Galactic David and Goliath

Date:

Share post:

The gravitational dance between two galaxies in our local neighbourhood has led to intriguing visual features in both as witnessed in this new NASA/ESA Hubble Space Telescope image. The tiny NGC 1510 and its colossal neighbour NGC 1512 are at the beginning of a lengthy merger, a crucial process in galaxy evolution. Despite its diminutive size, NGC 1510 has had a significant effect on NGC 1512’s structure and amount of star formation.

Galactic David and Goliath
This composite image, created out of two different pointings from Hubble, shows the barred spiral galaxy NGC 1512 (left) 
and the dwarf galaxy NGC 1510 (right). Both galaxies are about 30 million light-years away from Earth and currently
 in the process of merging. At the end of this process NGC 1512 will have cannibalised its smaller companion 
[Credit: ESA/Hubble, NASA]

Galaxies come in a range of shapes and sizes, and astronomers use this fact to classify them based on their appearance. NGC 1512, the large galaxy to the left in this image, is classified as a barred spiral, named after the bar composed of stars, gas and dust slicing through its centre. The tiny NGC 1510 to the right, on the other hand, is a dwarf galaxy. Despite their very different sizes, each galaxy affects the other through gravity, causing slow changes in their appearances.

The bar in NGC 1512 acts as a cosmic funnel, channelling the raw materials required for star formation from the outer ring into the heart of the galaxy. This pipeline of gas and dust in NGC 1512 fuels intense star birth in the bright, blue, shimmering inner disc known as a circumnuclear starburst ring, which spans 2400 light-years.

Both the bar and the starburst ring are thought to be at least in part the result of the cosmic scuffle between the two galaxies — a merger that has been going on for 400 million years.

NGC 1512, which has been observed by Hubble in the past , is also home to a second, more serene, star-forming region in its outer ring. This ring is dotted with dozens of HII regions, where large swathes of hydrogen gas are subject to intense radiation from nearby, newly formed stars. This radiation causes the gas to glow and creates the bright knots of light seen throughout the ring.

Remarkably, NGC 1512 extends even further than we can see in this image — beyond the outer ring — displaying malformed, tendril-like spiral arms enveloping NGC 1510. These huge arms are thought to be warped by strong gravitational interactions with NGC 1510 and the accretion of material from it. But these interactions are not just affecting NGC 1512; they have also taken their toll on the smaller of the pair.

The constant tidal tugging from its neighbour has swirled up the gas and dust in NGC 1510 and kick-started star formation that is even more intense than in NGC 1512. This causes the galaxy to glow with the blue hue that is indicative of hot new stars.

NGC 1510 is not the only galaxy to have experienced the massive gravitational tidal forces of NGC 1512. Observations made in 2015 showed that the outer regions of the spiral arms of NGC 1512 were indeed once part of a separate, older galaxy. This galaxy was ripped apart and absorbed by NGC 1512, just as it is doing now to NGC 1510.

Together, the pair demonstrate how interactions between galaxies, even if they are of very different sizes, can have a significant influence on their structures, changing the dynamics of their constituent gas and dust and even triggering starbursts. Such interactions between galaxies, and galaxy mergers in particular, play a key role in galactic evolution.

Source: ESA/Hubble Information Centre [July 27, 2017]

ADVERTISEMENT

spot_img

Related articles

NASA spots giant debris cloud created by clashing celestial bodies

Major smashups between rocky bodies shaped our solar system. Observations of a similar crash give clues about how...

Yury Gagarin: a symbol of modernization

"Let's go!" With these words Yury Gagarin blasted off on a flight that would shock the world. How...

Dark energy targeted in European space mission

So-called dark energy, believed to play a role in the accelerated expansion of the Universe, will be studied...

Distant galaxies and the true nature of dark matter

At the centre of spiral galaxies -- those near to us but also those billions of light-years away...

Hubble inspects a contorted spiral galaxy

This striking image showcases the unusually contorted appearance of NGC 2276, an appearance caused by two different astrophysical...

Examination of Theia 456 finds its nearly 500 stars were born at same time

The Milky Way houses 8,292 recently discovered stellar streams — all named Theia. But Theia 456 is special.Artistic...

Mysterious white dwarf pulsar discovered

An exotic binary star system 380 light-years away has been identified as an elusive white dwarf pulsar --...

VST captures three-in-one

Sharpless 2-54 and the Eagle and Omega Nebula e are located roughly 7000 light-years away -- the first...