Hubble captures image of a galactic ‘hit and run’

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About 30 million light-years from Earth, two galaxies came together in an epic collision, and the beautiful fallout was captured by the Hubble Space Telescope.

Galaxy NGC 4485 collieded with its larger galactic neighbor NGC 4490 millions of years ago, leading to the creation of new stars seen in the right side of the image.

The collision was more like an accidental hit and run between two neighboring galaxies, NGC 4485 and NGC 4490, that can be found in the Hunting Dogs constellation. Given the distance of these galaxies from us, the collision wasn’t captured in real time. It happened millions of years ago, but we’re just now seeing it.

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NGC 4490, a spiral galaxy with a central bar structure made of stars, is the larger galactic neighbor of NGC 4485, an irregular galaxy with no defined shape. The spiral galaxy was passing the irregular galaxy when the collision happened. The gravity of the larger galaxy warped the structure of gas, dust and stars in NGC 4485.

Now, the galaxies are moving away from each other, and the gravitational force between them is warping the shape of each. There’s a 25,000 light-years-long stream of stars and gas between the two galaxies.

This is a ground-based telescope's view of the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The inset image, taken by the Hubble Space Telescope, reveals one of many star clusters scattered throughout the dwarf galaxy. CREDIT: NASA, ESA, Adam Riess, and Palomar Digitized Sky Survey

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But rather than being destructive, the violent encounter encouraged new star formation.

In the image captured by Hubble, the right side of NGC 4485 is bright with the birth of blue stars and pink nebulas signifying that stars are “incubating.” On the left are the remnants of its structure that was evolving normally before the collision.

On the bottom right is a hint of the fleeing NGC 4490.

Astronomers developed a mosaic of the distant Universe, called the Hubble Legacy Field, that documents 16 years of observations from the NASA/ESA Hubble Space Telescope. The image contains 200,000 galaxies that stretch back through 13.3 billion years of time to just 500 million years after the Big Bang. The new set of Hubble images, created from nearly 7,500 individual exposures, is the first in a series of Hubble Legacy Field images. The image comprises the collective work of 31 Hubble programs by different teams of astronomers. Hubble has spent more time on this small area than on any other region of the sky, totaling more than 250 days, representing nearly three-quarters of a year. The team is working on a second set of images, totaling more than 5,200 Hubble exposures, in another area of the sky.

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These blue stars have a short life span, quickly burning through their fuel and exploding. But those explosions also release material and heavy elements into space, which leads to the creation of new stars.

These collisions were common in the early universe, when it was smaller and galaxies were in closer proximity, sideswiping and bumping into each other.

This image, along with the other unique views of our galaxy captured by Hubble, is shedding light on galactic evolution.