This is a very rare phenomenon produced by the Sun!
"Tonight I photographed the setting sun and suddenly when it was about to disappear behind the treetops there was a mighty blue flash," wrote Peter RosÚn,
Stockholm, Sweden who took this picture on February 29, 2012.
Blue flashes are normally harder to see than green flashes, because blue flashes blend into the surrounding blue sky. When the air is exceptionally clear,
however, the blue flash emerges.
A Blue flash. Photo Credits: Peter RosÚn, Stockholm, Sweden
They are formed in the same way as green flashes: a mirage magnifies tiny differences in the atmospheric refraction of red, green and blue light.
Once believed to be a fable, the green flash was popularized by Jules Verne in his 1882 novel "Le Rayon Vert" (The Green Ray).
Now it is generally known to be real event.
Verne described the green flash as something "which no artist could ever obtain on his palette, a green of which neither the varied tints of vegetation
nor the shades of the most limpid sea could ever produce the like!
If there is a green in Paradise, it cannot be but of this shade, which most surely is the true green of Hope."
Now, the blue flash is a real - but very rare - phenomenon.
Abnormal Star Discovered In The 'Forbidden Zone'
A team of astrophysicists from Germany, France and Italy have discovered in the constellation Leo is an old star.
The star's existence raised at once many questions for scientists.
The object is definitely not as its "contemporaries" that appeared immediately after the Big Bang event.
The Eyes Of A Future Alien Astronomer - What Will They See?
Have you ever wondered what the Universe will look like for a future alien astronomer?
It will in fact be entirely different from what it is today.
One trillion years from now, an alien astronomer in our galaxy will have great difficulties figuring out how the universe began.
The Milky Way will have merged with the Andromeda galaxy to form the Milkomeda galaxy. Many of its stars, including our Sun, will have burned out.
Violent Dragon Clash Billions Of Years Ago
NGC 5907 is sometimes called the "Splinter" or Knife Edge Galaxy because of its unusual appearance.
It is a spiral galaxy lying in the Dragon constellation,
about 40 million light-years from Earth that could have been formed through a gigantic collision of galaxies, 8 to 9 billion years ago.