote to his brother and described the work in detail.

The painting itself has had a turbulent history.

It was hidden from Nazi looters when seized by Russian soldiers during World War II.

It was though lost but re-emerged in Russia in 1995, after the fall of the Soviet Union.