Unexpected Early Spiral Galaxy

Spiral
Composite of BX442 from Hubble Space Telescope and Keck Telescope in Hawaii
Image Credit: David Law; Dunlap Institute for Astronomy and Astrophysics

Only one galaxy with a redshift (z) greater than 2 (about 10 billion years ago) has been observed, but may be a merger viewed at an odd angle.

Now, astronomers report in the 19 July issue of Nature the discovery of a primordial galaxy (Q2343-BX442) at z = 2.18 with three distinct spiral arms.

The images were from the Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3), and BX442 was the only galaxy with a spiral shape among the 306 galaxies surveyed at this depth (z between 1.5 and 3.6). A small companion was observed, and the astronomers note that the collision of such a companion with BX442 can produce the spiral arms that are observed. If this is the case, they expect the galaxy to relax into a more primitive shape within the next 100 million years.

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