The cosmic object that no one can explain: a galaxy within a galaxy within a galaxy

 

It is the Hoag object, an annular galaxy that lies about 600 million light years. This 'galactic scroll', located in the constellation of the Serpent, has been the subject of conjecture in the astronomical community since it was discovered by Arthur Hoag in 1950. The celestial body, imaged by the Hubble telescope and processed by geophysicist Benoit Blanco, spans about 100,000 light years and represents a perfect ring of blue stars around a denser sphere of yellow stars. In the dark gap between the two galaxies, a third annular galaxy is seen, most likely located at an even greater distance from Earth. Ring galaxies represent less than 0.1% of all known galaxies and are not easy to study. Hoag himself suggested that the galaxy's peculiar structure was merely due to an optical illusion caused by the gravitational lensing effect - distortion of light from a bright object as extremely high-mass objects pass. However, later studies discarded this idea. Another popular hypothesis assumes that Hoag's object had been a more common, spiral galaxy before colliding with another galaxy that penetrated it at the center, reducing its gravitational pull. If such a collision had occurred in the last 3 billion years, some remains could have been detected, but there are none.
_______________
Source: NASA, Telescope Special Hubble.