Science

Hoag’s object: A galaxy within a galaxy within a galaxy

This interstellar object could provide the perfect setting for Christopher Nolan’s next movie as this is found to be a galaxy within a galaxy within another galaxy, much like the Russian Matryoshka dolls, wooden dolls of decreasing size placed inside one another.

This object, named Hoag’s object after it’s discoverer astronomer Arthur Hoag, was discovered in 1950 and has ever since confounded astronomers seeking for an explanation.

Hoag’s object can be found in the Serpens constellation, which is one of the 48 constellations catalogued by the Greek astronomer Ptolemy, located around 600 million light years from Earth.

This object is a ring shaped galaxy spanning roughly 100,000 light years. The Hubble Space Telescope (HST) has recently taken a picture of this uncanny object, which was processed by geophysicist Benoit Blanco who found that it consists of 3 different nested layers: a bright blue ring containing billions of stars around a much smaller and denser sphere of reddish stars and another ring galaxy between the two layers which is much farther away from us.

Astronomers are grappling to explain this inscrutable object to find the reason for its split into two, and since these objects account for less than 0.1% of all known galaxies, not much has been studied about these types of galaxies.

The discoverer of this object, Arthur Hoag himself suggested that the rings were caused due to gravitational lensing, a revelation from Einstein’s general theory of relativity, where the presence of a huge mass between the source and the observer would bend light, changing the apparent position of the source, a prediction famously confirmed by Arthur Eddington during the 1919 solar eclipse.

Later careful studies of the object disproved this hypothesis. Another popular conjecture is that the Hoag’s object was once a run of the mill disc shaped galaxy, but a collision with another galaxy, which would have changed the gravitational configuration of the stars, would have resulted in the present structure being formed.

Provided the alleged collision happened in the last 3 billion years, our radio telescopes would have been able to detect the aftermath of the cosmic cataclysm, however nothing has been detected so far and hence the collision, if it happened, would have been happened so long ago that the evidence would have been lost forever.

As these types of galaxies are rare and occur sporadically, and many don’t typically have this ring formation, this object still remains a mystery for astronomers.

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