David and Goliath Battle Between Galaxies Could End With One Being Cannibalized

Astronomers have used the Hubble Space Telescope to observe a David and Goliath-type battle between a massive galaxy and a much smaller one, 220 million light-years from Earth.

One of the outcomes of this gravitational struggle could see NGC 7752 ripped apart and its stars dispersed into the larger spiral galaxy, a form of cosmic cannibalization that links these galaxies to our own.

The larger spiral galaxy is NGC 7753, and its smaller galactic companion, known as NGC 7752, both lie in the constellation of Pegasus.

The fact that the smaller galaxy appears to be attached to the larger galaxy led to the two being added to the Atlas of Peculiar Galaxies compiled by the astronomer Halton Arp in 1966, with the designation Arp 86.

NASA predicts that the gravitational battle between the two galaxies will eventually result in NGC 7752 either being flung into interstellar space, or the encounter will lead to the destruction of the smaller galaxy, with its stars, gas, and dust spread throughout the larger galaxy.

This consumption of a smaller galaxy by a larger one could be similar to an event that astrophysicists suspect happened in the history of our galaxy, which has a similar spiral shape to NGC 7753, when it was less than 5 billion years old.

The form that the Milky Way takes today could have been influenced by an encounter with a smaller galaxy, Gaia-Enceladus, and ours, in which the more diminutive galaxy was shredded and consumed.

Research published in the journal Nature suggests that this violent encounter took place around 10 billion years ago, triggering a burst of rapid star formation about 4 billion years later that gave rise to the final segment of the Milky Way.

This probably isn't the only galactic collision that the Milky Way has undergone, and it certainly won't be the last. Our galaxy and its nearest cosmic neighbor Andromeda are currently on a collision course.

When this happens, NASA says that the Milky Way will be majorly reordered and that the portion of our galaxy containing the sun and our planet could be flung into an entirely different region. If this causes concern, this collision will only occur in 4 billion years as the two galaxies are still 25 million light-years apart.

Milky way Collision
A diagram of the potential impact between the Milky Way and Andromeda in 4 billion years that could majorly reshape our galaxy. ESA; A. Feild and R. van der Marel, STScI/NASA

These kinds of galactic collisions are not uncommon in the universe and researchers believe that they can play an important role in cosmic evolution. Galaxies with spiral arms like the Milky Way and NGC 7753 could have obtained those features through collisions with other galaxies.

A collision between galaxies redistributes gas and dust, often creating massive clouds of gas, which has the effect of triggering bursts of star-formation.

Hubble observed Arp 86 as part of an effort to better understand the connection between infant stars and the clouds of cold gas in which they form. With the aid of the space telescope, astronomers gazed into star clusters and clouds of gas and dust in a variety of environments dotted throughout nearby galaxies.

The observations they collected were then combined with measurements from the Atacama Large Millimeter/submillimeter Array, comprised of 66 radio telescopes distributed across the Atacama Desert in northern Chile.

Described by NASA as "a treasure trove of data for astronomers working to understand how stars are born," it is hoped that these observations could be used to guide the mission of the James Webb Space Telescope, following its launch later this year.

Galaxy Battle
Illustration of a large galaxy locked in a gravitational battle with a smaller counterpart. The Observation made by Hubble could guide the James Webb Space Telescope's future investigations. Hubble and NASA, Dark Energy Survey, J. Dalcanton/ESA