February 23, 2024

After last week’s image of the week from the Hubble Space Telescope showed a cluster of galaxies that appeared to be very close to each other but actually weren’t, this week’s image shows two images that are practically on top of each other. The two galaxies shown in the image below, NGC 6040 and LEDA 59642, are so close that they are interacting and have a shared name as a pair, Arp 122.

This NASA/ESA Hubble Space Telescope image features Arp 122, a peculiar galaxy that in fact comprises two galaxies – NGC 6040, the tilted, warped spiral galaxy and LEDA 59642, the round, face-on spiral – that are in the midst of a collision. ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Acknowledgement: L. Shatz

NGC 6040 is the galaxy on the top, which is stretched into a long, thin shape by the tremendous force of gravity from the rounder, face-on galaxy in the center-right, LEDA 59642. When galaxies come close together, the forces of gravity from both massive objects can interact and twist or distort one or both of the galaxies into unusual shapes, as has happened here.

The colliding of two galaxies is an epic event, and it can result in the destruction of one galaxy. At other times, the two colliding galaxies can merge into one. After hundreds of millions of years, the two can become one even larger galaxy, as may happen to Arp 122.

“Galaxies are composed of stars and their solar systems, dust, gas, and invisible dark matter. In galactic collisions, therefore, these constituent components may experience enormous changes in the gravitational forces acting on them,” Hubble scientists explain. “In time, this completely changes the structure of the two (or more) colliding galaxies, and sometimes ultimately results in a single, merged galaxy. That may well be what results from the collision pictured in this image.”

Our own galaxy, the Milky Way, is scheduled to collide with our galactic neighbor, the Andromeda galaxy, in around four billion years. That collision would likely create a giant elliptical galaxy as a merger between the two.

However, another theory states that before that happens, the Milky Way could collide with a smaller satellite galaxy called the Large Magellanic Cloud in around two billion years’ time. This theory states that the forces of the two colliding galaxies could spur the supermassive black hole at the center of our galaxy into overdrive, causing it to swell in size and send out powerful jets of radiation.

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