NGC 772: Galaxy with the “stretched ” spiral arm

The presented image was obtained by the Gemini North telescope installed on the top of Hawaii’s Maunakea Mountain. It shows the spiral galaxy NGC 772.

Galaxy NGC 772. Source: International Gemini Observatory/NOIRLab/NSF/AURA

NGC 772 is located at a distance of 100 million light-years from Earth in the direction of the constellation Aries. Already at the first glance at the Gemini North image in its lower part, we can notice the main distinguishing feature of its structure: a very elongated and deformed spiral arm. 

Such an unusual shape of the arm is explained by the influence of its neighbor, the dwarf elliptical galaxy NGC 770. The tidal interactions led to one of the spiral arms of NGC 772 being greatly stretched, acquiring a “lopsided” appearance seen in this image.

NGC 772 also lacks a bar: a bright structure of stars and gas in the center, from the ends of which arms usually sweep out. Most of the spiral galaxies (including our Milky Way) have bars.

In the background of the Gemini North image, we can see a number of bright spots. Almost all of them are even more distant galaxies. Some of them have a spiral structure, some are elliptical, and some cannot be attributed to any particular type. In general, according to the latest estimates of astronomers, there are about 2 trillion galaxies in the observable part of the Universe.

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