An unusual composite image created by ESO astronomers reveals the aftermath of a catastrophic collision between two similar disk galaxies, which happened 600 million years ago; the result is an oddly shaped galaxy called NGC 7252.
VLT map of gas within NGC 7252’s minispiral. Image credit: ESO / NASA / ESA / Hubble / J. Weaver et al.
NGC 7252, a peculiar galaxy in the constellation Aquarius, about 212 million light-years away, has an odd nickname.
In December 1953, President Eisenhower gave a speech that was dubbed Atoms for Peace.
The theme was promoting nuclear power for peaceful purposes — a particularly hot topic at the time.
This speech and the associated conference made waves in the scientific community and beyond to such an extent that NGC 7252 was named the Atoms for Peace galaxy.
This nickname is quite ironic, as the galaxy’s past was anything but peaceful. Its peculiar appearance is the result of a merger of two similar gas-rich disk galaxies.
At the heart of this merger remnant lies a fascinating ‘minispiral’ — a rotating disk of glowing gas, bursting with star formation.
NGC 7252. Image credit: NASA / ESA / Judy Schmidt, www.geckzilla.com.
Using the VIsible Multi-Object Spectrograph on ESO’s Very Large Telescope (VLT), Dr. John Weaver from the University of St Andrews and co-authors were able to measure the movement of the gas within this disk, allowing them to map its rotation.
Red regions indicate gas moving away from us, and blue regions towards us. Together, these colors reveal the galaxy’s steadily rotating center, as well as highlighting two flowing streams of hot gas north-west and south-east of the central region.
Past studies suggested that the central spiral was rotating counter to the rest of the galaxy, but by comparing the movement of stars around the galaxy with the gas ionized by newly formed stars in the minispiral, astronomers now know that they are in fact rotating in the same direction.
The team’s findings were published recently online in the journal Astronomy & Astrophysics (arXiv.org preprint).
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J. Weaver et al. 2018. History and destiny of an emerging early-type galaxy. New IFU insights on the major-merger remnant NGC 7252. A&A, in press; doi: 10.1051/0004-6361/201732448
