In a recent image captured by the Hubble Space Telescope, a massive star bridge spanning 250,000 light-years, formed of stars stretching from one galaxy to another within the Arp 295 galactic group, has been revealed. This discovery offers a spectacular glimpse into the dynamics at play in the Universe and could even shed light on the distant future of our own galaxy, the Milky Way.
Arp 295 is a trio of galaxies, located about 270 million light-years from Earth, in the Aquarius constellation. The Hubble image focuses on the galaxy Arp 295a, from which this impressive stellar bridge emanates, observable in profile. Nearby, the galaxy Arp 295c can also be spotted, appearing as a bright blue spiral.
Image of the ARP 295 galactic group and a star bridge emerging from one of its galaxies.
Credit: NASA/ESA/J. Dalcanton (University of Washington)/R. Windhorst (Arizona State University)/Processing: Gladys Kober (NASA/Catholic University of America) This remarkable cosmic phenomenon results from gravitational interactions between neighboring galaxies. When galaxies get close enough to disturb each other's structure, they are described as "interacting galaxies." In the case of Arp 295, these interactions have led to the stretching of a bridge of stars, gas, and dust, reaching between the galaxies. This type of galactic interaction can extend over billions of years, with the galaxies brushing against and intertwining with each other multiple times.
Eventually, repeated passages between these galaxies can lead to a complete merger, transforming their initial shapes into a single irregular galaxy. This merging process causes an increase in the rate of star formation, known as a "starburst," due to the influx of gas conducive to the birth of new stars.
Moreover, the supermassive black holes, residing at the core of each galaxy and weighing millions or billions of times the mass of the Sun, also tend to merge. This union produces powerful gravitational waves, a phenomenon crucial for understanding cosmic evolution.
Understanding these interacting and merging galaxies gives astronomers clues about what might happen to the Milky Way when it collides with the Andromeda galaxy, anticipated in about 4.5 billion years. Our two spiral galaxies, currently 2.5 million light-years apart, are approaching each other at a breathtaking speed. This future merger could move our solar system closer to the supermassive black hole at the heart of our galaxy, Sagittarius A*, or even eject it completely from the Milky Way.