Megalithic tombs could have been designed as ingenious tools to observe the faintest stars – effectively telescopes without lenses – astronomers in Britain suggest.
They say the long, narrow entrance passageways of so-called passage graves, dating from around 6,000 years ago, are aligned to certain stars.
The focus of 13 of the tombs in Carregal do Sal, Portugal appears to be Aldebaran, the brightest star in the constellation of Taurus.
The researchers suggest that this could be for ceremonial purposes.
“To accurately time the first appearance of this star in the season, it is vital to be able to detect stars during twilight,” said Fabio Silva, of the University of Wales Trinity Saint David.
“Rock art and paintings, some of which are present inside similar passage graves, could and have been interpreted as red stars, much like Aldebaran itself.”
When the tombs were built, around 4,300 – 3,700 BCE, Aldebaran would have risen between 18 and 27 April and appear from within all of the entrance passages of the tombs.
The team presented the study at the National Astronomy Meeting in Nottingham.
The researchers said they believed the initiate in the ceremonies would spend the night inside the tomb, with no natural light apart from that shining down the narrow entrance.
“It is quite a surprise that no one has thoroughly investigated how for example the colour of the night sky impacts on what can be seen with the naked eye,” Kieran Simcox from Nottingham Trent University and a leader of the project said.