The celestial eagle is in full flight at this time of the year for the northern hemisphere. The constellation of Aquila is one of the 48 constellations defined by Ptolemy in the 2nd century, though it had been mentioned in Greek tradition as long ago as the 4th century BC by Eudoxus. In mythology, Aquila represents the eagle that holds Zeus’s thunderbolts. The chart shows the view looking due south at 21:00 BST on 26 September, though the view will be broadly similar throughout the week at this time. Unlike visualising some constellations, it is relatively easy to imagine an eagle with outstretched wings from the stars of Aquila. The brightest star in the constellation is Altair, which is one of the closest stars to Earth that is also visible to the naked eye. At just 17 light years away, it contains about 1.8 times the mass of our sun, and gives out 11 times more light. Together with Deneb in Cygnus, the swan, and Vega in Lyra, the lyre, Altair forms a trio of bright stars that are nicknamed the summer triangle. From the southern hemisphere, Aquila can be seen on the north-western sky.