Free Astronomy Magazine May-June 2022
50 ASTRO PUBLISHING A ‘space triangle’ spawned by a galaxy collision A spectacular head-on colli- sion between two galaxies, known as Arp 143, has fu- eled the unusual triangular-shaped star-formation frenzy as captured by the NASA/ESA Hubble Space Tele- scope. The interacting galaxy duo Arp 143 contains the distorted, star-forming spiral galaxy NGC 2445, at right, along with its less flashy companion, NGC 2444, at left. Their frenzied col- lision takes place against the tapes- try of distant galaxies, of which some can be seen through the inter- acting pair. Astronomers suggest that the two galaxies passed through each other, igniting the uniquely shaped firestorm of star formation in NGC 2445, where thousands of stars are bursting into life. This galaxy is awash with new stars because it is rich in gas, the raw material from which stars are made. However, it hasn’t yet escaped the gravitational clutches of its partner at left. The pair is waging a cosmic tug-of-war, which NGC 2444 appears to be win- ning. That galaxy has pulled gas by NASA/ESA Bethany Downer H ubble’s Observation of Arp 143. [NASA, ESA, STScI, and J. Dalcan- ton (Center for Computational Astro- physics/Flatiron Inst., UWashington)] from NGC 2445, forming the oddball triangle of newly minted stars. NGC 2444 is also responsible for yanking strands of gas from its part- ner, stoking the streamers of young, blue stars that appear to form a bridge between the two galaxies. These streamers are among the first in what appears to be a wave of star formation that started on the galaxy’s outskirts and continued in- ward. Researchers estimate the streamer stars were born between 50 million and 100 million years ago. But these infant stars are being left behind as NGC 2445 continues to pull slowly away from NGC 2444. Stars no older than one million to two million years old are forming closer to the centre of NGC 2445. Hubble’s keen vision reveals some individual stars, the brightest and most massive in the galaxy. Most of the brilliant blue clumps are group- ings of stars and the pink blobs are
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