Friday, April 23, 2021

All about Arp 147

Arp 147 is a pair of interacting galaxies 400 million light years away from Earth, visible in the constellation Cetus.

The two galaxies are arranged as if they form the number 10.

By studying their current form we are able to reconstruct the evolutionary history of the system. This was in fact initially formed by a spiral galaxy (right) and an elliptical galaxy (left). The collision began when the elliptical galaxy passed through the spiral one.

The latter is the one that was most distorted during the interaction: the shock waves generated during the passage have in fact radically changed the appearance of the galaxy, making it take on a ring shape. As a further effect, the shock waves triggered very intense star formation phenomena, as can be understood from the bright blue color of the ring.

The elliptical galaxy on the left, on the other hand, suffered less from the effects of the collision. Its original structure is in fact still recognizable, even if its core is also surrounded by a ring. Unlike in the case of the spiral galaxy, no star formation phenomena are active in this ring.

Credit: NASA, ESA, Hubble, M. Livio.


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